UBC Theses and Dissertations

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UBC Theses and Dissertations

Beach profiles and sediment activity Mattila, Mark Ronald 1988

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BEACH  PROFILES AND  SEDIMENT  ACTIVITY  By Mark Ronald  Mattila  B . A . S c . ( C i v i l E n g i n e e r i n g ) , University of B r i t i s h C o l u m b i a , 1 9 8 5  A THESIS S U B M I T T E D IN P A R T I A L F U L F I L L M E N T O F THE REQUIREMENTS MASTER  FOR T H EDEGREE OF  OF APPLIED  SCIENCE  in THE FACULTY OF GRADUATE CIVIL  STUDIES  ENGINEERING  W e a c c e p t t h i s thesis as c o n f o r m i n g to t h e r e q u i r e d s t a n d a r d  THE  UNIVERSITY O F BRITISH  COLUMBIA  ' November 1988  (c) M a r k R o n a l d M a t t i l a , 1 9 8 8  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.  I further agree that permission for extensive copying of this  thesis for scholarly purposes may be granted by the head of my department or by his or her representatives.  It is understood that copying or publication of this thesis for  financial gain shall not be allowed without my written permission.  C i v i l Engineering T h e University of B r i t i s h C o l u m b i a 2075 Wesbrook Place Vancouver. Canada  V6T 1W5  Date:  ABSTRACT  A s t u d y of b e a c h profiles a n d s e d i m e n t a c t i v i t y has been u n d e r t a k e n i n v e s t i g a t i n g n a t u r a l beaches of i n n e r c o a s t a l s o u t h w e s t B r i t i s h C o l u m b i a a n d p u b l i s h e d d a t a o n l a b o r a t o r y beaches. T w o s e p a r a t e t y p e s of s e d i m e n t a c t i v i t y are f o c u s e d u p o n : l o n g s h o r e sediment, a c t i v i t y <>< c u r i n g o n i n n e r coast beaches a n d o n - offshore s e d i m e n t a c t i v i t y o c c u r i n g on wave H u m e c o n s t r a i n e d l a b o r a t o r y beaches. Field i n v e s t i g a t i v e w o r k on t w e n t y - f i v e n a t u r a l beaches has i n c l u d e d r e v i e w of pastfield s t u d i e s , p r o f i l e s u r v e y s , s e d i m e n t t r a c i n g e x p e r i m e n t s , i n v e s t i g a t i o n of surface a n d s u b s u r f a c e sediment, size d i s t r i b u t i o n a n d s t r u c t u r e , m e a s u r e m e n t of slopes a n d e l e v a t i o n s of s h o r e l i n e features, r e v i e w of a v a i l a b l e w a v e c l i m a t e d a t a a n d wave h i n d c a s t i n g for the p e r i o d of p r o f i l e s u r v e y s .  T h e w o r k has s h o w n t h a t i n n e r c o a s t a l beaches are p r e d o m -  i n a n t l y s h i n g l e beaches or c o b b l e a r m o u r e d beaches w i t h l o n g s h o r e s e d i m e n t  transport,  o c c u r i n g in a n a r r o w u p p e r foreshore z o n e u n d e r wave a c t i o n at h i g h t i d e s .  T h e r e is  also e v i d e n c e that coarse m a t e r i a l s (gravels a n d c o b b l e s ) m o v e s e l e c t i v e l y i n an o n s h o r e d i r e c t i o n a n d fine m a t e r i a l s (silts a n d s a n d s ) m o v e i n a n offshore d i r e c t i o n . T h e s e d i m e n t t r a n s p o r t processes a n d b e a c h c h a r a c t e r i s t i c s i d e n t i f i e d are different f r o m t h e s u m m e r / w i n t e r b e a c h process k n o w n to o c c u r on o p e n coasts. L a b o r a t o r y beaches h a v e been s t u d i e d t o i d e n t i f y t h e g e n e r a l response of a b e a c h profile t o waves.  O n e p r o b l e m i n the s t u d y of beaches has been t h e l a c k of a r e a d i l y  m e a s u r e d v a r i a b l e to i n t e r r e l a t e w a v e a c t i o n a n d s e d i m e n t m o v e m e n t . B y s t u d y i n g l a b o r a t o r y b e a c h profiles a v a r i a b l e r e p r e s e n t i n g on-offshore sediment, m o v e m e n t has been a b s t r a c t e d as an a r e a swept out by d i f f e r e n c i n g t w o profiles as a f u n c t i o n of t i m e .  The  v a r i a b l e has been i n v e s t i g a t e d u s i n g l a b o r a t o r y b e a c h d a t a a n d c o r r e l a t i o n b e t w e e n it  ii  and wave parameters such as height, and period is evident. A dimensional analysis of onoffshore sediment transport is performed using the swept, area variable.  (  iii  Table of C o n t e n t s  ABSTRACT  ii  List of Tables  viii  L i s t of F i g u r e s  ix  List, o f P h o t o g r a p h s  xi  Nomenclature  xiii  Acknowledgement  xv  1  2  INTRODUCTION  1  1.1  General  1  .1.2  Inner Coast Beaches - Current Status of Knowledge  2  1.3  Previous W o r k  3  1.4  Research Justification  6  TECHNICAL WORK A N D EXPERIMENTS  8  2.1  General  8  2.2  Surveys  8  2.3  Analysis of Sediments  9  2.4  Sediment Tracing  10  2.4.1  Background  10  2.4.2  Beach experiment  11  2.5  Wave Hindcasting  12  2.6  Volume Calculations  16  iv  2.7  3  Laboratory Beach Data  16  FIELD INVESTIGATIVE W O R K  18  3.1  Background  18  3.2  Study Area  18  3.2.1  Geography  18  3.2.2  Physiography  19  3.2.3  Geology and geomorphic history  19  3.2.4  L i t t o r a l materials  20  3.2.5  W i n d a n d wave c l i m a t o l o g y  20  3.2.6  Tides  21  3.2.7  Shoreline classification  22  3.3  Sites S t u d i e d  24  3.4  Sediments  26  3.4.1  B e a c h slope a n d g r a i n size  26  3.4.2  S h i n g l e beaches  26  3.4.3  A r m o u r e d beaches  27  3.5  3.6  Profiles  29  3.5.1  Discussion  3.5.2  Tsawwassen Beach  30  3.5.3  T o w e r B e a c h at Point. G r e y  32  3.5.4  Dundarave  33  3.5.5  E l e v a t i o n s of shore features  33  3.5.6  H i n d c a s t waves a n d p r o f i l e changes  35  :  29  Sediment Transport  36  3.6.1  36  G e n e r a l field o b s e r v a t i o n s  v  3.6.2 3.7  Sediment transport experiments  B l u f f E r o s i o n - C u r r e n t S t a t u s of K n o w l e d g e  4 L A B O R A T O R Y BEACHES  5  6  37 40  44  4.1  General  44  4.2  Active Volume  45  4.3  Dimensional Analysis  46  4.4  A n a l y s i s of B e a c h P r o f i l e s  50  4.4.1  M e t h o d of a n a l y s i s  50  4.4.2  A c t i v e v o l u m e versus wave height  50  4.4.3  A c t i v e v o l u m e versus w a v e p e r i o d  52  4.4.4  A c t i v e v o l u m e versus t i m e  53  DISCUSSION  56  5.1  Beach Response  56  5.2  Differences B e t w e e n N a t u r a l a n d L a b o r a t o r y B e a c h e s  57  5.3  C o a s t a l Processes  58  FURTHER R E S E A R C H  62  7 CONCLUSIONS  64  7.1  F i e l d Investigative W o r k  64  7.2  L a b o r a t o r y Beaches  6'  Bibliography  69  Figures  75  Photographs  116 vi  Appendices  124  List, o f T a b l e s  1  Point Atkinson Tides  22  2  S o m e I n n e r S o u t h Coast. B e a c h e s  25  3  B e r m Crest and Debris Line Elevations  34  4  T r a n s p o r t of P a r t i c l e s  39  4(a)  L o n g s h o r e T r a n s p o r t of P a r t i c l e s  39  4(b)  O n s h o r e T r a n s p o r t of P a r t i c l e s  39  5  S o m e E r o d i n g C o a s t a l Bluffs  40  vm  List  of  Figures  1  Location Plan  76  2  Site Plan  77  3  G r a i n Size and Permeability Classification  78  4  Beach Profile Envelopes  79  5  Comparison of Measured and Hindcast Wave Heights  80  6  Laboratory Profiles - D a t a Set 1  81  7  Laboratory Beach Profiles - D a t a Set 2  82  8  Laboratory Beach Profiles - D a t a Set 3  83  9  D i s t r i b u t i o n of Wave Heights and Periods  84  10  Frequency of W i n d and Waves - Strait of Georgia  85  11  Tsawwassen Beach  86  12  Tower Beach - Point Grey  87  13  Dundarave - West Vancouver  14  Beach Face Slope Versus G r a i n Size  89  15  Shingle Beach - T y p i c a l Cross Section  90  16  A r m o u r e d Beach - T y p i c a l Cross Section  91  17  Tsawwassen Beach Profiles  92  18  Tower Beach Profiles  93  19  Dundarave Profiles  94  20  Cross Shore Sediment Size Distribution  95  21  G r a i n Size Distributions  96  22  Beach Elevation and Tide Level  97  23  Number of 38mm Particles per Square Metre of Beach Surface  98  24  Number of 38mm Particles per Square Metre of Beach Surface  99  .  88  25  N u m b e r of 7 5 m m P a r t i c l e s per S q u a r e M e t r e of B e a c h S u r f a c e  100  26  N u m b e r of 7 5 m m P a r t i c l e s p e r S q u a r e M e t r e of B e a c h S u r f a c e  101  27  B e a c h Cliff T y p i c a l Cross Section  102  28  Bluff Recession G e o m e t r y  103  29  On-Offshore Transport  104  30  Waves, A c t i v e V o l u m e and T i m e Derivatives  105  31  V  32  V  . . . .,  Versus H ,  D= 50  0.7mm, m=  0.1  106  Versus H ,  D =  0 . 7 m m , m=  0.05  107  33  V Versus H ,  D=  0.2mm,  0.1  108  34  V' Versus H ,  D=  0.2mm, m=  0.05  109  35  V  36  V  37  B e a c h Sediment A c t i v i t y Inner and O p e n Coasts  112  38  Open Coast Wave Period Distribution  113  39  I n n e r C o a s t D i s t r i b u t i o n s of W a v e Steepness a n d I n t e n s i t y  114  40  O u t e r C o a s t D i s t r i b u t i o n s of W a v e Steepness a n d I n t e n s i t y  115  a  0  a  a  t t  0  a  a  a  0  5Q  50  50  r  t  r  Versus T Versus t  110 . . .  Ill  x  List, o f P h o t o g r a p h s  1  A U G U S T 1987 - S e d i m e n t t r a c i n g e x p e r i m e n t s . . .•  117  2  .. A U G U S T 1987 - S e d i m e n t t r a c i n g e x p e r i m e n t s  3  A U G U S T 1987 - S e d i m e n t t r a c i n g e x p e r i m e n t s  4  A U G U S T 1987 - S e d i m e n t t r a c i n g e x p e r i m e n t s  117  5  M A Y 1987 - S t e e p s h i n g l e b e a c h , C a m p B y n g , R o b e r t s C r e e k  118  6  M A Y 1987 - Steep s h i n g l e b e a c h , T r a i l B a y , Sechelt  118  7  J U N E 1987 - C o b b l e c o l o n i z e d b y seaweed, F r e n c h B e a c h , S o o k e  118  8  M A Y 1987 - T y p i c a l s h i n g l e  118  9  J U N E 1987 - S t e e p s h i n g l e b e a c h , G o r d o n ' s B e a c h , S o o k e  119  10  J U N E 1987 - S t e e p b a c k s h o r e b e r m , G o r d o n ' s B e a c h , S o o k e  119  11  M A Y 1987 - S h i n g l e b e a c h , L o c k B a y , G a b r i o l a I s l a n d  119  12  M A Y 1987 - S h i n g l e b e a c h subsurface, L o c k B a y G a b r i o l a I s l a n d  119  13  M A Y 1987 - G r a v e l b e a c h , s o u t h e r n s h o r e , S a v a r y I s l a n d  120  14  M A Y 1987 - A r m o u r e d foreshore, D u n d a r a v e , W e s t V a n c o u v e r  120  15  M A Y 1987 - C o b b l e a r m o u r e d b e a c h , Q u a l i c u r r i , V a n c o u v e r I s l a n d  16  J U L Y 1988 - H o u r g l a s s i n g of t i m b e r p i l e , W i f f e n S p i t , S o o k e  17  M A Y 1987 - B l u f f t o p c o b b l e s u p p l y , C a p e M u d g e , Q u a d r a I s l a n d  18  M A Y 1987 - C o b b l e a n d b o u l d e r foreshore, C a p e M u d g e , Q u a d r a I s l a n d .  121  19  M A Y 1987 - R e b e c c a S p i t , Q u a d r a I s l a n d  121  20  M A Y 1987 - B e a c h surface, R e b e c c a S p i t , Q u a d r a I s l a n d  121  21  M A Y 1987 - S u m m e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  122  22  J A N U A R Y 1988 - W i n t e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  122  23  M A Y 1987 - S u m m e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  122  24  J A N U A R Y 1988 - W i n t e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  122  X]  117 .  . . . .  117  120 120  . . . .  121  25  M A Y 1987 - S u m m e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  123  26  JANUARY  123  27  M A Y 1987 - S u m m e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  123  28  JANUARY  123  1988 - W i n t e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  1988 - W i n t e r bluff e r o s i o n , W i l l e m a r B l u f f s , C o m o x  xii  Nomenclature C= d=  o n - offshore p a r a m e t e r ; d e p t h of water;  D = 5Q  m e d i a n particle diameter;  E— wave energy d e n s i t y or specific e n e r g y ; Fg=  fetch l e n g t h ; a c c e l e r a t i o n d u e to g r a v i t y ;  H H W - = h i g h e r h i g h water; H W — h i g h water; H~  deep w a t e r m o n o c h r o m a t i c wave h e i g h t ;  c  H — significant wave height; s  /=  wave i n t e n s i t y  (E/T);  L L W — lower low water; L— 0  LW=  deep w a t e r wave l e n g t h ; low water;  ??i,;= i n i t i a l b e a c h slope; M S L = : m e a n sea level; MWL=  m e a n water level;  p= fluid density; p— s  Q= a  p a r t i c l e density; dV /dt=a  sediment, a c t i v i t y ;  / ? = h o r i z o n t a l bluff recession; \Vaeq '~ ^ a i | / | K e | = profile s t a t e p a r a m e t e r ; 9  T— T~ p  wave p e r i o d ; peak period;  xm  T — significant period; s  t— d u r a t i o n of wave event; td=  d u r a t i o n of wave event;  U=  w i n d velocity;  / / = k i n e m a t i c viscosity; v— d y n a m i c viscosity; V— a  a c t i v e v o l u m e r e l a t i v e to a reference profile;  V ~ e q u i l i b r i u m a c t i v e v o l u m e r e l a t i v e to a reference profile; aeq  Vai~ V— g  i n i t i a l active v o l u m e r e l a t i v e to a reference profile; gross v o l u m e .  xiv  Acknowledgement,  T h a n k s m u s t b e g r a n t e d to t h e m a n y p e o p l e w h o c o n t r i b u t e d i n v a r i o u s c a p a c i t i e s t o t h e c o m p l e t i o n of t h i s w o r k . M y sincerest t h a n k s go t o m y a d v i s e r D r . M . de S t . Q . Isaacson for his g u i d a n c e a n d p a t i e n c e t h r o u g h o u t t h e d e v e l o p m e n t of m y thesis.  T h a n k s are  also e x t e n d e d t o D r . M . C . Q u i c k for his o p i n i o n s a n d suggestions. M r . D . M c C o n n e l l , P . E n g . of H a y a n d C o m p a n y C o n s u l t a n t s I n c . is a c k n o w l e d g e d for ideas t h a t l e a d t o t h e o r i g i n a t i o n of the thesis t o p i c . F i n a l l y , I a m i n d e b t e d t o A n g e l a a n d J a s o n B a r t o n , R o n Byres, K e v i n McTaggart, C a r o l Mihelcic, Brock Nanson, John Pattle, P. Eng., and B r e n d a S t e l n i c k i for t h e i r a s s i s t a n c e w i t h field w o r k .  xv  Chapter 1  INTRODUCTION  1.1  General  Beach profiles and sediment activity are the focus of this study; both laboratory and natural beaches have been investigated. The profiles studied have indicated two types of sediment activity: natural beaches within the inner coast of southwest B r i t i s h C o l u m b i a are active predominantly in the upper foreshore due to longshore sediment transport; wave flume constrained laboratory beaches are active across the profile due to on- offshore sediment transport. Profile shape and envelopes between successive profiles can indicate of the type of sediment transport process occuring on a beach. The study of natural beaches has involved twenty-five sites on the Strait of Georgia and Juan de Fuca Strait of coastal southwest B r i t i s h C o l u m b i a , figures 1 and 2. Three beaches; Tsawwassen Beach, Tower Beach at Point Grey Vancouver and the Dundarave foreshore at West. Vancouver have been studied in detail, figure 2. A t the three sites a sequence of shore normal profiles was surveyed to identify sediment activity on the beaches. Wave height, and period as a function of time was hindcast for part of the time during which profiles were surveyed in an attempt to identify wave conditions causing sediment movement and possibly correlate measured foreshore changes with the hindcast waves. Sediment, size distributions were determined for various points along the surface and subsurface of the beaches to identify the structure formed through wave action.  1  Chapter  1.  INTRODUCTION  2  A t t h e r e m a i n i n g t w e n t y t w o sites i n v e s t i g a t i o n s were m a d e on a n o c c a s i o n a l b a s i s , i n v e s t i g a t i o n f o c u s i n g u p o n field c o n d i t i o n s w h i c h h a v e been r e l a t i v e l y u n s t u d i e d t o d a t e : b e a c h g e o m o r p h o l o g y , slopes, s e d i m e n t sizes a n d e l e v a t i o n s of s h o r e l i n e features. c o m b i n e d o b s e r v a t i o n s at each site h a v e p r o d u c e d a n o v e r a l l d e s c r i p t i o n o f t h e L  The coast.  D u r i n g t h e i n v e s t i g a t i o n sites were classified a n d test p i t s were d u g t o i d e n t i f y t h e character of the beach subsurface, a sediment transport experiment using a range of m a t e r i a l sizes was c o n d u c t e d a n d a n i n v e n t o r y of beaches a s s e m b l e d .  O p e n coast beaches  waves h a v e also been r e v i e w e d for c o m p a r i s o n since t h e s e d i m e n t t r a n s p o r t  and  processes  o c c u r i n g w i t h i n t h e i n n e r coast are a s s u m e d t o be o n l y a s m a l l p a r t of a n o v e r a l l p h y s i c a l process of m u c h b r o a d e r s c o p e . B l u f f e r o s i o n o n t h e i n n e r coast has b e e n r e v i e w e d as a s i d e l i n e b e c a u s e of its l o c a l s i g n i f i c a n c e . T h e s t u d y of l a b o r a t o r y beaches has i n v o l v e d c o l l e c t i n g p u b l i s h e d b e a c h p r o f i l e d a t a , d e f i n i n g a v a r i a b l e i n t e r r e l a t i n g on-offshore s e d i m e n t m o v e m e n t a n d waves, p e r f o r m i n g d i m e n s i o n a l a n a l y s i s u s i n g the v a r i a b l e a n d i n v e s t i g a t i n g on-offshore s e d i m e n t m o v e m e n t under wave action in various laboratory experiments.  T h e a r e a swept out b e t w e e n t w o  s h o r e n o r m a l profiles as a f u n c t i o n of t i m e is p r o p o s e d as a v a r i a b l e for i n t e r r e l a t i n g waves a n d on-offshore s e d i m e n t m o v e m e n t . T h e v a r i a b l e has been t e r m e d a c t i v e v o l u m e . A c o n c e p t of b e a c h r e s p o n s e t o waves b a s e d u p o n g e n e r a l b e h a v i o u r o b s e r v e d i n l a b o r a t o r y beaches a n d i n t h e field is p r e s e n t e d t o e x p l a i n i n p a r t t h e r o l e of t h e l o c a l w a v e r e g i m e i n d e t e r m i n i n g i n n e r coast b e a c h m o r p h o l o g y . W a v e c l i m a t e d a t a for i n n e r a n d o u t e r coasts h a v e b e e n r e v i e w e d t o p r o v i d e s o m e s u p p o r t for t h e c o n c e p t .  1.2  Inner Coast Beaches - C u r r e n t Status of K n o w l e d g e  M o s t beaches w i t h i n t h e i n n e r s o u t h coast, of B r i t i s h C o l u m b i a m a y be g e n e r a l l y d e s c r i b e d as s h i n g l e or a r m o u r e d beaches c o n s i s t i n g of g r a v e l s , c o b b l e s a n d b o u l d e r s , f i g u r e 3.  Chapter 1.  INTRODUCTION  3  S e d i m e n t a c t i v i t y o c c u r i n g o n i n n e r coast beaches o c c u r s o n a different scale t h a n o p e n coast beaches as i n d i c a t e d b y p r o f i l e e n v e l o p e s , figure 4, w h i c h e x e m p l i f y t h e r e l a t i v e scale of t h e processes b e i n g d i s c u s s e d . O p e n coast beaches are k n o w n t o h a v e s e a s o n a l m o r p h o l o g i c changes c a u s e d b y seas o n a l v a r i a t i o n i n wave c l i m a t e , t h e w e l l k n o w n s u m m e r / w i n t e r b e a c h c o n c e p t a p p e a r i n g i n t h e l i t e r a t u r e o n the t o p i c [42],[2]. T h e G e o l o g i c a l S u r v e y of C a n a d a has s t u d i e d seas o n a l changes i n b e a c h m o r p h o l o g y a l o n g t h e B . C . coast [18]. T h e i r f i n d i n g s i n d i c a t e t h a t t h e s u m m e r / w i n t e r b e a c h m o d e l is n o t a p p r o p r i a t e for s h o r e l i n e r e s p o n s e w i t h i n t h e i n ner c o a s t a l w a t e r s , h o w e v e r , t h e m o d e l b e c o m e s r e p r e s e n t a t i v e of r e a l b e a c h  response  as one a p p r o a c h e s t h e o p e n o c e a n . L o n g b e a c h , near T o f i n o on V a n c o u v e r I s l a n d , is an o p e n c o a s t s a n d y b e a c h e x p o s e d t o t h e N o r t h Pacific, t h a t e x h i b i t s seasonal m o r p h o l o g i c changes.  1.3  Previous Work  T h o r o u g h b i b l i o g r a p h i e s of s t u d i e s c o n d u c t e d o n t h e B . C . coast is i n c l u d e d i n " M o r p h o l o g y a n d L i t t o r a l P r o c e s s e s of t h e P a c i f i c C o a s t of C a n a d a " [6] a n d " C o a s t a l R e s o u r c e s F o l i o " [33]. M o s t of the p a p e r s l i s t e d i n these b i b l i o g r a p h i e s cover e n v i r o n m e n t a l , geologi c a l , g e o m o r p h i c or o c e a n g r a p h i c , t o p i c s at specific, sites, s t u d i e s f o c u s i n g o n i n n e r coast beaches i n p a r t i c u l a r are few. In t h e s t u d y of b e a c h profiles a n d sediment, a c t i v i t y t h e o p p o r t u n i t y t o e x p a n d u p o n t h e k n o w l e d g e of i n n e r coast beaches was p u r s u e d . T h e l i t e r a t u r e on c o a s t a l e n g i n e e r i n g a n d r e l a t e d t o p i c s has e x t e n s i v e coverage of s a n d beaches o n o p e n c o a s t l i n e s .  T h e w o r k of t h e U . S . A r m y C o r p s of E n g i n e e r s has  t h o r o u g h l y s t u d i e d beaches of t h i s t y p e l o c a t e d on t h e s o u t h e a s t coast of t h e States, C a l i f o r n i a and H a w a i i .  United  O p e n coast s a n d beaches are b y far t h e m o s t s t u d i e d  i n t e r m s of l e n g t h of c o a s t l i n e a n d are also of t h e m o s t e n g i n e e r i n g interest since the  Chapter J .  INTRODUCTION  4  b a c k s h o r e areas are h e a v i l y p o p u l a t e d a n d d e v e l o p e d .  T h e beaches of i n n e r c o a s t a l  B r i t i s h C o l u m b i a , h o w e v e r , are p r e d o m i n a n t l y coarse m a t e r i a l a n d e x p e r i e n c e waves of l o w e r h e i g h t a n d p e r i o d t h a n o p e n coast beaches.  F e w s t u d i e s h a v e been f o u n d o n  beaches of such sedimentary character a n d under a similar wave regime.  Some papers  h a v e a p p e a r e d o n s h i n g l e beaches i n G r e a t B r i t a i n [47]. E a r l y e m p i r i c a l o b s e r v a t i o n s s t a r t i n g a b o u t 100 years ago [43] o n t h e U . S . west coast f o c u s e d o n s e a s o n a l changes i n s a n d beaches.  E a r l y i n v e s t i g a t o r s h a d f o u n d t h e sea-  s o n a l changes m y s t e r i o u s ; the. forces a n d m e c h a n i s m s i n v o l v e d i n s a n d m o v e m e n t were i m p e r c e p t i b l e since m o s t p r o f i l e c h a n g e takes p l a c e u n d e r w a t e r .  O n t h e west coast steep  i n t e n s e s h o r t p e r i o d s t o r m waves are t y p i c a l of t h e w i n t e r a n d l o w steepness l o w i n t e n s i t y l o n g e r p e r i o d s w e l l waves are t y p i c a l of t h e s u m m e r . F i e l d studies o n o p e n coast beaches by S h e p a r d [42] a n d B a s c o m [2] r e c o g n i z e d t h a t s a n d moves offshore u n d e r t h e intense s t o r m waves of w i n t e r a n d m o v e s o n s h o r e u n d e r less i n t e n s e s w e l l waves of s u m m e r , t h u s the t e r m i n o l o g y s u m m e r a n d winter profile developed. F u r t h e r insight, i n t o t h e process c a m e i n the 1940's a n d 50's w h e n t h e B e a c h E r o s i o n B o a r d of t h e U . S . A r m y C o r p s of E n g i n e e r s a n d o t h e r researchers c a r r i e d out  field  and  l a b o r a t o r y i n v e s t i g a t i o n s . J o h n s o n [25] a n d R e c t o r [38] d e m o n s t r a t e d u s i n g m o d e l s t u d i e s that, w a v e steepness H /L 0  0  was a factor i n t h e c h a n g e f r o m a n erosive s t a t e t o a n a c c r e t i v e  s t a t e o f a b e a c h . I n v e s t i g a t o r s of t h e t i m e also r e c o g n i z e d t h e l a c k of a r e a d i l y d e f i n a b l e v a r i a b l e i n t e r r e l a t i n g s e d i m e n t s a n d waves. Subsequent investigations focused further on distinguishing between conditions which result, i n b e a c h e r o s i o n a n d c o n d i t i o n s w h i c h p r o d u c e a c c r e t i o n . O n o c c a s i o n it is a s s u m e d t h a t a b e r m c h a r a c t e r i z e s a n a c c r e t e d profile a n d t h a t n e a r s h o r e b a r s c h a r a c t e r i z e a n e r o d e d profile. T h i s is a r e a s o n a b l e i d e a l i z a t i o n b u t o v e r s i m p l i f i e d i n t h a t a b e r m m a y be a b s e n t o n an a c c r e t e d b e a c h , n e a r s h o r e bars d o n o t n e c e s s a r i l y i n d i c a t e an e r o d e d b e a c h a n d b o t h b e r m s a n d b a r s m a y be present, o n a b e a c h .  I n v e s t i g a t o r s have f o c u s e d o n  Chapter  1.  INTRODUCTION  5  c o m b i n i n g wave and sediment variables into a single dimensionless number called an onoffshore t r a n s p o r t p a r a m e t e r w h i c h represents t h e d i r e c t i o n of s e d i m e n t m o t i o n . D e a n [9] p r o p o s e d a d i m e n s i o n l e s s f a l l v e l o c i t y p a r a m e t e r t o d e s c r i b e t h e s t a t e of a beach, i n t e r m s of w a v e a n d s e d i m e n t v a r i a b l e s :  w h e r e F —~ d i m e n s i o n l e s s f a l l v e l o c i t y ; H = 0  0  deep w a t e r w a v e h e i g h t ; wj=  p a r t i c l e fall  b e a c h e r o s i o n o c c u r s for F  > 0.85 a n d  velocity; T - wave period. A c c o r d i n g to the fall velocity parameter a c c r e t i o n for F  0  0  < 0.85. T h e d i m e n s i o n l e s s fall v e l o c i t y p a r a m e t e r has been  supported  by l a b o r a t o r y investigations. P a r t i c l e fall v e l o c i t y is a p a r t i c u l a r l y m e a n i n g f u l c h a r a c t e r i s t i c w i t h w h i c h t o d e s c r i b e s e d i m e n t s s i n c e it s u m m a r i z e s the effects of g r a i n size, s h a p e , c o m p o s i t i o n , fluid p r o p erties a n d v i s c o s i t y i n t o a single p a r a m e t e r .  