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UBC Theses and Dissertations

Beach profiles and sediment activity Mattila, Mark Ronald 1988

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B E A C H P R O F I L E S A N D S E D I M E N T A C T I V I T Y B y M a r k R o n a l d M a t t i l a B . A . S c . ( C i v i l Eng inee r ing ) , Un ive r s i t y of B r i t i s h C o l u m b i a , 1 9 8 5 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F A P P L I E D S C I E N C E in T H E F A C U L T Y O F G R A D U A T E S T U D I E S C I V I L E N G I N E E R I N G W e accept th is thesis as con fo rming to the requi red s t andard T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A ' N o v e m b e r 1 9 8 8 (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 Bri t ish 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 The University of Bri t ish Columbia 2075 Wesbrook Place Vancouver. Canada V6T 1W5 Date: A B S T R A C T A s tudy of beach profiles and sediment a c t i v i t y has been unde r t aken inves t iga t ing n a t u r a l beaches of inner coas ta l southwest B r i t i s h C o l u m b i a and p u b l i s h e d d a t a on l abora to ry beaches. T w o separate types of sediment a c t i v i t y are focused u p o n : longshore sediment, a c t i v i t y <>< c u r i n g o n inner coast beaches and on- offshore sediment a c t i v i t y o c c u r i n g on wave Hume cons t r a ined l a b o r a t o r y beaches. Field i nves t iga t ive work on twenty-f ive n a t u r a l beaches has i n c l u d e d review of past-field s tudies , profi le surveys , sediment t r a c i n g exper imen t s , inves t iga t ion of surface and subsurface sediment, size d i s t r i b u t i o n and s t ruc ture , measurement of slopes and elevat ions of shorel ine features, rev iew of avai lable wave c l ima t e d a t a and wave h indcas t ing for the pe r iod of profi le surveys. T h e work has shown tha t inner coas ta l beaches are predom-inan t ly shingle beaches or cobble a r m o u r e d beaches w i t h longshore sediment transport, o c c u r i n g in a nar row upper foreshore zone under wave ac t ion at h igh t ides. T h e r e is also evidence that coarse mate r ia l s (gravels and cobbles) move select ively in an onshore d i r ec t ion and fine mate r i a l s (sil ts and sands) move i n an offshore d i r ec t i on . T h e sediment t r anspor t processes and beach character is t ics ident i f ied are different f rom the s u m m e r / win te r beach process k n o w n to occur on open coasts. L a b o r a t o r y beaches have been s tudied to ident i fy the general response of a beach profi le to waves. O n e p r o b l e m i n the s tudy of beaches has been the lack of a read i ly measured va r i ab le to in ter re la te wave ac t ion and sediment movement . B y s t u d y i n g lab-ora to ry beach profiles a va r iab le represent ing on-offshore sediment, movement has been abs t rac ted as an area swept out by differencing two profiles as a func t ion of t ime . T h e var iable has been inves t iga ted us ing l a b o r a t o r y beach d a t a and cor re la t ion between i t ii and wave parameters such as height, and period is evident. A dimensional analysis of on-offshore sediment transport is performed using the swept, area variable. ( i i i T a b l e of C o n t e n t s A B S T R A C T i i L i s t o f Tab le s v i i i L i s t o f F i g u r e s ix List , o f P h o t o g r a p h s x i N o m e n c l a t u r e x i i i A c k n o w l e d g e m e n t xv 1 I N T R O D U C T I O N 1 1.1 General 1 .1.2 Inner Coast Beaches - Current Status of Knowledge 2 1.3 Previous Work 3 1.4 Research Justification 6 2 T E C H N I C A L W O R K A N D E X P E R I M E N T S 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 L a b o r a t o r y B e a c h D a t a 16 3 F I E L D I N V E S T I G A T I V E W O R K 18 3.1 B a c k g r o u n d 18 3.2 S t u d y A r e a 18 3.2.1 G e o g r a p h y 18 3.2.2 P h y s i o g r a p h y 19 3.2.3 G e o l o g y a n d geomorph ic h i s to ry 19 3.2.4 L i t t o r a l mater ia l s 20 3.2.5 W i n d and wave c l i m a t o l o g y 20 3.2.6 T i d e s 21 3.2.7 Shore l ine c lass i f icat ion 22 3.3 Si tes S t u d i e d 24 3.4 Sed iments 26 3.4.1 B e a c h slope and gra in size 26 3.4.2 Sh ing le beaches 26 3.4.3 A r m o u r e d beaches 27 3.5 Prof i les 29 3.5.1 D i s c u s s i o n : 29 3.5.2 Tsawwassen B e a c h 30 3.5.3 Tower Beach at Point. G r e y 32 3.5.4 D u n d a r a v e 33 3.5.5 E l eva t i ons of shore features 33 3.5.6 H i n d c a s t waves and profi le changes 35 3.6 Sediment T ranspo r t 36 3.6.1 G e n e r a l field observat ions 36 v 3.6.2 Sediment t r anspo r t exper iments 37 3.7 B l u f f E r o s i o n - C u r r e n t S ta tus of K n o w l e d g e 40 4 LABORATORY BEACHES 44 4.1 G e n e r a l 44 4.2 A c t i v e V o l u m e 45 4.3 D i m e n s i o n a l A n a l y s i s 46 4.4 A n a l y s i s of B e a c h Prof i les 50 4.4.1 M e t h o d of analys is 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 wave pe r iod 52 4.4.4 A c t i v e vo lume versus t i m e 53 5 DISCUSSION 56 5.1 B e a c h Response 56 5.2 Differences Be tween N a t u r a l and L a b o r a t o r y Beaches 57 5.3 C o a s t a l Processes 58 6 FURTHER RESEARCH 62 7 CONCLUSIONS 64 7.1 F i e l d Inves t iga t ive 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 v i A p p e n d i c e s 124 List, o f Tab le s 1 P o i n t A t k i n s o n T i d e s 22 2 Some Inner S o u t h Coast. Beaches 25 3 B e r m Cres t and D e b r i s L i n e E l e v a t i o n s 34 4 T r a n s p o r t of Pa r t i c l e s 39 4(a) Longshore T r a n s p o r t of Pa r t i c l e s 39 4 (b) Onshore T r a n s p o r t of Pa r t i c l e s 39 5 Some E r o d i n g C o a s t a l Bluffs 40 v m L i s t o f F i g u r e s 1 Location Plan 76 2 Site Plan 77 3 Grain Size and Permeability Classification 78 4 Beach Profile Envelopes 79 5 Comparison of Measured and Hindcast Wave Heights 80 6 Laboratory Profiles - Data Set 1 81 7 Laboratory Beach Profiles - Data Set 2 82 8 Laboratory Beach Profiles - Data Set 3 83 9 Distr ibut ion 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 . 88 14 Beach Face Slope Versus Grain Size 89 15 Shingle Beach - Typical Cross Section 90 16 Armoured Beach - Typical Cross Section 91 17 Tsawwassen Beach Profiles 92 18 Tower Beach Profiles 93 19 Dundarave Profiles 94 20 Cross Shore Sediment Size Distr ibution 95 21 Grain 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 25 N u m b e r of 7 5 m m Par t i c l e s per Square M e t r e of Beach Surface 100 26 N u m b e r of 7 5 m m Par t i c l e s per Square M e t r e of B e a c h Surface 101 27 B e a c h C l i f f T y p i c a l Cross Sec t ion . . . ., 102 28 B l u f f Recess ion G e o m e t r y 103 29 On-Offshore T r a n s p o r t 104 30 Waves , A c t i v e V o l u m e and T i m e Der iva t ives 105 31 Va Versus H0, D50= 0 . 7 m m , mr= 0.1 106 32 Va Versus Ha, D5Q= 0 . 7 m m , mt= 0.05 107 33 V t t Versus H0, D50= 0 . 2 m m , 0.1 108 34 V ' a Versus H0, D50= 0 . 2 m m , mr= 0.05 109 35 Va Versus T 110 36 Va Versus t . . . I l l 37 B e a c h Sediment A c t i v i t y Inner and O p e n Coas t s 112 38 O p e n Coas t W a v e P e r i o d D i s t r i b u t i o n 113 39 Inner Coas t D i s t r i b u t i o n s of W a v e Steepness and Intensi ty 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 and In tens i ty 115 x List , of P h o t o g r a p h s 1 A U G U S T 1987 - Sediment t r ac ing exper iments . . .• 117 2 .. A U G U S T 1987 - Sed iment t r ac ing exper imen t s 117 3 A U G U S T 1987 - Sediment t r ac ing exper iments . 117 4 A U G U S T 1987 - Sediment t r ac ing exper iments 117 5 M A Y 1987 - Steep shingle beach, C a m p B y n g , R o b e r t s Creek 118 6 M A Y 1987 - Steep shingle beach, T r a i l B a y , Sechelt 118 7 J U N E 1987 - C o b b l e co lon ized by seaweed, F r ench B e a c h , Sooke 118 8 M A Y 1987 - T y p i c a l shingle 118 9 J U N E 1987 - Steep shingle beach, G o r d o n ' s B e a c h , Sooke 119 10 J U N E 1987 - Steep backshore b e r m , G o r d o n ' s B e a c h , Sooke 119 11 M A Y 1987 - Shingle beach , L o c k B a y , G a b r i o l a Is land 119 12 M A Y 1987 - Sh ing le beach subsurface, L o c k B a y G a b r i o l a Is land 119 13 M A Y 1987 - G r a v e l beach , southern shore, Savary Is land 120 14 M A Y 1987 - A r m o u r e d foreshore, D u n d a r a v e , West 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 beach , Qua l i cu r r i , V a n c o u v e r Is land . . . . 120 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 le , Wi f f en S p i t , Sooke 120 17 M A Y 1987 - B l u f f top cobble supply , C a p e M u d g e , Q u a d r a Is land . . . . 121 18 M A Y 1987 - C o b b l e and bou lder foreshore, C a p e M u d g e , Q u a d r a Is land . 121 19 M A Y 1987 - R e b e c c a Sp i t , Q u a d r a I s land 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 Is land 121 21 M A Y 1987 - S u m m e r bluff eros ion, W i l l e m a r Bluf fs , C o m o x 122 22 J A N U A R Y 1988 - W i n t e r bluff e ros ion , W i l l e m a r Bluf f s , C o m o x 122 23 M A Y 1987 - S u m m e r bluff eros ion, W i l l e m a r Bluf 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 ros ion , W i l l e m a r Bluf f s , C o m o x 122 X ] 25 M A Y 1987 - S u m m e r bluff eros ion, W i l l e m a r Bluf fs , C o m o x 123 26 J A N U A R Y 1988 - W i n t e r bluff eros ion, W i l l e m a r Bluffs , C o m o x 123 27 M A Y 1987 - S u m m e r bluff eros ion, W i l l e m a r Bluf fs , C o m o x 123 28 J A N U A R Y 1988 - W i n t e r bluff eros ion, W i l l e m a r Bluf fs , C o m o x 123 x i i Nomenclature C= on- offshore parameter; d= depth of water; D5Q= m e d i a n particle diameter; E— wave energy density or specific energy; F - fetch length; g= acceleration due to gravity; H H W - = higher high water; H W — high water; Hc~ deep water m o n o c h r o m a t i c wave height; Hs — significant wave height; / = wave intensity (E/T); L L W — lower low water; L0— deep water wave length; L W = low water; ??i,;= ini t ia l beach slope; M S L = : mean sea level; M W L = mean water level; p= fluid density; ps— particle density; Qa= dVa/dt=- sediment, act ivi ty; /?= horizontal bluff recession; \Vaeq '~ ^ a i | / | K e 9 | = profile state parameter; T— wave period; Tp~ peak per iod; x m T s — significant per iod; t— dura t ion of wave event; td= dura t ion of wave event; U= w i n d velocity; / /= k inemat i c viscosity; v— d y n a m i c viscosity; Va— active vo lume relative to a reference profile; Vaeq~ e q u i l i b r i u m active vo lume relative to a reference profile; Vai~ init ial active vo lume relative to a reference profile; Vg— gross vo lume. xiv A c k n o w l e d g e m e n t , T h a n k s must be granted to the m a n y people who c o n t r i b u t e d in var ious capaci t ies to the c o m p l e t i o n of th is work. M y sincerest thanks go to m y adviser D r . M . de St . Q . Isaacson for his gu idance and pat ience th roughou t the development of m y thesis. T h a n k s are also ex tended to D r . M . C . Q u i c k for his op in ions a n d suggestions. M r . D . M c C o n n e l l , P . E n g . of H a y and C o m p a n y C o n s u l t a n t s Inc. is acknowledged for ideas that lead to the o r i g i n a t i o n of the thesis t op i c . F i n a l l y , I a m indeb ted to A n g e l a a n d Jason B a r t o n , R o n B y r e s , K e v i n M c T a g g a r t , C a r o l M i h e l c i c , B r o c k N a n s o n , J o h n P a t t l e , P . E n g . , and B r e n d a S t e ln i ck i for the i r assistance w i t h field work . x v C h a p t e r 1 I N T R O D U C T I O N 1.1 G e n e r a l 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 Br i t i sh Columbia 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 Bri t ish Columbia , 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. At 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 the r e m a i n i n g twenty two sites inves t iga t ions were made on an occas iona l basis , i n -ves t iga t ion focus ing u p o n field cond i t ions w h i c h have been re la t ive ly uns tud ied to date: beach geomorpho logy , slopes, sediment sizes a n d elevat ions of shorel ine features. T h e c o m b i n e d observa t ions at each site have p r o d u c e d an overa l l desc r ip t ion of the coast. L D u r i n g the inves t iga t ion sites were classified and test pi ts were dug to ident i fy the char-acter o f the beach subsurface, a sediment t r anspor t exper imen t us ing 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 an inven tory of beaches assembled. O p e n coast beaches a n d waves have also been reviewed for c o m p a r i s o n since the sediment t r anspor t processes o c c u r i n g w i t h i n the inner coast are assumed to be o n l y a s m a l l par t of an overa l l p h y s i c a l process of m u c h broader scope. B l u f f erosion on the inner coast has been rev iewed as a s idel ine because of its loca l s ignif icance. T h e s t u d y of l a b o r a t o r y beaches has i nvo l ved co l l ec t ing pub l i shed beach profi le da ta , def in ing a va r i ab le in t e r r e l a t ing on-offshore sediment movement 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 ana lys is us ing the var iab le a n d inves t iga t ing on-offshore sediment movemen t under wave ac t ion i n var ious l a b o r a t o r y exper iments . T h e area swept out be tween two shore n o r m a l profiles as a func t ion of t i m e is p roposed as a var iab le for i n t e r r e l a t i ng waves and on-offshore sediment movement . T h e va r i ab le has been t e rmed ac t ive vo lume . A concept of beach response to waves based u p o n general behav iour observed i n l a b o r a t o r y beaches and in the field is presented to e x p l a i n i n par t the role of the l o c a l wave reg ime i n d e t e r m i n i n g inner coast beach morpho logy . W a v e c l ima t e d a t a for inner and outer coasts have been reviewed to p rov ide some suppor t for the concept . 1.2 I n n e r C o a s t B e a c h e s - C u r r e n t S t a t u s o f K n o w l e d g e M o s t beaches w i t h i n the inner south coast, of B r i t i s h C o l u m b i a m a y be general ly desc r ibed as shingle or a r m o u r e d beaches cons i s t ing of gravels , cobbles a n d bou lders , f igure 3. Chapter 1. INTRODUCTION 3 Sed iment a c t i v i t y o c c u r i n g on inner coast beaches occurs on a different scale t han open coast beaches as i nd i ca t ed by profi le envelopes, figure 4, wh ich exempl i fy the re la t ive scale of the processes be ing discussed. O p e n coast beaches are k n o w n to have seasonal m o r p h o l o g i c changes caused by sea-sonal v a r i a t i o n i n wave c l ima te , the wel l k n o w n s u m m e r / w in te r beach concept appea r ing i n the l i t e ra tu re on the top ic [42],[2]. T h e G e o l o g i c a l Su rvey of C a n a d a has s tudied sea-sonal changes i n beach m o r p h o l o g y a long the B . C . coast [18]. T h e i r f indings ind ica te tha t the s u m m e r / win te r beach m o d e l is not appropr i a t e for shorel ine response w i t h i n the i n -ner coas ta l waters , however, the m o d e l becomes representa t ive of real beach response as one approaches the open ocean. L o n g beach , near Tof ino on V a n c o u v e r I s land , is an open coast sandy beach exposed to the N o r t h Pacific, tha t exh ib i t s seasonal morpho log i c changes. 1.3 P r e v i o u s W o r k T h o r o u g h b ib l iographies of s tudies c o n d u c t e d on the B . C . coast is i n c l u d e d i n " M o r p h o l -ogy and L i t t o r a l Processes of the Pac i f i c C o a s t of C a n a d a " [6] and " C o a s t a l Resources F o l i o " [33]. M o s t of the papers l i s t ed i n these b ib l iograph ies cover e n v i r o n m e n t a l , geolog-i c a l , geomorph ic or oceangraphic, top ics at specific, sites, s tudies focus ing on inner coast beaches i n p a r t i c u l a r are few. In the s t udy of beach profiles and sediment, a c t i v i t y the o p p o r t u n i t y to e x p a n d u p o n the knowledge of inner coast beaches was pursued . T h e l i t e ra tu re on coastal eng ineer ing and re la ted topics has extens ive coverage of sand beaches on open coast l ines . T h e work of the U . S . A r m y C o r p s of Engineers has t h o r o u g h l y s tud ied beaches of th is type loca ted on the southeast coast of the U n i t e d States , C a l i f o r n i a and H a w a i i . O p e n coast sand beaches are by far the most s tud ied i n t e rms of l eng th of coas t l ine a n d are also of the most engineer ing interest since the Chapter J . INTRODUCTION 4 backshore areas are h e a v i l y popu la t ed and developed. T h e beaches of inner coas ta l B r i t i s h C o l u m b i a , however , are p r e d o m i n a n t l y coarse m a t e r i a l and experience waves of lower height and p e r i o d than open coast beaches. Few studies have been found on beaches of such sed imenta ry character a n d under a s i m i l a r wave regime. Some papers have appeared on shingle 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 observat ions s t a r t ing abou t 100 years ago [43] on the U . S . west coast focused on seasonal changes i n sand beaches. E a r l y inves t iga tors h a d found the sea-sona l changes mys te r ious ; the. forces and mechan i sms i nvo l ved in sand movement were i m p e r c e p t i b l e since most profi le change takes p lace underwate r . O n the west coast steep intense shor t p e r i o d s t o r m waves are t y p i c a l of the win te r and low steepness low in tens i ty longer p e r i o d swel l waves are t y p i c a l of the summer . F i e l d studies on open coast beaches by S h e p a r d [42] and B a s c o m [2] recognized that sand moves offshore under the intense s t o r m waves of win te r and moves onshore under less intense swel l waves of summer , thus the t e r m i n o l o g y s u m m e r a n d win te r profi le deve loped . F u r t h e r insight, in to the process came i n the 1940's and 50's when the B e a c h E r o s i o n B o a r d of the U . S . A r m y C o r p s of Engineers and other researchers car r ied out field and l a b o r a t o r y inves t iga t ions . J o h n s o n [25] and R e c t o r [38] demons t r a t ed us ing m o d e l studies that, wave steepness H0/L0 was a factor i n the change f r o m an erosive state to an accret ive s tate of a beach. Invest igators of the t i m e also recognized the lack of a r ead i ly definable va r i ab le in t e r r e l a t ing sediments and waves. Subsequent inves t iga t ions focused fur ther on d i s t i n g u i s h i n g between cond i t ions w h i c h result, i n beach erosion and cond i t ions w h i c h p roduce acc re t ion . O n occas ion it is assumed tha t a b e r m character izes an accreted profile and that nearshore bars charac ter ize an e roded profi le . T h i s is a reasonable i d e a l i z a t i o n bu t overs impl i f i ed i n tha t a b e r m m a y be absent o n an accreted beach , nearshore bars do not necessar i ly ind ica t e an eroded beach and b o t h berms and bars m a y be present, on a beach. Invest igators have focused on Chapter 1. INTRODUCTION 5 c o m b i n i n g wave and sediment var iables in to a s ingle d imensionless number ca l led an on-offshore t r an spo r t pa ramete r wh ich represents the d i r ec t ion of sediment m o t i o n . D e a n [9] p roposed a d imensionless fa l l ve loc i ty pa ramete r to descr ibe the state of a beach, i n te rms of wave and sediment var iables : where F0—~ d imensionless fa l l ve loc i ty ; H0= deep water wave height ; wj= pa r t i c l e fa l l ve loc i ty ; T - wave p e r i o d . A c c o r d i n g to the fa l l ve loc i ty pa ramete r beach erosion occurs for F0 > 0.85 and accre t ion for F0 < 0.85. T h e dimensionless fa l l ve loc i ty paramete r has been suppor t ed by l abo ra to ry inves t iga t ions . P a r t i c l e fa l l ve loc i ty is a p a r t i c u l a r l y mean ingfu l charac te r i s t i c w i t h w h i c h to descr ibe sediments since it summar izes the effects of g ra in size, shape, c o m p o s i t i o n , fluid p rop-erties and v iscos i ty i n to a single parameter . D a l r y m p l e [8] used the dimensionless fa l l ve loc i ty pa ramete r to 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 beach slopes based u p o n g ra in size and inc iden t wave charac ter i s t ics . Recent inves t iga t ion by Q u i c k and H a r [35] has iden-t if ied tha t the d imensionless fa l l ve loc i ty pa ramete r alone is insufficient, to de termine the d i r ec t i on of sediment, m o t i o n because the wave h i s to ry of the beach must be t aken in to account . T h e i r i nves t iga t ion s ta ted sediment movement onshore or offshore cou ld be de te rmined by e x a m i n i n g i n i t i a l and final f a l l ve loc i ty paramete r values. H a t t o r i a n d K a w a m a t a [22] developed an on-offshore pa ramete r w h i c h combines wave var iables H, L, sediment var iab le D50 and i n i t i a l beach slope mx i n to a single d imens ion-less n u m b e r tha t represents the d i r ec t ion of sediment t r anspor t . T h e paramete r i n a general way descr ibes the character of fluid tu rbu lence , sediment pa r t i c l e en t ra inment a n d the co r re spond ing d i r e c t i o n of sediment movement . M o s t on-offshore parameters deve loped to date neglect wave power or wave in tens i ty ; thus they descr ibe the d i r ec t i on Chapter 1. INTRODUCTION 6 of sediment movement i f it is to occur but not i ts m a g n i t u d e or rate. Studies to date have been based u p o n l i m i t e d number of l a b o r a t o r y inves t iga t ions . N u m e r i c a l m o d e l l i n g of beach profi le shape change has also been developed. A n i n i -t i a l l y k n o w n beach profi le and a n u m e r i c a l l y p red ic ted post s t o r m beach profi le provides the requi red d a t a to de te rmine the d i r ec t i on of mass movemen t , vo lumes , shorel ine retreat and dep th of beach ac t iv i t y . T h i s i n f o r m a t i o n is of engineer ing interest since coast l ine response to m a jo r s to rms or hurr icanes can be p red ic t ed . A l t h o u g h such models p roduce reasonable profi le shapes the t i m e over w h i c h the profi le develops m a y not be accura te ly mode l l ed ; de ta i l ed inves t iga t ion in to the t i m e scale of profi le e v o l u t i o n appears l i m i t e d . 1.4 R e s e a r c h J u s t i f i c a t i o n C o a s t a l E n g i n e e r i n g work is the m o t i v a t i o n beh ind this s tudy. T h e na tu re of past and current coas ta l engineer ing work inc ludes the fo l lowing : • r ec rea t iona l beach cons t ruc t i on and res tora t ion; • r ubb l e m o u n d b reakwate r s t ructures ; • toe p ro t ec t i on for e rod ing bluffs; • g e o m o r p h o l o g i c a l and sediment t r anspo r t studies; • w ind -wave analyses; • coastal deve lopment (ha rbours , ma r ina s etc.) ; • seawalls. T h i s research effort is based la rgely o n field inves t iga t ive work w h i c h is jus t i f ied i n coas ta l engineer ing , p a r t i c u l a r l y where regional processes are i n v o l v e d . D a t a col lec ted Chapter 1. INTRODUCTION 7 f r o m field inves t iga t ive work provides an engineer ing d a t a base for design and reference as we 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 on of n u m e r i c a l and p h y s i c a l models . A s wel l i t m a y p r o v i d e insight, in to processes not. yet exp la ined by theory. Fu r the r , a t ho rough u n d e r s t a n d i n g of coas ta l processes on the inner sou th 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 beaches have been s tud ied to p rov ide a d d i t i o n a l scope to this invest iga-t i o n . L a b o r a t o r y beach studies demons t ra te an i d e a l i z a t i o n of rea l beaches; it is possible to observe sediment a c t i v i t y on a t i m e scale not possible i n the field due to the p rac t i ca l p rob lems of d a t a co l l ec t ion . T h e processes observed i n the l a b o r a t o r y are assumed to occur on s i m i l a r beaches in the field but on a different scale and w i t h be t ter def in i t ion . C h a p t e r 2 T E C H N I C A L W O R K A N D E X P E R I M E N T S 2.1 G e n e r a l T h e s tudy of n a t u r a l beaches invo lved survey of profiles, g ra in size analys is , subsurface i nves t i ga t i on , sediment t r a c i n g exper imen t s and n u m e r i c a l m o d e l l i n g of w i n d generated waves. 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 rev iewed for the s tudy of l abo ra to ry beach profi les. 2.2 S u r v e y s Shore n o r m a l profiles of n a t u r a l beaches were measured by s t ad ia transit, survey. T h e i n s t r u m e n t used was a Pen t ax G T - 4 B o p t i c a l t rans i t w i t h a s t ad ia constant of 100. H o r i z o n t a l d i s tance across a profi le was measured re la t ive to an i n i t i a l a r b i t r a r y basel ine and e leva t ion was measured re la t ive to a loca l bench m a r k . E l e v a t i o n was con t ro l led to w i t h i n 1 c m a n d ho r i z on t a l d i s tance to 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 ca r r i ed out at very low tides so that, as m u c h of the beach profi le as poss ible cou ld be measured . N i g h t t i m e low tides over the win te r months requ i red tha t a t r i p o d m o u n t e d f lashl ight a i m e d on the r o d be used to fac i l i t a te reading . T h e r o d m a n also h a d a flashlight to i l l u m i n a t e the r o d i f r ead ing was di f f icul t , however, th is was u s u a l l y not necessary as the l ight b e a m f r o m the t r i p o d m o u n t e d flashlight, was suff icient ly bright, to i l l u m i n a t e the rod at distances up to 60 metres . A gas l an te rn was also used at the t rans i t to p rov ide a d d i t i o n a l l igh t . 8 Chapter 2. TECHNICAL WORK AND EXPERIMENTS 9 T h e r o d was p l aced at poin ts on the beach where v i s ib le changes in s lope or changes i n beach mate r ia l s occu red and the e leva t ion of the profiles w i t h respect to geodetic d a t u m was de t e rmined by measu r ing the water level re la t ive to the bench m a r k and reco rd ing the exact Pac i f i c S t a n d a r d T i m e . Measu remen t s were m a d e at a t ime when the water was c a l m so tha t the effects of waves a n d m o m e n t u m set up w o u l d be negl igible . C a l c u l a t i o n s were t hen pe r fo rmed to correct for l o c a t i o n and t i m e us ing P o i n t A t k i n s o n t ides as a reference fo l l owing the 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 and C u r r e n t Tables [3]. Slopes t y p i c a l l y i n the range 1:1 to 1:12 were measured us ing a home m a d e level , pho to 10, w h i c h was tes ted a n d checked against slopes ob ta ined f r o m beach profile d a t a and found to be very accura te . B e a c h slopes tha t were very sha l low ( t y p i c a l l y less t h a n I V : 12H) or that changed frequent ly were measured w i t h an o p t i c a l level and a cha in . B e r m crest and debris l ine elevat ions and elevat ions of other features were also mea-sured us ing an o p t i c a l level . 2.3 A n a l y s i s o f S e d i m e n t s M a t e r i a l size and size d i s t r i b u t i o n at the beach surface and subsurface was quant i f ied us ing bu lk seive ana lys is and photographic , ana lys is . Seive analyses were per formed on l o c a l beaches us ing samples n o m i n a l l y of 10 k g mass co l lec ted i n cookie t ins , oven dr ied a n d seived i n the C i v i l E n g i n e e r i n g undergradua te soils l a b o r a t o r y at U B C . T h e sediment sizes on beaches v i s i t ed one t i m e were measured us ing a pho tograph ic ana lys is technique [1]. A 4 0 0 m m by 3 5 0 m m s a m p l i n g g r i d was p l aced over a representa-t ive sect ion of beach for scale and a p h o t o g r a p h t aken , pho to 19. T h e sizes of about a dozen representat ive stones were then scaled off the p h o t o g r a p h a n d i n p u t to a compu te 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 frequency d i s t r i b u t i o n , sample s ta t is t ics a n d seive equiva-lent sizes. A s s i g n m e n t of a l inear g r a i n size d imens ion was made us ing the v i s ib le short axis of par t ic les over 8 m m in 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 representat ive wel l sor ted area of beach surface was selected by eye; an area of at least 500 square metres was inves t iga ted before a p h o t o g r a p h was t aken . C a m e r a out of v e r t i c a l error was corrected by ad jus t ing the p h o t o g r a p h scal ing factor. 