D a l r y m p l e [8] u s e d t h e d i m e n s i o n l e s s fall  v e l o c i t y p a r a m e t e r t o n u m e r i c a l l y m o d e l e q u i l i b r i u m b e a c h slopes based u p o n g r a i n size a n d i n c i d e n t w a v e c h a r a c t e r i s t i c s . R e c e n t i n v e s t i g a t i o n b y Q u i c k a n d H a r [35] has i d e n tified t h a t t h e d i m e n s i o n l e s s f a l l v e l o c i t y p a r a m e t e r alone is insufficient, t o d e t e r m i n e t h e d i r e c t i o n of sediment, m o t i o n b e c a u s e t h e w a v e h i s t o r y of t h e b e a c h m u s t be t a k e n i n t o account.  T h e i r i n v e s t i g a t i o n s t a t e d s e d i m e n t m o v e m e n t o n s h o r e or offshore c o u l d  be  d e t e r m i n e d b y e x a m i n i n g i n i t i a l a n d final f a l l v e l o c i t y p a r a m e t e r v a l u e s . H a t t o r i a n d K a w a m a t a [22] d e v e l o p e d a n on-offshore p a r a m e t e r w h i c h c o m b i n e s w a v e v a r i a b l e s H, L, s e d i m e n t v a r i a b l e D  50  a n d i n i t i a l beach slope m  x  into a single dimension-  less n u m b e r t h a t r e p r e s e n t s t h e d i r e c t i o n o f s e d i m e n t t r a n s p o r t .  T h e parameter i n a  g e n e r a l w a y d e s c r i b e s t h e c h a r a c t e r of fluid t u r b u l e n c e , s e d i m e n t p a r t i c l e e n t r a i n m e n t a n d t h e c o r r e s p o n d i n g d i r e c t i o n of s e d i m e n t m o v e m e n t .  M o s t on-offshore  parameters  d e v e l o p e d t o d a t e neglect w a v e p o w e r or w a v e i n t e n s i t y ; t h u s t h e y d e s c r i b e t h e d i r e c t i o n  Chapter 1.  INTRODUCTION  6  of s e d i m e n t m o v e m e n t i f it is t o o c c u r b u t not its m a g n i t u d e or r a t e .  Studies to date  h a v e b e e n based u p o n l i m i t e d n u m b e r o f l a b o r a t o r y i n v e s t i g a t i o n s . N u m e r i c a l m o d e l l i n g o f b e a c h p r o f i l e s h a p e c h a n g e has also b e e n d e v e l o p e d . A n i n i tially k n o w n beach profile and a n u m e r i c a l l y predicted post s t o r m beach profile provides t h e r e q u i r e d d a t a t o d e t e r m i n e t h e d i r e c t i o n of m a s s m o v e m e n t , v o l u m e s , s h o r e l i n e r e t r e a t a n d d e p t h of b e a c h a c t i v i t y . T h i s i n f o r m a t i o n is of e n g i n e e r i n g interest since c o a s t l i n e r e s p o n s e t o m a j o r s t o r m s or h u r r i c a n e s c a n be p r e d i c t e d . A l t h o u g h such m o d e l s p r o d u c e r e a s o n a b l e p r o f i l e s h a p e s t h e t i m e over w h i c h t h e p r o f i l e d e v e l o p s m a y not be a c c u r a t e l y m o d e l l e d ; d e t a i l e d i n v e s t i g a t i o n i n t o t h e t i m e scale of p r o f i l e e v o l u t i o n a p p e a r s l i m i t e d .  1.4  Research Justification  C o a s t a l E n g i n e e r i n g w o r k is t h e m o t i v a t i o n b e h i n d t h i s s t u d y .  T h e n a t u r e of p a s t a n d  current coastal engineering work includes the following:  • recreational beach construction and restoration;  • rubble m o u n d breakwater  structures;  • t o e p r o t e c t i o n for e r o d i n g bluffs;  • geomorphological and sediment transport  studies;  • wind-wave analyses;  •  c o a s t a l d e v e l o p m e n t ( h a r b o u r s , m a r i n a s etc.);  •  seawalls.  T h i s r e s e a r c h effort is b a s e d l a r g e l y o n field i n v e s t i g a t i v e w o r k w h i c h is j u s t i f i e d i n c o a s t a l e n g i n e e r i n g , p a r t i c u l a r l y w h e r e r e g i o n a l processes are i n v o l v e d .  D a t a collected  Chapter  1.  INTRODUCTION  7  f r o m field i n v e s t i g a t i v e w o r k p r o v i d e s a n e n g i n e e r i n g d a t a base for d e s i g n a n d  reference  as w e l l as p r o t o t y p e d a t a for c a l i b r a t i o n of n u m e r i c a l a n d p h y s i c a l m o d e l s .  A s well  it m a y p r o v i d e insight, i n t o processes not. yet e x p l a i n e d b y t h e o r y .  Further, a thorough  u n d e r s t a n d i n g of c o a s t a l processes o n t h e i n n e r s o u t h coast of B r i t i s h C o l u m b i a is sparse. L a b o r a t o r y b e a c h e s have been s t u d i e d t o p r o v i d e a d d i t i o n a l scope to t h i s i n v e s t i g a t i o n . L a b o r a t o r y b e a c h s t u d i e s d e m o n s t r a t e a n i d e a l i z a t i o n of r e a l beaches; it is p o s s i b l e t o o b s e r v e s e d i m e n t a c t i v i t y o n a t i m e scale not p o s s i b l e i n t h e field due t o the p r a c t i c a l p r o b l e m s of d a t a c o l l e c t i o n . T h e processes o b s e r v e d i n t h e l a b o r a t o r y are a s s u m e d  to  o c c u r o n s i m i l a r b e a c h e s i n t h e field b u t o n a different scale a n d w i t h b e t t e r d e f i n i t i o n .  Chapter 2  TECHNICAL WORK A N D EXPERIMENTS  2.1  General  T h e s t u d y of n a t u r a l beaches i n v o l v e d s u r v e y of profiles, g r a i n size a n a l y s i s , subsurface i n v e s t i g a t i o n , s e d i m e n t t r a c i n g e x p e r i m e n t s a n d n u m e r i c a l m o d e l l i n g of w i n d waves.  generated  P u b l i s h e d e x p e r i m e n t a l d a t a was r e v i e w e d for the s t u d y of l a b o r a t o r y  beach  profiles.  2.2  Surveys  S h o r e n o r m a l profiles of n a t u r a l beaches were m e a s u r e d b y s t a d i a transit, survey. instrument  used was a P e n t a x G T - 4 B o p t i c a l t r a n s i t  w i t h a stadia constant  The  of 100.  H o r i z o n t a l d i s t a n c e across a p r o f i l e was m e a s u r e d r e l a t i v e t o a n i n i t i a l a r b i t r a r y b a s e l i n e a n d e l e v a t i o n was m e a s u r e d r e l a t i v e t o a l o c a l b e n c h m a r k . E l e v a t i o n was c o n t r o l l e d to w i t h i n 1 c m a n d h o r i z o n t a l d i s t a n c e t o w i t h i n 10 c m . S u r v e y i n g was t y p i c a l l y c a r r i e d o u t at v e r y l o w t i d e s so that, as m u c h of t h e b e a c h p r o f i l e as p o s s i b l e c o u l d be m e a s u r e d .  N i g h t t i m e l o w tides over the w i n t e r  months  r e q u i r e d t h a t a t r i p o d m o u n t e d f l a s h l i g h t a i m e d o n t h e r o d be u s e d t o f a c i l i t a t e r e a d i n g . T h e r o d m a n also h a d a  flashlight  t o i l l u m i n a t e t h e r o d i f r e a d i n g was d i f f i c u l t , h o w e v e r ,  t h i s was u s u a l l y not n e c e s s a r y as t h e l i g h t b e a m f r o m t h e t r i p o d m o u n t e d  flashlight,  was  s u f f i c i e n t l y bright, t o i l l u m i n a t e the r o d at d i s t a n c e s u p to 60 m e t r e s . A gas l a n t e r n was also u s e d at t h e t r a n s i t t o p r o v i d e a d d i t i o n a l l i g h t .  8  Chapter 2. TECHNICAL  WORK AND  EXPERIMENTS  9  T h e r o d was p l a c e d at p o i n t s o n t h e b e a c h w h e r e v i s i b l e changes i n s l o p e or changes i n b e a c h m a t e r i a l s o c c u r e d a n d the e l e v a t i o n of t h e profiles w i t h respect t o g e o d e t i c d a t u m was d e t e r m i n e d b y m e a s u r i n g t h e w a t e r level r e l a t i v e to t h e b e n c h m a r k a n d recording the exact Pacific S t a n d a r d T i m e .  M e a s u r e m e n t s were m a d e at a t i m e w h e n  t h e w a t e r was c a l m so t h a t t h e effects o f waves a n d m o m e n t u m set u p w o u l d be n e g l i g i b l e . C a l c u l a t i o n s were t h e n p e r f o r m e d t o c o r r e c t for l o c a t i o n a n d t i m e u s i n g P o i n t A t k i n s o n t i d e s as a reference f o l l o w i n g t h e i n t e r p o l a t i o n a l g o r i t h m o u t l i n e d i n C a n a d i a n T i d e a n d C u r r e n t T a b l e s [3]. S l o p e s t y p i c a l l y i n t h e r a n g e 1:1 t o 1:12 were m e a s u r e d u s i n g a h o m e m a d e l e v e l , p h o t o 10, w h i c h was t e s t e d a n d c h e c k e d a g a i n s t slopes o b t a i n e d f r o m b e a c h profile d a t a a n d f o u n d t o b e v e r y a c c u r a t e . B e a c h slopes t h a t were v e r y s h a l l o w ( t y p i c a l l y less t h a n I V : 1 2 H ) o r t h a t c h a n g e d f r e q u e n t l y w e r e m e a s u r e d w i t h an o p t i c a l l e v e l a n d a c h a i n . B e r m crest a n d d e b r i s l i n e e l e v a t i o n s a n d e l e v a t i o n s of o t h e r features were also m e a sured using an o p t i c a l level.  2.3  Analysis of Sediments  M a t e r i a l size a n d size d i s t r i b u t i o n at t h e b e a c h surface a n d s u b s u r f a c e was q u a n t i f i e d u s i n g b u l k seive a n a l y s i s a n d p h o t o g r a p h i c , a n a l y s i s . Seive a n a l y s e s were p e r f o r m e d o n l o c a l beaches u s i n g s a m p l e s n o m i n a l l y of 10 k g m a s s collected i n cookie tins, oven dried a n d seived i n the C i v i l E n g i n e e r i n g undergraduate soils l a b o r a t o r y at U B C . T h e s e d i m e n t sizes o n beaches v i s i t e d one t i m e were m e a s u r e d u s i n g a p h o t o g r a p h i c a n a l y s i s t e c h n i q u e [1]. A 4 0 0 m m b y 3 5 0 m m s a m p l i n g g r i d was p l a c e d over a r e p r e s e n t a t i v e s e c t i o n of b e a c h for scale a n d a p h o t o g r a p h t a k e n , p h o t o 19. T h e sizes of a b o u t a d o z e n r e p r e s e n t a t i v e stones were t h e n s c a l e d off the p h o t o g r a p h a n d i n p u t t o a c o m p u t e r  Chapter 2.. TECHNICAL  WORK AND  EXPERIMENTS  10  p r o g r a m w h i c h c o m p u t e d the f r e q u e n c y d i s t r i b u t i o n , s a m p l e s t a t i s t i c s a n d seive e q u i v a l e n t sizes. A s s i g n m e n t of a l i n e a r g r a i n size d i m e n s i o n was m a d e u s i n g t h e v i s i b l e short a x i s of p a r t i c l e s over 8 m m i n w i d t h .  T o m i n i m i z e s a m p l i n g error a representative well  s o r t e d a r e a o f b e a c h surface was selected b y eye; a n a r e a of at least 500 s q u a r e m e t r e s was i n v e s t i g a t e d before a p h o t o g r a p h was t a k e n . C a m e r a o u t of v e r t i c a l e r r o r was c o r r e c t e d by adjusting the p h o t o g r a p h scaling factor.  2.4  Sediment Tracing  2.4.1  Background  A s i m p l e s e d i m e n t t r a c i n g e x p e r i m e n t d e m o n s t r a t i n g the d i s p e r s i o n of coarse p a r t i c l e s o n a b e a c h was c o n d u c t e d . T h e e x p e r i m e n t i n v o l v e d p l a c i n g w e l l s o r t e d a n d r o u n d e d s a m p l e s of t r a c e r p a r t i c l e s o n a n i n n e r coast b e a c h a n d o b s e r v i n g t h e p a r t i c l e m o t i o n u n d e r the a c t i o n of waves a n d t i d e s over a p e r i o d of several clays. T h e f o l l o w i n g a s s u m p t i o n s  are  made w i t h regard to this type of experiment: 1. A q u a n t i t y of n a t u r a l m a t e r i a l is m a r k e d s u c h t h a t it is d i s t i n g u i s h a b l e f r o m n a t u r a l s e d i m e n t . T h e t r a c e r s h o u l d have the s a m e h y d r o m e c h a n i c a l p r o p e r t i e s (size, shape, density) of the natural sediment; 2. T h e t r a c e r is i n j e c t e d i n t o t h e l i t t o r a l e n v i r o n m e n t so t h a t it e x p e r i e n c e s the same c o n d i t i o n s c a u s i n g m o v e m e n t of n a t u r a l s e d i m e n t ; 3. T h e d i s p e r s a l p a t t e r n of n a t u r a l s e d i m e n t is i n f e r r e d b y t h e d i s p e r s e d p a t t e r n of the tracer sediment. T r a c e r p a r t i c l e s were p r e p a r e d i n a l a b o r a t o r y b y p a i n t i n g w e l l r o u n d e d stones of G m m , 3 8 m m a n d 7 5 m m m e d i a n d i a m e t e r w i t h t w o coats of a h i g h q u a l i t y m a r i n e e n a m e l paint.  T h e 7 5 m m m e d i a n size s a m p l e m a s s was 6 0 k g ( a p p r o x i m a t e l y 210 p a r t i c l e s ) ,  Chapter 2. TECHNICAL  WORK AND  EXPERIMENTS  11  t h e 3 8 m m m e d i a n size s a m p l e m a s s was 4 0 k g ( a p p r o x i m a t e l y 1100 p a r t i c l e s ) a n d  the  6 m m m e d i a n size m a s s was 2 5 k g ( n u m b e r of p a r t i c l e s not c o u n t e d ) . T h e p a r t i c l e s were c o l l e c t e d f r o m a l o c a l b e a c h , w a s h e d a n d d r i e d before p a i n t i n g . P r i o r t o c o n d u c t i n g t h e e x p e r i m e n t a p r e l i m i n a r y test of p a i n t d u r a b i l i t y was c o n d u c t e d . T h r e e t y p e s of p a i n t were t e s t e d for d u r a b i l i t y a g a i n s t a b r a s i o n a n d wear w h e n p l a c e d o n a b e a c h u n d e r t h e a c t i o n of waves. T h e o b j e c t i v e was t o h a v e a p a i n t w h i c h w o u l d r e m a i n o n a p a r t i c l e for a n u m b e r o f d a y s or weeks w i t h o u t w e a r i n g off. A n e p o x y r e s i n p a i n t t e s t e d was i n a d e q u a t e a n d w o r e off m o s t stones of a test s a m p l e p l a c e d o n a l o c a l b e a c h i n a b o u t 2 d a y s . S p r a y e n a m e l s a p p l i e d i n s i t u w h e r e f o u n d t o wear s i m i l a r l y a n d were a d v e r s e l y affected b y t e m p e r a t u r e  a n d m o i s t u r e on t h e r o c k surface.  Marine  g r a d e e n a m e l p a i n t was f o u n d t o b e t h e m o s t successful a n d r e m a i n e d o n t h e test, s a m p l e for w e l l over t h r e e m o n t h s . It was o b s e r v e d t h a t t h e surface r o u g h n e s s of a stone affects its a b i l i t y to r e t a i n p a i n t . R o u g h s u r f a c e d stones were f o u n d t o r e t a i n p a i n t b e t t e r i n t h e i n t e r s t i c e s of the surface r o u g h n e s s therefore b e i n g i d e n t i f i a b l e for a l o n g e r p e r i o d of t i m e . P a i n t a b r a d e d  more  q u i c k l y off of s m o o t h s u r f a c e d stones t h u s m a k i n g t h e m less i d e n t i f i a b l e i n a s h o r t e r p e r i o d of t i m e a n d therefore less effective as a t r a c e r p a r t i c l e . A f t e r 2 days o n the b e a c h s o m e of t h e s m o o t h e r e n a m e l e d 3 8 m m t r a c e r p a r t i c l e s were s h o w i n g wear of t h e p a i n t .  2.4.2  Beach experiment  T h e e x p e r i m e n t was c o n d u c t e d o n a s e c t i o n of s h o r e l i n e 1000 m e t r e s west of C h a s t e r C r e e k at G i b s o n s , B r i t i s h C o l u m b i a , site 4, figure 2. T h e e x p e r i m e n t i n v o l v e d p l a c i n g t h r e e w e l l s o r t e d a n d r o u n d e d s a m p l e s of t r a c e r p a r t i c l e s of m e d i a n sizes 6 m m , 3 8 m m a n d 7 5 m m o n a n a r m o u r e d s e c t i o n of s h o r e l i n e a n d o b s e r v i n g t h e p a r t i c l e m o t i o n u n d e r t h e a c t i o n o f waves, c u r r e n t s a n d t i d e s over a p e r i o d of s e v e r a l d a y s , p h o t o s 1 to 4. T h e e x p e r i m e n t was c o n d u c t e d t o s u p p o r t field o b s e r v a t i o n s t h a t coarse m a t e r i a l  Chapter 2. TECHNICAL  WORK AND  EXPERIMENTS  12  m o v e s o n s h o r e u n d e r t h e a c t i o n of waves, c u r r e n t s a n d tides a n d t h a t the h i g h e s t l o n g s h o r e s e d i m e n t t r a n s p o r t rates o n i n n e r coast beaches o c c u r i n a n a r r o w u p p e r foreshore zone. A t C h a s t e r C r e e k a 4 m g r i d was l a i d o u t on t h e b e a c h surface u s i n g large m a r k e r stones ( t y p i c a l l y 4 0 k g ) t o m a r k the g r i d i n t e r s e c t i o n s . T h e g r i d w a s . c a r e f u l l y t a p e d a n d at g r i d l i n e i n t e r s e c t i o n s crosses were s p r a y p a i n t e d o n t h e m a r k e r stones. w e r e m a d e t o r u n p a r a l l e l a n d n o r m a l t o t h e shore.  Gridlines  A t l o w t i d e o n the first d a y of t h e  e x p e r i m e n t p a r t i c l e s w e r e p l a c e d at s e p a r a t e o r i g i n s o n the b e a c h for each size, p h o t o 2. F o u r t i d e c y c l e s p a s s e d d u r i n g t h e t w o d a y e x p e r i m e n t a n d t h e wave c o n d i t i o n s a n d p a r t i c l e m o v e m e n t s were r e c o r d e d . T o assist i n c o u n t i n g the n u m b e r of p a r t i c l e s on t h e b e a c h surface a l m s u b g r i d was l a i d o u t . A f t e r t h e e x p e r i m e n t the< 38 m m a n d 75 m m p a r t i c l e s were r e c o v e r e d for f u r t h e r use.  2.5  Wave Hindcasting  A w a v e h i n d c a s t m o d e l was d e v e l o p e d w h i c h uses h o u r l y w i n d d a t a f r o m t h e A t m o s p h e r i c E n v i r o n m e n t S e r v i c e ( A E S ) t o s y n t h e s i z e s i g n i f i c a n t w a v e h e i g h t a n d p e r i o d d a t a for the p e r i o d of b e a c h s u r v e y . T h e s y n t h e s i z e d d a t a was g e n e r a t e d i n a n a t t e m p t t o i d e n t i f y a n d if p o s s i b l e c o r r e l a t e waves t o m e a s u r e d changes i n foreshore profiles.  T h e theory  b e h i n d t h e w a v e h i n d c a s t i n g m e t h o d u s e d is d i s c u s s e d : W a v e h i n d c a s t i n g i n v o l v e s u s i n g p a s t w e a t h e r r e c o r d s to r e c o n s t r u c t p a s t w a v e c o n d i t i o n s . S e v e r a l s e m i - e m p i r i c a l s p e c t r a have b e e n d e v e l o p e d to h i n d c a s t or forecast waves f r o m w i n d d a t a . T h e S v e r d r u p - M u n k - B r e t s c h n e i d e r ( S M B ) s p e c t r u m was u s e d because of i t s s i m p l i c i t y a n d ease of a p p l i c a t i o n ; the h i n d c a s t e q u a t i o n s are transfer  functions  w h i c h i n p u t w i n d s p e e d a n d y i e l d a w a v e h e i g h t or p e r i o d . W a v e s p e c t r a s u c h as the S M B s p e c t r u m a s s u m e the w a v e c o n d i t i o n s to b e a f u n c t i o n of t h e f o l l o w i n g p a r a m e t e r s :  Chapter  2.  TECHNICAL  WORK  AND  EXPERIMENTS  13  1. w i n d v e l o c i t y U ;  2. w i n d d u r a t i o n  t; d  3. f e t c h F ;  4. d e p t h of w a t e r d;  5. w a v e decay.  T h e s i g n i f i c a n t d e e p w a t e r w a v e h e i g h t a n d s i g n i f i c a n t w a v e p e r i o d c a n be expressed functionally:  H  s  T  s  w h e r e t h e f o l l o w i n g is defined:  =  MU,F,t ,g)  =  f {U,F,t ,g)  d  2  H= s  d  significant height; T = s  s i g n i f i c a n t h e i g h t ; g—  a c c e l e r a t i o n d u e to g r a v i t y ; T h e S M B h i n d c a s t i n g r e l a t i o n s h i p s for s i g n i f i c a n t wave h e i g h t a n d p e r i o d are:  = 0.283*a7iM0.0125(^7)  ^ ^  =  a 4 2  ]  1.2*anM0.077(^) - ] 0  2 5  T h e a c c u r a c y of wave h i n d c a s t s is h i g h l y d e p e n d e n t u p o n the w i n d d a t a i n p u t t o the equations.  T h e use of w i n d d a t a c o l l e c t e d over w a t e r as o p p o s e d t o l a n d p r o d u c e s  more  a c c u r a t e h i n d c a s t wave h e i g h t s a n d p e r i o d s ; f o r t u n a t e l y the A E S has m a i n t a i n e d w i n d r e c o r d s at c o a s t a l l i g h t h o u s e s i n s o u t h w e s t B r i t i s h C o l u m b i a for m a n y y e a r s .  Sandheads  L i g h t S t a t i o n w h i c h is l o c a t e d over w a t e r was u s e d as t h e source of w i n d d a t a ; assumed  t h e w i n d speeds at S a n d h e a d s  s o u t h e r n S t r a i t of G e o r g i a , figure 2.  are g e n e r a l l y r e p r e s e n t a t i v e  of w i n d s over  i t is the  Chapter  2.  TECHNICAL  WORK  AND  EXPERIMENTS  14  T h e M a r i n e E n v i r o n m e n t a l D a t a S e r v i c e has some deep w a t e r w a v e r e c o r d s w i t h i n t h e Strait, of G e o r g i a for w h i c h t h e r e is c o i n c i d e n t w i n d d a t a . A c o m p a r i s o n of h i n d c a s t a n d m e a s u r e d deep w a t e r w a v e h e i g h t d a t a was m a d e at R o b e r t s B a n k , P o i n t G r e y a n d W e s t V a n c o u v e r to e v a l u a t e t h e a c c u r a c y of t h e hindcast. m o d e l , figure 5. H i n d c a s t wave heights show reasonable agreement  w i t h m e a s u r e d w a v e h e i g h t s , h o w e v e r , the m o d e l  t e n d s t o o v e r p r e d i c t t h e h i g h e r waves b u t a c c u r a t e l y m o d e l s t h e t r e n d of s t o r m s . T h e A E S w i n d d a t a was m e a s u r e d w i t h a n i n t e g r a t i n g t y p e 4 5 B a n e m o m e t e r  thus  the i n p u t d a t a are h o u r l y m e a n s , a p p e n d i x A . F o r e x a m p l e , a w i n d speed q u o t e d as 10 k p h N W m e a n s t h a t 1 0 k m of a t m o s p h e r e c o m i n g f r o m t h e n o r t h w e s t has passed  the  a n e m o m e t e r i n one h o u r . T h e w i n d speed U i n t h e B r e t s c h n e i d e r r e l a t i o n s h i p s are defined for a reference a n n e m o m e t e r height of 10 m e t r e s a b o v e t h e e a r t h ' s surface. W i n d s m e a s u r e d at a height o t h e r t h a n 1 0 m s h o u l d b e c o r r e c t e d t o a c c o u n t for t h e d i s t r i b u t i o n of w i n d v e l o c i t y w i t h e l e v a t i o n ; t h e f o l l o w i n g v e l o c i t y p r o f i l e c o r r e c t i o n was i n c o r p o r a t e d i n t h e h i n d c a s t i n g program:  z where U= 0  U— w  w i n d speed at t h e  anemometer;  w i n d v e l o c i t y at 10 m e t r e s a b o v e t h e e a r t h ' s surface;  z— a n n e m o m e t e r h e i g h t a b o v e g r o u n d . W a v e g e n e r a t i o n is also affected b y fetch w i d t h .  T h e c o n c e p t of effective fetch is  i n c o r p o r a t e d i n t o t h e h i n d c a s t i n g p r o g r a m u s i n g an e m p i r i c a l fetch l i m i t i n g p r o c e d u r e [41]. S e p a r a t e s u b h i n d c a s t s o n r a y s s p a c e d at 15 degrees over a 90 degree w i n d o w w i t h 45 degrees t o e i t h e r side of t h e w i n d d i r e c t i o n are used i n t h e effective fetch c o m p u t a t i o n .  Chapter 2. TECHNICAL  WORK AND  EXPERIMENTS  15  T h e effective fetch w i d t h is c a l c u l a t e d u s i n g t h e f o l l o w i n g r e l a t i o n s h i p :  E:=i cose, where H=  fetch l i m i t e d w a v e h e i g h t ;  H=  hindcasts wave height along the i t h ray;  r  Bi~ angle, t o i t h r a y m e a s u r e d f r o m c e n t r a l ray. T h e h i n d c a s t i n g m o d e l incorporates the following assumptions:  1. t h e w a t e r is deep; 2. w i n d s p e e d is c o n s t a n t t e m p o r a l l y a n d s p a t i a l l y over t h e h i n d c a s t a r e a at h i n d c a s t time; 3. a fully a r i s e n sea p r e v a i l s at each h i n d c a s t h o u r ; 4. s e c o n d a r y w a v e sources such as swell or s h i p waves are not s i g n i f i c a n t .  T h e m o d e l w i l l h i n d c a s t o r forecast s i g n i f i c a n t w a v e heights a n d p e r i o d s for deep w a t e r , h o w e v e r , t h i s does n o t n e c e s s a r i l y m e a n t h a t t h e s y n t h e s i z e d d a t a is r e p r e s e n t a t i v e of w h a t is h a p p e n i n g at t h e shore. T h e w a v e c o n d i t i o n s at t h e shore are a f u n c t i o n of t h e offshore w a v e c o n d i t i o n s , d i r e c t i o n of w a v e p r o p a g a t i o n a n d t h e n e a r s h o r e  bathemetry  w h i c h t r a n s f o r m s t h e waves as t h e y a p p r o a c h t h e s h o r e . E q u a t i o n s h a v e been d e v e l o p e d t o m o d e l t h e w a v e t r a n s f o r m a t i o n as deep w a t e r waves a p p r o a c h a s h o r l i n e , h o w e v e r , t h e y h a v e n o t b e e n i n c o r p o r a t e d i n t o t h e m o d e l . H i n d c a s t s were p e r f o r m e d for p o i n t s i n deep w a t e r j u s t offshore of t h e s u r v e y sites a n d t h e s i m p l i f y i n g a s s u m p t i o n was m a d e that, t h e s a m e c o n d i t i o n s p r e v a i l e d at the shore. A c o m p u t e r p r o g r a m was w r i t t e n to process t h e w i n d d a t a . T h e effects of w a v e b u i l d u p a n d d e c a y are e m p i r i c a l l y s i m u l a t e d b y f i l t e r i n g t h e o u t p u t d a t a t h r o u g h a m o v i n g  Chapter 2. TECHNICAL  WORK AND  EXPERIMENTS  average w i t h a 2 h o u r t r a i l i n g or l e a d i n g w i d t h .  16  T h e m o v i n g average has t h e effect of  s m o o t h i n g t h e o u t p u t wave height d a t a b y a v e r a g i n g t h e h e i g h t at forecast h o u r w i t h the p r e c e e d i n g t w o or s u b s e q u e n t t w o h o u r s of h i n d c a s t w a v e h e i g h t s thus s i m u l a t i n g wave b u i l d u p a n d decay. T h e p r o g r a m was u s e d sucessfully i n p r e d i c t i n g w a v e h e i g h t s d u r i n g p a r t of t h e b e a c h s u r v e y p e r i o d . C o m p a r i s o n of h i n d c a s t w i t h m e a s u r e d wave h e i g h t d a t a , figure 5, i n d i cates o v e r h i n d c a s t i n g o f h i g h e r waves w h i c h is l i k e l y a r e s u l t of t h e a s s u m p t i o n of fully a r i s e n sea w h i c h is a h i g h e r energy sea s t a t e t h a n t h a t w h i c h a c t u a l l y o c c u r s .  2.6  Volume Calculations  In t h e a n a l y s i s of l a b o r a t o r y b e a c h d a t a t h e a r e a b e t w e e n sucessive profiles was r e q u i r e d t o d e t e r m i n e t h e a c t i v e v o l u m e of s e d i m e n t . T h e h i g h l y i r r e g u l a r areas b e t w e e n sucessive profiles were c a l c u l a t e d u s i n g a c o m p u t e r p r o g r a m w r i t t e n for t h e p u r p o s e .  2.7  Laboratory Beach Data  B e a c h p r o f i l e d a t a f r o m three l a b o r a t o r y e x p e r i m e n t s were r e v i e w e d :  1. D a t a was r e v i e w e d f r o m a s t u d y c a r r i e d o u t b y W a t a n a b e , R i h o a n d H o r i k a w a [46] w h i c h i n v o l v e d f o u r beaches at slopes of 1 V : 1 0 H a n d 1 V : 2 0 H c o n s t r u c t e d of w e l l s o r t e d q u a r t z s a n d sizes of 0.7 m m a n d 0.2 m m . S e d i m e n t s of each size were i n i t i a l l y g r a d e d flat at t h e specified slopes a n d s u b j e c t t o m o n o c h r o m a t i c waves g e n e r a t e d in a t w o d i m e n s i o n a l wave f l u m e 2 5 m l o n g , 1.5m deep a n d 0 . 8 m w i d e for a p e r i o d of 1 h o u r . W a v e p e r i o d s were k e p t at 1.0, 1.5 or 2.0 seconds a n d f o u r or five w a v e h e i g h t s were selected for each r u n r e s u l t i n g i n a t o t a l of cases, figure 6.  fifty-eight  experimental  ha.pf.er 2,  TECHNICAL  WORK  AND  EXPERIMENTS  17  2. A s t u d y b y R e c t o r [38] c a r r i e d o u t o n b e h a l f of t h e B e a c h E r o s i o n B o a r d w a s also r e v i e w e d . T h e e x p e r i m e n t s were c o n d u c t e d i n t w o w a v e t a n k s : one of c o n c r e t e 85 feet l o n g , 14 feet w i d e a n d 4 feet deep a n d t h e o t h e r of steel p l a t e c o n s t r u c t i o n 42 feet l o n g , 1.5 feet w i d e a n d 2 feet deep. T h e beaches were c o n s t r u c t e d of t h r e e b a s i c sands a n d a f o u r t h s a n d w h i c h was a m i x t u r e of t w o b a s i c s a n d s . S a n d m e d i a n d i a m e t e r s were 0.22, 0.47, 0.90 a n d 3.44 m m ; t h e 0.90 m m m e d i a n d i a m e t e r s a n d was a m i x t u r e o f t h e 0.47 a n d 3.44 m m s a n d s . W a v e h e i g h t was h e l d n e a r l y c o n s t a n t i n each case b u t p e r i o d was v a r i e d as 1.30, 1.75, 2.20, 2.75 a n d 3.30 seconds r e s u l t i n g i n four sets of profiles, figure 7.  3. A s t u d y c a r r i e d out b y J a p a n e s e researchers H a t t o r i a n d K a w a m a t a [22] t o d e v e l o p a n on-offshore t r a n s p o r t p a r a m e t e r was r e v i e w e d . T w o beaches i n a w a v e f l u m e were i n v e s t i g a t e d ; t h e flume was 0 . 4 m w i d e a n d 0 . 7 m deep a n d 1 6 m l o n g w i t h glass s i d e w a l l s . T w o waves of c o n s t a n t steepness were u s e d i n t h e e x p e r i m e n t : H = 0  c m a n d T— 1.6s, H = 0  2.4  5 . 5 c m a n d T = 1.0s. In t h e first case profiles were r e c o r d e d  at 0, 3, 6 a n d 12 h o u r s ; i n t h e s e c o n d case profiles were r e c o r d e d at 0, 4, 8 a n d 14 h o u r s , figure 8.  Chapter 3  FIELD INVESTIGATIVE  3.1  WORK  Background  F i e l d i n v e s t i g a t i v e w o r k c a r r i e d o u t o n beaches w i t h i n c o a s t a l s o u t h w e s t B r i t i s h C o l u m b i a has i n c l u d e d p r o f i l e s u r v e y s over a p e r i o d of t i m e , sediment t r a n s p o r t e x p e r i m e n t s , g r a i n size a n a l y s i s , subsurface i n v e s t i g a t i o n a n d s t u d y of b e a c h g e o m o r p h o l o g y .  Bluff erosion  on t h e i n n e r coast has been r e v i e w e d b e c a u s e of its l o c a l s i g n i f i c a n c e . W a v e h i n d c a s t i n g d u r i n g t h e p e r i o d of p r o f i l e s u r v e y s a n d a wave c l i m a t e i n v e s t i g a t i o n was also c a r r i e d o u t . T h r e e beaches at T s a w w a s s e n , D u n d a r a v e i n W e s t V a n c o u v e r a n d T o w e r B e a c h at P o i n t G r e y were s t u d i e d i n d e t a i l ; t w e n t y - t w o o t h e r beaches o n t h e i n n e r coast were s t u d i e d on a o n e t i m e or o c c a s i o n a l b a s i s .  3.2 3.2.1  Study Area Geography  T h e s t u d y a r e a is defined b y t h e S t r a i t of G e o r g i a w h i c h is a t i d a l w a t e r b o d y b o u n d e d b y V a n c o u v e r I s l a n d o n t h e west, t h e m a i n l a n d of B r i t i s h C o l u m b i a o n the east, C a p e M u d g e at Q u a d r a I s l a n d on t h e n o r t h a n d the s o u t h e r n g u l f i s l a n d s , figure 2. T h e Strait, is an i n l a n d sea w h o s e a x i s r u n s n o r t h w e s t t o s o u t h e a s t s t r e t c h i n g 2 2 2 k m (120 n a u t i c a l m i l e s ) w i t h a n average w i d t h of 3 3 k m (18 n a u t i c a l m i l e s ) . T h e s t u d y a r e a also i n c l u d e s beaches on J u a n de Fuca. S t r a i t w h i c h is l o c a t e d b e t w e e n V a n c o u v e r I s l a n d a n d W a s h i n g t o n s t a t e , figure  1. T h e J u a n de F u c a S t r a i t has a n o r t h w e s t t o s o u t h e a s t a l i g n m e n t a n d is e x p o s e d  18  Chapter 3. FIELD INVESTIGATIVE  WORK  19  o n its w e s t e r n end to t h e N o r t h P a c i f i c .  3.2.2  Physiography  T h e B r i t i s h C o l u m b i a coast has b e e n d i v i d e d b r o a d l y i n t o t h r e e p h y s i o g r a p h i c , regions: a n o u t e r m o u n t a i n a r e a w h i c h i n c l u d e s t h e i n s u l a r m o u n t a i n s of t h e Q u e e n  Charlotte  I s l a n d s a n d V a n c o u v e r I s l a n d , a c o a s t a l t r o u g h w h i c h i n c l u d e s the G e o r g i a D e p r e s s i o n a n d t h e C o a s t M o u n t a i n s [6].  T h e G e o r g i a D e p r e s s i o n i n c l u d e s the S t r a i t of G e o r g i a  a n d t h e G e o r g i a L o w l a n d a l o n g t h e m a i n l a n d coast a n d t h e N a n a i m o L o w l a n d a l o n g the w e s t e r n coast of t h e S t r a i t .  3.2.3  Geology and geomorphic history  T h e i n n e r s o u t h coast has been m o d i f i e d by r e p e a t e d g l a c i a t i o n s s e p a r a t e d b y n o n - g l a c i a l i n t e r v a l s d u r i n g W i s c o n s i n t i m e l a t e i n t h e p l e i s t o c e n e e p o c h . T h e F r a s e r G l a c i a l ion is t h e last m a j o r  W i s c o n s i n g l a c i a t i o n w h i c h d e p o s i t e d s i g n i f i c a n t q u a n t i t i e s of t i l l  and  s t r a t i f i e d drift.  A n o t a b l e s e d i m e n t source w i t h i n the S t r a i t of G e o r g i a is t h e h o r i z o n -  t a l l y s t r a t i f i e d p l e i s t o c e n e o u t w a s h s e d i m e n t c a l l e d Q u a d r a S a n d [5]. Q u a d r a S a n d s are u n i f o r m silts and sands, deposited d u r i n g the Fraser G l a c i a t i o n , that currently form a b e a c h / sea cliff e r o s i o n e n v i r o n m e n t characteristic, of the i n n e r coast. T h e Q u a d r a S a n d sea cliffs h a v e been s t u d i e d e x t e n s i v e l y at P o i n t G r e y . Sea cliffs of n o n - s t r a t i f i e d drift of p l e i s t o c e n e o r i g i n also o c c u r i n l o c a t i o n s s u c h as s o u t h e r n P o i n t R o b e r t s a n d C o r d o v a Bay  on Vancouver Island.  M o s t of t h e i n n e r coast, is p r e d o m i n a n t l y r o c k y w i t h t h i n  sediment, cover, h o w e v e r , i n areas w h e r e t h e c r u s t is o v e r l a i n b y t h i c k s e d i m e n t s  such  as Q u a d r a S a n d s or i n t h e v i c i n i t y of f l u v i a l d e p o s i t s s a n d , g r a v e l , c o b b l e a n d b o u l d e r b e a c h e s have f o r m e d .  Chapter 3. FIELD INVESTIGATIVE  3.2.4  WORK  20  Littoral materials  M o s t l o c a l beaches are f o r m e d of coarse m a t e r i a l i n t h e g r a v e l , c o b b l e a n d b o u l d e r size r a n g e , figure 3.  S o m e s a n d y beaches o c c u r a r o u n d t h e ' coast, m o s t n o t a b l y the p o c k e t  b e a c h at T r i b u n e B a y o n H o r n b y I s l a n d , figure 2, or d o w n c o a s t of the s a n d a n d  till  bluffs w h i c h o c c u r a r o u n d t h e S t r a i t . G e n e r a l l y , t h e s a n d beaches o c c u r w h e r e t h e r e is a sufficient s u p p l y of s a n d size m a t e r i a l t o create a l o c a l s a n d y b e a c h . T h o u g h s m a l l s a n d y pocket, beaches are n u m e r o u s o n t h e i n n e r coast t h e y are n o t t h e focus of t h i s s t u d y , e m p h a s i s is u p o n t h e coarse m a t e r i a l beaches e x p o s e d t o the S t r a i t of G e o r g i a a n d J u a n de F u c a S t r a i t since t h e y are m o r e c h a r a c t e r i s t i c of t h e i n n e r s o u t h coast.  T h e coastal  e n v i r o n m e n t u n d e r s t u d y m a y be t h o u g h t of as a t h i n c i r c u m f e r e n c i a l b a n d of s e d i m e n t s , p r e d o m i n a n t l y of l a t e p l e i s t o c e n e g l a c i a l o r i g i n , o v e r l y i n g c r u s t a l r o c k a n d a c t e d u p o n a n d s h a p e d b y a r a n g e o f tides a n d specific, wave c l i m a t e .  3.2.5  W i n d and wave c l i m a t o l o g y  T h e w a v e c l i m a t e o l t h e S t r a i t of G e o r g i a is g o v e r n e d b y t h e fact t h a t for m o s t w i n d s t h e w a t e r b o d y is fetch l i m i t e d . T h u s t h e r e are l i m i t s o n t h e w a v e h e i g h t a n d p e r i o d a n d c o r r e s p o n d i n g l y t h e w a v e e n e r g y a n d wave i n t e n s i t y t h a t w i n d s c a n g e n e r a t e w i t h i n its wa.ters. S e a s o n a l v a r i a t i o n i n t h e p e r i o d of o c e a n swell is a t t r i b u t e d t o s e a s o n a l changes i n b e a c h m o r p h o l o g y i d e n t i f i e d o n o p e n o c e a n coast beaches. the r a n g e of 15 t o 20 s e c o n d s ) are g e n e r a t e d  S w e l l waves ( t y p i c a l l y i n  b y s t o r m s over t h e o p e n o c e a n a n d have  b e e n k n o w n t o reach t h e west coast of N o r t h A m e r i c a f r o m s t o r m s i n t h e S o u t h P a c i f i c . O c e a n s w e l l i n t h i s r a n g e is c o m m o n off t h e west coast, of B r i t i s h C o l u m b i a b u t does not o c c u r w i t h i n t h e Strait, of G e o r g i a b e c a u s e of the a t t e n u a t i n g effect of t h e G u l f I s l a n d s a n d J u a n de F u c a and " J o h n s t o n e S t r a i t s . In o t h e r w o r d s , a l l waves w i t h i n t h e S t r a i t of 5  Chapter  3.  FIELD  INVESTIGATIVE  WORK  21  Georgia are locally generated by winds or secondary sources such as ships as exemplified by the distribution of wave periods and heights, figure 9, which has been derived from short term records at Roberts B a n k and Tofino, appendices B and C . T h e short term records are considered representative of the predominant wave climate at the sites. The attenuating effect of the G u l f Islands and the Juan de Fuca Strait to ocean swell should be noted since there are no waves over an 8 . 5 second period evident on the wave period distribution for the Strait of Georgia, however, ocean swell has been reported as far as V i c t o r i a Harbour where it has been measured at greatly reduced amplitudes. E x a m i n a t i o n of the available wind and wave data for the Strait of Georgia helps in establishing a picture of the wind and wave climate of the area as indicated by the annual wind and wave roses, figure 10. T h e predominant directions for both winds and waves are Southeast and Northwest, the southeast winds and waves preceeding the passage of a storm front and the northwest winds and waves following it or also in association with a high pressure ridge or 'anticyclone'. T h e data also indicate significant periods of calm within the inner coast. T y p i c a l plots of significant wave height as a function of time for the inner coast, figure 5 , show that on the inner coast the wave climate is essentially either calm or storm.  From a practical point of view, this type of wave climate is ideal for research  into the response of shoreline with respect to waves. T h e storms are well defined and there are periods of intervening calm which permit safe and easy field investigative work such as the surveying of beach profiles. This characteristic of the local wave climate was exploited in field investigation of local beaches.  3.2.6  Tides  Tides w i t h i n the Strait of Georgia are mixed semi-diurnal. This means that there are usually two complete oscillations daily with marked differences between high and low  Chapter 3.  FIELD INVESTIGATIVE  WORK  22  t i d e s . T i d a l r a n g e for P o i n t A t k i n s o n o n the S t r a i t of G e o r g i a , figure 2, is s u m m a r i z e d i n t a b l e 1.  POINT ATKINSON TIDE TIDE  ELEVATIONS metres (Geodetic D a t u m )  H I G H E X T R E M E ( i n c l u d e s s t o r m surge)  2.6  ANNUAL  2.0  MEAN  HIGH  HIGH  WATER  WATER  MEAN WATER  1.4  LEVEL  0.0  MEAN LOW WATER  -1.9  ANNUAL  -3.0  LOW  LOW WATER  EXTREME  -3.4  table 1 T i d e s are i m p o r t a n t i n t h e g e o m o r p h i c d e v e l o p m e n t of i n n e r coast beaches, the m a i n effect b e i n g t h a t t h e p o s i t i o n of b r e a k i n g waves shifts across t h e p r o f i l e w i t h t h e  tide  c y c l e . T h e d a t a i n t a b l e 1 s h o w s t h a t a n n u a l t i d a l r a n g e at Point. A t k i n s o n is 5.0 m e t r e s ; a s s u m i n g a t y p i c a l i n n e r coast b e a c h s l o p e of 1 V : 1 0 H , t h i s m e a n s t h a t t h e b r e a k i n g wave shifts p o s i t i o n over t h e b e a c h a h o r i z o n t a l d i s t a n c e of 50 m e t r e s o n a n a n n u a l t i d e . T h u s , i n n e r coast beaches are r e l a t i v e l y w i d e b y v i r t u e of t h e r a n g e of t i d e s .  3.2.7  Shoreline classification  T h e s h o r e l i n e of t h e i n n e r s o u t h coast has b e e n classified based u p o n specific foreshore c h a r a c t e r i s t i c s , s e d i m e n t sources a n d l i t t o r a l processes: L i n e a r C o a s t l i n e . L i n e a r c o a s t l i n e is c h a r a c t e r i z e d b y s e d i m e n t c o v e r e d s h o r e l i n e t h a t is not i n t e r r u p t e d by h e a d l a n d s , i n l e t s , p i e r s or g r o y n e s c a u s i n g s t o r a g e or d e p o s i t i o n of l i t t o r a l m a t e r i a l . B e a c h e s o n t h e l i n e a r c o a s t l i n e of t h e i n n e r coast t y p i c a l l y  Chapter  3.  FIELD  INVESTIGATIVE  WORK  23  e x h i b i t cross shore s o r t i n g at t h e surface w i t h fine sands a n d gravels i n the u p p e r foreshore a n d coarser cobbles a n d b o u l d e r s i n t h e l o w e r foreshore, p h o t o 14.  The  b o u l d e r c o b b l e l o w e r foreshores e x h i b i t n a t u r a l self a r m o u r i n g s i m i l a r t o g r a v e l b e d r i v e r s , figure 16. S a n d y b e a c h e s o c c u r o n l i n e a r sections of c o a s t l i n e b u t are often t r a n s i e n t i n n a t u r e d u e t o t h e h i g h m o b i l i t y of s a n d a n d t h e v a r i a b l i t y o f its s u p p l y . T h e s a n d b e a c h is often a lens of s a n d over a n a t i v e c o b b l e or b o u l d e r b e a c h , p h o t o s 21 a n d 22. S a n d a n d t i l l bluffs are a s o u r c e of s a n d size l i t t o r a l m a t e r i a l a l o n g t h e coast; s a n d beaches u s u a l l y a p p e a r d o w n d r i f t of these sites for s e v e r a l m i l e s .  S t o r a g e S e c t i o n s . H e a d l a n d s , groynes or piers m a y i n t e r r u p t s e d i m e n t t r a n s p o r t  re-  s u l t i n g i n s t o r a g e of s e d i m e n t s r e s u l t i n g i n steep s h i n g l e beaches s i n c e the r a t e of b y p a s s i n g of coarse s e d i m e n t s is l o w r e l a t i v e t o finer s e d i m e n t s . A p r i m e e x a m p l e is t h e steep s h i n g l e b e a c h at C a m p B y n g near R o b e r t s C r e e k , p h o t o 5, t h e b e a c h is s h i n g l e w i t h a D  50  of a b o u t 20 m m .  P o c k e t B e a c h e s . P o c k e t beaches m a y f o r m of s e d i m e n t s r a n g i n g f r o m s a n d size t o c o b b l e size s e c u r e d b e t w e e n n a t u r a l or a r t i f i c i a l h e a d l a n d s .  S e d i m e n t s are  trapped  w i t h i n t h e p o c k e t b e a c h ; there is n o net l o n g t e r m l i t t o r a l d r i f t t h u s t h e p o c k e t b e a c h is c o n s i d e r e d a c l o s e d s e d i m e n t a r y e n v i r o n m e n t . S e d i m e n t sources for p o c k e t beaches t y p i c a l l y i n c l u d e  fluvial  s e d i m e n t s o r i g i n a t i n g f r o m u p l a n d sources  and  b a c k s h o r e e r o s i o n . P o c k e t beaches w h e r e s h i n g l e has a c c u m u l a t e d t e n d t o be acc r e t i v e as i n d i c a t e d b y t h e steep g r a v e l a n d c o b b l e b e r m s w h i c h f o r m .  Lock B a y  o n G a b r i o l a I s l a n d is a p r i m e e x a m p l e , p h o t o 1 1 .  Deltaic.  D e l t a i c fans of fine t o coarse  fluvial  s e d i m e n t s f o r m at t h e m o u t h s of s t r e a m s ,  creeks a n d r i v e r s . T h e m o s t n o t a b l e d e l t a i c c o a s t l i n e o n t h e i n n e r coast, is t h e F r a s e r  Chapter 3. FIELD INVESTIGATIVE  WORK  24  R i v e r d e l t a . T h e d e l t a s are g e n e r a l l y c h a r a c t e r i s e d b y finer s e d i m e n t s e r o d e d f r o m u p l a n d s o u r c e s , h o w e v e r , steep m o u n t a i n s t r e a m s m a y t r a n s p o r t coarse  sediments  t o t h e shore f o r m i n g d e l t a i c fans.  Rocky  C o a s t l i n e . T h e r e are no beaches o n r o c k y c o a s t l i n e d u e t o t h i n or n o n e x i s t a n t  s e d i m e n t cover over b e d r o c k .  In areas w h e r e the p o s t g l a c i a l s e d i m e n t cover was  t h i n or n o n e x i s t a n t a n d t h e r e is c u r r e n t l y insufficient l o c a l s u p p l y of u p l a n d or l i t t o r a l s e d i m e n t b e d r o c k is e x p o s e d . M o s t of t h e i n n e r coast is r o c k y .  3.3  Sites S t u d i e d  T h e beaches at T s a w w a s s e n , T o w e r B e a c h at P o i n t G r e y a n d D u n d a r a v e at W e s t V a n couver,  figures  2 and  11 t o 13, were selected for d e t a i l e d s t u d y p r i m a r i l y b e c a u s e of  r e l a t i v e l y easy access, each site b e i n g a different t y p e of b e a c h a n d the a v a i l a b i l i t y of p r e v i o u s s t u d i e s for b a c k g r o u n d at T s a w w a s s e n a n d P o i n t G r e y . T w e n t y - t w o o t h e r beaches were s t u d i e d o n a o n e t i m e or o c c a s i o n a l basis t h r o u g h t h e S t r a i t o f G e o r g i a a n d lower J u a n de F u c a S t r a i t , t a b l e 2 a n d figure 2. Tsawwa.ssen,  T o w e r B e a c h at P o i n t G r e y a n d D u n d a r a v e at W e s t V a n c o u v e r  are  d i s c u s s e d s u b s e q u e n t l y i n d e t a i l , m o s t of t h e r e m a i n i n g sites are n o t d i s c u s s e d s p e c i f i c a l l y , rather the  findings  at t h e t w e n t y - t w o sites are s u m m a r i z e d i n t a b l e s a n d d i a g r a m s  are d i s c u s s e d i n t h e c o n t e x t of t y p i c a l c o n d i t i o n s o c c u r i n g o n t h e i n n e r coast.  and  apter 3.  FIELD  INVESTIGATIVE  WORK  SOME INNER SOUTH COASTAL  BEACHES  Index  Site  Brief Description  1  Dundarave, West Vancouver  armoured  2  Tsawwassen Beach  bluffs, t i d a l flats  3  Tower B e a c h , Point G r e y  artifical shingle beach  4  Chaster Creek West, Gibsons  armoured shoreline  5  C a m p B y n g , Roberts Creek  steep s h i n g l e b e a c h  6  E a s t of P i e r , R o b e r t s C r e e k  armoured  7  T r a i l B a y , Sechelt  steep s h i n g l e b e a c h  8  Westview, Powell River  armoured  9  Savary Island Southeast  a c t i v e bluff e r o s i o n , t i d a l  10  Cape M u d g e , Q u a d r a Island  active bluff erosion, b o u l d e r beach  11  Rebecca Spit, Q u a d r a Island  cobble/ boulder beach  12  Tyee Spit, C a m p b e l l River  gravel beach  13  Cape Lazo, Comox  e r o d i n g bluff, c o b b l e b e a c h  14  K i n Beach, Comox  cobble beach  15  Goose Spit, C o m o x  cobble beach  16  W i l l i m a r Bluffs, C o m o x  a c i t v e bluff e r o s i o n , c o b b l e b e a c h  17  Columbia Beach, Qualicum  cobble beach  18  Qualicum Bay, Qualicum  cobble beach  19  K o m a s Bluff, D e n m a n Island  a c t i v e bluff e r o s i o n  20  Lock Bay, G a b r i o l a Island  steep s h i n g l e b e a c h  21  Orveas Bay, Sooke  steep s h i n g l e b e a c h  22  French B e a c h , Sooke  steep s h i n g l e b e a c h  23  Parry Bay, Victoria  gravel beach  24  Clover Point West, V i c t o r i a  a c t i v e bluff e r o s i o n , g r a v e l b e a c h  25  Island V i e w B e a c h , Saanich  active bluff erosion, spit  table 2  shoreline,  shoreline  shoreline flats  Chapter 3.  3.4  FIELD INVESTIGATIVE  WORK  26  Sediments  3.4.1  B e a c h slope a n d g r a i n size  M a n y o p e n coast s a n d y b e a c h e s e x h i b i t a c o r r e l a t i o n b e t w e e n m e d i a n s a n d p a r t i c l e size a n d b e a c h face slope; s u c h a r e l a t i o n s h i p has b e e n e x p l o r e d for i n n e r coast  beaches,  figure 14. A c o r r e l a t i o n b e t w e e n g r a i n size a n d b e a c h face s l o p e is n o t e v i d e n t , h o w e v e r , a r m o u r e d b e a c h e s a n d s h i n g l e beaches are t w o d i s t i n c t p o p u l a t i o n s a n d p l o t separately. Inner coast a r m o u r e d beaches a l l have slopes t y p i c a l l y i n t h e r a n g e of 5 t o 10 degrees as i n d i c a t e d by t h e b a n d of p o i n t s i n t h e s h a d e d a r e a w h e r e a s t h e s h i n g l e beaches are m u c h steeper, t y p i c a l l y 16 t o 26 degrees. O n t h e i n n e r coast t h e s h i n g l e beaches a p p a r e n t l y h a v e a n u p p e r l i m i t o n m e d i a n g r a i n size as s h i n g l e beaches were n o t f o u n d l o c a l l y w h e r e t h e m e d i a n g r a i n size exceeds 40 m m . T h e s h i n g l e size l i m i t is l i k e l y due t o l i m i t s o n w a v e e n e r g y w i t h i n i n n e r c o a s t a l w a t e r s c a p a b l e of b u i l d i n g a b e r m of larger size m a t e r i a l .  3.4.2  Shingle beaches  S h i n g l e beaches o c c u r w i t h i n t h e i n n e r s o u t h coast w h e r e t h e r e is sufficient s u p p l y a n d s t o r a g e of l i t t o r a l m a t e r i a l .  T h e s h i n g l e beaches h a v e a m e d i a n p a r t i c l e size t y p i c a l l y  i n t h e r a n g e 1 0 - 4 0 m m ; m a n y of t h e s h i n g l e t a k e o n a d i s t i n c t flat shape, p h o t o 8. It is u n k n o w n w h e t h e r t h e p a r t i c l e s are w o r n t o t h e flat s h a p e t h r o u g h s h e a r i n g w i t h i n the beach m a t r i x d u r i n g sediment  activity under  p a r t i c l e s were o r g i n a l l y s u p p l i e d l i t t o r a l l y or  fluvially  movement  wave a c t i o n or w h e t h e r  the  t o t h e b e a c h as flat s h i n g l e .  In cross s e c t i o n t h e s h i n g l e beaches are steep b e r m s a n d are r e l a t i v e l y h o m o g e n e o u s , c o n s i s t i n g of gravels or c o b b l e s , p h o t o 12 a n d figure 15. B y v i r t u e o f t h e i r coarse g r a i n size t h e b e a c h s e d i m e n t s have r e l a t i v e l y h i g h p e r m e a b i l i t y , figure 3, a n d f o r m m u c h steeper  Chapter 3. FIELD INVESTIGATIVE  WORK  27  slopes t h a n s a n d y beaches. P e r m e a b l i t y has been r e l a t e d t o b e a c h s l o p e by the o b s e r v a t i o n t h a t b r e a k i n g or s u r g i n g waves p e r c o l a t e i n t o t h e b e a c h o n r u n - u p c a u s i n g m o s t of t h e b a c k s w a s h flow t o r e t u r n t h r o u g h t h e sediment, p a r t i c l e m a t r i x . T h e rate of p e r c o l a t i o n i n t o t h e b e a c h is a f u n c t i o n of t h e s e d i m e n t p e r m e a b i l i t y t h u s o n s h i n g l e beaches b r e a k i n g waves i m p o s e d r a g forces o n t h e s h i n g l e p r e d o m i n a n t l y o n r u n - u p c a u s i n g t h e m t o m o v e o n s h o r e b u i l d i n g a steep b e r m u n t i l a n e q u i l i b r i u m w i t h t h e i m p o s e d w a v e c o n d i t i o n a n d g r a v i t y is a c h i e v e d [29], P r i m e e x a m p l e s of s u c h beaches on t h e i n n e r coast i n c l u d e C l a m p B y n g at R o b e r t s C r e e k , T r a i l B a y at S e c h e l t , L o c k B a y o n G a b r i o l a I s l a n d and  G o r d o n ' s B e a c h , near R i v e r J o r d a n , V a n c o u v e r I s l a n d , p h o t o s 5, 6, 9 a n d 10. C o b b l e c o l o n i z e d b y s e a p l a n t s has been f o u n d h i g h i n t h e u p p e r foreshore of m a n y  s h i n g l e beaches.  C l a w - l i k e roots firmly attached to cobble w i t h n o m i n a l diameters up  t o 200 m m has been o b s e r v e d t h u s i n d i c a t i n g t h a t s o m e of the m a t e r i a l o r i g i n a t e s f r o m offshore, p h o t o 7. Intense w a t e r m o t i o n at t h e seabed i n d u c e d b y s t o r m waves are b e l i e v e d t o d i s l o d g e t h e p l a n t s f r o m t h e s e a b e d w h i l e w i n d d r i v e n c u r r e n t s c a r r y the p l a n t s w i t h t h e i r a t t a c h e d rocks t o the shore w h e r e t u r b u l e n t b r e a k i n g waves w a s h t h e s h i n g l e h i g h i n t o t h e u p p e r foreshore.  3.4.3  A r m o u r e d beaches  A r m o u r e d beaches at t h e surface consist, of c o b b l e s w i t h a m e d i a n d i a m e t e r t y p i c a l l y i n excess o f 100 m m , p h o t o s 14, 15, 16 a n d 19. U n l i k e s h i n g l e beaches t h e s u b s u r f a c e m a t r i x is not h o m o g e n e o u s b u t r a t h e r a r a n g e of m a t e r i a l sizes f r o m s a n d t o c o b b l e . A r m o u r e d beaches e x h i b i t a b e d a r m o u r i n g s t r u c t u r e s i m i l a r to the n a t u r a l a r m o u r i n g t h a t o c c u r s in g r a v e l b e d r i v e r s . T h e surface is a d i s t i n c t g r a v e l or c o b b l e layer u p t o s e v e r a l p a r t i c l e d i a m e t e r s t h i c k as e x e m p l i f i e d by figure 16 a n d p h o t o 15. The, a r m o u r e d b e a c h surface is c e n s o r e d of finer s e d i m e n t s a n d t e n d s to f o r m a n a t u r a l filter against, finer subsurface s e d i m e n t s .  Sieve, a n a l y s i s d a t a for D u n d a r a v e has  been  Chapter 3.  FIELD  INVESTIGATIVE  WORK  28  checked against the filter criterion: (•^15 )filter < 5 ( - D  85  ) ,; 50  and it has been found that the median grain sizes at the surface and of the subsurface m a t r i x represent a filter. T h e structure of the beach surface also has the appearance of a filter. T h e filter criterion states that the D  1 5  of the filter must be less than five times  the D 5 of the soil in order for a filter to form. Soil S  void size for the filter; D  85  is representative of an average  is a representative size of larger particles in the soil.  