2.4 S e d i m e n t T r a c i n g 2.4.1 B a c k g r o u n d A s imp le sediment t r a c i n g exper iment d e m o n s t r a t i n g the d i spers ion of coarse par t ic les on a beach was c o n d u c t e d . T h e exper imen t i nvo l ved p l ac ing wel l sor ted and rounded samples of t racer par t i c les on an inner coast beach and obse rv ing the pa r t i c l e m o t i o n under the ac t ion of waves a n d t ides over a p e r i o d of several clays. T h e fo l lowing assumpt ions are made w i t h regard to th is type of exper iment : 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 such tha t i t is d i s t i ngu i shab le f r o m na tu r a l sediment . T h e t racer shou ld have the same h y d r o m e c h a n i c a l proper t ies (size, shape, dens i ty ) of the n a t u r a l sediment ; 2. T h e t racer is in jec ted in to the l i t t o r a l env i ronment so tha t i t experiences the same cond i t ions caus ing movement of n a t u r a l sediment ; 3. T h e d i spersa l p a t t e r n of na tu r a l sediment is inferred by the dispersed pa t t e rn of the t racer sediment . T race r par t ic les were prepared in a l a b o r a t o r y by p a i n t i n g wel l r o u n d e d stones of G m m , 3 8 m m and 7 5 m m m e d i a n d iamete r w i t h two coats of a h i g h qua l i ty m a r i n e enamel pa in t . T h e 7 5 m m m e d i a n size sample mass was 60kg ( a p p r o x i m a t e l y 210 par t ic les ) , Chapter 2. TECHNICAL WORK AND EXPERIMENTS 11 the 3 8 m m m e d i a n size sample mass was 40kg ( a p p r o x i m a t e l y 1100 par t ic les ) and the 6 m m m e d i a n size mass was 25kg (number of par t ic les not counted) . T h e par t ic les were co l lec ted f r o m a l o c a l beach , washed and d r i ed before p a i n t i n g . P r i o r to c o n d u c t i n g the exper iment a p r e l i m i n a r y test of pa in t d u r a b i l i t y was con-d u c t e d . T h r e e types of pa in t were tes ted for d u r a b i l i t y against ab ras ion a n d wear when p laced on a beach under the ac t ion of waves. T h e ob jec t ive was to have a pa in t w h i c h w o u l d r e m a i n on a pa r t i c l e for a n u m b e r of days or weeks w i t h o u t wear ing off. A n epoxy resin pa in t tes ted was inadequa te a n d wore off most stones of a test sample p laced on a l oca l beach i n about 2 days . Spray enamels app l i ed i n s i t u where found to wear s i m i l a r l y and were adversely affected by t empera tu re and moi s tu re on the rock surface. M a r i n e grade ename l pa in t was found to be the mos t successful and r ema ined on the test, sample for we l l over three mon ths . It was observed that the surface roughness of a stone affects its a b i l i t y to r e ta in pa in t . R o u g h surfaced stones were found to r e t a in pa in t be t ter i n the inters t ices of the surface roughness therefore be ing ident i f iable for a longer p e r i o d of t i m e . P a i n t ab raded more q u i c k l y off of s m o o t h surfaced stones thus m a k i n g t h e m less ident i f iable i n a shorter p e r i o d of t i m e a n d therefore less effective as a t racer pa r t i c le . A f t e r 2 days on the beach some of the smoothe r enameled 3 8 m m tracer par t ic les were showing wear of the pa in t . 2.4.2 Beach experiment T h e expe r imen t was conduc ted on a sec t ion of shorel ine 1000 metres west of Chas 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, f igure 2. T h e expe r imen t i nvo l ved p l a c i n g three wel l sor ted and rounded samples of t racer par t ic les of m e d i a n sizes 6 m m , 3 8 m m and 7 5 m m on an a r m o u r e d sect ion of shorel ine and obse rv ing the pa r t i c l e m o t i o n under the a c t i o n of waves, currents and t ides over a p e r i o d of several days , photos 1 to 4. T h e expe r imen t was conduc t ed to suppor t field observat ions that coarse m a t e r i a l Chapter 2. TECHNICAL WORK AND EXPERIMENTS 12 moves onshore under the ac t ion of waves, currents a n d tides and that the highest long-shore sediment t r anspo r t rates on inner coast beaches occur i n a na r row upper foreshore zone. A t C h a s t e r Creek a 4 m gr id was l a i d out on the beach surface us ing large marker stones ( t y p i c a l l y 40kg) to m a r k the g r i d in tersect ions . T h e g r i d was .careful ly t aped and at g r i d l ine in tersec t ions crosses were spray pa in t ed o n the marke r stones. G r i d l i n e s were made to r u n p a r a l l e l and n o r m a l to the shore. A t low t ide on the first day of the exper imen t par t i c les were p laced at separate or ig ins o n the beach for each size, pho to 2. F o u r t ide cycles passed d u r i n g the two day exper imen t a n d the wave cond i t ions and pa r t i c l e movemen t s were recorded. T o assist i n c o u n t i n g the n u m b e r of par t ic les on the beach surface a l m subgr id was la id out . Af t e r the exper iment the< 38 m m and 75 m m par t ic les were recovered for further use. 2.5 W a v e H i n d c a s t i n g A wave h indcas t m o d e l was developed w h i c h uses h o u r l y w i n d d a t a f r o m the A t m o s p h e r i c E n v i r o n m e n t Serv ice ( A E S ) to synthesize s ignif icant wave height and p e r i o d d a t a for the p e r i o d of beach survey. T h e synthes ized d a t a was generated in an a t t empt to ident i fy and if poss ib le corre la te waves to measured changes i n foreshore profi les. T h e theory b e h i n d the wave h i n d c a s t i n g m e t h o d used is d iscussed: W a v e h i n d c a s t i n g involves us ing past weather records to recons t ruc t past wave condi -t ions . Severa l semi- e m p i r i c a l spec t ra have been deve loped to h indcas t or forecast waves f r o m w i n d da ta . T h e Sve rd rup- M u n k - Bre t schne ide r ( S M B ) s p e c t r u m was used because of i ts s i m p l i c i t y a n d ease of app l i c a t i on ; the h indcas t equat ions are transfer funct ions w h i c h i n p u t w i n d speed and y i e l d a wave height or p e r i o d . W a v e spec t ra such as the S M B s p e c t r u m assume the wave cond i t ions to be a func t ion of the fo l lowing parameters : Chapter 2. TECHNICAL WORK AND EXPERIMENTS 13 1. w i n d ve loc i ty U ; 2. w i n d d u r a t i o n td; 3. fetch F ; 4. dep th of water d; 5. wave decay. T h e s ignif icant deepwater wave height and s ignif icant wave p e r i o d can be expressed func t iona l ly : Hs = MU,F,td,g) Ts = f2{U,F,td,g) where the fo l lowing is defined: Hs= s ignif icant height; Ts= s ignif icant height ; g— acce le ra t ion due to g rav i ty ; T h e S M B h i n d c a s t i n g re la t ionsh ips for s ignif icant wave height and p e r i o d are: ^ = 0 . 2 8 3 * a 7 i M 0 . 0 1 2 5 ( ^ 7 ) a 4 2 ] ^ = 1 . 2 * a n M 0 . 0 7 7 ( ^ ) 0 - 2 5 ] T h e accuracy of wave h indcas t s is h i g h l y dependent u p o n the w i n d d a t a i npu t to the equat ions . T h e use of w i n d d a t a co l lec ted over water as opposed to l a n d produces more accura te h indcas t wave heights and per iods ; fo r tuna te ly the A E S has m a i n t a i n e d w i n d records at coas ta l l ighthouses i n southwest B r i t i s h C o l u m b i a for m a n y years. Sandheads L i g h t S t a t i o n w h i c h is loca ted over water was used as the source of w i n d da ta ; i t is assumed the w i n d speeds at Sandheads are genera l ly representat ive of w inds over the sou thern S t r a i t of G e o r g i a , figure 2. 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 Service has some deep water wave records w i t h i n the Strait, of G e o r g i a for w h i c h there is co inc ident w i n d da ta . A c o m p a r i s o n of h indcas t and measured deep water wave height da 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 and Wes t V a n c o u v e r to evaluate the accuracy of the 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 measured wave heights , however , the m o d e l tends to overpredic t the h igher waves but accura te ly models the t r e n d of s torms . T h e A E S w i n d d a t a was measured w i t h an in t eg ra t ing t y p e 4 5 B anemometer thus the i n p u t d a t a are h o u r l y means , a p p e n d i x A . For example , a w i n d speed quo ted as 10 k p h N W means that 1 0 k m of a tmosphere c o m i n g f r o m the nor thwes t has passed the anemomete r i n one hour . T h e w i n d speed U i n the Bre t schne ide r re la t ionships are defined for a reference an-nemomete r height of 10 metres above the earth 's surface. W i n d s measured at a height o ther t h a n 10m should be cor rec ted to account for the d i s t r i b u t i o n of w i n d ve loc i ty w i t h e leva t ion ; the fo l lowing ve loc i ty profi le cor rec t ion was i n c o r p o r a t e d i n the h i n d c a s t i n g p r o g r a m : z where U0= w i n d speed at the anemometer ; Uw— w i n d ve loc i ty at 10 metres above the ear th 's surface; z— annemomete r height above g r o u n d . W a v e generat ion is also affected by fetch w i d t h . T h e concept of effective fetch is i n c o r p o r a t e d in to the h i n d c a s t i n g p r o g r a m us ing an e m p i r i c a l fetch l i m i t i n g procedure [41]. Separa te subhindcas t s on rays spaced at 15 degrees over a 90 degree w i n d o w w i t h 45 degrees to ei ther side of the w i n d d i r ec t i on are used in the 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 ca l cu la t ed us ing the fo l lowing re la t ionsh ip : E:=i cose, where H= fetch l i m i t e d wave height ; Hr= h indcas t s wave height a long the i t h ray; Bi~ angle, to i t h ray measured f rom cen t ra l ray. T h e h i n d c a s t i n g m o d e l incorpora tes the fo l lowing assumpt ions : 1. the water is deep; 2. w i n d speed is cons tan t t e m p o r a l l y and spa t i a l l y over the h indcas t area at h indcas t t ime; 3. a ful ly ar isen sea prevai l s at each h indcas t hour; 4. secondary wave sources such as swell or sh ip waves are not s ignif icant . T h e m o d e l w i l l h indcas t or forecast s ignif icant wave heights and per iods for deep water , however , th is does not necessar i ly mean tha t the synthes ized d a t a is representat ive of w h a t is h a p p e n i n g at the shore. T h e wave cond i t i ons at the shore are a func t ion of the offshore wave cond i t i ons , d i r e c t i o n of wave p r o p a g a t i o n and the nearshore ba themet ry w h i c h t ransforms the waves as they approach the shore. E q u a t i o n s have been developed to m o d e l the wave t r a n s f o r m a t i o n as deep water waves approach a shor l ine , however, they have not been i n c o r p o r a t e d in to the m o d e l . H i n d c a s t s were per formed for po in t s i n deep water jus t offshore of the survey sites and the s i m p l i f y i n g a s sumpt ion was m a d e that, the same cond i t i ons p reva i led 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 the w i n d da ta . T h e effects of wave b u i l d up and decay are e m p i r i c a l l y s imula t ed by f i l t e r ing the 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 16 average w i t h a 2 hour t r a i l i n g or l ead ing w i d t h . T h e m o v i n g average has the effect of s m o o t h i n g the o u t p u t wave height d a t a by averaging the height at forecast hour w i t h the preceeding two or subsequent two hours of h indcas t wave heights thus s i m u l a t i n g wave b u i l d up a n d decay. T h e p r o g r a m was used sucessfully i n p r e d i c t i n g wave heights d u r i n g par t of the beach survey p e r i o d . C o m p a r i s o n of h indcas t w i t h measured wave height da t a , f igure 5, i n d i -cates ove rh indcas t i ng of h igher waves w h i c h is l i ke ly a result of the a s s u m p t i o n of ful ly ar isen sea w h i c h is a h igher energy sea state t han that w h i c h ac tua l l y occurs . 2.6 V o l u m e C a l c u l a t i o n s In the ana lys is of l a b o r a t o r y beach d a t a the area between sucessive profiles was required to de t e rmine the ac t ive v o l u m e of sediment . T h e h i g h l y i r regular areas be tween sucessive profiles were ca l cu la t ed us ing a compu te r p r o g r a m w r i t t e n for the purpose . 2.7 L a b o r a t o r y B e a c h D a t a B e a c h profi le d a t a f r o m three l a b o r a t o r y exper iments were rev iewed: 1. D a t a was reviewed f rom a s tudy ca r r i ed out by W a t a n a b e , R i h o and H o r i k a w a [46] w h i c h i n v o l v e d four beaches at slopes of 1 V : 1 0 H and 1 V : 2 0 H cons t ruc t ed of we l l sor ted qua r t z sand sizes of 0.7 m m and 0.2 m m . Sediments of each size were i n i t i a l l y g raded flat at the specified slopes and subject to m o n o c h r o m a t i c waves generated in a two d i m e n s i o n a l wave f lume 2 5 m long , 1.5m deep a n d 0 .8m w i d e for a pe r iod of 1 hour . W a v e per iods were kept at 1.0, 1.5 or 2.0 seconds a n d four or five wave heights were selected for each r u n r e su l t ing i n a to t a l of fifty-eight e x p e r i m e n t a l cases, figure 6. ha.pf.er 2, TECHNICAL WORK AND EXPERIMENTS 17 2. A s tudy by R e c t o r [38] ca r r i ed out on beha l f of the B e a c h E r o s i o n B o a r d was also rev iewed. T h e exper iments were conduc ted in two wave tanks : one of concrete 85 feet long , 14 feet wide a n d 4 feet deep a n d the other of steel p la te cons t ruc t ion 42 feet l o n g , 1.5 feet w ide and 2 feet deep. T h e beaches were cons t ruc ted of three bas ic sands a n d a four th sand w h i c h was a m i x t u r e of two basic sands. S a n d m e d i a n d iameters were 0.22, 0.47, 0.90 and 3.44 m m ; the 0.90 m m m e d i a n d iameter sand was a m i x t u r e of the 0.47 a n d 3.44 m m sands. W a v e height was he ld near ly constant i n each case bu t p e r i o d was va r i ed as 1.30, 1.75, 2.20, 2.75 a n d 3.30 seconds resu l t ing i n four sets of profiles, f igure 7. 3. A s tudy ca r r i ed out by Japanese researchers H a t t o r i a n d K a w a m a t a [22] to develop an on-offshore t r anspor t pa ramete r was rev iewed . T w o beaches i n a wave f lume were inves t iga ted ; the flume was 0 .4m w i d e and 0 .7m deep a n d 1 6 m long w i t h glass side wal ls . T w o waves of constant steepness were used i n the exper imen t : H0= 2.4 c m and T— 1.6s, H0= 5 .5cm a n d T = 1.0s. In the first case profiles were recorded at 0, 3, 6 and 12 hours; i n the second case profiles were recorded at 0, 4, 8 and 14 hours , figure 8. C h a p t e r 3 F I E L D I N V E S T I G A T I V E W O R K 3.1 B a c k g r o u n d F i e l d inves t iga t ive work car r ied out on beaches w i t h i n coastal southwest B r i t i s h C o l u m b i a has i n c l u d e d profi le surveys over a pe r iod of t ime , sediment t r anspor t exper iments , g ra in size ana lys i s , subsurface inves t iga t ion a n d s tudy of beach geomorphology . B l u f f erosion on the inner coast has been reviewed because of its loca l s ignif icance. W a v e h i n d c a s t i n g d u r i n g the p e r i o d of profi le surveys and a wave c l ima te inves t iga t ion was also ca r r ied out . T h r e e beaches at Tsawwassen , D u n d a r a v e i n Wes t V a n c o u v e r and Tower B e a c h at Po in t G r e y were s tud ied i n de ta i l ; twenty- two other beaches on the inner coast were s tud ied on a one t i m e or occas iona l basis . 3.2 S t u d y A r e a 3.2.1 G e o g r a p h y T h e s tudy area is defined by the S t ra i t of G e o r g i a w h i c h is a t i d a l water b o d y b o u n d e d by V a n c o u v e r I s land o n the west, the 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 Is land on the n o r t h and the southern gul f i s lands , figure 2. T h e Strait, is an i n l a n d sea whose axis runs nor thwes t to southeast s t re tch ing 2 2 2 k m (120 n a u t i c a l mi les ) w i t h an average w i d t h of 3 3 k m (18 n a u t i c a l mi l e s ) . T h e s tudy area also inc ludes beaches on J u a n de Fuca. Strai t w h i c h is loca ted between V a n c o u v e r Is land and W a s h i n g t o n state, figure 1. T h e J u a n de F u c a S t ra i t has a nor thwest to southeast a l ignment and is exposed 18 Chapter 3. FIELD INVESTIGATIVE WORK 19 on i ts western end to the N o r t h Pac i f i c . 3.2.2 P h y s i o g r a p h y T h e B r i t i s h C o l u m b i a coast has been d i v i d e d b road ly in to three physiographic , regions: an outer m o u n t a i n area w h i c h includes the insu la r moun ta in s of the Q u e e n C h a r l o t t e Is lands and V a n c o u v e r I s land , a coas ta l t r ough w h i c h inc ludes the G e o r g i a Depress ion a n d the 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 Depress ion inc ludes the S t r a i t of G e o r g i a and the G e o r g i a L o w l a n d a long the m a i n l a n d coast and the N a n a i m o L o w l a n d a long the western coast of the S t r a i t . 