If the armour layer of a beach is disturbed or removed the beach should rearmour with time if a sufficient fraction of armouring size material remains on the surface, exists in the subsurface matrix or is resupplied by longshore drift. Removal of an armour layer may result from municipal works such as burial of pipelines, scrap cleaning of a beach surface after an oil spill or removal of cobble for construction purposes.  It is possible  that disturbance or removal may result in a lowering of the foreshore through loss of sand washed from the original beach subsurface until the beach subsequently rearmours. Lowering of the foreshore through removal of armouring w i l l likely aggravate backshore erosion due to wave run-up further into backshore areas. Inner coast armoured beaches are believed to be a stable remnant of an early post glacial surficial sediment cover. Towards the end of the Fraser Glaciation, the most recent of a series of pleistocene glaciations, retreating ice left till deposits over the surface of the Georgia Depression. In many exposed coastal bluffs the till exists at the top of the stratigraphic sequence, photo 17, and is usually underlain by Q u a d r a Sand which in turn buries older estuarine and marine sediments deposited during preceding nonglacial intervals. T h e retreat of ice and stabilization of the sea near present day levels about 11000 years ago marked the end of a period of rapid geomorphic change of the inner coast induced by wave, tides and changing sea levels. T h e early sediment cover is  Chapter 3. FIELD INVESTIGATIVE  WORK  29  b e l i e v e d t o h a v e c o n s i s t e d of a w i d e r a n g e of sizes ( c l a y s , s i l t s , s a n d s , c o b b l e s , b o u l d e r s ) w h i c h f o u n d e d t h e p a r e n t m a t e r i a l for t h e present a r m o u r e d s h o r e l i n e .  Beneath  the  a r m o u r l a y e r e x i s t s a c o m p a r i t i v e l y w i d e r a n g e of s e d i m e n t sizes t h a t has c h a n g e d l i t t l e over t i m e . a n d is l i k e l y r e p r e s e n t a t i v e of e a r l y surface s e d i m e n t s .  Over time the shifting  p o s i t i o n of b r e a k i n g waves over the s h o r e l i n e due t o t i d a l f l u c t u a t i o n s has s e l e c t i v e l y r e m o v e d t h e finer f r a c t i o n of s e d i m e n t f r o m t h e m o r e e x p o s e d lower foreshore. T h e u p p e r foreshore, h o w e v e r , b e c a u s e of its d e c r e a s e d e x p o s u r e t o wave a c t i o n r e t a i n s m o b i l e sands a n d g r a v e l s w h i c h are a n i n t e g r a l p a r t of t h e n a t u r a l t r a n s p o r t processes o c c u r i n g o n t h e s h o r e l i n e , p h o t o 14, w h i l e t h e lower foreshore has d e v e l o p e d t o a c o b b l e a r m o u r e d s t a t e resisting further erosion.  3.5  Profiles  3.5.1  Discussion  M o n t h l y b e a c h profiles were s u r v e y e d at T s a w w a s s e n B e a c h , T o w e r B e a c h at P o i n t G r e y a n d D u n d a r a v e at W e s t V a n c o u v e r f r o m O c t o b e r 1986 t o J u l y 1987, figures 17 t o 19. B e a c h profiles were s u r v e y e d t o i d e n t i f y t h e t e m p o r a l a n d s p a t i a l m a g n i t u d e of shoreline changes d u e t o waves a c t i n g o n t h e beaches. T h e f o l l o w i n g c o n c l u s i o n s have been d r a w n f r o m t h e field  measurements:  1. T h e scale o f changes i n b e a c h s h a p e is s m a l l c o m p a r e d t o changes w h i c h o c c u r t y p i c a l l y o n o p e n coast beaches as e x e m p l i f i e d by figure 4.  Seasonal  on-offshore  s e d i m e n t c y c l i n g k n o w n t o o c c u r o n o p e n coast beaches is n o t i n d i c a t e d b y t h e s e q u e n c e of profiles m e a s u r e d .  2. S e d i m e n t a c t i v i t y o c c u r s p r i m a r i l y i n t h e u p p e r foreshore m o s t l y s h o r e w a r d of t h e w a v e b r e a k i n g p o i n t at n o r m a l h i g h t i d e as s h o w n b y t h e p r o f i l e v a r i a t i o n s i n  figures  Chapter 3. FIELD INVESTIGATIVE  WORK  30  17 t o 19. T h e profile v a r i a t i o n s are due t o l o n g s h o r e s e d i m e n t t r a n s p o r t i n t h e u p p e r foreshore, p h o t o 14.  3. C o b b l e d l o w e r foreshores a n d t i d a l flats are s t a b l e . A t T s a w w a s s e n a n d P o i n t G r e y t h e t i d a l flats, a n d at D u n d a r a v e a n d P o i n t G r e y t h e c o b b l e lower foreshores, h a d n e g l i g i b l e changes i n e l e v a t i o n d u r i n g t h e 9 m o n t h s t u d y p e r i o d . T h i s is consist e n t w i t h o b s e r v e d b a r n a c l e c o l o n i z a t i o n a n d a l g a l s t a i n i n g of foreshore c o b b l e a n d eel grass c o l o n i z a t i o n of t h e t i d a l flats at T s a w w a s s e n i n d i c a t i n g s t a b i l i t y of t h e sediment.  4. T h e m a x i m u m m e a s u r e d c h a n g e i n d e p t h of u p p e r foreshore s e d i m e n t at t h e t h r e e sites was 0.5 m e t r e s .  5. T h e h i g h e s t e l e v a t i o n of m e a s u r e d b e a c h s e d i m e n t a c t i v i t y at t h e t h r e e sites is 2.5 m e t r e s a b o v e g e o d e t i c d a t u m .  T h i s e l e v a t i o n c o r r e s p o n d s to b e r m crests a n d  o n s h o r e g r a v e l m o v e m e n t i n t o b a c k s h o r e areas a n d represents the l i m i t of s t o r m wave r u n - u p a n d high tides d u r i n g the study p e r i o d .  6. S c o u r t r e n c h e s p a r a l l e l i n g the shore are f r e q u e n t l y f o r m e d i n t h e u p p e r foreshore b e n e a t h t h e p l u n g e p o i n t of b r e a k i n g waves i n d i c a t i n g b o t h o n s h o r e a n d offshore s e d i m e n t m o v e m e n t s h o r e w a r d a n d s e a w a r d of the b r e a k e r p l u n g e p o i n t .  T h i s is  e x e m p l i f i e d i n figures 17 t o 19 as t h e z i g z a g i n the surface profile.  3.5.2  Tsawwassen Beach  T s a w w a s s e n b e a c h is l o c a t e d j u s t s o u t h of t h e ferry c a u s e w a y o n the west side of P o i n t R o b e r t s , figures 2 a n d 11. T s a w w a s s e n B e a c h has d e v e l o p e d g e o m o r p h i c a l l y t o a profile t h a t is s i m i l a r to m a n y beaches o n t h e i n n e r s o u t h coast; the profile has a coarse s a n d a n d g r a v e l u p p e r b e a c h  Clu,pur 3. FIELD INVESTIGATIVE  WORK  31  w i t h slopes t y p i c a l l y 1 V : 8 H a n d a silt a n d s a n d t i d a l flat w i t h s l o p e t y p i c a l l y  1V:20H  near t h e u p p e r b e a c h f l a t t e n i n g t o 1 V : 2 5 0 H f u r t h e r offshore. T h e interface b e t w e e n the steep u p p e r b e a c h a n d the t i d a l flats o c c u r s at an e l e v a t i o n of a p p r o x i m a t e l y 0 m e t r e s g e o d e t i c d a t u m ( m e a n sea level) a n d is d e l i n e a t e d b y a n a b r u p t c h a n g e i n s l o p e , figure 17, w h e r e coarse u p p e r b e a c h s e d i m e n t s e n d a n d t i d a l flat s a n d s b e g i n . S e d i m e n t size d i s t r i b u t i o n s show t h a t t h e u p p e r b e a c h , s h o r e w a r d of t h e t i d a l  flat,  is p r e d o m i n a n t l y g r a v e l w h i c h grades t o coarse s a n d i n t h e u p p e r foreshore, figure 21. B e a c h s u b s u r f a c e s e d i m e n t s c o l l e c t e d at 0.5 m e t r e s b e l o w the surface r a n g e f r o m sands t o gravels i n size. T h e cross shore s o r t i n g of surface s e d i m e n t s f r o m coarse t o fine as one moves f r o m l o w e r t o u p p e r foreshore is s i m i l a r to o t h e r i n n e r coast beaches.  Tidal  flat  are b u i l t of fluvial s e d i m e n t s s u p p l i e d b y t h e F r a s e r R i v e r . T h e t i d a l flat d i d not c h a n g e e l e v a t i o n d u r i n g t h e p e r i o d of the s u r v e y ; t h i s measurem e n t is s u p p o r t e d by t h e fact t h a t e x t e n s i v e eel grass b e d s cover m o s t of t h e t i d a l  flats  indicating stability. L i t t o r a l d r i f t is n o r t h w a r d a l o n g the u p p e r b e a c h as i n d i c a t e d b y s i g n i f i c a n t d e p o s i t i o n at t h e foot of t h e ferry c a u s e w a y , figure 11, a p o r t i o n of w h i c h f o u n d t o b e f r o m a r t i f i c i a l i n f i l l i n g |19]. N o r t h w a r d l i t t o r a l m o v e m e n t is also e v i d e n c e d by filling o n t h e s o u t h sides of several g r o y n e s a l o n g the s h o r e l i n e . S u r v e y s s h o w s t h a t m o s t of t h e s e d i m e n t a c t i v i t y is i n t h e u p p e r foreshore as e x e m plified b y t h e p l o t s of u p p e r foreshore profile v a r i a t i o n , figure 17. S u r v e y s a n d a wave h i n d c a s t a n a l y s i s also show a significant, l o w e r i n g of t h e foreshore f o l l o w i n g a series of s t o r m s i n l a t e N o v e m b e r 1986, t h e m o s t s i g n i f i c a n t of w h i c h o c c u r r e d o n N o v e m b e r 2 5 t h a p p r o x i m a t e l y 600 h o u r s i n t o t h e m o n t h , a p p e n d i x D . P e a k h i n d c a s t s i g n i f i c a n t wave h e i g h t s at the e n d of the c a u s e w a y were a b o u t  1.5 m e t r e s ; news of t h e d a y r e p o r t e d  o v e r n i g h t p o w e r o u t a g e s a n d c a n c e l l a t i o n of ferry s a i l i n g s . T h e u p p e r foreshore l o w e r e d a b o u t 0.3 m e t r e s over p r e s t o r m e l e v a t i o n s as i n d i c a t e d b y the profiles, figure 17. A site  Chapter 3. FIELD INVESTIGATIVE  WORK  32  v i s i t o n N o v e m b e r 2 8 t h r e v e a l e d t h a t t h e u p p e r b e a c h was d e v o i d of the g r a v e l veneer c h a r a c t e r i s t i c of t h e b e a c h e x c e p t for g r a v e l b e r m s f o u n d i n t h e e x t r e m e u p p e r  foreshore  a p p a r e n t l y p u s h e d a s h o r e b y b r e a k i n g wave s w a s h at h i g h t i d e . E x t e n s i v e eel grass m a t s u p t o o n e m e t r e t h i c k , a p p a r e n t l y t o r n u p f r o m the t i d a l flat by wave a c t i o n , h a d a c c u m u l a t e d at t h e foot, of t h e causeway, figure 11. A s u b s e q u e n t s u r v e y o n J a n u a r y 13th s h o w e d t h a t t h e foreshore h a d d e v e l o p e d a profile s i m i l a r t o t h e p r e N o v e m b e r 2 5 t h s t o r m a n d gravel had reappeared  over the b e a c h surface.  A p o r t i o n of t h e u p p e r foreshore g r a v e l  b e r m s , a p p a r e n t l y a c t e d u p o n b y waves, was e r o d e d away.  3.5.3  T o w e r B e a c h at P o i n t G r e y  T o w e r B e a c h at Point. G r e y is l o c a t e d at the w e s t e r n side of t h e U n i v e r s i t y of B r i t i s h C o l u m b i a c a m p u s a n d is e x p o s e d t o t h e S t r a i t of G e o r g i a , figures 2 a n d 12. T o w e r B e a c h at Point. G r e y is an a r t i f i c i a l c o b b l e b e r m c o n s t r u c t e d i n 1980 a n d 1981 t o arrest foreshore e r o s i o n c a u s i n g r e c e s s i o n of the P o i n t G r e y bluffs [10]. P r o f i l e s i n d i c a t e t h a t t h e b e r m e x h i b i t s c o n s i d e r a b l e u p p e r foreshore s e d i m e n t a c t i v i t y a n d t h u s qualifies for s t u d y as a s h i n g l e b e a c h .  I n fact, t h e c o b b l e b e r m e x h i b i t e d  s e d i m e n t a c t i v i t y g r e a t e r t h a n t h e n a t u r a l beaches at D u n d a r a v e a n d T s a w w a s s e n based u p o n t h e e n v e l o p e f o r m e d b y sucessive profiles over a p e r i o d of t i m e ,  figure  17.  The  g r e a t e r s e d i m e n t a c t i v i t y m a y b e a t t r i b u t e d t o m o r e d i r e c t e x p o s u r e of P o i n t G r e y t o p r e d o m i n a n t n o r t h west waves i n t h e S t r a i t of G e o r g i a . B e a c h profiles s u r v e y e d over t h e p e r i o d O c t o b e r 26, 1986 t o J u n e 10, 1987 i n d i c a t e t h a t t h e t i d a l flats a n d lower c o b b l e b e a c h d i d n o t c h a n g e e l e v a t i o n over t h e period,  figure  18.  survey  Sediment, is m o v i n g l o n g s h o r e i n a n a r r o w u p p e r foreshore zone as  i n d i c a t e d b y t h e u p p e r foreshore p r o f i l e s h a p e w h i c h is c o n s t a n t l y c h a n g i n g u n d e r wave a c t i o n . M i n o r changes i n e l e v a t i o n of t h e t i d a l flats are l i k e l y d u e t o s u r v e y e r r o r . T h e d i r e c t i o n of net. l o n g s h o r e s e d i m e n t t r a n s p o r t is n o r t h w a r d as i n d i c a t e d b y g r o y n e  Chapter  3.  FIELD  INVESTIGATIVE  WORK  33  i n f i l l i n g a n d b y p a i n t e d c o b b l e p l a c e d on t h e foreshore w h i c h also h a d a net n o r t h w a r d movement.  3.5.4  Dundarave  T h e s h o r e l i n e at D u n d a r a v e i n W e s t V a n c o u v e r is e x p o s e d to B u r r a r d Inlet a n d the S t r a i t of G e o r g i a t h r o u g h a w i n d o w f o r m e d b y P o i n t A t k i n s o n a n d P o i n t G r e y , figure 2. P r o f i l e s s u r v e y e d show s e d i m e n t a c t i v i t y p r e d o m i n a n t l y i n t h e u p p e r foreshore, figure 19. S a n d a n d gravels i n t h e u p p e r foreshore are b e l i e v e d t o o r i g i n a t e f r o m s t r e a m s a l o n g the W e s t V a n c o u v e r foreshore a n d f r o m b a c k s h o r e e r o s i o n w h e r e seawalls are absent. It has been o b s e r v e d t h a t t h e u p p e r foreshore is s a n d i e r i n the w i n t e r c o m p a r e d to the s u m m e r l i k e l y d u e t o s e a s o n a b l y v a r i a b l e s e d i m e n t s u p p l y ; s t r e a m s c o n t r i b u t i n g sediment t o t h i s s e c t i o n of coast h a v e t h e i r h i g h e s t flows a n d a s s u m e d s e d i m e n t discharges d u r i n g t h e w i n t e r m o n t h s . T h e w i n t e r s e d i m e n t d i s c h a r g e is l i k e l y e n h a n c e d b y c o n s t r u c t i o n i n t h e w a t e r s h e d d u r i n g p r e v i o u s d r y seasons. T h e s h o r e l i n e e x h i b i t s cross s h o r e s o r t i n g at the surface w i t h m o b i l e s a n d s a n d gravels i n t h e u p p e r foreshore a n d c o b b l e a n d b o u l d e r a r m o u r i n g i n t h e lower foreshore, figure 20 a n d p h o t o 14.  M e a s u r e d s e d i m e n t size d i s t r i b u t i o n s f r o m b u l k sieve a n a l y s i s also  i n d i c a t e a n a r m o u r e d s t r u c t u r e by t h e t h r e e p a r a l l e l ' S ' s h a p e d g r a i n size d i s t r i b u t i o n c u r v e s , figure 2 1 .  A t the t h r e e s a m p l i n g p o i n t s o n t h e foreshore s e d i m e n t s are  u n i f o r m b u t g r a d e coarse t o fine f r o m t h e lower foreshore t o t h e u p p e r foreshore.  quite The  b e a c h s u b s u r f a c e , h o w e v e r , has a w i d e r a n g e of s e d i m e n t sizes. N e t l o n g s h o r e s e d i m e n t t r a n s p o r t d i r e c t i o n is e a s t w a r d a l o n g D u n d a r a v e as e v i d e n c e d b y the g r a v e l b e a c h w h i c h has f o r m e d u p d r i f t of the 2 5 t h street p i e r .  Chapter 3. FIELD INVESTIGATIVE  3.5.5  WORK  34  E l e v a t i o n s of shore features  B e r m crest a n d o l d debris l i n e e l e v a t i o n s were m e a s u r e d at v a r i o u s sites a r o u n d the i n n e r s o u t h coast d u r i n g t h e field i n v e s t i g a t i o n a n d are s u m m a r i z e d i n t a b l e 3.  The  berm  crests were t h e highest e l e v a t i o n of a c t i v e s e d i m e n t m e a s u r e d o n a b e a c h as e x e m p l i f i e d by figures 15 a n d 16 a n d o l d d e b r i s lines were a c c u m u l a t i o n s of d r i f t w o o d w h i c h a p p e a r e d t o be f r o m t h e p r e v i o u s w i n t e r , n o t t h e m o s t recent t i d e .  B E R M  CREST A N D DEBRIS LINE ELEVATIONS  BEACHES OF INNER Index  SOUTH COASTAL BRITISH Berm  Location  Crest  COLUMBIA  Debris  Line  metres - Geodetic D a t u m 1  Dundarave, West Vancouver  2  Tsawwassen  2.5  3  Tower Beach, Point G r e y  2.6  4  Chaster Creek West, Gibsons  5  C a m p B y n g , Roberts Creek  9  Savary Island Southeast  2.7  10  C a p e M u d g e , Q u a d r a Island  2.2  13  Cape Lazo, Comox  3.1  3.4  17  Columbia Beach, Qualicum  2.9  3.7  20  Lock Bay, G a b r i o l a Island  . 4.8  3.7  21  Orveas Bay, Sooke  3.8  3.2  24  Clover Point West, Victoria  1.7  25  Island V i e w Beach, Saanich  0.7  table 3  !  2.4  2.5 3.2 2.3  Chapter 3. FIELD INVESTIGATIVE  WORK  35  T h e d a t a i n t a b l e 3 is p r e s e n t e d as p a r t of a n o v e r a l l d e s c r i p t i o n o f t h e i n n e r coast. T h e e l e v a t i o n s r e p r e s e n t t h e l i m i t of wave a c t i v i t y o n e x p o s e d s h o r e l i n e i n a s s o c i a t i o n w i t h s t o r m w a v e r u n - u p , a s t r o n o m i c a l h i g h tides a n d p o s s i b l e s t o r m surge.  Elevations  v a r y f r o m site t o site p r i m a r i l y b e c a u s e of e x p o s u r e a n d t i d a l r a n g e . D e p o s i t i o n of t h e h i g h e s t debris l i n e o n a shore o c c u r s d u r i n g s t o r m s w h e n h i g h tides, wave r u n - u p a n d p o s s i b l e s t o r m surge cause waves t o p e n e t r a t e h i g h i n t h e u p p e r foreshore or b a c k s h o r e . C o a s t a l s t r u c t u r e s s h o u l d i d e a l l y be f o u n d e d a b o v e t h i s e l e v a t i o n a l l o w i n g for f r e e b o a r d . T h e f o u n d a t i o n e l e v a t i o n of a c o a s t a l s t r u c t u r e is u s u a l l y c a l c u l a t e d u s i n g the e x t r e m e r e c o r d e d h i g h t i d e ( w h i c h i n c l u d e s s t o r m surge) p l u s w a v e r u n - u p for a wave of specified r e t u r n p e r i o d p l u s f r e e b o a r d a l l o w a n c e . T h i s e l e v a t i o n s h o u l d b e greater t h a n t h e m e a s u r e d d e b r i s l i n e e l e v a t i o n at t h e site i n q u e s t i o n . T h e s e e l e v a t i o n s are p r e s e n t e d as a d e s c r i p t i o n of t h e v e r t i c a l e x t e n t of w a v e a c t i v i t y o n t h e i n n e r coast a n d m a y serve as a check i n t h e c a l c u l a t i o n of c o a s t a l w a t e r levels; the e l e v a t i o n s i n t h e m s e l v e s d o n o t have a n y s i g n i f i c a n c e .  3.5.6  Hindcast, waves and profile changes  W a v e s were h i n d c a s t for t h e p e r i o d f r o m O c t o b e r 1986 to F e b r u a r y 1987 at T s a w w a s s e n , Point. G r e y a n d D u n d a r a v e . O b s e r v e d a n d m e a s u r e d sediment, movement, c a n be r e l a t e d t o h i n d c a s t waves, for e x a m p l e , a l o w e r i n g of t h e foreshore at T s a w w a s s e n m e a s u r e d o n N o v e m b e r 3 0 t h , 1986 is a t t r i b u t e d t o t h e s t o r m wave a c t i o n o n N o v e m b e r 2 5 t h , 1986, a p p r o x i m a t e l y 600 h o u r s i n t o t h e m o n t h , a p p e n d i x E . T h e m o n t h l y s e q u e n c e of b e a c h profiles does not a l w a y s b r a c k e t i n d i v i d u a l s t o r m wave events c a u s i n g t h e m e a s u r e d p r o f i l e c h a n g e s . F o r t h i s r e a s o n , c o r r e l a t i o n b e t w e e n specific h i n d c a s t s t o r m w a v e c o n d i t i o n s a n d m e a s u r e d profile v o l u m e t r i c , changes was not f o u n d . F u r t h e r , since t h e m e a s u r e d profile changes were due p r i m a r i l y t o l o n g s h o r e t r a n s p o r t no m e a n s of c o r r e l a t i n g t h e profile changes t o wave c o n d i t i o n s c o u l d b e i d e n t i f i e d .  Chapter 3.  3.6  FIELD INVESTIGATIVE  Sediment  3.6.1  WORK  36  Transport  G e n e r a ] field  observations  C o a s t a l l a n d f o r m s s u c h as r o c k y R e b e c c a S p i t o h Q u a d r a I s l a n d a n d G o o s e S p i t n e a r C o m o x h a v e left a r e c o r d of t h e r a n g e of m a t e r i a l sizes m o b i l i z e d b y wave a c t i o n o n t h e coast. F o r e x a m p l e , t h e m e d i a n c o b b l e size o n t h e b e a c h surface at R e b e c c a S p i t is a b o u t 70 m m , p h o t o s 19 a n d 20. M u c h of t h e c o b b l e o r i g i n a t e s f r o m a b l u f f t o p c o b b l e l a y e r at C a p e M u d g e a b o u t 5 k m away, p h o t o s 17 a n d 18, w h e r e t h e m e d i a n c o b b l e size is a b o u t 120 m m . T h i s i n d i c a t e s t h a t a coarse f r a c t i o n of b e a c h m a t e r i a l s i n t o t h e c o b b l e a n d b o u l d e r size r a n g e are m o b i l e u n d e r wave a c t i o n o n t h e i n n e r coast. T h e c o b b l e a n d b o u l d e r s are p r e s u m e d t o m o v e as b e d l o a d a l o n g t h e b e a c h surface u n d e r intense s t o r m waves a n d have c o n t r i b u t e d t o h o u r g l a s s i n g o f t i m b e r piles t h r o u g h a b r a s i o n at s e v e r a l c o a s t a l sites, p h o t o 16. S e d i m e n t t r a n s p o r t p r e d o m i n a n t l y is b e d l o a d ; t r a n s p o r t of coarse sands, gravels a n d c o b b l e s o c c u r i n g i n t h e upj)er foreshore at h i g h t i d e . W a v e s a p p r o a c h i n g at a n a n g l e t o t h e shore w i l l r u n - u p o b l i q u e l y m o v i n g a v o l u m e of l i t t o r a l m a t e r i a l , t h e r e t u r n flow of t h e wave s w a s h is d i r e c t e d b y g r a v i t y d o w n t h e b e a c h slope n o r m a l t o t h e shore, t h u s by t h i s process l i t t o r a l m a t e r i a l moves i n a s a w t o o t h f a s h i o n i n t h e u p p e r foreshore.  Upper  foreshore p r o f i l e v a r i a t i o n s m e a s u r e d at T s a w w a s s e n , T o w e r B e a c h a n d D u n d a r a v e are d u e t o t h i s t y p e of s e d i m e n t m o v e m e n t .  T h u s l o n g s h o r e s e d i m e n t t r a n s p o r t is p e r i o d i c  o c c u r i n g o n l y d u r i n g t h e u p p e r p o r t i o n s of t h e t i d e c y c l e . L o w t i d e s p l a c e the s w a s h z o n e over a n a r m o u r e d p o r t i o n o f t h e b e a c h w h e r e m a s s t r a n s p o r t w i l l o c c u r o n l y i f t h e r e is sufficient w a v e e n e r g y t o m o b i l i z e t h e foreshore a r m o u r i n g as b e d l o a d . U p p e r foreshore l o n g s h o r e t r a n s p o r t of coarse gravels a n d c o b b l e s is t y p i c a l o f i n n e r coast  beaches.  Chapter 3. FIELD INVESTIGATIVE  3.6.2  Sediment transport  WORK  37  experiments  T w o s i m p l e s e d i m e n t t r a n s p o r t e x p e r i m e n t s d e m o n s t r a t i n g t h e d i s p e r s i o n of coarse particles o n a b e a c h b y w a v e a c t i o n were c o n d u c t e d . T h e first, of these e x p e r i m e n t s was c o n d u c t e d o n a s e c t i o n of s h o r e l i n e 1000 m e t r e s west of C h a s t e r C r e e k at G i b s o n s , B r i t i s h C o l u m b i a , site 4, figure 2. T h e e x p e r i m e n t i n v o l v e d p l a c i n g t h r e e w e l l s o r t e d a n d r o u n d e d s a m p l e s of t r a c e r p a r t i c l e s of m e d i a n sizes 6 m m , 3 8 m m a n d 7 5 m m o n a s e c t i o n of c o b b l e a r m o u r e d s h o r e l i n e a n d o b s e r v i n g the p a r t i c l e m o t i o n u n d e r t h e a c t i o n of waves, c u r r e n t s a n d tides over a p e r i o d of several d a y s , figure 22. T h e s e c o n d e x p e r i m e n t i n v o l v e d p l a c i n g t h e r e c o v e r e d 3 8 m m a n d 7 5 m m p a r t i c l e s on t h e Point. G r e y t i d a l flat for a p e r i o d of weeks. T h e b e a c h e x p e r i m e n t s d e m o n s t r a t e t h a t coarse m a t e r i a l m o v e s o n s h o r e u n d e r  the  a c t i o n of waves a n d t i d e s . S p e c i f i c a l l y , i n t h e e x p e r i m e n t p a r t i c l e s s t a r t e d a p p r o x i m a t e l y m i d foreshore w i l l creep o n s h o r e a n d t h e n m o v e i n t h e l o n g s h o r e d i r e c t i o n i n t h e wave s w a s h z o n e at h i g h t i d e . T h e p a r t i c l e m o t i o n is i n e x t r i c a b l y l i n k e d w i t h t h e t i d a l range, r i s i n g t i d e s a d v a n c e t h e p o s i t i o n of t h e b r e a k i n g w a v e across t h e p r o f i l e c a u s i n g o n s h o r e m o v e m e n t over d i s t a n c e s g r e a t e r t h a n t h a t p o s s i b l e i n t h e absence o f t i d e s . T h e course p a r t i c l e s were o b s e r v e d t o m o v e o n l y i n the i m m e d i a t e v i c i n i t y of t h e b r e a k i n g wave. M o v e m e n t , of the 3 8 m m p a r t i c l e s o n s h o r e was h i n d e r e d b y the fact t h a t t h e y t e n d e d to b e c o m e n e s t e d w i t h i n t h e l a r g e r c o b b l e m a t r i x o n w h i c h t h e y were p l a c e d as i n d i c a t e d b y t h e m a p of p a r t i c l e d i s p e r s i o n , figures 23 a n d 24.  It shows t h a t p a r t i c l e d i s p e r s i o n  is slow or h i n d e r e d i n t h e v i c i n i t y of t h e t r a c e r o r i g i n b u t o n c e t h e p a r t i c l e s r e a c h the u p p e r foreshore swash z o n e d i s p e r s i o n is r a p i d . A p p r o x i m a t e l y 10 p e r c e n t of t h e 3 8 m m p a r t i c l e s p l a c e d o n t h e b e a c h were b u r i e d a n d n o t r e c o v e r e d . T h e 7 5 m m m e d i a n size p a r t i c l e s s h o w e d l i t t l e m o v e m e n t over t h e t w o days of the  Chapter 3. FIELD INVESTIGATIVE  WORK  38  e x p e r i m e n t , figures 25 a n d 26. T h e 38 m m p a r t i c l e s s h o w e d c o n s i d e r a b l e m o b i l i t y , w h i l e t h e 6 m m p a r t i c l e s were v e r y m o b i l e a n d were so w i d e l y d i s p e r s e d t h a t c o u n t i n g t h e p a r t i c l e s was n o t a t t e m p t e d , p h o t o s 2 a n d 3. It also was a p p a r e n t t h a t a large f r a c t i o n of t h e 6 m m p a r t i c l e s p l a c e d o n t h e shore b e c a m e b u r i e d , h o w e v e r , t h e r a n g e of p a r t i c l e m o v e m e n t a n d a p p r o x i m a t e c e n t r o i d of the p a r t i c l e mass was r e c o r d e d , t a b l e s 4 ( a ) a n d 4(b).  