3.2.3 G e o l o g y a n d g e o m o r p h i c h i s t o r y T h e inner south coast has been modi f i ed by repeated g lac ia t ions separated by non-glac ia l in tervals d u r i n g W i s c o n s i n t i m e late in the p le is tocene epoch . T h e Fraser G l a c i a l ion is the last ma jo r W i s c o n s i n g l a c i a t i o n wh ich depos i ted s ignif icant quant i t i es of t i l l and s t ra t i f ied drift . A no tab le sediment source w i t h i n the St ra i t of G e o r g i a is the hor i zon-t a l ly s t ra t i f ied ple is tocene ou twash sediment ca l led Q u a d r a S a n d [5]. Q u a d r a Sands are u n i f o r m si l ts and sands, depos i ted d u r i n g the Fraser G l a c i a t i o n , tha t cu r ren t ly form a b e a c h / sea cliff erosion env i ronmen t characterist ic, of the inner coast. T h e Q u a d r a Sand sea cliffs have been s tud ied ex tens ive ly at P o i n t G r e y . Sea cliffs of non-s t ra t i f i ed drift of p le is tocene o r ig in also occur i n loca t ions such as southern P o i n t R o b e r t s and C o r d o v a B a y on V a n c o u v e r I s land . M o s t of the inner 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, however, in areas where the crust is over la in by th i ck sediments such as Q u a d r a Sands or in the v i c i n i t y of f l u v i a l deposi ts sand, gravel , cobble and bou lder beaches have formed. Chapter 3. FIELD INVESTIGATIVE WORK 20 3.2.4 L i t t o r a l m a t e r i a l s M o s t l o c a l beaches are fo rmed of coarse m a t e r i a l i n the gravel , cobble and bou lder size range, figure 3. Some sandy beaches occur a round the ' coast, most n o t a b l y the pocket beach at T r i b u n e B a y on H o r n b y Is land , figure 2, or downcoas t of the sand and t i l l bluffs w h i c h o c c u r a r o u n d the S t r a i t . Gene ra l ly , the sand beaches occu r where there is a sufficient s u p p l y of sand size m a t e r i a l to create a l o c a l sandy beach. T h o u g h s m a l l sandy pocket, beaches are numerous on the inner coast they are not the focus of this s tudy, emphas is is u p o n the coarse m a t e r i a l beaches exposed to the S t ra i t of G e o r g i a a n d J u a n de F u c a S t ra i t since they are more charac te r i s t i c of the inner south coast. T h e coas ta l env i ronmen t under s t u d y m a y be thought of as a t h i n c i r cumferenc ia l b a n d of sediments , p r e d o m i n a n t l y of la te p le is tocene g l a c i a l o r i g i n , o v e r l y i n g c rus ta l rock and acted u p o n and shaped by a range of t ides and specific, wave c l i m a t e . 3.2.5 W i n d a n d wave c l i m a t o l o g y T h e wave c l i m a t e o l the S t ra i t of G e o r g i a is governed by the fact tha t for most w inds the water b o d y is fetch l i m i t e d . T h u s there are l i m i t s o n the wave height and p e r i o d a n d co r r e spond ing ly the wave energy a n d wave in tens i ty tha t w inds can generate w i t h i n i ts wa.ters. Seasonal v a r i a t i o n i n the p e r i o d of ocean swell is a t t r i b u t e d to seasonal changes i n beach m o r p h o l o g y ident i f ied o n open ocean coast beaches. Swe l l waves ( t y p i c a l l y i n the range of 15 to 20 seconds) are generated by s torms over the open ocean and have been k n o w n to reach the west coast of N o r t h A m e r i c a f r o m s torms i n the S o u t h Pac i f i c . O c e a n swel l in this range is c o m m o n off the west coast, of B r i t i s h C o l u m b i a bu t does not occur w i t h i n the Strait, of G e o r g i a because of the a t t enua t ing effect of the G u l f Islands and J u a n de F u c a and5" Johns tone S t ra i t s . In other words , a l l waves w i t h i n the S t ra i t of 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 Bank and Tofino, appendices B and C. The short term records are considered representative of the predominant wave climate at the sites. The attenuating effect of the Gul 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 Vic to r i a Harbour where it has been measured at greatly reduced amplitudes. Examinat ion 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. The 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'. The data also indicate significant periods of calm within the inner coast. Typica 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. The 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 T i d e s Tides within 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 ides . T i d a l range for P o i n t A t k i n s o n on the S t ra 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 ab le 1. P O I N T A T K I N S O N T I D E E L E V A T I O N S T I D E me t re s ( G e o d e t i c D a t u m ) H I G H E X T R E M E ( includes s t o r m surge) 2.6 A N N U A L H I G H W A T E R 2.0 M E A N H I G H W A T E R 1.4 M E A N W A T E R L E V E L 0.0 M E A N L O W W A T E R -1.9 A N N U A L L O W W A T E R -3.0 L O W E X T R E M E -3.4 t a b l e 1 T i d e s are i m p o r t a n t i n the geomorph ic development of inner coast beaches, the m a i n effect be ing tha t the p o s i t i o n of b r eak ing waves shifts across the profi le w i t h the t ide cycle . T h e d a t a in tab le 1 shows that a n n u a l t i d a l range at Point. A t k i n s o n is 5.0 metres; a s suming a t y p i c a l inner coast beach s lope of 1 V : 1 0 H , this means tha t the b reak ing wave shifts pos i t i on over the beach a h o r i z o n t a l d i s tance of 50 metres on an a n n u a l t ide . T h u s , inner coast beaches are r e l a t ive ly wide by v i r t u e of the range of t ides . 3.2.7 S h o r e l i n e c l a s s i f i c a t i on T h e shorel ine of the inner sou th coast has been classified based u p o n specific foreshore charac ter i s t ics , sediment sources and 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 coas t l ine is charac te r ized by sediment covered shorel ine tha t is not i n t e r rup ted by headlands , in le t s , piers or groynes caus ing storage or depos i -t i o n of l i t t o r a l m a t e r i a l . Beaches on the l inear coas t l ine of the inner coast t y p i c a l l y Chapter 3. FIELD INVESTIGATIVE WORK 23 exh ib i t cross shore sor t ing at the surface w i t h fine sands a n d gravels i n the upper foreshore and coarser cobbles a n d boulders in the lower foreshore, pho to 14. T h e bou lde r cobb le lower foreshores exh ib 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 to gravel bed r ivers , figure 16. S a n d y beaches occu r on l inear sections of coas t l ine but are often t ransient i n na ture due to the h i g h m o b i l i t y of sand and the v a r i a b l i t y of its supply . T h e sand beach is often a lens of sand over a na t ive cobble or bou lde r beach , photos 21 and 22. S a n d a n d t i l l bluffs are a source of sand size l i t t o r a l m a t e r i a l a long the coast; sand beaches u s u a l l y appear downdr i f t of these sites for several mi 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 in te r rup t sediment t ranspor t re-su l t i ng in s torage of sediments r e su l t ing i n steep shingle beaches since the rate of bypass ing of coarse sediments is low re la t ive to finer sediments . A p r i m e example is the steep shingle beach at C a m p B y n g near R o b e r t s Creek , pho to 5, the beach is sh ingle w i t h a D50 of abou t 20 m m . P o c k e t B e a c h e s . Pocke t beaches m a y f o r m of sediments r ang ing f rom sand size to cob-ble size secured between n a t u r a l or a r t i f i c i a l headlands . Sediments are t r a p p e d w i t h i n the pocket beach; there is no net l ong t e r m l i t t o r a l drif t thus the pocket beach is cons idered a closed sed imen ta ry env i ronment . Sed iment sources for pocket beaches t y p i c a l l y i nc lude fluvial sediments o r i g i n a t i n g f r o m u p l a n d sources a n d backshore e ros ion . Pocke t beaches where shingle has a c c u m u l a t e d t end to be ac-cret ive as i n d i c a t e d by the steep gravel a n d cobble berms w h i c h fo rm. L o c k B a y on G a b r i o l a I s land is a p r i m e example , p h o t o 1 1 . D e l t a i c . D e l t a i c fans of fine to coarse fluvial sediments fo rm at the m o u t h s of s t reams, creeks and r ivers . T h e most no tab le de l t a ic coas t l ine on the inner coast, is the Fraser Chapter 3. FIELD INVESTIGATIVE WORK 24 R i v e r de l t a . T h e deltas are general ly charac ter i sed by finer sediments e roded f r o m u p l a n d sources, however, steep m o u n t a i n s t reams m a y t ranspor t coarse sediments to the shore f o r m i n g de l t a ic fans. R o c k y C o a s t l i n e . T h e r e are no beaches on r o c k y coast l ine due to t h i n or non exis tant sed iment cover over bedrock . In areas where the pos tg l ac i a l sediment cover was t h i n or n o n ex is tan t a n d there is cu r r en t ly insufficient l oca l supp ly of u p l a n d or l i t t o r a l sediment bedrock is exposed . M o s t of the inner coast is rocky. 3.3 S i tes S t u d i e d T h e beaches at Tsawwassen , Tower B e a c h at P o i n t G r e y and D u n d a r a v e at West V a n -couver , figures 2 and 11 to 13, were selected for de ta i led s tudy p r i m a r i l y because of r e l a t ive ly easy access, each site be ing a different type of beach and the ava i l ab i l i t y of p rev ious s tudies for b a c k g r o u n d at Tsawwassen and P o i n t Grey . T w e n t y - t w o o ther beaches were s tud ied o n a one t ime or occas iona l basis t h r o u g h the S t r a i t of G e o r g i a and lower J u a n de F u c a S t r a i t , t ab le 2 and figure 2. Tsawwa.ssen, Tower B e a c h at P o i n t G r e y and D u n d a r a v e at Wes t V a n c o u v e r are discussed subsequent ly i n de ta i l , most of the r e m a i n i n g sites are not discussed specif ical ly , ra ther the findings at the twenty- two sites are s u m m a r i z e d i n tables and d iag rams a n d are discussed i n the con tex t of t y p i c a l cond i t i ons o c c u r i n g on the inner coast . apter 3. FIELD INVESTIGATIVE WORK S O M E I N N E R S O U T H C O A S T A L B E A C H E S I n d e x S i t e B r i e f D e s c r i p t i o n 1 D u n d a r a v e , West V a n c o u v e r a rmoured shorel ine, 2 Tsawwassen B e a c h bluffs, t i d a l flats 3 Tower B e a c h , P o i n t G r e y a r t i f i ca l shingle beach 4 Chas t e r Creek W e s t , G i b s o n s a r m o u r e d shorel ine 5 C a m p B y n g , R o b e r t s Creek steep shingle beach 6 Eas t of P i e r , R o b e r t s Creek a rmoured shorel ine 7 T r a i l B a y , Sechelt steep shingle beach 8 W e s t v i e w , P o w e l l R i v e r a rmoured shorel ine 9 Savary I s land Southeas t act ive bluff eros ion, t i d a l flats 10 C a p e M u d g e , Q u a d r a I s land act ive bluff eros ion, b o u l d e r beach 11 R e b e c c a S p i t , Q u a d r a I s land c o b b l e / bou lder beach 12 Tyee Sp i t , C a m p b e l l R i v e r gravel beach 13 C a p e L a z o , C o m o x e rod ing bluff, cobble beach 14 K i n B e a c h , C o m o x cobble beach 15 Goose Sp i t , C o m o x cobble beach 16 W i l l i m a r Bluf f s , C o m o x aci tve bluff eros ion, cobble beach 17 C o l u m b i a B e a c h , Q u a l i c u m cobble beach 18 Q u a l i c u m B a y , Q u a l i c u m cobble beach 19 K o m a s Bluf f , D e n m a n I s l and act ive bluff erosion 20 L o c k B a y , G a b r i o l a I s l and steep shingle beach 21 Orveas B a y , Sooke steep shingle beach 22 French B e a c h , Sooke steep shingle beach 23 P a r r y B a y , V i c t o r i a gravel beach 24 C l o v e r P o i n t Wes t , V i c t o r i a ac t ive bluff eros ion, gravel beach 25 Is land V i e w B e a c h , S a a n i c h ac t ive bluff erosion, spi t t a b l e 2 Chapter 3. FIELD INVESTIGATIVE WORK 26 3.4 S e d i m e n t s 3.4.1 B e a c h s lope a n d g r a i n size M a n y open coast sandy beaches exh ib i t a co r re la t ion between m e d i a n sand par t i c le size and beach face slope; such a re la t ionsh ip has been exp lo red for inner coast beaches, f igure 14. A cor re la t ion between g ra in size and beach face s lope is not evident , however, a r m o u r e d beaches and shingle beaches are two d i s t inc t p o p u l a t i o n s and plot 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 the range of 5 to 10 degrees as i nd i ca t ed by the b a n d of po in t s i n the shaded area whereas the shingle beaches are m u c h steeper, t y p i c a l l y 16 to 26 degrees. O n the inner coast the shingle beaches apparen t ly have an upper l i m i t on med ian g ra in size as shingle beaches were not found l o c a l l y where the med ian gra in size exceeds 40 m m . T h e shingle size l i m i t is l i ke ly due to l i m i t s on wave energy w i t h i n inner coastal waters capab le 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 S h i n g l e beaches Shing le beaches occur w i t h i n the inner south coast where there is sufficient supp ly and storage of l i t t o r a l m a t e r i a l . T h e shingle beaches have a m e d i a n pa r t i c l e size t y p i c a l l y i n the range 10-40mm; m a n y of the shingle take on a d i s t inc t flat shape, pho to 8. It is u n k n o w n whether the par t i c les are worn to the flat shape t h r o u g h shear ing movement w i t h i n the beach m a t r i x d u r i n g sediment a c t i v i t y under wave ac t ion or whether the par t ic les were o r g i n a l l y supp l i e d l i t t o r a l l y or fluvially to the beach as flat shingle . In cross sect ion the shingle beaches are steep berms a n d are re la t ive ly homogeneous , cons i s t ing of gravels or cobbles , pho to 12 and figure 15. B y v i r t u e of the i r coarse g ra in size the beach sediments have r e l a t ive ly h igh pe rmeab i l i t y , f igure 3, and f o r m m u c h steeper Chapter 3. FIELD INVESTIGATIVE WORK 27 slopes t h a n sandy beaches. P e r m e a b l i t y has been related to beach slope by the observa-t ion tha t b r e a k i n g or su rg ing waves percola te in to the beach on run-up caus ing most of the backswash flow to re tu rn t h rough the sediment, pa r t i c l e m a t r i x . T h e rate of perco-l a t i o n in to the beach is a func t ion of the sediment p e r m e a b i l i t y thus on shingle beaches b r e a k i n g waves impose d rag forces on the shingle p r e d o m i n a n t l y on run -up caus ing t h e m to move onshore b u i l d i n g a steep b e r m u n t i l an e q u i l i b r i u m w i t h the imposed wave con-d i t i o n and g rav i ty is achieved [29], P r i m e examples of such beaches on the inner coast i n c l u d e C lamp B y n g at R o b e r t s Creek , T r a i l B a y at Sechelt , L o c k B a y on G a b r i o l a I s land and G o r d o n ' s Beach , near R i v e r J o r d a n , V a n c o u v e r I s land , photos 5, 6, 9 and 10. C o b b l e co lon ized by seaplants has been found h igh i n the uppe r foreshore of m a n y shingle beaches. C l a w - l i k e roots f i rm ly a t tached to cobble w i t h n o m i n a l d iameters up to 200 m m has been observed thus i n d i c a t i n g that some of the ma te r i a l or iginates f rom offshore, pho to 7. Intense water m o t i o n at the seabed induced by s t o r m waves are be l ieved to d i s lodge the p lan ts f rom the seabed whi le w i n d d r iven currents ca r ry the p lants w i t h the i r a t t ached rocks to the shore where tu rbu len t b r eak ing waves wash the shingle h i g h in to the upper foreshore. 3.4.3 Armoured beaches A r m o u r e d beaches at the surface consist, of cobbles w i t h a m e d i a n d iameter t y p i c a l l y i n excess of 100 m m , photos 14, 15, 16 and 19. U n l i k e shingle beaches the subsurface m a t r i x is not homogeneous bu t ra ther a range of m a t e r i a l sizes f rom sand to cobble . A r m o u r e d beaches e x h i b i t a bed a r m o u r i n g s t ruc tu re s imi l a r to the n a t u r a l a r m o u r i n g that occurs in gravel bed r ivers . T h e surface is a d i s t i nc t gravel or cobble layer up to several pa r t i c l e d iamete rs th i ck as exempl i f ied by figure 16 and pho to 15. The, a r m o u r e d beach surface is censored of finer sediments and tends to fo rm a na tu r a l filter against, finer subsurface sediments . Sieve, analys is 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 8 5 ) 5 0 , ; and it has been found that the median grain sizes at the surface and of the subsurface matrix represent a filter. The structure of the beach surface also has the appearance of a filter. The filter criterion states that the D 1 5 of the filter must be less than five times the DS5 of the soil in order for a filter to form. Soil is representative of an average void size for the filter; D85 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 unti l the beach subsequently rearmours. Lowering of the foreshore through removal of armouring wi 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 Glaciat ion, the most recent of a series of pleistocene glaciations, retreating ice left t i l l deposits over the surface of the Georgia Depression. In many exposed coastal bluffs the t i l l exists at the top of the stratigraphic sequence, photo 17, and is usually underlain by Quadra Sand which in turn buries older estuarine and marine sediments deposited during preceding non-glacial intervals. The 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. The early sediment cover is Chapter 3. FIELD INVESTIGATIVE WORK 29 be l ieved to have consis ted of a w ide range of sizes (c lays , s i l ts , sands, cobbles , boulders) w h i c h founded the parent m a t e r i a l for the present a rmoured shorel ine. B e n e a t h the a r m o u r layer exists a c o m p a r i t i v e l y w i d e range of sediment sizes tha t has changed l i t t l e over t i m e . a n d is l i ke ly representa t ive of ear ly surface sediments . O v e r t i m e the shif t ing p o s i t i o n of b r e a k i n g waves over the shorel ine due to t i d a l f luc tua t ions has select ively r emoved the finer f rac t ion of sediment f rom the more exposed lower foreshore. T h e upper foreshore, however , because of i ts decreased exposure to wave ac t ion retains mob i l e sands and gravels wh ich are an in tegra l pa r t of the n a t u r a l t ranspor t processes o c c u r i n g on the shorel ine , pho to 14, wh i l e the lower foreshore has deve loped to a cobble a rmoured state res is t ing fur ther eros ion. 3.5 P ro f i l e s 3.5.1 D i s c u s s i o n M o n t h l y beach profiles were surveyed at Tsawwassen B e a c h , Tower B e a c h at P o i n t G r e y and D u n d a r a v e at Wes t V a n c o u v e r f rom O c t o b e r 1986 to J u l y 1987, figures 17 to 19. B e a c h profiles were surveyed to ident i fy the t e m p o r a l and spa t i a l m a g n i t u d e of shoreline changes due to waves ac t i ng on the beaches. T h e fo l lowing conclus ions have been d r a w n f rom the field measurements : 1. T h e scale of changes in beach shape is s m a l l c o m p a r e d to changes w h i c h occur t y p i c a l l y on o p e n coast beaches as exempl i f i ed by figure 4. Seasonal on-offshore sediment c y c l i n g k n o w n to occur on open coast beaches is not i n d i c a t e d by the sequence of profiles measured . 2. Sed iment a c t i v i t y occurs p r i m a r i l y i n the upper foreshore m o s t l y shoreward of the wave b r e a k i n g poin t at n o r m a l h i g h t ide as shown by the profi le var ia t ions i n figures Chapter 3. FIELD INVESTIGATIVE WORK 30 17 to 19. T h e profi le va r ia t ions are due to longshore sediment t r anspor t i n the uppe r foreshore, pho to 14. 3. C o b b l e d lower foreshores and t i d a l flats are stable. A t Tsawwassen and P o i n t G r e y the t i d a l flats, and at D u n d a r a v e and P o i n t G r e y the cobble lower foreshores, h a d neg l ig ib le changes i n e levat ion d u r i n g the 9 m o n t h s tudy p e r i o d . T h i s is consis-tent w i t h observed barnac le c o l o n i z a t i o n and algal s t a in ing of foreshore cobble a n d eel grass c o l o n i z a t i o n of the t i d a l flats at Tsawwassen i n d i c a t i n g s t ab i l i t y of the sed iment . 4. T h e m a x i m u m measured change i n dep th of upper foreshore sediment at the three sites was 0.5 metres. 5. T h e highest e leva t ion of measured beach sediment a c t i v i t y at the three sites is 2.5 metres above geodetic d a t u m . T h i s e levat ion corresponds to b e r m crests a n d onshore grave l movement in to backshore areas and represents the l i m i t of s t o r m wave r u n - u p and h igh t ides d u r i n g the s tudy p e r i o d . 6. Scour t renches pa ra l l e l i ng the shore are frequently formed i n the upper foreshore benea th the p lunge po in t of b reak ing waves i n d i c a t i n g b o t h onshore and offshore sediment movement shoreward and seaward of the breaker p lunge po in t . T h i s is exempl i f i ed i n figures 17 to 19 as the z igzag in the surface profile. 3.5.2 Tsawwassen Beach Tsawwassen beach is loca ted jus t south of the ferry causeway o n the west side of P o i n t R o b e r t s , figures 2 and 11. Tsawwassen B e a c h has developed geomorph i ca l l y to a profi le tha t is s i m i l a r to m a n y beaches on the inner south coast; the profi le has a coarse sand and gravel upper beach 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 and a sil t and sand t i d a l flat w i t h s lope t y p i c a l l y 1 V : 2 0 H near the uppe r beach f la t t en ing to 1 V : 2 5 0 H further offshore. T h e interface between the steep u p p e r beach and the t i d a l flats occurs at an e levat ion of a p p r o x i m a t e l y 0 metres geodet ic d a t u m (mean sea level) and is de l inea ted by an ab rup t change i n slope, figure 17, where coarse upper beach sediments end a n d t i d a l flat sands beg in . Sed imen t size d i s t r i bu t ions show tha t the upper beach , shoreward of the t i d a l flat, is p r e d o m i n a n t l y gravel wh ich grades to coarse sand in the upper foreshore, figure 21. B e a c h subsurface sediments col lec ted at 0.5 metres below the surface range f rom sands to gravels i n size. T h e cross shore sor t ing of surface sediments f r o m coarse to fine as one moves f r o m lower to upper foreshore is s imi l a r to other inner coast beaches. T i d a l flat are b u i l t of fluvial sediments supp l ied by the Fraser R i v e r . T h e t i d a l flat d i d not change e levat ion d u r i n g the p e r i o d of the survey; th is measure-ment is s u p p o r t e d by the fact tha t extens ive eel grass beds cover mos t of the t i da l flats i n d i c a t i n g s tab i l i ty . L i t t o r a l dr i f t is n o r t h w a r d a long the upper beach as ind ica ted by signif icant depos i t ion at the foot of the ferry causeway, figure 11, a po r t i on of w h i c h found to be f rom ar t i f ic ia l i n f i l l i ng |19]. N o r t h w a r d l i t t o r a l movement is also ev idenced by filling on the south sides of several groynes a long the shorel ine. Surveys shows that most of the sediment a c t i v i t y is i n the upper foreshore as exem-plif ied by the p lo ts of uppe r foreshore profi le v a r i a t i o n , figure 17. Surveys and a wave h indcas t ana lys i s also show a significant, lower ing of the foreshore fo l lowing a series of s torms in late N o v e m b e r 1986, the most s ignif icant of w h i c h occur red on N o v e m b e r 25th a p p r o x i m a t e l y 600 hours in to the m o n t h , a p p e n d i x D . Peak h indcas t s ignif icant wave heights at the end of the causeway were abou t 1.5 metres; news of the day repor ted overnight power outages and cance l l a t ion of ferry sa i l ings . T h e upper foreshore lowered about 0.3 metres over p r e s t o r m elevat ions as i nd i ca t ed by the profiles, figure 17. A site Chapter 3. FIELD INVESTIGATIVE WORK 32 v i s i t on N o v e m b e r 28 th revealed that the upper beach was devo id of the gravel veneer cha rac te r i s t i c of the beach except for gravel berms found i n the ext reme upper foreshore a p p a r e n t l y pushed ashore by b r e a k i n g wave swash at h igh t ide. E x t e n s i v e eel grass mats up to one metre t h i ck , appa ren t ly to rn up f rom the t i d a l flat by wave ac t ion , h a d accumu-la t ed at the foot, of the causeway, figure 11. A subsequent survey o n J a n u a r y 13th showed tha t the foreshore had developed a profile s imi l a r to the pre N o v e m b e r 25th s t o r m and gravel had reappeared over the beach surface. A p o r t i o n of the upper foreshore gravel be rms , appa ren t ly acted u p o n by waves, was eroded away. 3 .5 .3 T o w e r B e a c h at P o i n t G r e y Tower B e a c h at Point. G r e y is l oca ted at the western side of the 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 campus a n d is exposed to the S t ra i t of G e o r g i a , figures 2 and 12. Tower B e a c h at Point. G r e y is an a r t i f i c ia l cobble b e r m cons t ruc ted in 1980 and 1981 to arrest foreshore erosion caus ing recession of the P o i n t G r e y bluffs [10]. Prof i les i nd ica t e tha t the b e r m exh ib i t s cons iderable uppe r foreshore sediment a c t i v i t y and thus qualifies for s t udy as a shingle beach. In fact , the cobble b e r m exh ib i t ed sediment a c t i v i t y greater t h a n the n a t u r a l beaches at D u n d a r a v e and Tsawwassen based u p o n the envelope formed by sucessive profiles over a p e r i o d of t ime , figure 17. T h e greater sediment a c t i v i t y m a y be a t t r i b u t e d to more d i rec t exposure of P o i n t G r e y to p redominan t n o r t h west waves i n the S t ra i t of G e o r g i a . B e a c h profiles surveyed over the p e r i o d O c t o b e r 26, 1986 to June 10, 1987 ind ica te tha t the t i d a l flats and lower cobble beach d i d not change e leva t ion over the survey p e r i o d , figure 18. Sediment, is m o v i n g longshore in a na r row upper foreshore zone as i n d i c a t e d by the upper foreshore profi le shape w h i c h is cons t an t ly chang ing under wave a c t i o n . M i n o r changes i n e levat ion of the t i d a l flats are l i ke ly due to survey error. T h e d i r ec t ion of net. longshore sediment t r anspor t is n o r t h w a r d as i nd i ca t ed by groyne Chapter 3. FIELD INVESTIGATIVE WORK 33 i n f i l l i n g and by pa in t ed cobble p l aced on the foreshore w h i c h also had a net n o r t h w a r d movemen t . 3.5.4 Dundarave T h e shorel ine at D u n d a r a v e in W e s t V a n c o u v e r is exposed to B u r r a r d Inlet and the S t ra i t of G e o r g i a t h r o u g h a w i n d o w fo rmed by P o i n t A t k i n s o n and P o i n t G r e y , figure 2. Prof i les surveyed show sediment a c t i v i t y p r e d o m i n a n t l y in the u p p e r foreshore, figure 19. S a n d and gravels i n the upper foreshore are bel ieved to o r ig ina te f rom streams a long the Wes t V a n c o u v e r foreshore and f rom backshore eros ion where seawalls are absent. It has been observed tha t the upper foreshore is sandier i n the win te r compared to the s u m m e r l ike ly due to seasonably va r i ab le sediment supp ly ; s t reams c o n t r i b u t i n g sediment to th is sect ion of coast have the i r h ighest flows and assumed sediment discharges d u r i n g the win te r mon ths . T h e win te r sediment discharge is l ike ly enhanced by cons t ruc t ion i n the watershed d u r i n g previous d r y seasons. T h e shorel ine exh ib i t s cross shore so r t ing at the surface w i t h mob i l e sands and gravels i n the upper foreshore and cobble a n d bou lde r a r m o u r i n g in the lower foreshore, figure 20 and pho to 14. M e a s u r e d sediment size d i s t r ibu t ions f rom b u l k sieve analysis also ind ica t e an a r m o u r e d s t ruc ture by the three pa ra l l e l ' S ' shaped g ra in size d i s t r i b u t i o n curves , figure 21. A t the three s a m p l i n g po in t s on the foreshore sediments are qui te u n i f o r m but grade coarse to fine f rom the lower foreshore to the upper foreshore. T h e beach subsurface, however , has a w ide range of sediment sizes. Ne t longshore sediment t r anspor t d i r e c t i o n is eas tward a long D u n d a r a v e as ev idenced by the gravel beach w h i c h has fo rmed updr i f t of the 25th street pier . Chapter 3. FIELD INVESTIGATIVE WORK 34 3 . 5 . 5 E l e v a t i o n s o f shore features B e r m crest and o ld debris l ine e levat ions were measured at var ious sites a r o u n d the inner sou th coast d u r i n g the field inves t iga t ion and are s u m m a r i z e d i n table 3. T h e b e r m crests were the highest e leva t ion of ac t ive sediment measured on a beach as exempl i f ied by figures 15 and 16 and o ld debris l ines were accumula t ions of d r i f twood w h i c h appeared to be f r o m the prev ious win te r , not the most recent t ide . B E R M C R E S T A N D D E B R I S L I N E E L E V A T I O N S B E A C H E S O F 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 I n d e x L o c a t i o n B e r m C r e s t D e b r i s L i n e me t res - G e o d e t i c D a t u m 1 D u n d a r a v e , Wes t V a n c o u v e r ! 2.4 2 Tsawwassen 2.5 3 Tower B e a c h , P o i n t G r e y 2.6 4 C h a s t e r Creek Wes t , G i b s o n s 2.5 5 C a m p B y n g , R o b e r t s C r e e k 3.2 9 Savary Is land Southeas t 2.7 2.3 10 C a p e M u d g e , Q u a d r a I s land 2.2 13 C a p e L a z o , C o m o x 3.1 3.4 17 C o l u m b i a B e a c h , Q u a l i c u m 2.9 3.7 20 L o c k B a y , G a b r i o l a I s l and . 