T h e 6 m m p a r t i c l e s r e m a i n e d i n t h e u p p e r foreshore i n w a v e s w a s h z o n e at h i g h  t i d e , n o p a r t i c l e s were f o u n d to m o v e i n t h e offshore d i r e c t i o n . T h e p a r t i c l e s were p l a c e d on t h e b e a c h s u c h t h a t the size p l a c e d was a p p r o x i m a t e l y i n t h e l o c a t i o n of n a t i v e m a t e r i a l of t h e s a m e size; the 6 m m p a r t i c l e s were p l a c e d i n t h e u p p e r foreshore a n d t h e l a r g e r 38 a n d 75 m m p a r t i c l e s were p l a c e d l o w e r o n t h e b e a c h , p h o t o 2. T h e t r a v e l o f t h e c e n t r o i d of t h e p a r t i c l e m a s s , t h e m a x i m u m d i s t a n c e t r a v e l l e d a n d e x p o s u r e t i m e of t h e p a r t i c l e s t o w a v e a n d t i d a l a c t i o n were r e c o r d e d a n d r a t e s of l i n e a r transport, of t h e p a r t i c l e s o n s h o r e a n d l o n g s h o r e were c a l c u l a t e d .  The  d a t a i n d i c a t e s that, t h e h i g h e s t t r a n s p o r t r a t e was t h a t of the 6 m m p a r t i c l e s p l a c e d i n t h e u p p e r foreshore. T h e result, is c o n s i s t e n t w i t h field o b s e r v a t i o n a n d m e a s u r e d b e a c h profiles i n d i c a t i n g u p p e r foreshore t r a n s p o r t . s u m m a r i z e d in tables 4(a) a n d 4(b).  R a t e a n d d i s t a n c e of p a r t i c l e t r a v e l are  Chapter 3. FIELD INVESTIGATIVE  WORK  LONGSHORE TRANSPORT  OF PARTICLES  Particle  Wave  Diameter  Exposure  Centroid  Maximum  Centroid  Maximum  (mm)  (hr)  (m)  (m)  (m/hr)  (m/hr)  6  4  10  75  2.5  18  6  8  26  102  3.3  13  38  5  1  23  0.2  4.6  38  10  2  40  0.2  4.0  75  8  1  4  0.13  0.5  75  16  2  5  0.13  0.31  Transport. Distances  Transport Rates  t a b l e 4(a)  ONSHORE  TRANSPORT  OF PARTICLES  Particle  Wave  Diameter  Exposure  Centroid  Maximum  Centroid  Maximum  (mm)  (hr)  (m)  (m)  (m/hr)  (m/hr)  6  4  0  9  0  2,3  6  8  0  9  0  2.3  38  5  0.5  6  0.1  1.2  38  10  1.0  9  0.1  0.9  75  8  0.5  4  0.063  0.5  75  16  1.0  4  0.063  0.25  Transport Distances  t a b l e 4(b)  Transport Rates  Chapter 3.  3.7  FIELD  INVESTIGATIVE  WORK  40  Bluff E r o s i o n - C u r r e n t Status of K n o w l e d g e  W a v e i n d u c e d bluff e r o s i o n is a l o c a l c o a s t a l e n g i n e e r i n g p r o b l e m a n d is r e v i e w e d i n t h i s s t u d y as a s i d e l i n e m a i n l y b e c a u s e of its l o c a l s i g n i f i c a n c e . T h e p r o b l e m is n o t d i s c u s s e d i n d e t a i l b u t r a t h e r a n o v e r v i e w of t h e c u r r e n t s i t u a t i o n is g i v e n w i t h reference to r e l a t e d studies. B l u f f s of s t r a t i f i e d p l e i s t o c e n e s e d i m e n t s such as Q u a d r a S a n d are c o m m o n a l o n g the i n n e r s o u t h coast of B r i t i s h C o l u m b i a [5]. I n d e v e l o p e d areas l a n d o w n e r s are  affected  b y r e c e d i n g bluffs, t h e loss of p r o p e r t y s o m e t i m e s p o s i n g a t h r e a t t o b u i l d i n g s , roads a n d o t h e r c i v i l w o r k s . S o m e l o c a l cases h a v e b e e n s t u d i e d e x t e n s i v e l y , most, n o t a b l y the e r o s i o n p r o b l e m at P o i n t G r e y . F i e l d i n v e s t i g a t i v e w o r k i n c l u d e d s t u d y of s e v e r a l bluff e r o s i o n sites o n t h e i n n e r s o u t h coast of B r i t i s h C o l u m b i a as s u m m a r i z e d i n t a b l e 5.  SOME ERODING COASTAL SOUTH WEST BRITISH  BLUFFS  COLUMBIA  Index  Site  2  E n g l i s h Bluff, Tsawwassen  2  Southern Shore, Point Roberts  3  Tower Beach, Point G r e y  9  Savary Island Southeast  10  C a p e M u d g e , Q u a d r a Island  13  Cape Lazo, Comox  16  W i l l e m a r Bluffs, C o m o x  19  K o m a s Bluff, D e n m a n Island  25  Cordova Bay, Saanich  table 5  Chapter 3. FIELD INVESTIGATIVE  WORK  41  B l u f f m a t e r i a l s c o n s i s t t y p i c a l l y of Q u a d r a S a n d o r u n c o n s o l i d a t e d s i l t - c l a y s of pleistocene origin.  W i t h t h e e x c e p t i o n of T o w e r B e a c h , P o i n t G r e y , t h e sites i n v e s t i g a t e d  were u n p r o t e c t e d a n d a c t i v e l y e r o d i n g . A t m a n y of t h e sites l o c a l residents h a v e m a d e a t t e m p t s t o c o n s t r u c t s t r u c t u r e s to r e d u c e bluff e r o s i o n , h o w e v e r , m o s t s t r u c t u r e s were not e n g i n e e r e d a n d were e i t h e r n o t w o r k i n g or f a i l i n g . W i l l e m a r Bluffs at C o m o x is one s u c h site w h e r e r e s i d e n t s h a v e c o n s t r u c t e d g r o y n e s a n d r i p r a p w i t h l i m i t e d success i n an a t t e m p t t o arrest t h e r e c e s s i o n , p h o t o s 21 a n d 22. T h e bluffs are a c t i v e c o n t r i b u t o r s t o s e d i m e n t t r a n s p o r t a l o n g t h e coast, a n d i n some cases s p i t s h a v e d e v e l o p e d d o w n c o a s t of t h e sites. S a n d y t i d a l flats of v a r y i n g w i d t h a n d a steep u p p e r b e a c h at t h e foot of t h e b l u f f s . a r e u s u a l .  S a n d y t i d a l flats are d e r i v e d  f r o m b l u f f s e d i m e n t s or are of f l u v i a l o r i g i n as is t h e case at T s a w w a s s e n a n d P o i n t G r e y w h e r e s e d i m e n t s are p r e d o m i n a n t l y f r o m t h e F r a s e r R i v e r . U p p e r b e a c h slopes are u s u a l l y a b o u t 1V:6H e x t e n d i n g f r o m t h e a b r u p t s l o p e c h a n g e at the i n t e r s e c t i o n of the ' t i d a l flat a n d u p p e r b e a c h s h o r e w a r d t o t h e bluff t o e , figure 27 a n d p h o t o 13. T h e u p p e r b e a c h c h a r a c t e r i s t i c a l l y has a g r a v e l or c o b b l e a r m o u r e d surface b u t m a y be o v e r l a i d w i t h a lens of s a n d of v a r y i n g t h i c k n e s s g i v i n g t h e b e a c h surface a s a n d y a p p e a r a n c e , figure 27 a n d p h o t o 21. T h e s a n d lens is t r a n s i e n t i n n a t u r e , p h o t o 22, its presence o n t h e foreshore a f u n c t i o n of u p c o a s t s u p p l y a n d recent w a v e a c t i v i t y . Test p i t s at s e v e r a l sites i n d i c a t e t y p i c a l s a n d lens t h i c k n e s s e s of 0.5 m e t r e s a n d a c o b b l e a r m o u r e d forshore b e n e a t h the s a n d lens s u g g e s t i n g t h a t t h e c o b b l e a r m o u r is a m o r e p e r m a n e n t a n d s t a b l e feature. A c o b b l e layer of g l a c i a l o r i g i n c a n u s u a l l y be f o u n d at m o s t sites at t h e bluff t o p or w i t h i n t h e b l u f f s t r a t i g r a p h y , p h o t o 17. T h r o u g h the e r o s i o n process t h e c o b b l e finds its w a y t o t h e foreshore p r o v i d i n g a degree of p r o t e c t i o n a g a i n s t f u r t h e r foreshore e r o s i o n . F o r e s h o r e c o b b l e densities m a y v a r y f r o m a few s c a t t e r e d c o b b l e s u c h as t h a t at C o r d o v a B a y , S a a n i c h t o dense c o b b l e b o u l d e r beaches s u c h as t h o s e at C a p e M u d g e , Q u a d r a  Chapter  3.  FIELD  INVESTIGATIVE  WORK  42  I s l a n d , p h o t o 18, t h e d e n s i t y of t h e bluff t o p c o b b l e s u p p l y i n p a r t d e t e r m i n i n g t h e s t a t e of foreshore a r m o u r i n g .  D e n s e bluff t o p c o b b l e sources s u c h as t h a t at C a p e M u d g e ,  Q u a d r a I s l a n d , for e x a m p l e , h a v e c r e a t e d h e a v i l y a r m o u r e d beaches.  T h e cobble and  b o u l d e r foreshores m a y be m o b i l e u n d e r s t o r m w a v e a c t i o n as i n d i c a t e d b y s e d i m e n t t r a n s p o r t e x p e r i m e n t s a n d c o b b l e / b o u l d e r s p i t s d o w n c o a s t of t h e bluffs such as R e b e c c a S p i t , Q u a d r a I s l a n d a n d G o o s e S p i t , C o m o x , p h o t o s 19 a n d 20. F o r e s h o r e s t a b i l i t y is t h e c o n t r o l l i n g process i n bluff r e c e s s i o n , t h e e l e v a t i o n of t h e foreshore u l t i m a t e l y affecting r u n - u p d i s t a n c e s i n t o b a c k s h o r e areas.  Considering only  w a v e b a s e d e r o s i o n , b l u f f recession m a y be t h o u g h t of as a f u n c t i o n of foreshore e l e v a t i o n change.  B l u f f r e c e s s i o n m a y be e x p r e s s e d as R = my  w h e r e m=  beach slope and y =  f o r e s h o r e e l e v a t i o n c h a n g e , figure 28. O t h e r factors c o n t r i b u t i n g t o bluff recession i n c l u d e w i n d e r o s i o n , r a i n , freeze/ t h a w c y c l i n g a n d  floating  debris impacts.  L o g s a n d o t h e r b u o y a n t d e b r i s f r e q u e n t l y l i n e t h e u p p e r foreshore c o n t r i b u t e signific a n t l y t o t h e e r o s i o n process t h r o u g h i m p a c t s at t h e bluff t o e u n d e r wave a c t i o n , p h o t o 18. S a n d a p r o n s t e n d t o f o r m a r o u n d t h e bluff toe d u r i n g t h e s u m m e r w h e n t h e r e is l i t t l e s t o r m w a v e a c t i o n i n i n n e r c o a s t a l w a t e r s , p h o t o s 2 1 , 2 3 , 25 a n d 27, s a n d  flowing  down  t h e b l u f f face p r i m a r i l y b y w i n d e r o s i o n d u r i n g s u m m e r m o n t h s . E l e v a t i o n s m e a s u r e d at t h e t o e of t h e s a n d a p r o n s i n d i c a t e t h a t t h e y are t y p i c a l l y a m e t r e or m o r e b e l o w w i n t e r d e b r i s l i n e s . T h u s a l a r g e c o n t r i b u t i o n of s a n d size s e d i m e n t s t o t h e coast f r o m the bluffs o c c u r s t h r o u g h t h e e r o s i o n of the s a n d a p r o n s p r i m a r i l y f r o m w i n t e r s t o r m w a v e a c t i v i t y associated w i t h high tides.  T h e s e a s o n a l changes f r o m s u m m e r t o w i n t e r at t h e bluff  sites c a n b e d r a m a t i c as e x e m p l i f i e d by p h o t o s 21 t o 28. G l a c i a l t i l l bluffs a l o n g t h e n o r t h shore of L a k e E r i e h a v e also b e e n s t u d i e d b y K a m p h i u s [27]. T h e bluffs s t u d i e d were t y p i c a l l y h a r d c o h e s i v e m a t e r i a l w i t h t e n p e r c e n t of  Chapter 3. FIELD INVESTIGATIVE  WORK  4 3  t h e t o t a l b l u f f m a s s b e a c h size s a n d or coarser. A l t h o u g h t h e bluff e r o s i o n r a t e is a c o m b i n a t i o n o f l a n d a n d wave b a s e d processes K a m p h i u s i d e n t i f i e d t h e c o n t r o l l i n g process i n b l u f f r e c e s s i o n as e r o s i o n of t h e foreshore b y waves.  Bluffs a l o n g t h e n o r t h shore of  L a k e E r i e a p p a r e n t l y d o not e x h i b i t c o b b l e a r m o u r i n g as do the bluffs o n the i n n e r s o u t h coast. K a m p h i u s f o u n d t h a t t h e l o n g t e r m s h o r e l i n e recession r a t e is r e l a t e d t o t h e l o n g t e r m average w a v e p o w e r . H i s c o n c l u s i o n s were s u p p o r t e d b y a t h e o r e t i c a l l y d e v e l o p e d e x p r e s s i o n a n d field m e a s u r e m e n t s .  Chapter 4  LABORATORY  4.1  BEACHES  General  L a b o r a t o r y b e a c h e x p e r i m e n t s c a r r i e d o u t i n w a v e flumes d e m o n s t r a t e on-offshore sedim e n t t r a n s p o r t a n a l o g o u s t o t h e m o v e m e n t o f s a n d k n o w n t o o c c u r o n o p e n coast s a n d y beaches d u e t o s e a s o n a l v a r i a t i o n i n w a v e c l i m a t e .  L a b o r a t o r y beaches h a v e been re-  v i e w e d t o p r o v i d e a d d i t i o n a l scope t o t h i s i n v e s t i g a t i o n . In t h e s t u d y of beaches o n e o b j e c t i v e is t o r e l a t e t h e profile changes t o t h e w a v e c o n d i t i o n s c a u s i n g t h o s e changes. A p r o b l e m has b e e n t h e l a c k of a r e a d i l y m e a s u r a b l e v a r i a b l e i n t e r r e l a t i n g s e d i m e n t m o v e m e n t a n d waves.  A p r o b l e m identified i n defining  s u c h a v a r i a b l e has b e e n t h e fact t h a t a b e a c h p r o f i l e has n o l e n g t h scale. W a v e s m a y be a s s i g n e d a w a v e l e n g t h b u t t h e b e a c h profile c a n o n l y b e a s s i g n e d a s l o p e w h i c h is d i m e n s i o n l e s s ; a v a r i a b l e i n t e r r e l a t i n g b e a c h s e d i m e n t s a n d waves m u s t c i r c u m v e n t t h i s fact. S u c h a v a r i a b l e m a y be defined b y d i f f e r e n c i n g a n i n i t i a l b e a c h profile a n d the profile e v o l v i n g as a f u n c t i o n of t i m e u n d e r w a v e a c t i o n w h i c h r e s u l t s i n a n a r e a swept b e t w e e n t h e t w o profiles.  O v e r t i m e sediment, a c t i v i t y causes v o l u m e t r i c , changes i n a  b e a c h w h i c h m a y b e r e l a t e d t o t h e w a v e c o n d i t i o n s c a u s i n g t h e change t h r o u g h swept area variable.  out  the  T h e s w e p t a r e a is r e l a t e d t o t h e v o l u m e of m a t e r i a l t h a t moves  r e l a t i v e t o a n i n i t i a l p r o f i l e i n r e s p o n s e t o t h e p r o f i l e a d j u s t i n g its s h a p e t o a n i m p o s e d wave c o n d i t i o n .  44  Chapter 4. LABORATORY  BEACHES  45  B e a c h e s are d y n a m i c , i n t h a t t h e surface p r o f i l e r e s p o n d s a n d adjusts  its s h a p e t o  a n i m p o s e d w a v e c o n d i t i o n . S e d i m e n t a c t i v i t y i n d u c e d b y fluid t u r b u l e n c e g e n e r a t e d b y b r e a k i n g or s u r g i n g waves alters t h e profile over t i m e . A b e a c h has n o e l a s t i c i t y ; o n c e w a v e a c t i o n s t o p s t h e r e is n o f u r t h e r r e s p o n s e . B e a c h e s t e n d to e v o l v e t o a n e q u i l i b r i u m profile w h e n s u b j e c t t o a c o n s t a n t w a v e c o n d i t i o n a n d o n c e e q u i l i b r i u m has b e e n a c h i e v e d t h e r e w i l l be n o f u r t h e r s i g n i f i c a n t response p r o v i d e d t h a t the w a v e c o n d i t i o n r e m a i n s c o n s t a n t . T h e e q u i l i b r i u m b e a c h profile w i l l d i s s i p a t e a n d / or reflect a l l t h e wave-energy r e a c h i n g it i n such a m a n n e r t h a t n o net t r a n s p o r t of t h e b e a c h s e d i m e n t o c c u r s a n y w h e r e a l o n g t h e b e a c h profile. L a b o r a t o r y beaches i n w a v e flumes are i d e a l i z e d c l o s e d s e d i m e n t a r y e n v i r o n m e n t s i n w h i c h p a r t i c l e s are m o b i l i z e d b y b r e a k i n g or s u r g i n g waves.  I n such a n i d e a l s y s t e m  s e d i m e n t m a s s is c o n s e r v e d a n d therefore b e a c h s u b s u r f a c e v o l u m e is c o n s t a n t . field  beaches u s u a l l y h a v e a net offshore loss of m a t e r i a l a n d i n a d d i t i o n t h e r e m a y be  l o n g s h o r e sediment  4.2  In the  movement.  Active Volume  T o define b e a c h r e s p o n s e on-offshore s e d i m e n t t r a n s p o r t has been i d e a l i z e d as o c c u r i n g w i t h i n a c l o s e d s y s t e m b o u n d e d b y s h o r e w a r d a n d s e a w a r d l i m i t s of s e d i m e n t m o v e m e n t a n d u p p e r a n d l o w e r profiles. d e l i m i t e d b y these b o u n d a r i e s .  P a r t i c l e s are r e c y c l e d b y w a v e a c t i o n w i t h i n a n  area  T h e m e a s u r a b l e v o l u m e of m a t e r i a l d i s p l a c e d b y waves  d u r i n g a p e r i o d of t i m e w i t h i n t h i s i d e a l i z e d on-offshore t r a n s p o r t s y s t e m is defined as a c t i v e v o l u m e w h i c h is e q u a l t o h a l f of t h e a r e a s w e p t b e t w e e n t w o successive profiles, figure  29.  S i m i l a r d e f i n i t i o n s m a y be m a d e for gross v o l u m e a n d net v o l u m e , h o w e v e r ,  t h e y are of a c a d e m i c i n t e r e s t .  T h e r e is a f i x e d i n i t i a l l y k n o w n p r o f i l e a n d a n e v o l v i n g  profile that, varies w i t h t i m e , the a c t i v e v o l u m e as a f u n c t i o n of t i m e b e i n g defined as  Chapter  4.  LABORATORY  46  BEACHES  h a l f t h e a r e a s w e p t o u t b e t w e e n t h e t w o profiles as a f u n c t i o n of t i m e . is p o s i t i v e for a c c r e t i v e beaches a n d n e g a t i v e for erosive beaches.  Active volume  T h e volume actually  r e p r e s e n t s t h e a m o u n t of m a t e r i a l t h a t m u s t moves o n a b e a c h r e l a t i v e t o a reference or d a t u m p r o f i l e i n o r d e r for t h e b e a c h p r o f i l e t o adjust to t h e i m p o s e d w a v e c o n d i t i o n . S i n c e t h e swept a r e a r e p r e s e n t i n g a c t i v e v o l u m e evolves as a f u n c t i o n of t i m e t h e t i m e d e r i v a t i v e s of t h e areas m a y also be d e f i n e d t o g i v e rates of e r o s i o n or a c c r e t i o n a n d s i m i l a r l y t i m e d e r i v a t i v e s of these rates, figure 30. T h e height a n d p e r i o d of the i m p o s e d wave as a f u n c t i o n of t i m e c o m b i n e to f o r m a wave steepness as a f u n c t i o n of t i m e w h i c h d e t e r m i n e s t h e c h a r a c t e r of fluid t u r b u l e n c e a n d t h u s the d i r e c t i o n of s e d i m e n t m o v e m e n t .  4.3  Dimensional Analysis  T h e f o l l o w i n g f u n c t i o n a l r e l a t i o n s h i p m a y be e x p r e s s e d for on-offshore t r a n s p o r t o n i n i t i a l l y flat beaches subject, t o m o n o c h r o m a t i c waves:  V  a  = f{H ,T, 0  W h e r e t h e v a r i a b l e s are defined as f o l l o w s :  V  = a c t i v e v o l u m e of s e d i m e n t ;  a  H  — d e e p w a t e r wave h e i g h t ;  D  T  = wave period;  JD O — m e d i a n s e d i m e n t size; 5  p = p  s  fluid  density;  = sediment density;  p. = fluid  d y n a m i c viscosity;  D ,p,p ,g,fi,mi,t) 50  s  Chapter  4.  LABORATORY  47  BEACHES  g = a c c e l e r a t i o n d u e to g r a v i t y ;  ?7i,: = i n i t i a l b e a c h slope;  t  =  time.  T h e d e p e n d e n t v a r i a b l e is V ,  t h e r e m a i n i n g variables b e i n g i n d e p e n d e n t .  Using L  fi/p  a  = gT /2ir  a n d // =  2  0  where L —  water wave l e n g t h a n d v— kinematic,  0  viscosity, t h e r e l a t i o n s h i p m a y be r e d u c e d t o t h e f o l l o w i n g d i m e n s i o n l e s s  V  a  ( (  H  D  0  HL 0  L'  0  L"  0  vT  b0  -r—,  —— = J( —,  0  p  , —, m,-  HL' 0  p"  o  groups:  t,  ' T  l  s  It m i g h t be a s s u m e d t h a t t h e effects of f l u i d viscosity w o u l d b e n e g l i g i b l e a n d t h a t t h e r a t i o o f s a n d d e n s i t y to f l u i d d e n s i t y m i g h t be c o n s i d e r e d n e a r l y c o n s t a n t , thus  the  r e l a t i o n s h i p r e d u c e s to:  V*  H  HnL  L  n  D  Q  t  50  L,  n  r  for e q u i l i b r i u m profiles:  V  H  HL  L  a  0  0  D  0  50  ,  L  0  c  alternatively, the preceeding relationship m a y be written:  V„. H gT  2  0  t {  H  D  0  t  50  •'gT^gT '  T'  2  S i m i l a r l y , t h e s e d i m e n t a c t i v i t y m a y be e x p r e s s e d i n d i m e n s i o n l e s s f o r m for i n i t i a l l y flat profiles:  Qa  ,, Ho  D  H gT  L  L  is s e d i m e n t  activity.  a  where O  a  = dV /dt a  0  5Q  0  t T  Chapter  4.  LABORATORY  BEACHES  48  T h e c o n c e p t o f a c t i v e v o l u m e m a y b e e x t e n d e d t o n a t u r a l beaches, h o w e v e r , a d d i t i o n a l c o n s i d e r a t i o n s are r e q u i r e d . N a t u r a l b e a c h profiles are forever c h a n g i n g s h a p e a n d do n o t h a v e a flat s t a r t i n g p r o f i l e w h i c h m a y be u s e d as a d a t u m for m e a s u r i n g a c t i v e v o l u m e , t h u s a reference profile or d a t u m , w h i c h m a y n o t n e c e s s a r i l y b e flat as i n t h e l a b o r a t o r y , should be defined.  T h e reference profile s h o u l d l i e w i t h i n a n e n v e l o p e d e s c r i b e d b y  m a x i m u m a n d m i n i m u m o r d i n a t e s o f a series of shore n o r m a l profiles [7]. A reference p r o f i l e for n a t u r a l beaches m i g h t b e d e f i n e d as a c u r v e fit b e t w e e n o r d i n a t e p o i n t s d e s c r i b i n g u p p e r a n d l o w e r profiles or p e r h a p s as a n average t r a n s i t i o n profile for w h i c h t h e r e is n e i t h e r s t r o n g o n s h o r e or offshore t r a n s p o r t .  A d e f i n i t i o n o f a reference  profile w i l l l i k e l y i n v o l v e l o n g e r t e r m o b s e r v a t i o n a n d s t u d y of t h e e v o l u t i o n a r y shapes of n a t u r a l beaches a n d is t h u s a t o p i c for f u r t h e r r e s e a r c h . W h e t h e r o r n o t t h e e q u i l i b r i u m a c t i v e v o l u m e is t h e s a m e for b o t h a c c r e t i v e a n d erosive profiles w i l l l i k e l y d e p e n d u p o n t h e d e f i n i t i o n o f t h e reference profile a g a i n s t w h i c h t h e v o l u m e s are m e a s u r e d . F o r non-flat, i n i t i a l profiles a p a r a m e t e r for t h e s t a t e of t h e i n i t i a l profile is also r e q u i r e d i d e n t i f y i n g h o w close t h e i n i t i a l profile is t o e q u i l i b r i u m . S u c h a ' s t a t e ' p a r a m e t e r might, be d e f i n e d : g  w h e r e S= s t a t e p a r a m e t e r , V = aeq  I aeq 1  " ai \  e q u i l i b r i u m a c t i v e v o l u m e for t h e i m p o s e d wave  c o n d i t i o n measured relative to a d a t u m profile a n d V = a7  t o t h e reference profile.  initial active volume relative  F o r e x a m p l e , i f t h e i n i t i a l p r o f i l e is a l r e a d y at e q u i l i b r i u m for  t h e i m p o s e d wave c o n d i t i o n t h e n 5 = 0 i m p l y i n g n o response; i f t h e s t a r t i n g profile b y s o m e c h a n c e is e q u a l t o t h e reference p r o f i l e t h e n 5 = 1 i n d i c a t i n g b e a c h response; i f t h e s t a r t i n g p r o f i l e is erosive a n d t h e i m p o s e d wave c o n d i t i o n r e s u l t s i n a c c r e t i o n t h e n 5  > 1 i m p l y i n g a l a r g e r v o l u m e o f s e d i m e n t is i n v o l v e d i n t h e response.  T h e initial  s h a p e o f a b e a c h p r o f i l e does n o t affect t h e final s h a p e a t t a i n e d u n d e r a n i m p o s e d w a v e  Chapter  4.  LABORATORY  49  BEACHES  c o n d i t i o n , h o w e v e r , t h e t i m e t o achieve e q u i l i b r i u m is c e r t a i n l y affected as r e c o g n i z e d by most  researchers.  In g e n e r a l t h e a c t i v e v o l u m e of s e d i m e n t o n a b e a c h as a f u n c t i o n of t i m e is: V HL 0  a  ^  0  =  t  /(C,7,S -) )  ^ ' " ~ T  where C  = an on-offshore p a r a m e t e r c o m b i n i n g d i m e n s i o n l e s s g r o u p s H /L , 0  D /L  0  50  o  and  I = w a v e i n t e n s i t y t o a c c o u n t for t h e m a g n i t u d e o f v o l u m e t r i c change; S = s t a t e p a r a m e t e r for non-flat i n i t i a l profiles; t/T  — dimensionless time. A c t i v e v o l u m e m a y h a v e a p o s i t i v e or n e g a t i v e s i g n c o r r e s p o n d i n g t o o n s h o r e or  offshore t r a n s p o r t  respectively.  T h e s i g n m a y be d e t e r m i n e d b y i n t e g r a t i n g the  bed  e l e v a t i o n changes across t h e b e a c h profile f r o m o n s h o r e to offshore i n a m a n n e r s i m i l a r t o t h e m e t h o d u s e d b y v a r i o u s researchers [46], [22] t o d e t e r m i n e t r a n s p o r t rates across t h e profile. If t h e net s e d i m e n t v o l u m e is p r e d o m i n a n t l y o n s h o r e t h e n V  a  is c o r r e s p o n d i n g l y n e g a t i v e for p r e d o m i n a n t l y offshore t r a n s p o r t .  is p o s i t i v e a n d  T h u s active volume  is e v a l u a t e d b y e x a m i n i n g s e d i m e n t transport, across the e n t i r e profile a n d the sign is determined by the p r e d o m i n a n t transport d i r e c t i o n . R e s e a r c h e r s [46], [22] h a v e classified t h r e e b a s i c t y p e s of b e a c h profiles: profiles developed by strong onshore transport,  n e u t r a l profiles d e v e l o p e d b y b o t h o n s h o r e  and  offshore t r a n s p o r t s h o r e w a r d a n d s e a w a r d of t h e b r e a k e r zone a n d profiles d e v e l o p e d by s t r o n g offshore t r a n s p o r t . A c t i v e v o l u m e defines n e u t r a l profiles as e i t h e r b e i n g a c c r e t i v e or e r o s i v e d e p e n d i n g u p o n t h e p r e d o m i n a n t t r a n s p o r t d i r e c t i o n . T h u s , t h e a c t i v e v o l u m e a p p r o a c h t o on-offshore transport, has the d i s a d v a n t a g e of not c l e a r l y i d e n t i f y i n g n e u t r a l profiles w h e r e s e d i m e n t t r a n s p o r t m a y ' l o c a l l y be o c c u r i n g i n b o t h d i r e c t i o n s .  Chapter 4.  4.4  LABORATORY  BEACHES  50  A n a l y s i s of Beach Profiles  L a b o r a t o r y e x p e r i m e n t s o n beaches have not b e e n c a r r i e d out as p a r t of t h e present s t u d y , b u t r a t h e r , p r e v i o u s s t u d i e s were referred to for d a t a [46], [22] a n d [38]. P r o f i l e s are p r e s e n t e d i n figures 6 t o 8 a n d d e t a i l s of the e x p e r i m e n t s are o u t l i n e d i n s e c t i o n 2.7. It was f o u n d t h a t s o m e researchers present l a b o r a t o r y b e a c h profiles i n s u c h a m a n n e r t h a t t h e e x t r e m e s of t h e a c t i v e p r o f i l e are not i n c l u d e d . B e a c h profiles s h o u l d e n c o m p a s s a l l o f t h e p r o f i l e f r o m the offshore l i m i t t o t h e o n s h o r e l i m i t of s e d i m e n t m o v e m e n t a n d s h o u l d h a v e a p p r o p r i a t e h o r i z o n t a l a n d v e r t i c a l scales i n d i c a t e d .  