4.8 3.7 21 Orveas B a y , Sooke 3.8 3.2 24 C l o v e r P o i n t W e s t , V i c t o r i a 1.7 25 I s land V i e w B e a c h , Saan ich 0.7 t ab l e 3 Chapter 3. FIELD INVESTIGATIVE WORK 35 T h e d a t a i n tab le 3 is presented as par t of an overa l l desc r ip t ion of the inner coast. T h e elevat ions represent the l i m i t of wave a c t i v i t y on exposed shorel ine i n associat ion w i t h s t o r m wave run -up , a s t r o n o m i c a l h i g h tides and poss ib le s t o r m surge. E leva t ions vary f r o m site to site p r i m a r i l y because of exposure and t i d a l range. D e p o s i t i o n of the highest debris l ine on a shore occurs d u r i n g s torms w h e n h igh t ides, wave run -up a n d poss ible s t o r m surge cause waves to penetra te h igh i n the upper foreshore or backshore . C o a s t a l s t ruc tures shou ld i dea l l y be founded above this e leva t ion a l lowing for f reeboard. T h e founda t ion e levat ion of a coas ta l s t ruc ture is u sua l ly ca lcu la ted us ing the ex t r eme recorded h igh t ide ( w h i c h inc ludes s t o r m surge) p lus wave r u n - u p for a wave of specified r e tu rn p e r i o d p lus f reeboard a l lowance . T h i s e leva t ion shou ld be greater t h a n the measured debris l ine e levat ion at the site i n ques t ion . These elevat ions are presented as a de sc r i p t i on of the ve r t i ca l extent of wave ac t iv i ty on the inner coast a n d m a y serve as a check i n the ca l cu l a t i on of coas ta l water levels; the e levat ions i n themselves do not have any signif icance. 3.5.6 Hindcast, waves and profile changes Waves were h indcas t for the 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 Tsawwassen , Point. G r e y and D u n d a r a v e . Observed a n d measured sediment, movement, can be related to h indcas t waves, for example , a lower ing of the foreshore at T s a w w a s s e n measured on N o v e m b e r 30 th , 1986 is a t t r i b u t e d to the s t o r m wave ac t ion on N o v e m b e r 25th , 1986, a p p r o x i m a t e l y 600 hours in to the m o n t h , a p p e n d i x E . T h e m o n t h l y sequence of beach profiles does not a lways bracket i n d i v i d u a l s t o rm wave events caus ing the measured profi le changes. F o r th is reason, co r r e l a t i on between specific h indcas t s t o r m wave cond i t ions and measured profile volumetr ic , changes was not found. Fu r the r , since the measured profile changes were due p r i m a r i l y to longshore t ranspor t no means of co r re l a t ing the profile changes to wave cond i t ions c o u l d be ident i f ied . Chapter 3. FIELD INVESTIGATIVE WORK 36 3.6 S e d i m e n t T r a n s p o r t 3.6.1 G e n e r a ] f ie ld obse rva t i ons C o a s t a l l andforms such as rocky R e b e c c a Sp i t oh Q u a d r a Is land and Goose Sp i t near C o m o x have left a record of the range of m a t e r i a l sizes m o b i l i z e d by wave ac t ion o n the coast. For example , the m e d i a n cobble size on the beach surface at R e b e c c a Sp i t is about 70 m m , photos 19 and 20. M u c h of the cobble or ig inates f r o m a bluff top cobble layer at C a p e M u d g e abou t 5 k m away, photos 17 and 18, where the m e d i a n cobble size is about 120 m m . T h i s ind ica tes tha t a coarse f rac t ion of beach mate r i a l s in to the cobble and bou lde r size range are m o b i l e under wave a c t i o n on the inner coast. T h e cobble and boulders are p r e sumed to move as bed load a long the beach surface under intense s t o r m waves and have c o n t r i b u t e d to hourg lass ing of t i m b e r piles t h r o u g h abras ion at several coas ta l sites, p h o t o 16. Sed iment t r anspor t p r e d o m i n a n t l y is bed load ; t r anspor t of coarse sands, gravels a n d cobbles o c c u r i n g i n the upj)er foreshore at h i g h t ide . Waves app roach ing at an angle to the shore w i l l r un -up ob l ique ly 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 , the r e tu rn flow of the wave swash is d i r ec t ed by g r av i t y d o w n the beach slope n o r m a l to the shore, thus by this process l i t t o r a l m a t e r i a l moves in a sawtoo th fashion i n the upper foreshore. U p p e r foreshore profi le va r i a t ions measured at T s a w w a s s e n , Tower B e a c h and D u n d a r a v e are due to th is t ype of sediment movement . T h u s longshore sediment t r anspor t is pe r iod i c o c c u r i n g o n l y d u r i n g the upper por t ions of the t ide cycle . L o w tides place the swash zone over an a r m o u r e d p o r t i o n of the beach where mass t r anspor t w i l l occur on ly i f there is sufficient wave energy to m o b i l i z e the foreshore a r m o u r i n g as b e d l o a d . U p p e r foreshore longshore t r anspo r t of coarse gravels and cobbles is t y p i c a l of inner coast beaches. Chapter 3. FIELD INVESTIGATIVE WORK 37 3.6.2 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 T w o s imp le sediment t r anspor t exper iments d e m o n s t r a t i n g the d i spers ion of coarse par-t icles on a beach by wave ac t ion were conduc ted . T h e first, of these expe r imen t s was conduc ted o n a sect ion of shorel ine 1000 metres west of C h a s t e r Creek 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 exper iment i n v o l v e d p l a c i n g three we l l sor ted and rounded samples of t racer par t ic les of med ian sizes 6 m m , 3 8 m m and 7 5 m m on a sect ion of cobble a r m o u r e d shorel ine and observ ing the pa r t i c l e m o t i o n under the ac t ion of waves, currents a n d tides over a p e r i o d of several days, figure 22. T h e second expe r imen t i nvo lved p l ac ing the recovered 3 8 m m and 7 5 m m par t ic les on the Point. G r e y t i d a l flat for a p e r i o d of weeks. T h e beach expe r imen t s demons t ra te tha t coarse m a t e r i a l moves onshore under the a c t i o n of waves a n d t ides . Speci f ica l ly , i n the expe r imen t par t ic les s ta r ted a p p r o x i m a t e l y m i d foreshore w i l l creep onshore and then move i n the longshore d i r ec t ion i n the wave swash zone at h i g h t ide . T h e pa 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 nked w i t h the t i d a l range, r i s ing t ides advance the p o s i t i o n of the b reak ing wave across the profi le caus ing onshore movement over dis tances greater t h a n that poss ible i n the absence of t ides. T h e course par t ic les were observed to move on ly i n the i m m e d i a t e v i c i n i t y of the b r eak ing wave. Movement , of the 3 8 m m par t ic les onshore was h inde red by the fact tha t they tended to become nested w i t h i n the larger cobble m a t r i x on w h i c h they were p laced as i nd i ca t ed by the m a p of pa r t i c l e d i spe r s ion , figures 23 and 24. It shows tha t pa r t i c l e d ispers ion is slow or h inde red i n the v i c i n i t y of the t racer o r i g i n but once the par t ic les reach the upper foreshore swash zone d ispers ion is r a p i d . A p p r o x i m a t e l y 10 percent of the 3 8 m m par t ic les p l aced on the beach were bur i ed a n d not recovered. T h e 7 5 m m m e d i a n size par t ic les showed l i t t l e movement over the two days of the Chapter 3. FIELD INVESTIGATIVE WORK 38 e x p e r i m e n t , figures 25 and 26. T h e 38 m m par t ic les showed cons iderable mob i l i t y , wh i l e the 6 m m par t ic les were very m o b i l e and were so wide ly dispersed tha t c o u n t i n g the par t i c les was not a t t emp ted , photos 2 and 3. It also was apparent tha t a large f rac t ion of the 6 m m par t ic les p laced on the shore became bu r i ed , however , the range of pa r t i c l e movemen t a n d a p p r o x i m a t e cen t ro id of the pa r t i c l e mass was recorded , tables 4(a) and 4(b) . T h e 6 m m par t ic les r e m a i n e d i n the upper foreshore i n wave swash zone at h igh t ide , no par t ic les were found to move i n the offshore d i rec t ion . T h e par t ic les were p laced on the beach such that the size p laced was a p p r o x i m a t e l y i n the l o c a t i o n of na t ive m a t e r i a l of the same size; the 6 m m par t ic les were p laced i n the u p p e r foreshore and the larger 38 and 75 m m par t ic les were p laced lower on the beach , pho to 2. T h e t ravel of the cen t ro id of the pa r t i c l e mass , the m a x i m u m dis tance t r ave l l ed and exposure t i m e of the par t ic les to wave and t i d a l ac t ion were recorded a n d rates of l inear transport, of the par t ic les onshore and longshore were ca lcu la ted . T h e d a t a ind ica tes that, the highest t r anspor t ra te was that of the 6 m m par t ic les p laced i n the u p p e r foreshore. T h e result, is consis tent w i t h field observa t ion and measured beach profiles i n d i c a t i n g uppe r foreshore t r anspor t . R a t e and d is tance of pa r t i c l e t rave l are s u m m a r i z e d in tables 4(a) and 4 (b ) . Chapter 3. FIELD INVESTIGATIVE WORK L O N G S H O R E T R A N S P O R T O F P A R T I C L E S P a r t i c l e W a v e Transpor t . D i s t a n c e s T r a n s p o r t R a t e s D i a m e t e r E x p o s u r e C e n t r o i d M a x i m u m C e n t r o i d M a x i m u m ( m m ) (hr) (m) (m) ( m / h r ) ( m / h r ) 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 t a b l e 4(a) O N S H O R E T R A N S P O R T O F P A R T I C L E S P a r t i c l e W a v e T r a n s p o r t D i s t a n c e s T r a n s p o r t R a t e s D i a m e t e r E x p o s u r e C e n t r o i d M a x i m u m C e n t r o i d M a x i m u m ( m m ) (hr) (m) (m) ( m / h r ) ( m / h r ) 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 t a b l e 4(b) Chapter 3. FIELD INVESTIGATIVE WORK 40 3.7 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 o f K n o w l e d g e W a v e induced bluff erosion is a loca l coas ta l engineer ing p r o b l e m and is reviewed i n this s t udy as a s idel ine m a i n l y because of i ts l o c a l s ignif icance. T h e p r o b l e m is not discussed i n de ta i l bu t ra ther an overv iew of the current s i t ua t i on is g iven w i t h reference to re la ted s tudies . Bluf fs of s t ra t i f ied ple is tocene sediments such as Q u a d r a S a n d are c o m m o n a long the inner south coast of B r i t i s h C o l u m b i a [5]. In developed areas landowners are affected by receding bluffs, the loss of p r o p e r t y somet imes pos ing a threat to b u i l d i n g s , roads and other c i v i l works . Some l o c a l cases have been s tud ied extensively , most, no t ab ly the eros ion p r o b l e m at P o i n t G r e y . F i e l d inves t iga t ive work i n c l u d e d s tudy of several bluff erosion sites on the inner south 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 tab le 5. S O M E E R O D I N G C O A S T A L B L U F F S S O U T H W E S T B R I T I S H C O L U M B I A Index Si te 2 E n g l i s h Bluf f , Tsawwassen 2 Sou the rn Shore , P o i n t R o b e r t s 3 Tower B e a c h , P o i n t G r e y 9 Savary Is land Southeast 10 C a p e M u d g e , Q u a d r a Is land 13 C a p e L a z o , C o m o x 16 W i l l e m a r Bluf f s , C o m o x 19 K o m a s Bluf f , D e n m a n Is land 25 C o r d o v a B a y , Saan ich t a b l e 5 Chapter 3. FIELD INVESTIGATIVE WORK 41 B l u f f ma te r i a l s consist t y p i c a l l y of Q u a d r a S a n d or unconso l ida ted s i l t -c lays of pleis-tocene o r i g i n . W i t h the excep t ion of Tower B e a c h , P o i n t G r e y , the sites inves t iga ted were u n p r o t e c t e d and ac t ive ly e rod ing . A t m a n y of the sites l oca l residents have made a t t empt s to cons t ruc t s t ructures to reduce bluff eros ion, however , most s t ruc tures were not engineered a n d were ei ther not w o r k i n g or fa i l ing . W i l l e m a r Bluffs at C o m o x is one such site where residents have cons t ruc ted groynes and 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 to arrest the recession, photos 21 and 22. T h e bluffs are ac t ive con t r ibu to r s to sediment t ranspor t a long the coast, and i n some cases spi ts have developed downcoas t of the sites. Sandy t i d a l flats of v a r y i n g w i d t h and a steep u p p e r beach at the foot of the b luffs .are usua l . Sandy t i d a l flats are der ived f rom bluff sediments or are of f l u v i a l o r i g i n as is the case at Tsawwassen and Po in t G r e y where sediments are p r e d o m i n a n t l y f r o m the Fraser R i v e r . U p p e r beach slopes are u sua l ly abou t 1V:6H e x t e n d i n g f rom the ab rup t s lope change at the in tersec t ion of the ' t i d a l flat a n d uppe r beach shoreward to the bluff toe, figure 27 and photo 13. T h e uppe r beach cha rac te r i s t i ca l ly has a gravel or cobble a rmoured surface but may be over l a id w i t h a lens of sand of v a r y i n g th ickness g i v i n g the beach surface a sandy appearance , figure 27 and pho to 21. T h e sand lens is t rans ient i n na ture , pho to 22, its presence on the foreshore a func t i on of upcoas t supp ly and recent wave ac t iv i t y . Test pi ts at several sites i nd ica t e t y p i c a l sand lens thicknesses of 0.5 metres and a cobble a rmoured forshore benea th the sand lens suggest ing tha t the cobble a r m o u r is a more permanent and s table feature. A cobble layer of g lac ia l o r i g i n can usua l ly be found at most sites at the bluff top or w i t h i n the bluff s t ra t ig raphy , pho to 17. T h r o u g h the eros ion process the cobble finds i ts way to the foreshore p r o v i d i n g a degree of p r o t e c t i o n against further foreshore erosion. Foreshore cobble densit ies m a y va ry f rom a few scat tered cobble such as tha t at C o r d o v a B a y , Saan i ch to dense cobble bou lder beaches such as those 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 and , pho to 18, the densi ty of the bluff t op cobble s u p p l y i n par t d e t e r m i n i n g the state of foreshore a r m o u r i n g . Dense bluff t op cobble sources such as tha t at C a p e M u d g e , Q u a d r a I s l and , for example , have created heav i ly a r m o u r e d beaches. T h e cobble and bou lde r foreshores m a y be mob i l e under s t o r m wave a c t i o n as i n d i c a t e d by sediment t r anspor t expe r imen t s a n d c o b b l e / bou lde r spits downcoas t of the bluffs such as R e b e c c a S p i t , Q u a d r a I s l and and Goose S p i t , C o m o x , photos 19 and 20. Foreshore s t ab i l i t y is the c o n t r o l l i n g process i n bluff recession, the e levat ion of the foreshore u l t i m a t e l y affecting run -up dis tances in to backshore areas. C o n s i d e r i n g on ly wave based eros ion , b luff recession m a y be thought of as a func t ion of foreshore e levat ion change. B l u f f recession m a y be expressed as R = my where m= beach slope and y = foreshore e leva t ion change, figure 28. O t h e r factors c o n t r i b u t i n g to bluff recession inc lude w i n d e ros ion , r a i n , freeze/ thaw c y c l i n g and floating debris impac t s . Logs and other buoyan t debris f requent ly l ine the upper foreshore con t r ibu te signif i-c an t ly to the eros ion process t h r o u g h impac t s at the bluff toe under wave ac t ion , pho to 18. S a n d aprons t end to f o r m a r o u n d the bluff toe d u r i n g the s u m m e r when there is l i t t l e s t o r m wave a c t i o n i n inner coas ta l waters , photos 21, 23, 25 and 27, sand flowing down the bluff face p r i m a r i l y by w i n d eros ion d u r i n g s u m m e r mon ths . E leva t ions measured at the toe of the sand aprons ind ica t e tha t they are t y p i c a l l y a metre or more below win te r debris l ines . T h u s a large c o n t r i b u t i o n of sand size sediments to the coast f rom the bluffs occurs t h r o u g h the eros ion of the sand aprons p r i m a r i l y f r o m win te r s t o r m wave ac t i v i t y associa ted w i t h h igh t ides . T h e seasonal changes f rom s u m m e r to w in te r at the bluff sites can be d r a m a t i c as exempl i f ied by photos 21 to 28. G l a c i a l t i l l bluffs a long the n o r t h shore of L a k e E r i e have also been s tud ied by K a m -ph ius [27]. T h e bluffs s t ud i ed were t y p i c a l l y h a r d cohesive m a t e r i a l w i t h ten percent of Chapter 3. FIELD INVESTIGATIVE WORK 4 3 the t o t a l b luff mass beach size sand or coarser. A l t h o u g h the bluff erosion rate is a com-b i n a t i o n of l a n d a n d wave based processes K a m p h i u s ident i f ied the con t ro l l i ng process i n b luff recession as erosion of the foreshore by waves. Bluffs a long the n o r t h shore of L a k e E r i e appa ren t l y do not exh ib i t cobble a r m o u r i n g as do the bluffs o n the inner south coast . K a m p h i u s found tha t the long t e r m shore l ine recession rate is re la ted to the long t e r m average wave power . H i s conclus ions were suppor t ed by a theore t i ca l ly developed express ion and field measurements . C h a p t e r 4 L A B O R A T O R Y B E A C H E S 4.1 G e n e r a l L a b o r a t o r y beach exper iments car r ied out i n wave flumes demons t ra te on-offshore sedi-ment t r anspor t analogous to the movement of sand k n o w n to occur o n open coast sandy beaches due to seasonal v a r i a t i o n i n wave c l ima te . L a b o r a t o r y beaches have been re-v iewed to p r o v i d e a d d i t i o n a l scope to th is i nves t iga t ion . In the s t udy of beaches one ob jec t ive is to relate the profile changes to the wave cond i t i ons caus ing those changes. A p r o b l e m has been the lack of a read i ly measurab le va r i ab le in t e r r e l a t ing sediment movement and waves. A p r o b l e m ident i f ied i n def ining such a va r i ab le has been the fact tha t a beach profi le has no length scale. Waves m a y be assigned a wave l eng th but the beach profile can o n l y be assigned a slope w h i c h is d imensionless ; a va r iab le i n t e r r e l a t i ng beach sediments and waves must c i rcumvent this fact. Such a va r iab le m a y be defined by differencing an i n i t i a l beach profile and the profile e v o l v i n g as a func t ion of t i m e under wave a c t i o n w h i c h results i n an area swept out between the two profiles. O v e r t i m e sediment, a c t i v i t y causes volumetr ic , changes i n a beach wh ich m a y be re la ted to the wave cond i t ions caus ing the change t h r o u g h the swept area va r i ab le . T h e swept area is re la ted to the v o l u m e of ma te r i a l tha t moves re la t ive to an i n i t i a l profi le i n response to the profi le ad jus t ing its shape to an i m p o s e d wave c o n d i t i o n . 44 Chapter 4. LABORATORY BEACHES 4 5 Beaches are dynamic , i n tha t the surface profi le responds and adjusts its shape to an i m p o s e d wave c o n d i t i o n . Sediment a c t i v i t y i n d u c e d by fluid t u rbu lence generated by b r e a k i n g or su rg ing waves alters the profile over t i m e . A beach has no e las t ic i ty ; once wave a c t i o n stops there is no fur ther response. Beaches tend to evolve to an e q u i l i b r i u m profi le w h e n subject to a constant wave c o n d i t i o n and once e q u i l i b r i u m has been achieved there w i l l be no fur ther s ignif icant response p r o v i d e d tha t the wave c o n d i t i o n remains cons tant . T h e e q u i l i b r i u m beach profile w i l l d i ss ipa te a n d / or reflect a l l the wave-energy reach ing it in such a manne r that no net t r anspor t of the beach sediment occurs anywhere a long the beach profi le . L a b o r a t o r y beaches i n wave flumes are idea l i zed c losed sed imentary env i ronments i n w h i c h par t i c les are m o b i l i z e d by b r e a k i n g or su rg ing waves. In such an idea l sys t em sediment mass is conserved and therefore beach subsurface v o l u m e is constant . In the field beaches u sua l ly have a net offshore loss of m a t e r i a l and i n a d d i t i o n there m a y be longshore sediment movement . 4.2 A c t i v e V o l u m e T o define beach response on-offshore sediment t r an spo r t has been idea l i zed as o c c u r i n g w i t h i n a closed sy s t em b o u n d e d by shoreward and seaward l i m i t s of sediment movement and uppe r and lower profiles. Pa r t i c l e s are r ecyc led by wave a c t i o n w i t h i n an area d e l i m i t e d by these boundar ies . T h e measurab le v o l u m e of m a t e r i a l d i sp laced by 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 th is idea l i zed on-offshore t r anspor t sy s t em is defined as ac t ive v o l u m e w h i c h is equa l to ha l f of the area swept between two successive profiles, figure 29. S i m i l a r def ini t ions m a y be m a d e for gross v o l u m e and net v o l u m e , however, they are of academic interest . T h e r e is a f ixed i n i t i a l l y k n o w n profi le and an e v o l v i n g profi le that, varies w i t h t i m e , the ac t ive v o l u m e as a func t ion of t i m e be ing defined as Chapter 4. LABORATORY BEACHES 46 ha l f the area swept out be tween the two profiles as a func t ion of t ime . A c t i v e vo lume is pos i t i ve for accre t ive beaches and negat ive for erosive beaches. T h e v o l u m e ac tua l ly represents the amoun t of m a t e r i a l tha t mus t moves on a beach re la t ive to a reference or d a t u m prof i le i n order for the beach profi le to adjust to the i m p o s e d wave c o n d i t i o n . S ince the swept area represent ing ac t ive vo lume evolves as a func t ion of t ime the t i m e der iva t ives of the areas m a y also be defined to give rates of erosion or accre t ion and s i m i l a r l y t i m e der iva t ives of these rates, figure 30. T h e height and p e r i o d of the imposed wave as a func t i on of t i m e combine to fo rm a wave steepness as a func t i on of t ime w h i c h de termines the charac ter of fluid tu rbu lence a n d thus the d i r ec t ion of sediment movement . 4.3 D i m e n s i o n a l A n a l y s i s T h e fo l l owing f u n c t i o n a l r e l a t ionsh ip m a y be expressed for on-offshore t r anspor t on i n i -t i a l l y flat beaches subject, to m o n o c h r o m a t i c waves: Va = f{H0,T, D50,p,ps,g,fi,mi,t) W h e r e the var iables are defined as fol lows: Va = ac t ive v o l u m e of sediment ; HD — deep water wave height ; T = wave p e r i o d ; JD 5O — m e d i a n sediment size; p = fluid densi ty ; ps = sediment densi ty ; p. = fluid d y n a m i c v i scos i ty ; Chapter 4. LABORATORY BEACHES 4 7 g = acceleration due to gravity; ?7i,: = in i t ia l beach slope; t = t ime. T h e dependent variable is Va, the remain ing variables being independent . U s i n g L0 = gT2/2ir and // = fi/p where L0— water wave length a n d v— kinematic, viscosity, the relat ionship m a y be reduced to the following dimensionless groups: Va ( ( H 0 Db0 vT p t, —— = J( —, -r—, , —, m,-H0L0 L0' L0" H0Lo' ps" l' T It might be assumed that the effects of f luid viscosity would be negligible a n d that the rat io of sand density to fluid density might be considered nearly constant, thus the re lat ionship reduces to: V* HQ D50 t for e q u i l i b r i u m profiles: HnLn Ln Lr, Va H0 D50 , H0L0 L0 Lc alternatively, the preceeding re lat ionship m a y be written: V„. t { H0 D50 t H0gT2 •'gT^gT2' T' Simi lar ly , the sediment act iv i ty m a y be expressed in dimensionless f o r m for in i t ia l ly flat profiles: Qa ,, Ho D5Q t HagT L0 L0 T where Oa = dVa/dt is sediment act ivity. Chapter 4. LABORATORY BEACHES 4 8 T h e concept of ac t ive v o l u m e m a y be ex tended to n a t u r a l beaches, however , a d d i t i o n a l cons idera t ions are requ i red . N a t u r a l beach profiles are forever chang ing shape and do not have a flat s t a r t ing profi le w h i c h m a y be used as a d a t u m for m e a s u r i n g ac t ive vo lume , thus a reference profile or d a t u m , w h i c h m a y not necessar i ly be flat as i n the labora to ry , shou ld be defined. T h e reference profile s h o u l d l ie w i t h i n an envelope descr ibed by m a x i m u m and m i n i m u m ordina tes of a series of shore n o r m a l profiles [7]. A reference profi le for n a t u r a l beaches migh t be defined as a curve fit between o rd ina te po in t s desc r ib ing upper and lower profiles or perhaps as an average t r a n s i t i o n profile for w h i c h there is ne i ther s t rong onshore or offshore t r anspor t . A def in i t ion of a reference profi le w i l l l i k e ly invo lve longer t e r m observa t ion and s tudy of the e v o l u t i o n a r y shapes of n a t u r a l beaches and is thus a top ic for further research. W h e t h e r or not the e q u i l i b r i u m ac t ive v o l u m e is the same for b o t h accret ive and erosive profiles w i l l l i k e ly depend u p o n the def in i t ion of the reference profile against w h i c h the volumes are measured . For non-flat, i n i t i a l profiles a parameter for the state of the i n i t i a l profile is also requi red i den t i fy ing how close the i n i t i a l profile is to e q u i l i b r i u m . Such a ' s tate ' pa ramete r might, be defined: g I 1 aeq " ai \ where S= s tate pa ramete r , Vaeq= e q u i l i b r i u m ac t ive v o l u m e for the imposed wave c o n d i t i o n measured re la t ive to a d a t u m profi le and Va7= i n i t i a l ac t ive v o l u m e re la t ive to the reference profi le . For example , i f the i n i t i a l profi le is a l ready at e q u i l i b r i u m for the i m p o s e d wave c o n d i t i o n then 5 = 0 i m p l y i n g no response; i f the s t a r t i ng profile by some chance is equa l to the reference profi le then 5 = 1 i n d i c a t i n g beach response; if the s t a r t i n g profi le is erosive and the i m p o s e d wave c o n d i t i o n resul ts i n accre t ion then 5 > 1 i m p l y i n g a larger v o l u m e of sediment is i nvo lved i n the response. T h e i n i t i a l shape of a beach profi le does not affect the final shape a t t a ined under an imposed wave Chapter 4. LABORATORY BEACHES 49 c o n d i t i o n , however , the t i m e to achieve e q u i l i b r i u m is ce r t a in ly affected as recognized by most researchers. In general the ac t ive v o l u m e of sediment on a beach as a func t ion of t ime is: Va t ^ = / ( C , 7 , S ) - ) H0L0 ^ ' " ~ T where C = an on-offshore pa ramete r c o m b i n i n g d imensionless groups H0/L0, D50/Lo and I = wave in tens i ty to account for the m a g n i t u d e of v o l u m e t r i c change; S = state pa ramete r for non-flat i n i t i a l profiles; t/T — d imensionless t i m e . A c t i v e v o l u m e m a y have a pos i t ive or negat ive sign co r r e spond ing to onshore or offshore t r anspor t respect ively . T h e s ign m a y be de te rmined by in teg ra t ing the bed e leva t ion changes across the beach profile f rom onshore to offshore i n a manne r s imi l a r to the m e t h o d used by var ious researchers [46], [22] to de te rmine t r anspor t rates across the profi le . If the net sediment vo lume is p r e d o m i n a n t l y onshore then Va is pos i t ive and is co r r e spond ing ly negat ive for p r e d o m i n a n t l y offshore t r anspor t . T h u s ac t ive vo lume is eva lua ted by e x a m i n i n g sediment transport, across the entire profile and the sign is de t e rmined by the p r e d o m i n a n t t r anspor t d i r e c t i o n . Researchers [46], [22] have classified three bas ic types of beach profiles: profiles de-ve loped by s t rong onshore t r anspor t , neu t r a l profiles developed by b o t h onshore and offshore t r anspor t shoreward and seaward of the breaker zone a n d profiles developed by s t rong offshore t r anspo 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 ther be ing accret ive or erosive depend ing u p o n the p r edominan t t r anspor t d i r ec t i on . T h u s , the ac t ive v o l u m e a p p r o a c h to on-offshore transport, has the d isadvantage of not c lear ly iden t i fy ing neu t r a l profiles where sediment t r anspo r t m a y ' l o c a l l y be o c c u r i n g in b o t h d i rec t ions . Chapter 4. LABORATORY BEACHES 50 4.4 A n a l y s i s o f B e a c h P r o f i l e s L a b o r a t o r y exper iments on beaches have not been car r ied out as pa r t of the present s tudy, bu t ra ther , p rev ious s tudies were referred to for d a t a [46], [22] and [38]. Profi les are presented i n figures 6 to 8 and deta i l s of the exper iments are o u t l i n e d i n sect ion 2.7. It was found tha t some researchers present l a b o r a t o r y beach profiles i n such a manner tha t the ex t remes of the ac t ive profi le are not i nc luded . B e a c h profiles shou ld encompass a l l of the profi le f r o m the offshore l i m i t to the onshore l i m i t of sediment movement a n d shou ld have app rop r i a t e h o r i z o n t a l and ve r t i ca l scales i nd i ca t ed . 4.4.1 M e t h o d of ana ly s i s T h e m e t h o d of ana lys is of beach prof i le d a t a largely invo lved the d e t e r m i n a t i o n of h igh ly i r regu la r swept areas be tween profi les. T h e fo l lowing procedure was ca r r i ed out : 1. Swept areas or ac t ive vo lumes were de te rmined by p h o t o g r a p h i c a l l y enlarg ing scale beach profi le d rawings by four -hundred percent , p l ac ing a m y l a r g r i d over the en-largement, and iden t i fy ing x , y d a t a points tha t best descr ibe the i n i t i a l and final profi le and sca l ing those po in t s to l a b o r a t o r y scale. 2. T h e scaled x , y d a t a were entered in to a d a t a file w h i c h was i n p u t to a compu te r p r o g r a m w r i t t e n to ca l cu la t e ac t ive vo lumes . T h e ac t ive vo lumes were p l o t t e d against wave height , p e r i o d a n d t i m e d imens iona l l y and non- d i m e n s i o n a l l y us ing a compu te r spreadsheet and g r a p h p l o t t i n g p r o g r a m . 4.4.2 A c t i v e v o l u m e versus wave he igh t T h e r e l a t i onsh ip between ac t ive v o l u m e of sediment and wave height was inves t iga ted us ing beach profi le d a t a f r o m exper imen t s conduc ted 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]. Beaches were tested under different combina t ions of i n i t i a l s lope and m e d i a n pa r t i c l e d iamete r , f igure 6: B e a c h 1: D50= 0 . 7 m m , m,= 0.10; B e a c h 2: L > 5 0 = 0 . 7 m m , m F 0.05; B e a c h 3: D50 = 0 . 22mm, m , = 0.10; B e a c h 4: D50 = 0 . 