4.4.1  M e t h o d of analysis  T h e m e t h o d of a n a l y s i s of b e a c h p r o f i l e d a t a l a r g e l y i n v o l v e d t h e d e t e r m i n a t i o n of h i g h l y i r r e g u l a r s w e p t areas b e t w e e n p r o f i l e s . T h e f o l l o w i n g p r o c e d u r e was c a r r i e d o u t : 1. S w e p t areas or a c t i v e v o l u m e s were d e t e r m i n e d b y p h o t o g r a p h i c a l l y e n l a r g i n g scale b e a c h p r o f i l e d r a w i n g s b y f o u r - h u n d r e d p e r c e n t , p l a c i n g a m y l a r g r i d over the enlargement, a n d i d e n t i f y i n g x , y d a t a p o i n t s t h a t best d e s c r i b e t h e i n i t i a l a n d  final  profile a n d s c a l i n g t h o s e p o i n t s t o l a b o r a t o r y scale.  2. T h e s c a l e d x , y d a t a were e n t e r e d i n t o a d a t a file w h i c h was i n p u t to a c o m p u t e r p r o g r a m w r i t t e n to calculate active volumes. T h e a c t i v e v o l u m e s were p l o t t e d a g a i n s t wave h e i g h t , p e r i o d a n d t i m e d i m e n s i o n a l l y and non- d i m e n s i o n a l l y using a computer spreadsheet and g r a p h p l o t t i n g program.  4.4.2  A c t i v e v o l u m e versus wave height  T h e r e l a t i o n s h i p b e t w e e n a c t i v e v o l u m e of s e d i m e n t a n d w a v e h e i g h t was i n v e s t i g a t e d using beach profile d a t a f r o m experiments conducted by W a t a n a b e , R i h o and H o r i k a w a  Chapter 4. LABORATORY  BEACHES  51  [46]. B e a c h e s were t e s t e d u n d e r different c o m b i n a t i o n s of i n i t i a l slope a n d m e d i a n p a r t i c l e d i a m e t e r , figure 6:  B e a c h 1: D = 50  0 . 7 m m , m,=  B e a c h 2: L > = 0 . 7 m m , m 50  B e a c h 3: D  50  B e a c h 4:  50  D  0.10;  0.05;  F  = 0 . 2 2 m m , m , = 0.10;  = 0 . 2 2 m m , ??7,= 0.05. 7  W a v e s were m o n o c h r o m a t i c w i t h p e r i o d h e l d c o n s t a n t at T— 1.0, 1.5 a n d 2.0 seconds a n d h e i g h t v a r i e d for each of these p e r i o d s . D u r a t i o n of w a v e a c t i o n was 1 h o u r  therefore  t h e f i n a l profiles a n d a c t i v e v o l u m e s o b t a i n e d d o not n e c e s s a r i l y c o r r e s p o n d t o e q u i l i b r i u m conditions. D a t a has b e e n p l o t t e d d i m e n s i o n a l l y w i t h V  V /(H L ) a  0  0  versus  H /L Q  or  figures 31 t o 34.  a  versus H  0  and non-dimensionally with  L i n e s of c o n s t a n t  p e r i o d are d r a w n o n a l l  plots. A l l beaches are a c c r e t i v e for l o w steepness waves.  Typically, a transition  occurs  f r o m a n a c c r e t i v e b e a c h t o a n erosive b e a c h for wave steepnesses a r o u n d 0.03 w h i c h is c o n s i s t e n t w i t h w a v e steepness values r e p o r t e d i n the l i t e r a t u r e . It is n o t e d t h a t b e a c h 2 m o v e s f r o m a n a c c r e t i v e t o a n e r o s i v e s t a t e at  H /L = 0  0  0.05 a n d b e a c h 4 at  H /L = 0  D  0.01.  T h e r e a s o n for t h e t r a n s i s t i o n i n b e a c h s t a t e at different w a v e steepnesses is u n k n o w n . T h e coarser s a n d ( 0 . 7 m m ) beaches t e n d t o be a c c r e t i v e . T h i s is p a r t i c u l a r l y e v i d e n t for beaches 1 a n d 2 w h i c h show s t r o n g o n s h o r e m o v e m e n t for l o w f r e q u e n c y w a v e s , figures 31 a n d 32. T h e fine s a n d ( 0 . 2 m m ) b e a c h e s t e n d t o be erosive, h o w e v e r , b e a c h 3 shows a c c r e t i o n for l o w f r e q u e n c y waves, figures 33 a n d 34.  Chapter 4. LABORATORY  BEACHES  52  For beaches 1, 2 and 3 the effect of changing wave period is dramatic. For periods of 1.0 and 1.5 seconds there is little beach sediment activity, however, at 2.0 seconds the beach becomes very active showing strong onshore movement.  T h e wave period  and height combine to form a steepness which determines the character of bottom fluid turbulence and thus the direction of movement of sediments. A s one moves outward from the origin along a line of constant period, wave intensity and steepness increases, figures 31 to 34. A n additional parameter such as the wave intensity is presumed to determine the magnitude or rate of sediment movement; some investigators have simply used period in addition to steepness to specify rate of sediment movement.  4.4.3  A c t i v e v o l u m e versus wave p e r i o d  D a t a from experiments carried out by Rector on behalf of the Beach Erosion Board [38], were used to investigate the relationship between active volume of sediemnt and wave period. Four beaches were studied, figures 7 and 35: B e a c h 1: D =  0.22mm, m , = 0.033;  B e a c h 2: D =  0.47mm, m =  0.033;  B e a c h 3: D =  0.90mm, m =  0.033;  50  50  50  B e a c h 4: D  5 0  t  r  = 3.44mm,  = 0.033.  T h e beaches were subject to monochromatic waves w i t h heights nearly constant at about. 120mm and wave period varied over a range from 1.6 to 3.3 seconds. A l l tests were conducted for sufficient duration to achieve equilibrium profiles. D a t a is presented dimensionally with V versus T and non-dimensionally with a  versus gT /D 2  50  size, figure 35.  V /\H L ) a  0  with lines of constant wave height, through data points for each sediment  0  Chapter 4.  LABORATORY  BEACHES  53  T h e p l o t s are u n d e f i n e d for short p e r i o d waves less t h a n a b o u t 0.3 seconds since the l i m i t i n g w a v e steepness due t o b r e a k i n g is e x c e e d e d . A l l beaches, e x c e p t b e a c h 2, show a m a x i m u m r e s p o n s e or sediment, a c t i v i t y at a p a r t i c u l a r wave p e r i o d . A l o n g a l i n e of c o n s t a n t w a v e height, t h e wave i n t e n s i t y a n d steepness decreases as p e r i o d increases. A l l b e a c h r e s p o n s e curves w i l l fall to zero for v e r y l o n g p e r i o d waves since t h e i n t e n s i t y of the fluid t u r b u l e n c e b e c o m e s insufficient t o e n t r a i n a n d m o b i l i z e s e d i m e n t s . F o r s h o r t e r p e r i o d waves the r e s p o n s e decreases b u t does does n o t f a l l t o zero; t h e w a v e i n t e n s i t y is h i g h b u t t h e b e a c h is less a c t i v e b e c a u s e the i n t e n s i t y of the  fluid  t u r b u l e n c e at t h e b e d c a p a b l e of m o b i l i z i n g s e d i m e n t s does not r e a c h t h e d e p t h s a l o n g t h e p r o f i l e t h a t lower f r e q u e n c y waves d o . T h e p l o t of a c t i v e v o l u m e versus wave f r e q u e n c y or p e r i o d m a y b e t h o u g h t of as a r e s p o n s e c u r v e for a b e a c h defined i n t e r m s o f a n a c t i v e on-offshore v o l u m e o f s e d i m e n t a n d w a v e frequency.  F o r fine s e d i m e n t s ( 0 . 2 2 m m s a n d ) t h e c u r v e has t w o m a x i m a i n  s e d i m e n t a c t i v i t y , o n e c o r r e s p o n d i n g t o o n s h o r e t r a n s p o r t a n d one t o offshore  transport.  T h e d a t a shows coarse m a t e r i a l g e n e r a l l y m o v e s o n s h o r e over a w i d e r a n g e of w a v e p e r i o d s t h u s t h e c o n s t a n t h e i g h t c u r v e has one m a x i m a i n s e d i m e n t a c t i v i t y .  4.4.4 Active volume versus time T h e r e l a t i o n s h i p b e t w e e n a c t i v e s e d i m e n t v o l u m e a n d t i m e was also i n v e s t i g a t e d u s i n g profile d a t a f r o m H a t t o r i a n d K a w a m a t a [22]. A s i n g l e b e a c h w i t h m e d i a n p a r t i c l e size of 2 2 m m a n d i n i t i a l s l o p e of 0.05 was t e s t e d u n d e r wave steepnesses of 0.006 a n d 0.035 p r o d u c i n g a c c r e t i v e a n d erosive profiles. D a t a is p l o t t e d d i m e n s i o n a l l y a n d w i t h V /H L a  0  0  versus t/T,  figure  V  a  versus t a n d n o n d i m e n s i o n a l l y w i t h  36.  T h e b e a c h e s h a v e n o t r e a c h e d e q u i l i b r i u m b u t t h e c u r v e shows a n e x p o n e n t i a l increase in the active v o l u m e w i t h t i m e a s y m p t o t i c a l l y approaching an e q u i l i b r i u m active volume  Chapter  4.  LABORATORY  BEACHES  54  of s e d i m e n t as d e s c r i b e d b y t h e r e l a t i o n s h i p :  V (t) a  =  V (C,I)(l-e- ) rt  aeg  Where:  V (t)  = active sediment volume;  Vaeq  =  a  C  e q u i l i b r i u m active volume;  = o n - offshore p a r a m e t e r ;  I = wave i n t e n s i t y ;  r  = time  constant;  t — time.  W h a t t h e r e l a t i o n s h i p states is t h a t as t h e p r o f i l e evolves e x p o n e n t i a l l y t o a n e q u i l i b r i u m s h a p e u n d e r t h e i m p o s e d w a v e c o n d i t i o n t h e v o l u m e of s e d i m e n t t h a t m u s t m o v e r e l a t i v e t o t h e i n i t i a l p r o f i l e or d a t u m t o achieve t h e e q u i l i b r i u m s h a p e also e v o l v e s exponentially to an e q u i l i b r i u m value. T h e e x p o n e n t i a l increase i n active volume of sediment on a beach w i t h t i m e due to an o n s h o r e or offshore t r a n s p o r t m o d e is a c t u a l l y a step l i k e f u n c t i o n , each b r e a k i n g wave m o b i l i z i n g a d i s c r e t e a m o u n t of m a t e r i a l on t h e b e a c h c h a n g i n g the v o l u m e . T h e ' s t e p ' m a y n o t b e r e s o l v a b l e b y o r d i n a r y s u r v e y or m e a s u r e m e n t t e c h n i q u e s a n d i n a n y case t h e profile e v o l u t i o n w i t h t i m e m a y be r e a s o n a b l y a p p r o x i m a t e d w i t h a c o n t i n u o u s f u n c t i o n . T h e p l o t s i n d i c a t e t h a t t h e r e are t w o t y p e s of profiles: a p r o f i l e a s s o c i a t e d w i t h an a c c r e t i v e c o n d i t i o n a n d a profile a s s o c i a t e d w i t h a n e r o s i v e c o n d i t i o n , figure 36.  The  a c t i v e v o l u m e s a s s o c i a t e d w i t h each profile m a y be a s s i g n e d p o s i t i v e a n d n e g a t i v e signs  Chapter 4. LABORATORY  BEACHES  55  r e s p e c t i v e l y . T h e c u r v e s are lines o f c o n s t a n t w a v e steepness, t h u s different w a v e steepnesses p r o d u c e a f a m i l y of such c u r v e s .  A n e u t r a l c o n d i t i o n also e x i s t s w h e r e there is  b o t h o n s h o r e a n d offshore s e d i m e n t m o v e m e n t r e l a t i v e t o the b r e a k e r z o n e a n d t h e r e is r e l a t i v e l y s m a l l v o l u m e t r i c changes.  S i n c e a c t i v e v o l u m e assesses t h e changes  across  t h e e n t i r e p r o f i l e a n d is b a s e d o n t h e p r e d o m i n a n t s e d i m e n t t r a n s p o r t d i r e c t i o n n e u t r a l c o n d i t i o n s w h e r e b o t h o n s h o r e a n d offshore t r a n s p o r t o c c u r m a y n o t be r e a d i l y i d e n t i f i e d using this approach. W h e n a b e a c h has a c h i e v e d e q u i l i b r i u m its a c t i v e v o l u m e is at a m a x i m u m v a l u e for t h e w a v e c o n d i t i o n i m p o s e d , h o w e v e r , b e a c h s e d i m e n t a c t i v i t y is at a. m i n i m u m since n o s u b s t a n t i a l s e d i m e n t a c t i v i t y takes p l a c e at e q u i l i b r i u m . T h u s a r e l a t i o n s h i p m a y be expressed:  Qa(t) = where  Q (t)= dV /dt= a  a  V {CJ)e-  rt  aeq  sediment activity.  T h e t i m e c o n s t a n t r is h y p o t h e s i z e d t o b e a f u n c t i o n of t h e w a v e i n t e n s i t y / for t h e l a b o r a t o r y beaches.  F o r n a t u r a l beaches w h e r e the i n i t i a l profile is n o t flat as i n t h e  l a b o r a t o r y a n d a c t i v e v o l u m e is d e t e r m i n e d r e l a t i v e t o a reference p r o f i l e t h a t is not n e c e s s a r i l y t h e s a m e as t h e s t a r t i n g p r o f i l e t h e t i m e c o n s t a n t r is a f u n c t i o n of b o t h w a v e i n t e n s i t y a n d t h e p r o f i l e state.  Obviously, the t i m e required to reach e q u i l i b r i u m w i l l  be affected b y h o w close t h e s t a r t i n g p r o f i l e is t o e q u i l i b r i u m as i n d i c a t e d b y t h e profile state parameter discussed previously.  Chapter 5  DISCUSSION  Beach Response  5.1  A c o n c e p t o f b e a c h r e s p o n s e t o waves b a s e d u p o n i n v e s t i g a t i o n of field a n d l a b o r a t o r y beaches is s u m m a r i z e d :  • beaches are d y n a m i c , i n e l a s t i c a n d g o v e r n e d b y a n a t u r a l process of s e d i m e n t p a r t i c l e e n t r a i n m e n t a n d m o t i o n i n d u c e d b y f l u i d t u r b u l e n c e g e n e r a t e d b y b r e a k i n g or s u r g i n g waves;  •  beaches e v o l v e t o an e q u i l i b r i u m profile w h e n s u b j e c t t o a c o n s t a n t wave c o n d i t i o n ;  • t h e d i r e c t i o n of on-offshore s e d i m e n t m o v e m e n t o n s a n d y beaches is a f u n c t i o n of w a v e steepness a m o n g o t h e r p a r a m e t e r s ; h i g h steepness s h o r t p e r i o d waves i n i t i a t e offshore m o v e m e n t of s a n d w h i l e l o n g p e r i o d , l o w steepness waves i n i t i a t e o n s h o r e m o v e m e n t of s a n d ;  • w a v e steepness a l o n e m a y i n d i c a t e t h e d i r e c t i o n of s e d i m e n t m o v e m e n t , however, a n a d d i t i o n a l p a r a m e t e r s u c h as w a v e i n t e n s i t y or p e r i o d is r e q u i r e d t o specify t h e m a g n i t u d e or r a t e of s e d i m e n t m o v e m e n t ; • on-offshore m o v e m e n t of s e d i m e n t m a y b e c o n c e p t u a l i z e d by r e p r e s e n t i n g t h e v o l u m e of s e d i m e n t i n v o l v e d i n the e v o l u t i o n of a profile f r o m a n i n i t i a l t o a final s t a t e as a n a r e a s w e p t o u t b e t w e e n the i n i t i a l a n d f i n a l profiles;  56  Chapter  •  5.  DISCUSSION  57  c o a r s e m a t e r i a l beaches (gravels a n d c o b b l e ) g e n e r a l l y t e n d t o be a c c r e t i v e , fine m a t e r i a l beaches (silts a n d s a n d ) m a y b e a c c r e t i v e or erosive d e p e n d i n g u p o n the w a v e steepness, t h i s has been o b s e r v e d i n t h e field [39] as w e l l as i n t h e l a b o r a t o r y [15];  • for a g i v e n wave h e i g h t (or specific w a v e e n e r g y ) , s e d i m e n t size a n d i n i t i a l b e a c h s l o p e a b e a c h w i l l h a v e a m a x i m a i n s e d i m e n t a c t i v i t y at a p a r t i c u l a r w a v e freq u e n c y , fine s e d i m e n t s m a y e x h i b i t t w o m a x i m a i n s e d i m e n t a c t i v i t y , one corres p o n d i n g t o o n s h o r e m o v e m e n t a n d o n e t o offshore m o v e m e n t w h i l e coarse sediments e x h i b i t a single m a x i m a i n sediment a c t i v i t y corresponding to onshore movement.  5.2  Differences Between N a t u r a l a n d L a b o r a t o r y  Beaches  T h e on-offshore a c t i v i t y of b e a c h s e d i m e n t has b e e n d i s c u s s e d w i t h reference t o l a b o r a t o r y d a t a . N a t u r a l beaches m a y differ i n b e h a v i o r f r o m l a b o r a t o r y beaches b e c a u s e of v a r i o u s f a c t o r s , s o m e of w h i c h are o u t l i n e d :  1. N a t u r a l beaches are n o t c l o s e d s e d i m e n t a r y e n v i r o n m e n t s ; t h r o u g h on-offshore sediment transport  fine s e d i m e n t  is often p e r m a n e n t l y lost offshore a n d  longshore  t r a n s p o r t o c c u r s w h e n waves b r e a k o b l i q u e l y t o the shore.  2. T h e on-offshore r e s p o n s e of a b e a c h t o waves d e f i n e d i n t e r m s o f an a c t i v e v o l u m e of sediment, has b e e n s h o w n for l a b o r a t o r y b e a c h d a t a w i t h i n i t i a l l y flat profiles, h o w e v e r , flat i n i t i a l profiles do n o t o c c u r o n n a t u r a l beaches. N a t u r a l beaches s t i l l h a v e a n a c t i v e v o l u m e o f s e d i m e n t , h o w e v e r , t h e reference p r o f i l e or d a t u m r e q u i r e d t o d e t e r m i n e it r e m a i n s u n d e f i n e d . E q u i l i b r i u m b e a c h s h a p e is a s s u m e d t o b e not affected b y the s t a r t i n g profile b u t t h e t i m e t o a c h i e v e e q u i l i b r i u m is.  Chapter  5.  58  DISCUSSION  3. T h e t e r m a c t i v e v o l u m e does n o t i m p l y t h a t o n l y t h e v o l u m e of s e d i m e n t defined by t h e s w e p t a r e a b e t w e e n profiles is a c t u a l l y a c t i v e . F i e l d s t u d i e s h a v e r e p o r t e d t h a t at d e p t h s b e l o w t h e b e a c h surface the s u b s u r f a c e m a t r i x is a c t i v e a n d shearing m o t i o n .  undergoes  F i e l d studies have also suggested a f l u i d i z a t i o n or l i q u i f a c t i o n  l i k e s t a t e of t h e s u b s u r f a c e m a t r i x d u r i n g intense s t o r m waves. A c t i v e V o l u m e is a c t u a l l y a s u b v o l u m e of a c t i v e m a t e r i a l o n a b e a c h r e l a t i v e to a n i n i t i a l profile t h a t moves i n response to the profile evolving to an e q u i l i b r i u m shape.  4. N a t u r a l b e a c h s e d i m e n t s m a y have w i d e l y v a r y i n g -D50, s h a p e a n d d e n s i t y whereas t h e l a b o r a t o r y beaches i n v e s t i g a t e d h a d r e l a t i v e l y h o m o g e n e o u s  sediments.  5. O c e a n waves have a d i s t r i b u t i o n of h e i g h t s a n d p e r i o d s whereas l a b o r a t o r y waves are u s u a l l y m o n o c h r o m a t i c .  N a t u r a l beaches m a y a l w a y s be a d a p t i n g t o a n e w  e q u i l i b r i u m w i t h c h a n g i n g s t o r m w a v e h e i g h t a n d p e r i o d w h i l e l a b o r a t o r y beaches s u b j e c t t o m o n o c h r o m a t i c waves a d a p t t o o n l y a s i n g l e e q u i l i b r i u m s t a t e . 6. T h e effect of t i d e s has not b e e n a c c o u n t e d for i n the l a b o r a t o r y beaches i n v e s t i g a t e d . T i d e s c o n t r i b u t e t o t h e g e o m o r p h i c . d e v e l o p m e n t of beaches b y s h i f t i n g the b r e a k e r p o s i t i o n over t h e profile.  5.3  Coastal Processes  T h e m o r p h o l o g y of i n n e r coast beaches is a f u n c t i o n of i t s s e d i m e n t s , a n d the w a v e , current and tidal regime.  A c o n c e p t of on-offshore s e d i m e n t a c t i v i t y is p r e s e n t e d  for  i n n e r a n d o p e n coast beaches, figure 37. T h e figure presents a n a c t i v e v o l u m e o f s e d i m e n t versus w a v e p e r i o d for waves of c o n s t a n t h e i g h t (or specific, w a v e e n e r g y ) a n d fine m a t e r i a l a n d coarse s e d i m e n t s ; i d e n t i c a l beaches o n i n n e r a n d o p e n coasts are a s s u m e d . A f a m i l y of s u c h c u r v e s e x i s t s for v a r i o u s s e d i m e n t p a r t i c l e sizes a n d w a v e h e i g h t s .  Chapters.  DISCUSSION  59  T h e c u r v e shows fine m a t e r i a l u n d e r g o i n g t h e classic r e v e r s a l f r o m a n e r o s i v e t o a c c r e t i v e b e h a v i o r at a p a r t i c u l a r wave steepness w h i c h t y p i c a l l y is at a v a l u e of a b o u t 0.03 for l a b o r a t o r y beaches; it is u n k n o w n i f t h e r e v e r s a l f r o m erosive t o a c c r e t i v e b e h a v i o r o n n a t u r a l beaches o c c u r s at t h i s wave steepness. C o a r s e m a t e r i a l shows a c c r e t i v e b e h a v i o r regardless o f w a v e steepness.  S t u d i e s r e v i e w e d h a v e s h o w n t h a t coarse m a t e r i a l m o v e s  offshore o n l y i n t h e i m m e d i a t e v i c i n i t y o f b r e a k i n g waves; m o v e m e n t of coarse s e d i m e n t s offshore t o b a r s as s a n d moves w o u l d a p p e a r u n l i k e l y .  T h e s t u d i e s r e v i e w e d a n d field  d a t a c o l l e c t e d i n d i c a t e s t h a t coarse m a t e r i a l t e n d s to b e g e n e r a l l y a c c r e t i v e a n d t h u s t h e c u r v e i n figure 37 is presented as s u c h . T h e left p o r t i o n of t h e c u r v e is u n d e f i n e d d u e t o t h e w a v e steepness l i m i t . At. t h e s a m e h o r i z o n t a l scale m o n t h l y average p e a k wave p e r i o d versus m o n t h is p l o t t e d . O p e n coasts i n t h e n o r t h e r n h e m i s p h e r e t y p i c a l l y show a s e a s o n a l shift i n p e a k w a v e p e r i o d f r o m p r e d o m i n a n t l y l o n g p e r i o d waves i n t h e s u m m e r , w h i c h a r r i v e f r o m d i s t a n t g e n e r a t i n g sources often i n t h e s o u t h e r n h e m i s p h e r e , t o s h o r t e r p e r i o d waves i n t h e w i n t e r f r o m N o r t h P a c i f i c s t o r m s . A d i s t r i b u t i o n of wave p e r i o d s for o p e n coast n e a r T o r i n o , B r i t i s h C o l u m b i a , figure 1, for t h e m o n t h s of J a n u a r y a n d A u g u s t . 1982 show t h e shift i n p e a k w a v e p e r i o d , figure 38. T h e p e a k p e r i o d shifts f r o m 10.5 s e c o n d r e l a t i v e l y h i g h steepness waves i n J a n u a r y to 17.5 s e c o n d lower steepness waves i n A u g u s t .  The  G e o l o g i c a l S u r v e y of C a n a d a [18] s h o w e d t h a t s a n d y L o n g B e a c h n e a r T o f i n o has w e l l defined seasonal b e h a v i o r w i t h a c c r e t i v e profiles i n t h e s u m m e r a n d e r o s i v e profiles i n t h e winter.  R e v i e w of w a v e c l i m a t e d a t a for t h e o p e n coast near T o f i n o i n d i c a t e t h a t l o n g  p e r i o d l o w steepness waves a r r i v e for u p t o 5 to 6 d a y s c o n t i n u o u s l y l i k e l y i n i t i a t i n g a n e p i s o d e p f b e a c h b u i l d i n g . T h i s s a m e p h e n o m e n o n has been o b s e r v e d a n d  documented  e x t e n s i v e l y i n S o u t h e r n C a l i f o r n i a [42]. F e t c h r e s t r i c t e d S t r a i t of G e o r g i a has a n u p p e r l i m i t o n wave p e r i o d a n d p l o t s t o t h e left, of t h e o p e n coast c u r v e . F o r s h o r t p e r i o d waves t h e curves r e p r e s e n t waves of h i g h  Chapter 5.  DISCUSSION  60  steepness a n d c o r r e s p o n d i n g l y for l o n g p e r i o d waves t h e curves represent l o w steepness waves, f i g u r e 37. T h e w a v e c l i m a t e i n the S t r a i t of G e o r g i a has m o r e frequent h i g h steepness a n d l o w i n t e n s i t y waves i n c o m p a r i s o n to t h e o p e n .coast as i n d i c a t e d b y t h e w a v e steepness a n d i n t e n s i t y d i s t r i b u t i o n s , figures 39 a n d 4 0 , w h i c h h a v e been d e r i v e d f r o m w a v e s c a t t e r g r a m s for t h e S t r a i t of G e o r g i a a n d t h e N o r t h P a c i f i c , a p p e n d i c e s B a n d C . H e i g h t s a n d p e r i o d s f r o m t h e r e c o r d s were c o m b i n e d t o f o r m w a v e steepnesses a n d i n t e n s i t i e s a n d were p l o t t e d a g a i n s t p r o b a b i l i t y of o c c u r a n c e d e t e r m i n e d b y d i v i d i n g t h e n u m b e r of o c c u r a n c e s o f a p a r t i c u l a r h e i g h t p e r i o d c o m b i n a t i o n b y t h e t o t a l n u m b e r of o b s e r v a t i o n s i n the r e c o r d . T i d e s are a n i m p o r t a n t factor i n t h e s e l e c t i v e o n s h o r e t r a n s p o r t of coarse m a t e r i a l o b s e r v e d o n i n n e r coast beaches.  M o b i l i z a t i o n of coarse p a r t i c l e s o c c u r s i m m e d i a t e l y  b e n e a t h t h e p l u n g i n g w a v e a n d p a r t i c l e s h a v e been o b s e r v e d t o a d v a n c e o n s h o r e w i t h t h e a d v a n c i n g b r e a k e r p o s i t i o n o n a r i s i n g t i d e . T h u s t h e o n s h o r e m o v e m e n t of coarse p a r t i c l e s is a i d e d b y t h e s u b s t a n t i a l t i d a l r a n g e o n t h e i n n e r coast. A s h o r e w a r d a d v a n c i n g b r e a k e r p o s i t i o n on a r i s i n g t i d e m o b i l i z e s p a r t i c l e s u p the b e a c h t o t h e u p p e r foreshore w h e r e t h e y r e m a i n or c o n t i n u e m o v i n g i n t h e l o n g s h o r e d i r e c t i o n w h e n waves  break  o b l i q u e l y t o t h e shore. In t h e absense of tides coarse p a r t i c l e s w o u l d b e m o b i l i z e d i n t h e b r e a k i n g w a v e s w a s h a n d t y p i c a l l y m o v e o n l y a few m e t r e s s h o r e w a r d . T h e d a t a of t a b l e 1 shows a r a n g e of 5 m e t r e s for a n n u a l t i d e s . A s s u m i n g a t y p i c a l b e a c h slope of 1 V : 1 0 H t h e b r e a k i n g w a v e p o s i t i o n w i l l shift 50 m e t r e s across t h e p r o f i l e o n a n a n n u a l t i d e . D e v e l o p m e n t of a r m o u r e d beaches o n t h e i n n e r coast, is i n p a r t a f u n c t i o n of t i d e s . O v e r vast, p e r i o d s of t i m e b r e a k i n g waves s h i f t i n g p o s i t i o n over t h e profile due t o t i d a l fluctuations  h a v e r e m o v e d a l l b u t t h e largest s t a b l e c o b b l e f r o m t h e b e a c h surface. M o -  b i l e c o b b l e , g r a v e l a n d coarse s a n d s a c c u m u l a t e i n the u p p e r foreshore w h e r e t h e y  are  transported longshore. U n d e r the predominant  w a v e c l i m a t e o f t h e i n n e r coast finer s a n d s a n d s i l t s are  Chapter 5.  DISCUSSION  61  b e l i e v e d t o m o v e offshore a c c u m u l a t i n g o n lower foreshores a n d t i d a l flats.  T i d a l flats  g e n e r a l l y o c c u r at sites w h e r e t h e r e is a large source of fine s e d i m e n t s often of f l u v i a l or g l a c i a l o r i g i n , the fine s e d i m e n t s m o v i n g offshore u n d e r steep waves a i d e d b y . a f a l l i n g t i d e a n d r e t r e a t i n g b r e a k e r p o s i t i o n . . U n l i k e t h e o p e n coast, t h e i n n e r coast wave c l i m a t e l a c k s l o n g p e r i o d , l o w steepness waves necessary t o m o b i l i z e t i d a l flat sands for s a n d y b e a c h e s t o accrete.  onshore  I n v e s t i g a t i o n b y o t h e r s [20] have i n d i c a t e d l o c a l beaches  e x p e r i e n c e offshore s a n d loss w i t h d e p o s i t i o n t a k i n g p l a c e o n t o t i d a l flats. T h e t i d a l flat is a g e o m o r p h i c f e a t u r e t h a t has been a s s o c i a t e d w i t h fetch r e s t r i c t e d w a t e r b o d i e s a n d a s i g n i f i c a n t t i d a l range; t i d a l flats w i t h steep c o b b l e u p p e r beaches o c c u r i n t h e G u l f of C a l i f o r n i a w h i c h is a fetch r e s t r i c t e d w a t e r b o d y l i k e t h e waters of i n n e r s o u t h c o a s t a l B r i t i s h C o l u m b i a [24]. T h e s e l e c t i v e o n s h o r e m o v e m e n t of coarse m a t e r i a l a n d offshore m o v e m e n t of fine m a t e r i a l c a n e x p l a i n t h e g r a v e l a n d c o b b l e u p p e r beaches a n d s a n d y t i d a l flats f o u n d b e n e a t h s a n d y bluffs o n t h e i n n e r coast, p h o t o 13. T h i s process has also p r o d u c e d  the  a r m o u r e d profiles w i t h l o n g s h o r e s e d i m e n t t r a n s p o r t i n the u p p e r foreshore such as at D u n d a r a v e , W e s t V a n c o u v e r , p h o t o 14, i n t h e a b s e n c e of sufficient of s a n d s u p p l y for t i d a l flats t o f o r m .  W h e r e coarse m a t e r i a l moves o n s h o r e a n d l o n g s h o r e a n d s t o r a g e  e x i s t s steep s h i n g l e beaches f o r m , p h o t o s 5 t o 12. C o b b l e c o l o n i z e d b y seaweed m a y be c a r r i e d o n s h o r e f r o m deep w a t e r b y i n t e n s e s t o r m waves. T h e c o b b l e has b e e n f o u n d h i g h i n the u p p e r foreshore o n s e v e r a l s h i n g l e beaches o n t h e i n n e r c o a s t , p h o t o 7. It is b e l i e v e d t h a t i n t e n s e s t o r m waves tear t h e seaweed a n d a t t a c h e d c o b b l e f r o m t h e seabed offshore a n d w i n d a n d t i d a l l y g e n e r a t e d c u r r e n t s c a r r y it o n s h o r e w h e r e t h e s w a s h f r o m b r e a k i n g waves deposit, it h i g h i n the u p p e r foreshore. A p o r t i o n o f t h e c o b b l e o n i n n e r coast s h i n g l e b e a c h e s o r i g i n a t e s f r o m t h i s offshore source.  Chapter 6  FURTHER  RESEARCH  T h e r e is o p p o r t u n i t y for f u r t h e r research o n beaches i n b o t h t h e field a n d t h e l a b o r a t o r y . S o m e p o s s i b l e research t o p i c s are s u m m a r i z e d :  • Field Investigation S o m e s e c t i o n s of c o a s t l i n e w i t h i n t h e S t r a i t of G e o r g i a are l i n e d w i t h e x t e n t s i v e m a t r e s s e s o f f l o a t i n g logs such, as C a p e M u d g e o n Q u a d r a I s l a n d , p h o t o 18. L i t e r a t u r e o n t h e effect the f l o a t i n g m a t r e s s o f logs has o n the b r e a k i n g of waves or t h e c o n t r i b u t i o n t o b a c k s h o r e e r o s i o n b y m a t r e s s of logs has n o t b e e n f o u n d .  • L a b o r a t o r y Investigation  1. A t h e o r y of layers s h o u l d e x i s t w h i c h c o u l d d e s c r i b e the s t a b i l i t y of the a r m o u r l i k e layers w h i c h e x i s t on some i n n e r coast beaches.  H u d s o n ' s f o r m u l a for  r u b b l e m o u n d b r e a k w a t e r s , for e x a m p l e , c a n n o t be e x t e n d e d t o b e a c h slopes. 2. T h e t i m e scale of b e a c h p r o f i l e e v o l u t i o n t o a n e q u i l i b r i u m c o n d i t i o n has b e e n a s s u m e d t o be a f u n c t i o n of t h e s t a t e of the i n i t i a l p r o f i l e (ie. h o w close t h e p r o f i l e is t o t h e e q u i l i b r i u m p r o f i l e for the i m p o s e d w a v e c o n d i t i o n ) a n d w a v e i n t e n s i t y . T h e s e a s s u m p t i o n s s h o u l d be e x p l o r e d 3. W a v e i n t e n s i t y has b e e n a s s u m e d movement  of an a c t i v e on-offshore  s u m p t i o n should be investigated  to determine  further.  62  further.  the m a g n i t u d e  v o l u m e of s e d i m e n t  the  a n d r a t e of  on a beach; the  as-  Chapter  6.  FURTHER  RESEARCH  63  4. T h e s w e p t a r e a v a r i a b l e u s e d t o i n v e s t i g a t e on-offshore t r a n s p o r t o n l a b o r a t o r y beaches has s u c e s s f u l l y r e l a t e d t h e m o v e m e n t of b e a c h s e d i m e n t t o wave i  parameters  b e c a u s e l a b o r a t o r y beaches have i n i t i a l l y flat profiles w h i c h are  e s s e n t i a l l y a d a t u m r e q u i r e d t o define t h e swept a r e a v a r i a b l e .  For natural  beaches w h e r e t h e i n i t i a l profile is not flat t h e reference profile or d a t u m req u i r e d t o define a s w e p t a r e a v a r i a b l e r e m a i n s u n d e f i n e d . 5. T h e c o n c e p t of a n a c t i v e v o l u m e of s e d i m e n t o n a b e a c h r e p r e s e n t e d b y a swept a r e a v a r i a b l e m i g h t be u s e d as a basis for n u m e r i c a l m o d e l l i n g of on-offshore transport. 6. T h e c o n c e p t of a n a c t i v e v o l u m e of s e d i m e n t r e p r e s e n t e d  b y a swept  area  v a r i a b l e m i g h t be c o n s i d e r e d i n t h e i n v e s t i g a t i o n of b r i d g e p i e r s c o u r p r o b l e m s .  Chapter 7  CONCLUSIONS  7.1  The  Field Investigative W o r k  s u m m e r / w i n t e r b e a c h profiles k n o w n t o o c c u r on o p e n coast beaches d u e t o o n -  offshore t r a n s p o r t  of s a n d d o not o c c u r o n t h e beaches of i n n e r s o u t h c o a s t a l B r i t i s h  C o l u m b i a b e c a u s e t h e w a t e r s are fetch l i m i t e d a n d t h u s l a c k l o w f r e q u e n c y waves w h i c h g e n e r a t e t u r b u l e n c e at b e d l e v e l n e c e s s a r y for o n s h o r e m o v e m e n t of s a n d . W a v e c l i m a t e i n v e s t i g a t i o n has s h o w n deep w a t e r waves i n t h e S t r a i t of G e o r g i a d o not have p e r i o d s e x c e e d i n g a p p r o x i m a t e l y 8 seconds a n d t h e waves are p r e d o m i n a n t l y h i g h steepness a n d low i n t e n s i t y r e l a t i v e to t h e w a v e c l i m a t e of t h e N o r t h P a c i f i c . T h e r e is e v i d e n c e of m i n o r s e a s o n a l m o r p h o l o g i c , changes o n i n n e r coast beaches due t o s e a s o n a l l y v a r y i n g s e d i m e n t s u p p l y ; b e a c h s e d i m e n t of f l u v i a l o r i g i n m a y b e m o r e p r e v a lent a l o n g t h e c o a s t l i n e d u r i n g a n d i m m e d i a t e l y f o l l o w i n g p e r i o d s w h e n s o u r c e s t r e a m s a n d r i v e r s h a v e h i g h runoff, d u r i n g p e r i o d s of l o w r u n o f f l i t t o r a l s e d i m e n t is t r a n s p o r t e d away. A t D u n d a r a v e , W e s t V a n c o u v e r , it was o b s e r v e d t h a t beaches were m o r e s a n d y i n t h e w i n t e r as o p p o s e d t o t h e s u m m e r . C o a r s e p a r t i c l e s s u c h as gravels a n d c o b b l e s o n i n n e r s o u t h c o a s t a l beaches t e n d t o move selectively onshore i n d u c e d by a shoreward a d v a n c i n g breaker p o s i t i o n o n a rising t i d e a s . e v i d e n c e d by s e d i m e n t t r a c i n g e x p e r i m e n t s a n d t h e o c c u r e n c e of steep s h i n g l e beach berms.  T h e p l u n g i n g or s p i l l i n g w a t e r m a s s of b r e a k i n g waves a n d  subsequent  sheet flow u p t h e b e a c h face m o b i l i z e s s m a l l e r less s t a b l e gravels a n d c o b b l e s s h o r e w a r d  64  Chapter  7.  CONCLUSIONS  65  a n d longshore while larger cobbles a n d boulders r e m a i n a r m o u r i n g the beach  surface.  S e d i m e n t t r a n s p o r t e x p e r i m e n t s c o n d u c t e d u s i n g a r a n g e of coarse p a r t i c l e sizes have s h o w n t h a t t h e h i g h e s t s e d i m e n t t r a n s p o r t rates o c c u r i n t h e u p p e r foreshore w h i l e m i d d l e a n d l o w e r foreshores o f i n n e r coast beaches h a v e r e l a t i v e l y l o w t r a n s p o r t cobble boulder armouring.  rates due to  E v i d e n c e of m o v e m e n t of coarse p a r t i c l e s i n t h e  d i r e c t i o n has not b e e n f o u n d , h o w e v e r , it is r e c o g n i z e d t h a t i n g e n e r a l s e d i m e n t  offshore transport  across a p r o f i l e m a y o c c u r b o t h o n s h o r e a n d offshore ( s h o r e w a r d a n d s e a w a r d of the breaker zone respectively) depending u p o n the wave characteristics in the zone.  nearshore  T h e o b s e r v e d p r e d o m i n a n t d i r e c t i o n of m o v e m e n t of coarse s e d i m e n t s o n i n n e r  coast beaches is o n s h o r e a n d l o n g s h o r e w h e r e waves a p p r o a c h a b e a c h o b l i q u e l y . F u r t h e r , the o c c u r a n c e of silt a n d s a n d t i d a l flats t h r o u g h o u t t h e i n n e r coast  and  lack of a c c r e t i n g s a n d beaches is e v i d e n c e t h a t fine m a t e r i a l t e n d s to m o v e i n a n offshore d i r e c t i o n d e p o s i t i n g o n l o w e r foreshore t i d a l flats or offshore. C o a r s e s e d i m e n t s i n c l u d i n g c o b b l e s a n d b o u l d e r s m a y b e a c t i v e o n t h e i n n e r coast as e v i d e n c e d b y r o c k y s p i t s such as R e b e c c a S p i t o n Q u a d r a I s l a n d . M o b i l e coarse s e d i m e n t s c a n a c c e l e r a t e w e a r a n d d e t e r i o r a t i o n of t i m b e r piles as h o u r g l a s s i n g of p i l e s at t h e b e a c h surface has s h o w n . C o b b l e c o l o n i z e d b y seaweed f o u n d i n t h e u p p e r foreshore of s h i n g l e beaches i n d i c a t e s t h a t coarse b e a c h s e d i m e n t s m a y o r i g i n a t e f r o m offshore sources. W h e r e s h i n g l e beaches h a v e f o r m e d t h e coarse s e d i m e n t s are f r e q u e n t l y flat i n shape;  whether  t h e s e d i m e n t s are n a t u r a l l y flat or h a v e b e e n w o r n t o t h e i r flat s h a p e t h r o u g h s h e a r i n g m o t i o n w i t h i n t h e b e a c h b e r m or o t h e r forces r e m a i n s u n k n o w n .  Inner coast s h i n g l e  beaches are steep, slopes u p t o 26 degrees h a v e b e e n m e a s u r e d ; a r m o u r e d beaches a l l a p p r o x i m a t e l y t h e s a m e s l o p e f a l l i n g i n t h e r a n g e 5 t o 10 degrees.  are  A r m o u r e d beach  surface a n d s u b s u r f a c e g r a i n size d i s t r i b u t i o n s i n d i c a t e t h a t t h e a r m o u r l a y e r f o r m s a n a t u r a l filter i s o l a t i n g fine s u b s u r f a c e s e d i m e n t s f r o m e r o s i o n a n d e n t r a i n m e n t . A n i n v e s t i g a t i o n o f a series of shore n o r m a l b e a c h profiles m e a s u r e d at t h r e e sites  Chapter 7.  CONCLUSIONS  66  a n d s y n t h e s i z e d w a v e d a t a h i n d c a s t for t h e p e r i o d of profile s u r v e y s h o w e d t h a t s t o r m waves i n d u c e d p r o f i l e changes p r i m a r i l y i n t h e u p p e r foreshore of beaches.  T h e profile  changes were f o u n d t o be d u e to l o n g s h o r e s e d i m e n t a c t i v i t y , p e r i o d i c i n n a t u r e , o c c u r i n g p r e d o m i n a n t l y i n t h e u p p e r foreshore i n c o n j u n c t i o n w i t h h i g h tides a n d w a v e a c t i o n . T h e r e s u l t s of t h e p r o f i l e a n d h i n d c a s t i n g s t u d y are c o n s i s t e n t w i t h field o b s e r v a t i o n a n d s e d i m e n t t r a c i n g e x p e r i m e n t s w h i c h also show u p p e r foreshore s e d i m e n t a c t i v i t y . T h e l i t t o r a l processes o c c u r i n g o n t h e i n n e r coast are g o v e r n e d b y a r e g i m e of wave h e i g h t s , wave p e r i o d s a n d t i d a l ranges t h a t f a l l w i t h i n a s m a l l r a n g e of p o s s i b l e wave h e i g h t s , w a v e p e r i o d s a n d t i d a l ranges k n o w n t o o c c u r o n c o a s t l i n e s . T h i s wave c l i m a t e r e g i m e i n c o n j u n c t i o n w i t h a w i d e r a n g e of n a t i v e s e d i m e n t s r a n g i n g f r o m silts t o c o b b l e s a n d b o u l d e r s h a v e l e a d t o t h e d e v e l o p m e n t of i n n e r c o a s t a l features s u c h as t i d a l flats, c o b b l e / b o u l d e r a r m o u r e d beaches a n d steep s h i n g l e beaches. B l u f f r e c e s s i o n is p r i m a r i l y a f u n c t i o n of foreshore e r o s i o n a n d e l e v a t i o n c h a n g e . R e cession m a y be s i m p l y e x p r e s s e d as:  R = my w h e r e R=  bluff r e c e s s i o n , ???.= b e a c h slope a n d y= foreshore e l e v a t i o n c h a n g e .  O n t h e i n n e r s o u t h coast, s a n d bluffs m a y n a t u r a l l y d e v e l o p a p r o n s of loose e r o d e d s a n d at the a n g l e of repose a r o u n d t h e b l u f f t o e d u r i n g s u m m e r m o n t h s  w h e n wave  a c t i v i t y i n t h e u p p e r foreshore is l o w . W i n t e r s t o r m waves, l i k e l y a c c o m p a n i e d b y s t o r m surge, b r e a k i n g i n t h e u p p e r foreshore at h i g h t i d e erodes the s a n d a p r o n s  furthering  bluff recession t h r o u g h o v e r s t e e p e n i n g a n d s u b s e q u e n t e r o s i o n as e v i d e n c e d at W i l l e m a r Bluffs, C o m o x .  Chapter 7.  7.2  CONCLUSIONS  67  L a b o r a t o r y Beaches  O n - o f f s h o r e s e d i m e n t m o v e m e n t o n a b e a c h a n d waves p r o d u c i n g t h e m o v e m e n t m a y be i n t e r r e l a t e d u s i n g t h e a r e a swept o u t b e t w e e n an i n i t i a l , reference or d a t u m p r o f i l e a n d a f i n a l p r o f i l e e v o l v i n g as a f u n c t i o n of t i m e .  A variable termed active volume, equal  t o h a l f of t h e swept a r e a b e t w e e n profiles, has been i n v e s t i g a t e d u s i n g l a b o r a t o r y b e a c h d a t a a n d has been c o r r e l a t e d w i t h w a v e p a r a m e t e r s s u c h as w a v e h e i g h t a n d p e r i o d a n d time.  T h e a c t i v e v o l u m e of s e d i m e n t is t h e a m o u n t of s e d i m e n t t h a t has m o v e d o n a  b e a c h r e l a t i v e t o a n i n i t i a l p r o f i l e as a r e s u l t of a b e a c h a d j u s t i n g its profile s h a p e to a n imposed wave c o n d i t i o n . A c t i v e v o l u m e indicates the p r e d o m i n a n t sediment  transport,  across t h e e n t i r e profile a n d t h u s does not r e a d i l y i d e n t i f y c o n d i t i o n s w h e r e b o t h o n s h o r e a n d offshore t r a n s p o r t m a y o c c u r on a profile s h o r e w a r d a n d s e a w a r d of t h e b r e a k e r z o n e respectively. A dimensionless erosion parameter  V /(H L ), a  0  o  w h i c h is the a c t i v e v o l u m e p e r u n i t  w i d t h of b e a c h p e r u n i t t i m e d i v i d e d b y the p r o d u c t of deep w a t e r w a v e height, a n d wave l e n g t h , m a y b e defined a n d u s e d t o d e s c r i b e t h e on-offshore m o v e m e n t of b e a c h sediments. L a b o r a t o r y b e a c h d a t a p l o t t e d u s i n g t h e a c t i v e v o l u m e v a r i a b l e shows t h a t for a g i v e n w a v e h e i g h t t h e r e is a w a v e p e r i o d w h i c h w i l l p r o d u c e a m a x i m a of sediment, a c t i v i t y s u b j e c t t o s e d i m e n t size. F i n e s e d i m e n t s s u c h as s a n d s m a y s h o w t w o m a x i m a i n sediment, a c t i v i t y over a w i d e r a n g e of p e r i o d s ; o n e m a x i m a c o r r e s p o n d s t o o n s h o r e s e d i m e n t m o v e m e n t a n d one t o offshore s e d i m e n t m o v e m e n t . C o a r s e s e d i m e n t s h a v e o n l y one m a x i m a of sediment, a c t i v i t y c o r r e s p o n d i n g t o o n s h o r e m o v e m e n t of g r a v e l . A n e x p o n e n t i a l g r o w t h a n d d e c a y f u n c t i o n d e s c r i b e s t h e e v o l u t i o n of a b e a c h t o a n e q u i l i b r i u m s t a t e i n t e r m s of a c t i v e v o l u m e or sediment, a c t i v i t y . L a b o r a t o r y beaches show a n e v o l u t i o n of a c t i v e v o l u m e as a f u n c t i o n of t i m e f r o m a n i n i t i a l l y flat p r o f i l e to  Chapter 7.  CONCLUSIONS  68  a n e q u i l i b r i u m profile t h a t m a y be d e s c r i b e d b y t h e e q u a t i o n :  V {t) =  V (l-e- ) rt  a  where  r is a t i m e c o n s t a n t a n d V  aeq  aeq  is the e q u i l i b r i u m a c t i v e v o l u m e .  S i m i l a r l y , s e d i m e n t a c t i v i t y , w h i c h is t h e t i m e d e r i v a t i v e of a c t i v e v o l u m e , decreases e x p o n e n t i a l l y as a b e a c h a p p r o a c h e s e q u i l i b r i u m :  Va -  d  t  - v e aeg  T h e c o n c e p t of a c t i v e v o l u m e m a y also be e x t e n d e d t o n a t u r a l beaches, h o w e v e r , since n a t u r a l beaches h a v e forever c h a n g i n g profiles a n d d o n o t h a v e i n i t i a l l y  flat  reference  profiles f u r t h e r c o n s i d e r a t i o n s are r e q u i r e d :  •  A reference or d a t u m p r o f i l e , w h i c h m a y n o t n e c e s s a r i l y b e flat as i n t h e l a b o r a t o r y , remains undefined.  T h e d e f i n i t i o n of a reference p r o f i l e w i l l l i k e l y i n v o l v e l o n g e r  t e r m o b s e r v a t i o n a n d s t u d y of t h e e v o l u t i o n a r y s h a p e s of n a t u r a l beaches a n d is t h u s a t o p i c for f u r t h e r  •  research.  A ' s t a t e ' p a r a m e t e r is r e q u i r e d t o i d e n t i f y h o w close t h e i n i t i a l p r o f i l e is t o e q u i librium.  With  swept  areas m e a s u r e d  r e l a t i v e t o t h e reference  profile the  state  p a r a m e t e r m i g h t be defined as follows:  where  V  aeq  is t h e e q u i l i b r i u m a c t i v e v o l u m e for t h e i m p o s e d w a v e c o n d i t i o n m e a -  s u r e d r e l a t i v e t o t h e p r o f i l e a n d V is t h e a c t i v e v o l u m e of t h e i n i t i a l profile m e a at  s u r e d r e l a t i v e t o t h e reference p r o f i l e .  Bibliography  [1] A d a m s , J . , " G r a v e l A n a l y s i s F r o m P h o t o g r a p h s " ,  Journal of the Hydraulics Division,  A S C E , V o l . 105, N o . H Y 1 0 , O c t o b e r 1979, p p . 1247- 1255.  [2] B a s c o m , W . H . " C h a r a c t e r i s t i c s of N a t u r a l B e a c h e s " ,  Proceedings /jth Conference  on Coastal Engineering, A S C E , C h i c a g o , 1954, p p . 163- 180. 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H Y l l , N o v e m b e r , 1976, p p . 16471661. [32] M c C a n n S. B . a n d H a l e , P . B . , " S e d i m e n t D i s p e r s a l P a t t e r n s a n d S h o r e M o r p h o l o g y A l o n g the G e o r g i a Strait  Coastline of Vancouver Island",  Coastal Conference 1980, B u r l i n g t o n , O n t a r i o , p p . 151- 1 6 3 .  Proceedings Canadian  Bibliography  73  [33] M o o r e , D . M . , D u n n , M . w!, S u m m e r s , T . J . , W o l f f , D . A . , " C o a s t a l R e s o u r c e s F o l i o - East Vancouver Island", Lands Directorate, Enviroment Canada, Vancouver, B . C , N o v e m b e r 198.1. [34] N o d a , H . , " S c a l e R e l a t i o n s for E q u i l i b r i u m B e a c h P r o f i l e s " ,  Proceedings 16th Coastal  Engineering Conference, A S C E , H a m b e r g , 1978, p p . 1531- 1541. [35] Q u i c k , M . C . a n d H a r , B . 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H . , " C r o s s S h o r e T r a n s p o r t o f B i M o d a l S a n d s " ,  Proceedings 19th Coastal Engineering Conference, A S C E , H o u s t o n , 1984, p p . 19972008. [40] S a y a o , O . J . , N a i r n , R . B . , K a m p h u i s , J . W . , " D i m e n s i o n a l A n a l y s i s o f L i t t o r a l Drift",  Proceedings Canadian Coastal Conference 1985, S t . J o h n ' s , N e w f o u n d l a n d ,  p p . 241- 255. [41] S a v i l l e , T . J r . , " T h e Effect, o f F e t c h W i d t h o n W a v e G e n e r a t i o n " ,  Beach Erosion  Board, Technical Memo No. 70, U . S. A r m y C o r p s o f E n g i n e e r s , 1954.  Bibliography  74  [42] S h e p a r d , F . P . , " B e a c h C y c l e s i n S o u t h e r n C a l i f o r n i a " ,  Beach Erosion Board Tech-  nical Mem.o No. 20, U . S . A r m y C o r p s of E n g i n e e r s , 1950. [43] S h o r e P r o t e c t i o n M a n u a l , C o a s t a l E n g i n e e r i n g R e s e a r c h C e n t e r , U . S . A r m y C o r p s of E n g i n e e r s , W a s h i n g t o n , D . C , 1984.  [44] S o r e n s e n , R . M . , " B a s i c C o a s t a l E n g i n e e r i n g " , W i l e y P r e s s , 1978.  [45] T h o m s o n , R . E . , " O c e a n o g r a p h y of t h e B r i t i s h C o l u m b i a C o a s t " , D e p a r t m e n t of Fisheries and Oceans, C a n a d i a n Government P u b l i s h i n g Centre, O t t a w a , Ontario, 1981.  [46] W a t a n a b e , A . , R i h o , Y . , H o r i k a w a , K . , " B e a c h P r o f i l e s a n d O n - O f f s h o r e S e d i m e n t Transport",  Proceedings 11 th Coastal Engineering Conference, A S C E , S y d n e y , 1980,  p p . 1106- 1121. [47] M u i r W o o d , A . M . , " C h a r a c t e r i s t i c s of S h i n g l e B e a c h e s : Practical Problems",  T h e S o l u t i o n to  Some  Proceedings 12th Conference on Coastal Engineering, A S C E ,  V a n c o u v e r , 1972, p p . 1059- 1075.  figures  75  NORTH  PACIFIC  ?\9  x0  JJi  5*  •  1  —O"  ,0*  c 9l is  „,  •  \>f>  • ....  M>  vi*.-  Jt*,t A<  3 V  1  - V  «1 , * 5  8»'  ^  Q2>*  ?T\9  FA  \  1  .W""  V *1 ' **  c*  4  3?  1c<"  study area ft?  SITE S O U D I N G S S C A L E  PLAN IN  I  M  S  1 =525,  >sr  lure \ l 6  2 0?S  c  GRAIN  SIZE  A N D SOIL  PERMEABILITY  CLASSIFICATION  British Standards  Silt  Clay  Fine  0.002  Sand  Medium  0.02  0.006  0.001  Fine  Coarse  0.06  0.01  Gravel Fine  Medium Coarse  0.2  Medium  0.6  Coarse  20  0.1  Cobbles Boulders  60  200 100  10  Particle size (mm)  Coefficient of permeability (m/s) 1  10  Clean gravels  _1  10"  2  10  - 3  10"  Clean sands and sand-gravel mixtures  4  10"  s  10  - 6  Very fine sands, silts and clay-silt laminate  Dessicated and fissured clays  figure 3  10"  7  10  - 8  10  - 9  10"  Unfissured clays and clay-silts (>20% clay)  S^V  HHW  BEACH  PROFILE  OPEM  ANb  COAST  PROFILES  UPPER  PLOTTED  ENVELOPES  RESTRICTETs AT T H £  FETCH  SAME"  BEACHES  GEOMETRIC  SCALE  PROFILE ON - O F F S H O R E SANiD LA  BEACH,  JOLLA,  TRANSPORT SCRAPS  PIER  CALIFORNIA  SEPTEMBER \°)A0 TO APfML 5 ••  4"  3"  LLW  2 -  HORIZONTAL  AMD VERTICAL  -425  SCALE  IM  50  METRES  7 5  I0O  figure k  CHARACTERISTIC  z o m  SIGNIFICANT WAVE HEIGHT (metres)  O n ox H CD o m CD X mH x cn  "n 2> M X 01 X m z x m M m n cn z < x > M > Z X < a z o m O 2 I n m CDm m z> X cn r n > a> m x > rn D c n > rn o tu X < M  n  o o  o cn I i | I I II  i—  o  HEIGHT  IN METRES  r>5 c/i o  (V5  | I 1 I I | ! I I I | I I I I  1  m  CD > Z T;  m > cn c X m a  D  n > cn >  < m  >  m x m cn X cn  m  H  CT X H cn  z rn a -r\  X O H I  m  CHARACTERISTIC HEIGHT  IN METRES  SIGNIFICANT WAVE HEIGHT (rretres) 0.0  0.5  1.0  1.5  2.0  2.5  C_  X  Co  Z  M  m z CD CD  Nl x CD m -< • n > cn > < m x m i—i CD X H cn  X o  lO c CHARACTERISTIC  SIGNIFICANT WAVE HEIGHT (metres)  cn  > -< m cn CD CJ  o n > cn  H  > <  m x m M CD  X H cn  H  x cn  CD 10 > VJ Z 4i A  > M  O X no a m CD X  H CD  HEIGHT  IN METRES  82 EFFECT  ON PROFILE  20  SHAPE OF VARYING  25  H„/i_.  BY VARYING  L.  EFFECT ON PROFILE SHAPE OF VARYING H./  L  BY VARYING L.  30  Distance , In Feet, From 8«och Crist (i) Distance,In  EFFECT  ON PROFILE  S H A P E OF VARYING  H„/L„  BY VARYING  EFFECT  L.  ON PROFILE  10  Oistance,In Feet, From Beoch Crest (x)  Feet, From Beach Crest  SHAPE OF VARYING  15  {*)  H„/  L < ]  20  BY VARYING  L„  25  Distance, tn Feet, From Beach Crest (s)  LABORATORY  BEACH  PROFILES -  figure 7  DATA  SET 2  SOURCE: Rector, R. L., " L a b o r a t o r y Study o f t h e E q u i l i b r i u m P r o f i l e s o f Beaches", Beach E r o s i o n B o a r d T e c h n i c a l Memo N o . 4 1 , U . S . Army C o r p s o f E n g i n e e r s , 1954.  LABORATORY  BEACH  PROFILES - DATA SET  14 I I  Profile  0  1  changes  o f e r o s i v e beach  2  (sand) .  3  Distance (m)  Profile  changes  of a c c r e t i v e beach  (sand).  SOURCE: Hattori, Beach Coastal  M . and Kawamata, Profile Change", Engineering,  ASCE,  R . , "Onshore-Offshore Transport P r o c e e d i n g s 17th Conference Sydney,  figure  1980,  8  pp.  1175-  1193.  and on  84 DISTRIBUTION OF WAVE HEIGHTS STRAIT OF GEORGIA AND NORTH PACIFIC  2  w a  >-  pa <  o aK  '—I  2  4  '  6  SIGNIFICANT WAVE HEIGHT - (metres) STRAIT OF GEORGIA + NORTH PACIFIC  DISTRIBUTION OF WAVE PERIODS STRAIT OF GEORGIA AND NORTH PACIFIC  0.9 0.8 0.7 to Z  w a  >*  0.6  E-  0.5  5 <  0.4  3  c oa  0.3 0.2 0.1 0  "l  SIGNIFICANT WAVE PERIOD - (seconds) STRAIT OF GEORGIA + NORTH PACIFIC  figure 9  1— 18  20  FREQUENCY  OF  FREQUENCY OF WIND SPEED BY DIRECTION JAN 1 - DEC 31 1857 1979  20V.  AND  WAVES  STRAIT  OF  GEORGIA  - 50.3N  GEORGIA  07.  WIND  60 7.  407.  STRAIT  48.5 N  1007.  (a)  ( b )  figure 10  86  figure 11  87 N  LLW  6  TRA  IT  G£ORa/A  WAVES  TOWER BEACH/' PRORLE  B  PROFILE A /  POINT G^EY A  TOWER POINT SITE  3  -  BEACH GREY 1-15  OOO  figure 12  figure 13  B E A C H FACE S L O P E V E R S U S GRAIN SIZE LO  o  LO •  ro ^— (Si CD (D L CD (D "O ^ LLJ  0_  o a • M  •  a LO •  a a • r\i  CO LO  SHINGLE BEACHES  • • •  a a  ARMOURED BEACHES  o LO '  a  o.  0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 130.0 140.0 150.0  MEDIAN SIZE IN  MILLIMETRES  f i g u r e 14 oo  SHINGLE  BEACH -  TYPICAL  CROSS  SECTION  BERWCRE&T  HOMOGENEOUS 60A££E MATERIAL BERIA  LLW  FiKje/ COARSE M A T E R I A L NAATFU X  figure 15 U3 O  ARMOURED  BEACH - TYPICAL  CROSS  UPPER  SECTION  FoRtCHoRET  I  SArJc* AUJ>  -:::6vv-r !  x  /  MSL CEjJSofiEb  COBBlX  LAYER.  LLW  F i n e / COARSE. lAATERlAL.  figure  16  fMTfcl*  TSAWWASSEN  BEACH -  LAT.  49  PROFILE S U R V E Y A  01' 12" - LNG. 123  05' 48  TSAWWASSEN  BEACH -  LAT.  4  49  PROFILE SURVEY B  01' 12" - LNG. 123  05' 48"  numbers show sieve sampling locations  3  L  2  zo <  > w w E-t  W  o o w o  i *  HORIZONTAL DISTANCE (metres) o APR 17/ 87 A JUN 13/ 87  MAR 06/ 87  TSAWWASSEN  BEACH -  JUL 21/ 87  PROFILE SURVEY A  OCT 19/ 86  I  TSAWWASSEN J  I  i  i  HORIZONTAL DISTANCE (metres) 0 NOV 28/ 86 4 JAN 13/ 87  + NOV 01/ 86  UPPER FORESHORE PROFILE VARIATIONS  .  BEACH -  1  l  X MAR 06/ 87  V APR 17/ 87  PROFILE SURVEY B  UPPER FORESHORE PROFILE VARIATIONS  -  numbers show sieve sampling locations  2.8 2.6 2.4 2.2 2 -  zo  1.8 1.6 -  > W  ^Ov^  2  1.4 -  _ ) W  1.2 EW O  1 -  o w o  0.8 0.6 -  4  0.4 0.2 0 " I -10 +  MAR 06/ 87  HORIZONTAL DISTANCE (metres) o APR 1 7 / 8 7 A JUN 13/ 87  JUL 2 1 / 87  figure  OCT 19/ 86  •  I  i  I -6  I  i  I  + NOV 01/ 86  i  -2  I  I 2  I  I 6  I  I 10  I- •• I 14  HORIZONTAL DISTANCE (metres) 0 NOV 28/ 86 A JAN 13/ 87 X MAR 06/ 87  1  I 18  1  V APR 17/ 87  93 TOWER B E A C H LAT.  49  TOWER B E A C H -  PROFILE S U R V E Y A  19' 13" - LNG. 123  LAT. 49  15' 37  PROFILE S U R V E Y B  19' 15" - LNG. 123  15' 30"  o >  W Q O  w o  60 JAN 13/ 87  HORIZONTAL DISTANCE (metres) -t- FEB 1 4 / 8 7 o MAR 15/ 87  TOWER B E A C H -  A  JUN 10/ 87  OCT 26/ 86  + NOV 14/ 86  HORIZONTAL DISTANCE (metres) DEC 16/ 86 4 JAN 13/ 87  TOWER B E A C H -  PROFILE S U R V E Y A  X FEB 02/ 87  0  V  MAR 0 7 / 87  PROFILE SURVEY B  UPPER FORESHORE PROFILE VARIATION  UPPER FORESHORE PROFILE VARIATIONS  2 o >  W Q O W O  r  JAN 13/ 87  HORIZONTAL DISTANCE (metres) + FEB 14/ 87 o MAR 15/ 87  2 A JUN 10/ 87  OCT 26/ 86  figure 18  + NOV 14/ 86  6  10  14  (metres) X FEB 02/ 87 0HORIZONTAL DEC 16/ 86DISTANCE 4 JAN 13/ 87  V MAR 07/ 87  DUNDARAVE LAT.  PROFILE SURVEY A  49 20' 02" - LNG. 123  DUNDARAVE -  11' 02  PROFILE SURVEY B  LAT. 49 20' 00"  LNG. 123 10' 57"  z o H >  w w J'  L)  P  w a o w o  -20  60  FEB 02/ 87  HORIZONTAL DISTANCE (metres) MAR 07/ 87 o APR 17/87 A JUN 13/ 87  DUNDARAVE -  X  HORIZONTAL DISTANCE (metres) OCT 19/ 86 + NOV 02/ 86 o DEC 01/ 86 A DEC 30/ 86 x FEB 02/ 87  JUL 21/ 87  DUNDARAVE -  PROFILE SURVEY A  f MAR 07/ 87  PROFILE S U R V E Y B  UPPER FORESHORE PROFILE VARIATIONS  UPPER FORESHORE PROFILE VARIATION  z o >  < >  W  td E-  a o u o  FEB 02/ 87  4- MAR  HORIZONTAL DISTANCE (metres) 07/ 87 o APR 17/ 87 a  JUN 13/ 87  X  JUL 2 1 / 87  figure  OCT 19/ 86  + NOV 02/ 86  HORIZONTAL DISTANCE (metres) DEC 01/ 86 A DEC 30/ 86 X FEB 02/ 87  0  V MAR 07/ 87  CROSS S H O R E S E D I M E N T S I Z E  DISTRIBUTION  PROFILE B - DUNDARAVE 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60  -  lower foreshore  upper foreshore  50 40 30 20 10 0  —i  0  40  20 HORIZONTAL DISTANCE  (metres)  figure  20  60  96 GRAIN SIZE  DISTRIBUTIONS  TSAWWASSEN BEACH PROFILE SURVEY B o o  0.1  0.5  1  5  grain  1 . lower 2.  foreshore  upper  4.  foreshore  subsurface L ' i' 1 • I!  •  foreshore  middle  . 3.  :  ; ! 1  •  I ; • : ; ' .  1 i  1  1  ' !  " |  •!'  j  •  • 'i  1  "  I], i ' 11 _.. i!i' I i i ; i ,i : iiii •Tii .!:. JL i ! ! ! i i 1 I III! • : | .iii El = , 'ii' ,:i n ij 1111 ! ' 1 i1 •hi M TTTTiii % IIIn" i 1 !M 1 il i y IjM llli iiii MM i i i ! /11 THT T[TT jTlj iii' iii f:;: "ii M J. Jli M M /3r iiii Iiii M 1 i / i i i i ill Mi iir ! ! i 1 / i i i i|M ill! :li ><i. 1 'Ml 1 iii: iii! : /Alii  9  1  • /[iii n i i  ,.• .1.-..  ' j :  ! •  / " • 1 1  ...  "i i  • 'i: • !  1  i :  •  :  •i •  ; .;  1!'. ••  . i  °  100  (mm)  1  |.i< 1  -P C  50  DUNDARAVE, WEST VANCOUVER PROFILE SURVEY B  o o  L  size  10  i  i=  •  ]  i ! : M<  0.1  i•'  M  0.5  /Viijiii  i  /2  " i /  I •  •  E  nn.  ~  i '. •  1 •'  I  /..... .. M i >  T • | 1  1  i 1  is* 'jr i !  •  1  size  I  \1  I/ • ! JJ •TT i iiii 111' ; ijZ* 1 TiTi i  j  III! LY>> i I i i i  ill! j 111  'Ii :  ii  (mm)  f i g u r e 21  .-.  -  ,i'  1  ,, 'i.  1  1  1  — •H  i  M. M :_.|..:.  ,. ;  i  •: V/\4jrf j MI'M 1r,II '4 Mil i ' .L:.li. ii' Mi .;; MM 1 ! ; '-Mi.., •i'i ,l IIII ii.:l 'j I i r |||: < 1 m i llji •';'i 7 = i' v.-i II.. -JJL1111  • ! I Titr Hr  • I i nh ''!' MM / MM | i 1 Mil i i •Hi i, i(\ i i' ./!::::IM MMI.il i 1 4iJM:ri I M i I 1i y  ._.  • Ii.. 1  :F  . |j 10  1  '  /  • ><r  MI  ;  i; ':'  ;  '!: T  5  grain  i  M  ~i  "  !  4  'r  :  • : i  i. ! : ; ; /A i !.; •: i .,. M" I  '  7;  Mil 1  •.(!..• ••J*sZZ^.... . . _ , 11' i I j I I. ^—rr-?' ii" "l II .... f,M M i y i l l ! is ilif ill ii" I ' M  'i. i . |,  • '  50  100  B E A C H ELEVATION A N D TIDE  ©  ©  ©  ©  5.0 TRACER OftJ&IKJ  >  TRACER.  LEVEL  d  -2.0  75 mm TRACER.  3.0  h  ct <  I  2.0-  o  0.0. TIMECPt>T)o4 DATE  figure  22  08  IZ AU&.  lb 7/87  Zo  24  04  08 AUG-  IZ  lb 8/87  2.0  24  04 08 /6 AUG °> /87  /6  -3.0  NUMBER OF 38mm PARTICLES  PER SQUARE METRE OF B E A C H SURFACE  August 8, 1987  ©  ©  ®  ©  ®  ©  11=00 PDT  ©  ©  ©  ®  ©  © 0 0 0  ©  0 1  1  z  2  ©  1  1 3 7 8 8 5 3 4 37 '24 73 // 10  TRACES. 8 /S7 11027 ORl&IM 20 230110/a  ©  3 6  i  Z  2  7  4o  1  /  /  256 30Z  6 )  1  395  1  IZ O O  0 0  © I 29 434J366J/27 26 is- S 4 0 0 0 0 3  /  0  /  /  0  0 o 0  0  0  1 o 0  L.OM&'S'HofcEr  0 0 o o  o  o  W A V E  LOCATIOM CHASTEft.CteeK, GIBSONS, &.C. LATITUDE: 41' 24' 03" Sj LONGITUDE: 123*33' 54" W OF PARTICLE'S "• 1100 &ftib SPACING •• 4 ft. SLOPE- I -10 :  SHORE NORMAL 210*  WAVE ORIGIN 9=250°  figure 23  o O 0 0 0  0 0 0  0  DI-SPEj?SloW  TIME:  (PDT)  12 :oo 17: 40 Zl : OO || : OO : 3o |0:SO  O B S E R V A T I O N S  DATE:  AUG.. 7 / 8 7 AU<J- 7 / 8 7 Al>6. 7 / S 7 All 6. 8 / S 7  HsN 0.5 O.b  T  (s^  3.9  9 •  3.7  2G0 •  0-3  3.8  O.b  4-2  AUS.  8/87  OS  3.1  2S02SU " 2S0'  A 6-  9/87  o.s  4.2.  2.50 '  u  o< 10' jo-  BREAKCR SPILL. PL.UN&-  10-  SPILL-  10'  PLUNG.  io-  10'  PLUMS- S P L . +  LO 03  NUMBER OF 38mm PARTICLES P E R SQUARE METRE OF BEACH SURFACE A u g u s t 9.1987  ©  ©  ©  ©  ©  ©  ©  ©  ©  ©  ©  © 0  1 l  ©  1  1  1  4  m  1  3  1  /  i  1  ©  11=30 PDT  /  3 5 18 10 A 24 107HQ IA A  2  1  1  1  I  3  •  1  Z  1  0  1 6 1  1  5 44 273  /  5 '32 lib 38 A i TRACER i: t OAlGIO 134 33 IZ i  ©  n  i  296 383  (80 <?  25 13 1  49  1  1  0 0  ©  0  I* 2  348|3e7|226 43 10 5  2  i  i  i  l  /  <*= 10'  2  0  0  0  0  1 2  1 0  0 0  LOWlOfvJ: CHASTER, CREEK., G<6SOOS B.C. LATITUDE-' 4*r24*01" N LOKlCrlTOOE'- |23" 3 3 ' SA" W NUMBER OF PARTICLES'1100 GRID SPACINJ& '• 4m S L O P E - l : 10 T  5H0RE NORMAL EIO*  WAVEORIGIN 6 = 250*  /  LONGSHORE  figure 24  /  0  0  0  o  3  O  0  o i o o  ;  0  1  DISPERSION)  WAVE OBSERVATIONS DATE e Hs(m) T ( s | AUG. 7/87 2so' 0.5 3-9 3.-7 250 • o.fe AUG- 7/87 0.3 AO6. 7/87 2SO' 3.8 4.2 2S0O.fe AUG.. 8/87 I°l-i0 AUG.. 8 /87 o.s 2 SO' 3.1 10 = 50 250' 4.2. 0.5 AO6. V 8 7  TIME (POT) I2--00 17:40 21= 00 II : 00  «.  BREAKER  SPILL. PLUNI6 • 10 • SPILL. 10' PLl/NlG. 10' PUIIOG^ SPL-  10'  io-  io-  PLUU6. *SPL.  LD LD  N U M B E R OF 75mm PARTICLES PER SQUARE METRE OF BEACH SURFACE August 8, 1987 0  ®  ©  ®  ©  ©  11=00 PDT ©  ©  ©  ©  ©  0  0 0 0 0 0 0  ©  0  ©  0 0 1  I  © ORIGIN  © I  lb AA 86  2 fc b a 13 17 14 27 c  68 A  I42.|54|2|  72 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 L0N6 SHORE  0 0 0 o o o o  DlSPERSIOM  10  WAVE SHORE NORMAL 210'  9 = 250'  LOCATION}: CHASTER. CREEK, (SiB^oUS LATITUDE •• A}' 24' 03" N) L0M6ITUDE: |23" Zl' 54" W NlUIABER. OF PARTICLES 215 GRID -SPACDOG"- 4 " £. LO P E '• 1: 10 :  figure 25  WAVE  OBSERVATIONS mo T C«) 9  TIME (,PD"0 D A T E 12 oo AUG.. 7 /87 AU&. 7 / 8 7 17 AO 00 AUG. 7 / 8 7 11 -00 AU6. B /87 \°i30 AU6. 8 / 8 7 10• 50 Auc °)/Bl  0-5 o-b 03 O-fe 0.5 0.5  ot  3.^ 250' to • 3.7 250" IO" 3.8 250- 10' 4.2 250- 10' 3.1 250' 10' 4.2 2S0' 10 '  BREAKER SPILLPLuMGSPILL. PLUKJG. PLUMG. SPL PLuW6.-»SPL. 4  o  NUMBER OF 75mm PARTICLES PER SQUARE M E T R E OF BEACH August 9, 1987  0  ©  ©  ©  ©  ©  ©  11=00  ©  SURFACE  PDT  ©  ©  ©  ©  © 0  © ©TRACER ORIGIN)  3o  15 ZO ll 41 34  10  © I \0 l\z\l3\24  SI  0 0 0 O O O O O O LONGSHORE D15PERSI0NJ  O O O O  0  WAVE L O C A T I O N ) : CHASTER. C R E E K , LATITUDE:  49'  LOMGITODE::  WAVE SHORE NJORMAL 2i<r  9= 250"  MUrABER.  TIME" (POT)  24,' 0 3 " N  1 2 = 00  123' 3 ^ S 4 ' W  1 7 •• 4 0  OF P A R T I C L E S  SP/SC/NKS •SLOPE" =  6I8S0US  :  : 21*5  A(A  1 10 1  figure 26  *2-|:  OO  IP 00  19 =  3 0  1 0 = 50  OBSERVATION) S 0  /«•  6PIU.  O.fc  •3-*? 3-7  2 5 0 " 250"  / o -  PLUN6-  o-3  3.8  25-0-  /o '  SPILL-  /87  0.5  7 / 8 7  AUG. 7 AUG-  AL>6. 7 AUG-  8 / « 7  O.fo  4-2.  2S-0-  A  to-  0.5"  3.1  25T> •  0-5  4.2.  2SO-  to- PLOKJG. +SPL to • PLUtJG--+SPL-  AUG.. 8 AUG..  /87  c<  BREAKER.  TO)  DATE  9 /87  7  PLutOt.  BEACH  CLIFF  TYPICAL  CROSS  SECTION  COBBLE:  LAYER  CLIFF FACE  SAMb  APRONJ  TKA(JSlEMT SAMb LEWS STEEP £oBBUT UPPER B£A H C  LAS /  BOULPE-RS-\ _  MSL  LLIV TIDAL FLAT  figure 27 o ho  BLUFF  OTHER EROSION)  RECESSION  GEOMETRY  PROCESSES;  1. WINJD 2. RAIM 3. Ff2E.E2E"/T»AW 4. GROUhJD WATER SEEPAGE 5- FLOATING DEBRIS IMPACTS  '^P.&gy  BLUFF  FACE  COB&LE  LAYER,  (  I  I NEW BLUFF FACE AFTER ' WAVE INITIATED RECESS I OlO CAU5EB BY , FORESHORE LOIA/ERIM&  COBBLE FORE5HORE MSL  WAVE INITIATED BLUFF RECESSION] (R.) IS A FUMCTIOW OF FORESHORE" ELEVATION.  figure 28 o CO  104 ON-OFFSHORE TRANSPORT sign convention and volume definitions I.  Z.  SIGN  CONVENTIONS  VOLUME ACCRETED AND ERODED V+ V-  = VOLUME = VOLUME  IV+l = I V - ] (y ) + ( y o = +  3.  GROSS  ACCRETED ERODED o  VOLUME"  Vg  |V I= IV* I + IV-1 ~ A 3  A  4.  NET  VOLUME  ACTIVE  VOLUME  SWEPT  3ETWEENJ  PROFILES  Va V  5.  - AREA  V  n  = (.VO + ( V - ) - O  A  I W h l V j l / 2 =|V | = |V-[ +  figure 29  105 WAVES, ACTIVE VOLUME & TIME DERIVATIVES + = A66RET10M, - = EROSlONi, D S 0  COMSTAfOT  LABORATORY  FIELD  (HYPOTHETICAL)  -4 T  T  032  V  a  r ACTIVE VOLUME  Va = ACTIVE VOLUME Vaetj,-  t  o  Qa. = dVa = SEDIMEtOT ACTIVITY  Qo - JVo- = SEDIMEUT ACT/VITY  LU <J*> 2  £  0  t  o  JJJ  , aQa at  figure 30  V  VERSUS H  a  Q  D = 0.7mm, m; = 0.10, t= l h r 50  beach 1  I  l/i  s aa •J  m  O3 > o >£, O  <  14 T=  DEEPWATER WAVE H E I G H T + T = 1.5s  1.0s  V  A  /(H L ) 0  0  H Q (cm)  VERSUS  o  16  T=2.0s  HQ/LQ  D = 0.7mm, m = 0.1, t= l h r 50  t  beach 1  ca W <  Z o  55 o  a  w  0.04 T=  1.0s  WAVE S T E E P N E S S + T = 1.5s  0.06 H / L  figure 31  0  0  T=2.0s  0.08  107 V 1.2  VERSUS H  a  0  D50= 0.7mm, mj = 0.05, t= l h r beach 2  accretion  1 0.8 0.6 0.4 i ^_  0.2 0  5 o O 3 > o  -0.2 -0.4 -0.6 -0.8 -1 -1.2  1  T= 1.0s  r  ~\ 1 r—~i 8 10 DEEPWATER WAVE HEIGHT - H (cm) + T= 1.5s o 1  1  4  6  0  • V ^ L , , ) 2 1.8  VERSUS  r  16  T=2.0s  H /L o  T—~—i 14  ~i 12  0  D50= 0.7mm, m; = 0.05, t= l h r beach 2  accretion  1.6 1.4 1.2 1 0.8 PJ W H « «  CL,  2  O  So o «  0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 0.02 T= 1.0s  0.06  0.04 WAVE STEEPNESS + T= 1.5s  HQ/LQ  figure 32  T=2.0s  0.08  108 V  VERSUS H  a  D = 0.2mm, 50  0  0.10, t= l h r  accretion  beach 3  to D a O3 > o  O 2 points  ~i  r~  16  14 DEEPWATER WAVE HEIGHT - H (cm) + T= 1.5s o 0  T= 1.0s  V /(H L ) a  0  0  VERSUS  T=2.0s  H /L 0  G  D = 0.2mm, m, = 0.10, t= l h r 50  2  beach 3  accretion  1.8 1.6 3  1.4 1.2 1 0.8  K Ed H  S  CH <  2 o  So o Cd w  0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 0  0.02 ii  T= 1.0s  0.04 WAVE STEEPNESS - H o / L + T= 1.5s  figure 33  0.06 0  T=2.0s  0.08  109 V 1.2  a  VERSUS H  0  D o= 0.2mm, m; = 0.05, t= l h r 5  beach 4  accretion  1 0.8 0.6 0.4 0.2 D is  0  O 3 > o  -0.2  >~ O  -0.4 -0.6 -0.8 -1 -1.2  i—  12  10 DEEPWATER WAVE HEIGHT - H (cm) + T= 1.5s o  14  16  Q  T= 1.0s  Vd^Lo) 2  VERSUS  T=2.0s  H /L 0  Q  D5Q= 0.2mm, m;= 0.05, t= lhr beach 4  accretion  1.8 1.6 5>  5  1.4 1.2 1 0.8  OS  a  0.6  w <: <  0.4  E->  Z  o oo o ca w  0.2 0 -0.2 -0.4 -0.6 -0.8 -1 0.02  1  0.04  0.06  WAVE STEEPNESS - H / L + T= 1.5s 0  T= 1.0s  f i g u r e 34  Q  o  T=2.0s  0.08  110 V  V E R S U S T FOR E Q U I L I B R I U M P R O F I L E S  a  CONSTANT H = 12cm AND VARIOUS D Q  5 0  o  > 01  o < O w fr-  E-  CO  •  D = 0.22mm 50  +  WAVE PERIOD - T (seconds) Da = 0.47mm o 1)50= 0.90mm  4  0  V / ( H o ^ ) VERSUS  gT /D  D5Q= 3.44mm  2  a  CONSTANT H = 12cm FOR VARIOUS Ds 0  5 0  0  accretion 1.5  H  1 H 0.5  H  w  EW  < ca <  -0.5  2  o  55 o as «  -1  -1.5  H  200  •  D5Q= 0.22mm  (Thousands) „ DIMENSIONLESS PERIOD - g T V D + D5Q= 0.47mm 0 D o= 0.90mm  400  5 0  5  f i g u r e 35  A Dso= 3.44mm  111 V 1.6 1.4  VERSUS t  a  SAND BEACHES: D = 0.22mm, m; = 0.05 50  accretion  1.2 1 0.8 0.6 0.4 r  . tn  i-J (A  0.2 0 -0.2 -0.4 -0.6  u  -0.8 -1 -1.2 -1.4 -1.6 8  10  12  14  16  18  20  DURATION OF WAVE ATTACK - t (hours) Ho/lo= 0.006 + Ho/Lo= 0.035  V / ( H o L ) VERSUS t / T a  1.6 1.4  0  SAND BEACHES: D5CF 0.22mm, m; = 0.05 accretion  1.2 1  J  5  a?  0.8 0.6 0.4  as H W  c<a a. z o 55 o ca <  0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 -1.4 -1.6  erosion r—-1 2  1  1 4  1  1 6  1  1 8  1  r—  10  1 12  1  1 14  r  DURATION OF WAVE ATTACK - t / T H / 1 = 0.006 + Ho/Lo= 0.035 0  D  figure  36  16  \  1 18  r  20  112 B E A C H SEDIMENT A C T I V I T Y NNER AND OPEN COASTS LINES OF CONSTANT WAVE HEIGHT FOR COARSE AND FINE MATERIAL + 1 ACCRETION ONSHORE MOVEMENT  COARSE MATERIAL  V  UJ  M  a  Ld cn  LOW STEEPNESS WAVES  HIGH STEEPNESS WAVES  LL  o  WAVE PERIOD  UJ  D _I  a >  FINE MATERIAL  >  M  H O <  OFFSHORE MOVEMENT EROSION MONTHLY VARIATION OF WAVE PERIOD WINTER  WAVE PERIOD  n m o 2  ID  OPEN COAST  INNER COAST  IN CO 0)  (VI  WINTER  figure  37  113  O P E N 0.26  COAST  WAVE  PERIOD  DISTRIBUTION  NEAR TOFINO, BRITISH COLUMBIA  -i  0.24 0.22 0.2 H  •  WAVE PERIOD - (seconds) JANUARY 1982 + AUGUST 1982  figure  38  D I S T R I B U T I O N OF WAVE  STEEPNESS  NORTH PACIFIC NEAR TOFINO  0.15  w  o 2  Ed OS D u u o EL.  O  >•  "3 5 < a o  K  CL,  0.00  0.01  0.02  0.03  0.04  WAVE STEEPNESS -  0.05 H /L 0  0.06  0.07  0.08  0  D I S T R I B U T I O N OF WAVE I N T E N S I T Y NORTH PACIFIC NEAR TOFINO  0.35  -  Ed  o  z Ed  ca p o o  0.25  EK  o  P3 <!  0.15  -  0.05  -  CO O  ca cl,  1.0  2.0  3.0  WAVE INTENSITY (E/T) -  4.0 kJ/m /s  figure 39  2  6.0  DISTRIBUTION OF WAVE S T E E P N E S S STRAIT OF GEORGIA NEAR ROBERTS BANK  0.15  H U  td DJ D o o o o  a o es  0.00  0.01  0.02  0.03  0.04  IIIIII  WAVE STEEPNESS -  0.05  H /L 0  0.06  0.07  0.08  0  DISTRIBUTION OF WAVE INTENSITY STRAIT OF GEORGIA NEAR ROBERTS BANK  0.4  0.35  Cd  z  Cd CK D o u o  0.25  b O  >0.15 ra o «  OH  0.05  0.00  1.00  2.00  3.00  4.00  WAVE INTENSITY (E/T) - k J / m / s 2  f i g u r e AO  6.00  photographs  116  PHOTO 3 - AUGUST 1987 P a r t i c l e d i s p e r s i o n one  day  after  initial  placement.  PHOTO 4 -  AUGUST  1987  Typical plunging experiment, height  breaking wave 0.5m a n d p e r i o d  during 4s.  sediment  tracing  118  PHOTO 5 - MAY 1987 S t e e p s h i n g l e b e a c h a t Camp B y n g , f o r e s h o r e s l o p e i s 1V:3.5H, median  PHOTO 7 -  JUNE  Roberts shingle  Creek. size is  The u p p e r 20mm.  1987  C o b b l e c o l o n i z e d by s e a w e e d , F r e n c h B e a c h , S o o k e . The c o b b l e was F o u n d h i g h i n t h e u p p e r f o r e s h o r e , c a r r i e d onshore from d e e p w a t e r by s t o r m w a v e s .  PHOTO 8 - MAY 1987 F l a t stones are t y p i c a l  of  inner  coast  shingle  beaches.  PHOTO 9 -  JUNE  1987  Gordons Beach, Formation spaced  PHOTO  11 -  at  Sooke. 15m.  A  shingle  beach  with  cuspate  MAY 1987  Shingle beach, Lock Bay, G a b r i o l a g r a v e l o F 15mm m e d i a n d i a m e t e r .  Island.  The  sediment  is  a  PHOTO  12 -  MAY 1987  S h i n g l e beach s u b s u r f a c e , b e a c h i s a p r i s m oF g r a v e l  Lock Bay, Gabriola Island. i n the upper F o r e s h o r e .  The  PHOTO 13 - MAY 1987 Gravel upper f o r e s h o r e F a c i n g t i d a l F l a t s , Savary Island. The d i s t i n c t c h a n g e i n s l o p e Flat to the upper beach i s t y p i c a l of the  PHOTO 15 - MAY 1987 Heavily armoured cobble beach near I s l a n d . The c o b b l e l a y e r may be s e v e r a l  PHOTO southern shore, From t h e tidal inner coast.  PHOTO Qualicum, Vancouver stones thick.  14 -  MAY  1987  Dundarave F o r e s h o r e , West V a n c o u v e r . The l o w e r F o r e s h o r e i s cobble armoured and t h e upper f o r e s h o r e i s m o b i l e s a n d and gravel.  Timber beach  16 -  JULY  pile, level  1988  Wiffen is  Spit,  due t o  wear  Sooke.  Hourglassing  by m o b i l e  gravel  of  and  the  pile  cobble.  at  121  PHOTO  17 -  MAY  1987  PHOTO  Cape Mudge, Q u a d r a I s l a n d . The b l u f f t o p c o b b l e l a y e r , w h i c h is typical of many i n n e r c o a s t b l u f f s , is a source of foreshore cobble.  PHOTO 19 - MAY 1987 Rebecca S p i t , Quadra  18 -  PHOTO 20 Island.  The m e d i a n  cobble  size  is  70mm.  MAY  1987  Cobble and b o u l d e r f o r e s h o r e , The upper f o r e s h o r e c o b b l e a r e clean, abraded appearance.  MAY  Cape Mudge, Quadra I s l a n d . m o b i l e a s i n d i c a t e d by t h e i r  1987  Rebecca S p i t , Quadra I s l a n d . Longshore t r a n s p o r t cobble to the s p i t f r o m a s f a r a s Cape M u d g e ,  has 5km  brought away.  122  PHOTO 21  -  MAY  1987  Willemar B l u f f s , Comox. W e s t w a r d d r i f t o f s a n d i n t h e u p p e r foreshore. The sand i s t r a n s i e n t and u s u a l l y f o u n d i n the u p p e r f o r e s h o r e d u r i n g p e r i o d s o f low wave a c t i v i t y .  PHOTO 23 - MAY 1987 Willemar Bluffs, Comox. Sand aprons around the bluff toe during summer r e l a t i v e l y low wave a c t i o n i n t h e u p p e r  PHOTO 22 - JANUARY 1988 Willemar B l u f f s , Comox. R e c e n t s t o r m waves sand away from the b l u f f toe, note the concrete groynes.  PHOTO 24 are able to develop months because of foreshore.  JANUARY  Willemar B l u f f s , photo 23, shows recession.  have t r a n s p o r t e d failure of the  1988 Comox. erosion  The p h o t o , t a k e n 9 months of t h e sand apron and  after bluff  123  PHOTO 25  -  MAY  1987  Willemar Bluffs, Comox. Sand c o n t i n u a l l y e r o d e s from the b l u f f face accumulating around the b l u f f toe d u r i n g periods o f low u p p e r f o r e s h o r e wave a c t i v i t y .  PHOTO 27 Willemar toe .  MAY  1987  Bluffs,  Comox.  PHOTO 26 - JANUARY 1988 Willemar B l u f f s , Comox. The e r o d e d s a n d i s b e l i e v e d t o h a v e moved both downcoast and o f f s h o r e d e p o s i t i n g on t h e sandy tidal flats.  PHOTO 28 Sand a p r o n  developing  around  bluff  JANUARY  1988  Willemar B l u f f s , Comox. The s a n d i s e a s i l y storm wave a c t i o n i n the upper f o r e s h o r e o v e r s t e e p e n i n g o f t h e b l u f f s and subsequent  e r o d e d by w i n t e r which leads to erosion.  appendices  124  458 WIND 5UHHARY  1010 02  03  04  SE 5  E 2  SE 3  02  H W NW 18 16  Ntf 16  NW 13  03  NW H 16 .11  HE 8  ME 5  E 5  04  E 10  E 11  E 10  E 8  E 6  OS  SE 5  H 2  SE 5  W 24  w 34  W NW 37 43  06  NW 43  *w 39  NW 34  NW 32  N 23  NE 6  07  N 21  SE 13  SU 13  NW 21  NW 29  08  E 18  SE 31  SE 34  SE 29  E 18  E 16  E 13  E 26  E 23  11  E 24  12  PST  0«  SE 3  05  07  06  08  09  10  11  12  /HR)  14  16  S»HO HEIOS LICHTSTITIOO 17  18  19  20  21  22  23  24  19  NW 16  NW 21  NW 19  NW 16  NW 16  HW  19 NW  NW 21  Ntf 21  NW 13  W 14  HW 11  NW 14  NW  SW N w HE " 3" "5" " 5 ""5  E 5  W  E 6  E  NW HW HW 47 " «S "42  HW 42  NW  WW 39  NW 42  NW 43  HW  NW E E E -29" •16" "19 "19  E 18  HW  X 2  E 3  W 2  w 3  NW 5  NW 6  NW 6  NW  10  W  NW  13  13  14  18  W NW 13 13  N 11  N 6  N 10  N 10  N 8  N 10  NW  W  NW  NW  NW  E 3  NW 3  W SE 3 3  S 2  S 3  SW 3  SW  E 6  E 6  E 8  E 13  E 13  E 13  SE 14  SE 14  SE  10  SE 13  NW 45  NW 43  NW 42  NW  NW  W  W  W  W  E ]  W W 45 50  8  NW  11  14  16  18 SE  3  40  39  40  40  42  SW SW 10 8  SE 8  SE 10  SE SE  E 16  E 13  WW 55" "26" "2T NW  N  SE  SE  E 6  MEIH SPD  NW 10  W 10  W 13  W 10  NW 31  NW N> 31 -27  NW 26  NW 23  NW 23  NW 19  W  31  NW  27  19  SE 24  SE 24  E 23  E 19  E 27  E 29  E 23  E 16  £ 1)  E 10  SE 13  E 16  E 27  E 27  E 24  E 18  E IB  E  21  E 23  E 19  E 18  E 24  E 24  E 23  E 19  E 27  E 29  E 24  E 31  E 27  E E E 34 H ~iV  E 26  E 31  E 27  E 27  E 26  E  E 21  E 23  E 24  E 19  E 21  E 18  E 21  E 16  E 11  E 23  E 21  E 19  e  e  E 27  E 24  E  E 24  E 21  E 23  E 19  E 19  E 14  E 14  E 14  E 11  E 10  E 6  N SE 11 " 6  SE 10  E  E 11  E 10  e e  E 3  ME 6  E 11  £ 11  E 13  E 13  E 13  E 10  E 5  e 10  8 10  E  13  E 5  E 6  SE 5  S 3  SE 5  C  SE 2  SW 2  SW S  N 11  NW 10  HW 11  14  E e  E 3  E 5  E 3  H  3  N 2  NW 6  N 6  N 10  NE 6  H 11  N  10  15  E 19  E 19  E 19  E 14  S 14  S 11  S 14  S 18  5  24  S 24  S 24  S 31"  16  V  V  6  I  10  SE 14  SE 19  s 19  S 31  S 31  S 35  S 35  S 29  S 24  39  17  W 34  W 39  V 34  W W 27 31  W W 21 18  W 14  NW 10  E 13  E IB  E e 16 "23  18  E 51  E 47  E 42  E 48  S 47  S 32  S 31  S 29  S 32  S 31  SE  iv  V "23  10  6  E 48  W V W SW 23" ~2t "27 16  S 40  SW W SE SE "H ' 6 ' 5 " U  E 19  S S SE TI" ' 26""26  11  E 14  E 18  5  NW  E 23  I  E 21  E 19  NW  NW  18  NW IW 23" 19"  NW  NW  NW  13  >w 11  SW  •w 16  w B  19  S 27  S SE SE SE 26' "26- "76—2T"  w 11  w 6  W 5  S 1* NW 27  10  11  w 11  HW 13  W 13" 11  E 24  E E 21—2r  E  E  I  St 43  SE 47  S 47  S 45  W  W  S 53  TT 3 55  E 13  26  E 8  SE E E "14 "14 " 13  13  16  SE 13  SE 13  SE SE SE 3 5 5  21  N HW 21" 16  NW NW 13 11 NE 8  W 13  w 27  E 13  PRE* DIR  E 5  09  N 6  SE 6  10  IQf 1986  BC  S 53  E E 14" "11 "  HW  S 6  S B  SE 13  SW 8  W  MW 6  SW " B  S  W 32  w 35  H 39  NW 40  w  3  SVl  E E E E 34" 4 7 " 45 SO SW 35  SW 40  SW SW 37 32  SE SE SE SE SE SB SE SE S S SE "3"9—39—4T" TI—5TS—51—5T" T 5 — J 2 — 3 9 — 3 T  SE  Mil TEL  9.8  21  13.1  21  4.7  16  11.2  19  35.7  55  19.0  41  24.5  40  22.2  34  24.0  32  20.8  27  13.6  24  9.2  13  9.6  23  B.5  19  18.6  31  22.1  40  27.0  80  41.8  S3  30.6"  SI  >  z: v  >  "1 01  4 S B WN ID SUMMAR/MR) Y  S I S 0 KtlDS L I C M T S T 1 T I 0 K  BC  PST HR OL OY  02  20  S 31  s 21  S 27  S 34  S 40  S 40  S 37  S 34  S 31  SE 3S  39  S 40  S 39  S 40  S 35  S 31  S 29  S 27  SW '24  SW 21  w 21  SW 21  w 10  SW 14  S  21  SW 16  s 14  S 24  S 23  S 26  S 34  S 26  S 27  S 27  S 27  S 27  S 27  S 29  SE 29  SE 34  SE 37  E 31  E 32  E 35  E 42  SE 43  SE 39  SE 35  SE 26  s  22  E 24  E 21  E 21  E 16  NE 10  HE 6  E 3  SW 8  SW 11  E 8  E 13  £ 14  E 18  E 21  SE 18  SE 31  SE 32  SE SE SE SE SE 32" "34 '~35 ~37 " 4 2  SE SE "45 '42  SVL  23  SE 39  £ 35  SE 39  SE 45  SE 47  S 47  S 56  S 48  s 51  S 34  w 19  W 5  SW 14  SW 34  SW 34  S 34  S 34  S 32  24  S 18  S 21  S 27  S 23  S 23  SW 18  W 34  NW 32  NW 48  NW 43  N 48  NW 51  w W 51 "50  W 42  w 42  25  S 29  SE 35  SE 35  se 40  SE 37  SE 39  SE 39  SE 39  SE SO  SE 60  SE 53  SE 42  SE 47  SE 40  SE 40  SE 35  26  SW 35  SW 32  W 16  W 21  W 23  W 14  V 11  E 11  SE 14  E 19  SE 29  SE 31  SE 31  27  sw 39  S 13  S 27  s 37  W 32  SE 19  S 18  SW 27  S 16  E 13  SE 21  S 26  S 27  NE 3  N 14  N 24  N 24  N 23  NU 24  NW 27  NW 19  NW 21  NW 18  NW 19  NW 23  E 11  E 13  E 19  ie  E  E 16  E 13  E 14  E 16  E 21  E 21  E 19  E 26  E 24  E 24  E 26  E 26  E 26  E 29  E 26  E 26  E 27  E 27  28 29 30 HI  03  04  05  06  07  08  W 6  09  10  11  12  13  13  16  17  18  19  20  21  22  23  24  PREY OIR  S 18  S 19  S 19  S 16  SE 21  SE 19  S  W NW 35 2J  W 11  SW 10  S 13  E E 14 " 2 3  E 19  w  SE 35  SE SO  SE 51  SS 58  SE 66  S 56  S 50  SW 40  SE  E 26  E E E 23 '29 "39"  SE 48  E e 53"""37  E 39  E 37  S 37  E  S 32  S 21  S 24  SE 26  S 19  S 11  SW 8  NE 10  NE 10  « 6  S  NW 23  HW 21  NW 24  NW 21  MW NW 23 " 2 3  NW 2r  N M WE 19 "21 " 1 0  E " 8  NE 6  NW  E 23  E 23  E 24  E 23  E 21  E 23  E 24  e 27  E 24  E 26  E  E 27  E 29  E 31  E 31  E 26  E E '34 " 3 7  E 40  E  E 24  NE 8  E 27  E E E E E "37 "31 "32 "34 " 3 5  E 27  Ml  1986  MEAN SPO  mi  30. 4  40  29.2  43  22.6  45  31.6  56  3 0.0  51  4 4.4  46  27.5  53  20.4  39  "0  19.1  27  Z O  20.7  27  29.2  40  TEL  % • 9 16 22 24 15 11 3 •  TOT 1 62 5 115 17 159 4 171 7 108 78 25 1 720 33 5 22.4 11. .9  NE  ENE  3 12  17 31 67 83 25 10 3  15 2 7.1  MAXIMUM WIND  66  MAXIMUM GUST  M  E  238 33 20.3  ES E  SE IS 8 18 10 25 24 10 1 111 15 27.9  PUBLISHED  SSE  5  "SSW  ""SW" ~V5F~  5 4 17 30 30 13 7  5 "8 7  106 15 28.1  3S 5 "19.2  10 16 12 11 —r2 9 3  4  8""  DY 25  YECTOR MEAN OIR(DECS) 136 ( SE) SPO  DY  PREVAILINC DIRECTION  E  ~V—WWW  73 10 ""21V2" 7  OIR CRT  •HW  2 17  CALM  1  34  26  8""  19 2 108 15 23.0  MEA1 SPEED 720  SPO CUT  720  Mil* CRT  >  X  630 593 604 650 639 579 606 571 646 6 46 653 621 687 700 697 722 755 763 715 736 753 729 717 698 MONTHLY SUMMARY -  "SPEED 00 01-05 06-11 12-19 20-28 "29-38 39-49 50-61 63* TOTAL PRCNT ME1H  14  22.4 04/16/17  >  PAC-E  B  APPESJDIX  STATION 108 ROBERTS B A N K , B . C . FEB 7 . 1 9 7 4 TO A P R I L 3 , 1 9 7 6 NUMBER OF OBSERVATIONS 3880 OCCURRENCES OF CALM 1191  4.0 LU QC I— UJ  3.5 -  3.0  LU  2.5  cx  1  2.0 -  2  <x o  2  ± I .5 o  ,—i  I -0 -  0.5  7  1 1  1  13 28  2  44 40  1  36 134 32 32 229 176 9  1  1377 517119 9  13  1  8  413 287 60 53 28 11  0,0 2  ~1  1  1  1  3  4  5  6  1  1 1  1  1  1  1  1  1  1  1  1  1  7 8 9 10 1 1 12 13 14 15 16 L7 20 PEAK PERIOD IN SECONDS  127  PAGE  STATION 103 TOFINO B C JANUARY 1 , 1 9 8 2 TO DECEMBER 3 1 . 1 9 8 2 NUMBER OF OBSERVATIONS 2880 OCCURRENCES OF CALM 0 10 -.  CO UJ  8 -  DC t— UJ  7 -  ex o  h  3 -  o CO  55  1  2 -  1  2  1  1  2  1  2  2  1  1  1  1  2  1  3  1  2  3  4  5  4  5  6  4  3  9  11  10  9  6  5  4  o  tx'  1  1  6 -  5 -  1  2 2  1  10 14 19 25  19 12  12  2  3  4  26 28 24 20  16 30  10  3  2  5  24 47 23 33 37 40  7  1  3  13 21 28 44 46 57 48 43  19  11  4  41 60 70 90 89 58 71 43  29  17  86  90  100  87  1  38 62 58 86 138 92 69 68  8  10  9  14 48 48 20  81  18 24 95 1  ~i—i—r 2  3  4  5  T  6  T  "i  1  1  1  1  1  1  1  1  1  7 8 9 10 11 12 13 14 15 16 17 20 PEAK PERIOD IN SECONDS  iZS  FORECAST POINT: TSflWHflSSEN LATITUDE: 49 OO 20 N LONGITUDE: 123 07 24 U  HINDCRST  WAVE  N O V E M B E R  HEIGHTS  1 9 8 6  LD  > rn c;  360  TIME IN HOURS  480  600  720  > m  

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