22mm, ??7,7= 0.05. Waves were m o n o c h r o m a t i c w i t h p e r i o d he ld constant at T— 1.0, 1.5 a n d 2.0 seconds and height va r i ed for each of these per iods . D u r a t i o n of wave ac t ion was 1 hour therefore the f ina l profiles a n d act ive vo lumes o b t a i n e d do not necessar i ly co r respond to e q u i l i b r i u m cond i t ions . D a t a has been p lo t t ed d i m e n s i o n a l l y w i t h Va versus H0 and n o n - d i m e n s i o n a l l y w i t h Va/(H0L0) versus HQ/Lor figures 31 to 34. L ines of cons tant p e r i o d are d r a w n on al l p lo ts . A l l beaches are accret ive for low steepness waves. T y p i c a l l y , a t r a n s i t i o n occurs f r o m an accre t ive beach to an erosive beach for wave steepnesses a r o u n d 0.03 w h i c h is consis tent w i t h wave steepness values r epo r t ed i n the l i t e ra ture . It is no t ed tha t beach 2 moves f rom an accre t ive to an erosive state at H0/L0= 0.05 and beach 4 at H0/LD= 0.01. T h e reason for the t r ans i s t i on i n beach state at different wave steepnesses is u n k n o w n . T h e coarser sand (0 .7mm) beaches t end to be accret ive . T h i s is p a r t i c u l a r l y evident for beaches 1 a n d 2 w h i c h show s t rong onshore movement for low frequency waves, figures 31 a n d 32. T h e fine sand (0 .2mm) beaches t end to be erosive, however , beach 3 shows accre t ion for low frequency waves, figures 33 and 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 li t t le beach sediment activity, however, at 2.0 seconds the beach becomes very active showing strong onshore movement. The 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. As 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 Da ta 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: D50= 0.22mm, m,= 0.033; B e a c h 2: D50= 0.47mm, mt= 0.033; B e a c h 3: D50= 0.90mm, mr= 0.033; B e a c h 4: D 5 0 = 3.44mm, = 0.033. The beaches were subject to monochromatic waves with 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. Da ta is presented dimensionally with Va versus T and non-dimensionally with Va/\H0L0) versus gT2 /D50 with lines of constant wave height, through data points for each sediment size, figure 35. Chapter 4. LABORATORY BEACHES 53 T h e p lo ts are undef ined for short p e r i o d waves less t h a n about 0.3 seconds since the l i m i t i n g wave steepness due to b reak ing is exceeded. A l l beaches, except beach 2, show a m a x i m u m response or sediment, a c t i v i t y at a pa r t i cu l a r wave p e r i o d . A l o n g a l ine of constant wave height, the wave in tens i ty and steepness decreases as p e r i o d increases. A l l beach response curves w i l l fal l to zero for ve ry long p e r i o d waves since the in tens i ty of the fluid t u rbu lence becomes insufficient to e n t r a i n a n d m o b i l i z e sediments . Fo r shor ter p e r i o d waves the response decreases but does does not fa l l to zero; the wave in tens i ty is h igh but the beach is less ac t ive because the in t ens i ty of the fluid t u rbu lence at the b e d capable of m o b i l i z i n g sediments does not reach the depths a long the profi le tha t lower frequency waves do. T h e p lo t of ac t ive v o l u m e versus wave frequency or p e r i o d m a y be though t of as a response curve for a beach defined i n te rms of an ac t ive on-offshore v o l u m e of sediment and wave frequency. Fo r fine sediments ( 0 . 2 2 m m sand) the curve has two m a x i m a i n sediment ac t i v i t y , one co r r e spond ing to onshore t r anspor t and one to offshore t ranspor t . T h e d a t a shows coarse m a t e r i a l genera l ly moves onshore over a wide range of wave per iods thus the cons tan t height curve has one m a x i m a i n sediment ac t iv i ty . 4.4.4 Active volume versus time T h e r e l a t i onsh ip be tween act ive sediment v o l u m e and t i m e was also inves t iga ted us ing profi le d a t a f r o m H a t t o r i and K a w a m a t a [22]. A single beach w i t h m e d i a n pa r t i c l e size of 2 2 m m a n d i n i t i a l s lope of 0.05 was tes ted unde r wave steepnesses of 0.006 and 0.035 p r o d u c i n g accre t ive 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 Va versus t and non d i m e n s i o n a l l y w i t h Va/H0L0 versus t/T, figure 36. T h e beaches have not reached e q u i l i b r i u m bu t the curve shows an e x p o n e n t i a l increase i n the ac t ive 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 app roach ing an e q u i l i b r i u m ac t ive vo lume Chapter 4. LABORATORY BEACHES 54 of sediment as desc r ibed by the re la t ionsh ip : Va(t) = Vaeg(C,I)(l-e-rt) W h e r e : Va(t) = ac t ive sediment vo lume ; Vaeq = e q u i l i b r i u m ac t ive vo lume ; C = on- offshore parameter ; I = wave in tens i ty ; r = t i m e cons tant ; t — t i m e . W h a t the r e l a t i onsh ip states is tha t as the prof i le evolves exponen t i a l l y to an equ i l ib -r i u m shape unde r the i m p o s e d wave c o n d i t i o n the v o l u m e of sediment tha t mus t move re la t ive to the i n i t i a l profi le or d a t u m to achieve the e q u i l i b r i u m shape also evolves ex-p o n e n t i a l l y 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 ac t ive vo lume of sediment on a beach w i t h t i m e due to an onshore or offshore t r anspor t m o d e is a c t u a l l y a step l ike func t ion , each b r e a k i n g wave m o b i l i z i n g a discrete a m o u n t of m a t e r i a l on the beach chang ing the vo lume . T h e 's tep ' m a y not be resolvable by o r d i n a r y survey or measurement techniques a n d i n any case the profi le e v o l u t i o n w i t h t i m e m a y be reasonably a p p r o x i m a t e d w i t h a cont inuous func t ion . T h e p lo ts i nd i ca t e tha t there are two types of profiles: a profi le associated w i t h an accre t ive c o n d i t i o n and a profile associa ted w i t h an erosive c o n d i t i o n , figure 36. T h e ac t ive vo lumes associated w i t h each profile m a y be assigned pos i t ive and negat ive signs Chapter 4. LABORATORY BEACHES 55 respect ive ly . T h e curves are lines of constant wave steepness, thus different wave steep-nesses p r o d u c e a f a m i l y of such curves. A neu t ra l c o n d i t i o n also exists where there is b o t h onshore and offshore sediment movement re la t ive to the breaker zone and there is r e l a t i ve ly s m a l l v o l u m e t r i c changes. S ince ac t ive v o l u m e assesses the changes across the ent i re profi le and is based on the p r e d o m i n a n t sediment t r anspor t d i r ec t i on neu t r a l cond i t i ons where b o t h onshore and offshore t r anspor t occur m a y not be r ead i ly ident i f ied us ing th is app roach . W h e n a beach has achieved e q u i l i b r i u m its ac t ive v o l u m e is at a m a x i m u m value for the wave c o n d i t i o n i m p o s e d , however, beach sediment a c t i v i t y is at a. m i n i m u m since no s u b s t a n t i a l sediment a c t i v i t y takes place at e q u i l i b r i u m . T h u s a r e l a t ionsh ip m a y be expressed: Qa(t) = Vaeq{CJ)e-rt where Qa(t)= dVa/dt= sediment ac t iv i ty . T h e t i m e cons tant r is hypo thes i zed to be a func t ion of the wave in tens i ty / for the l a b o r a t o r y beaches. F o r n a t u r a l beaches where the i n i t i a l profile is not flat as i n the l a b o r a t o r y a n d ac t ive v o l u m e is de t e rmined re la t ive to a reference profi le tha t is not necessar i ly the same as the s t a r t ing profi le the t ime constant r is a func t ion of b o t h wave in tens i ty a n d the profi le state. O b v i o u s l y , the t i m e requi red to reach e q u i l i b r i u m w i l l be affected by how close the s t a r t i ng profi le is to e q u i l i b r i u m as i n d i c a t e d by the profile s tate pa r ame te r discussed previous ly . C h a p t e r 5 D I S C U S S I O N 5.1 B e a c h R e s p o n s e A concept of beach response to waves based u p o n inves t iga t ion of field and l abo ra to ry beaches is s u m m a r i z e d : • beaches are d y n a m i c , ine las t ic and governed by a n a t u r a l process of sediment par-t i c l e en t r a inmen t and m o t i o n induced by f lu id tu rbu lence generated by b r eak ing or su rg ing waves; • beaches evolve to an e q u i l i b r i u m profile when subject to a constant wave cond i t i on ; • the d i r e c t i o n of on-offshore sediment movement on sandy beaches is a func t ion of wave steepness a m o n g other parameters ; h igh steepness short p e r i o d waves in i t i a t e offshore movemen t of sand whi le long p e r i o d , low steepness waves in i t i a t e onshore movemen t of sand; • wave steepness alone m a y ind ica t e the d i r e c t i o n of sediment movemen t , however, an a d d i t i o n a l pa ramete r such as wave in tens i ty or p e r i o d is requi red to specify the m a g n i t u d e or ra te of sediment movement ; • on-offshore movement of sediment m a y be concep tua l i zed by represent ing the vo l -u m e of sediment i nvo lved i n the evo lu t i on of a profile f r o m an i n i t i a l to a final state as an area swept out between the i n i t i a l a n d f ina l profiles; 56 Chapter 5. DISCUSSION 57 • coarse m a t e r i a l beaches (gravels and cobble) general ly t end to be accret ive , fine m a t e r i a l beaches (sil ts and sand) m a y be accret ive or erosive depend ing u p o n the wave steepness, th is has been observed i n the field [39] as we l l as in the l abo ra to ry [15]; • for a g iven wave height (or specific wave energy) , sediment size a n d i n i t i a l beach s lope a beach w i l l have a m a x i m a i n sediment a c t i v i t y at a p a r t i c u l a r wave fre-quency, fine sediments m a y exh ib i t two m a x i m a i n sediment ac t iv i ty , one corre-s p o n d i n g to onshore movement a n d one to offshore movement w h i l e coarse sedi-ments exh ib i t a s ingle m a x i m a i n sediment a c t i v i t y co r respond ing to onshore move-ment . 5.2 Differences Between Natural and Laboratory Beaches T h e on-offshore a c t i v i t y of beach sediment has been discussed w i t h reference to l a b o r a t o r y da ta . N a t u r a l beaches m a y differ in behav io r f rom l a b o r a t o r y beaches because of var ious factors , some of w h i c h are ou t l i ned : 1. N a t u r a l beaches are not closed sed imenta ry env i ronments ; t h r o u g h on-offshore sed-imen t t r anspor t fine sediment is often p e r m a n e n t l y lost offshore and longshore t r anspo r t occurs w h e n waves break o b l i q u e l y to the shore. 2. T h e on-offshore response of a beach to waves defined i n terms of an ac t ive vo lume of sediment, has been shown for l a b o r a t o r y beach d a t a w i t h i n i t i a l l y flat profiles, however , flat i n i t i a l profiles do not occu r on n a t u r a l beaches. N a t u r a l beaches s t i l l have an ac t ive v o l u m e of sediment , however , the reference profi le or d a t u m requi red to de te rmine i t r emains undef ined. E q u i l i b r i u m beach shape is a ssumed to be not affected by the s t a r t i ng profile but the t i m e to achieve e q u i l i b r i u m is. Chapter 5. DISCUSSION 58 3. T h e t e r m ac t ive v o l u m e does not i m p l y tha t o n l y the v o l u m e of sediment defined by the swept area between profiles is a c t u a l l y act ive. F i e l d s tudies have repor ted tha t at depths below the beach surface the subsurface m a t r i x is ac t ive a n d undergoes shear ing m o t i o n . 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 qu i f ac t ion l ike s tate of the subsurface 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 subvo lume of ac t ive m a t e r i a l on a beach re la t ive to an i n i t i a l profile tha t moves i n response to the profi le evo lv ing to an e q u i l i b r i u m shape. 4. N a t u r a l beach sediments m a y have w i d e l y v a r y i n g -D50, shape and dens i ty whereas the l a b o r a t o r y beaches inves t iga ted h a d re la t ive ly homogeneous sediments . 5. O c e a n waves have a d i s t r i b u t i o n of heights and per iods whereas l a b o r a t o r y waves are u sua l ly 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 lways be a d a p t i n g to a new e q u i l i b r i u m w i t h chang ing s t o r m wave height and p e r i o d whi le l a b o r a t o r y beaches subject to m o n o c h r o m a t i c waves adapt to o n l y a single e q u i l i b r i u m state. 6. T h e effect of t ides has not been accounted for in the l a b o r a t o r y beaches inves t iga ted . T i d e s con t r i bu t e to the geomorphic. deve lopment of beaches by sh i f t ing the breaker p o s i t i o n over the profi le . 5.3 C o a s t a l P r o c e s s e s T h e m o r p h o l o g y of inner coast beaches is a func t ion of i ts sediments , and the wave, current and t i d a l regime. A concept of on-offshore sediment a c t i v i t y is presented for inner a n d open coast beaches, figure 37. T h e figure presents an ac t ive v o l u m e of sediment versus wave p e r i o d for waves of cons tant height (or specific, wave energy) and fine m a t e r i a l and coarse sediments; i den t i c a l beaches on inner and open coasts are assumed. A f a m i l y of such curves exists for var ious sediment pa r t i c l e sizes and wave heights . Chapters. DISCUSSION 59 T h e curve shows fine ma te r i a l unde rgo ing the classic reversal f r o m an erosive to accre t ive behav io r at a pa r t i cu l a r wave steepness w h i c h t y p i c a l l y is at a va lue of about 0.03 for l a b o r a t o r y beaches; i t is u n k n o w n i f the reversal f rom erosive to accre t ive behav io r on n a t u r a l beaches occurs at th is wave steepness. Coa r se ma te r i a l shows accret ive behav io r regardless of wave steepness. Studies rev iewed have shown tha t coarse m a t e r i a l moves offshore 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 b r e a k i n g waves; movement of coarse sediments offshore to bars as sand moves w o u l d appear un l ike ly . T h e studies reviewed and field d a t a co l lec ted ind ica tes tha t coarse m a t e r i a l tends to be general ly accre t ive and thus the curve i n figure 37 is presented as such. T h e left p o r t i o n of the curve is undef ined due to the wave steepness l i m i t . At. the same ho r i z on t a l scale m o n t h l y average peak 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 the no r the rn hemisphere t y p i c a l l y show a seasonal shift i n peak wave p e r i o d f r o m p r e d o m i n a n t l y long p e r i o d waves i n the s u m m e r , w h i c h a r r ive f r o m dis tan t genera t ing sources often i n the sou the rn hemisphere , to shorter p e r i o d waves i n the win te r f r o m N o r t h Pac i f ic s torms . A d i s t r i b u t i o n of wave per iods for open coast near Tor ino , B r i t i s h C o l u m b i a , figure 1, for the mon ths of J a n u a r y and August . 1982 show the shift i n peak wave p e r i o d , figure 38. T h e peak p e r i o d shifts f rom 10.5 second re la t ive ly h igh steepness waves i n J a n u a r y to 17.5 second lower steepness waves in A u g u s t . T h e G e o l o g i c a l Su rvey of C a n a d a [18] showed tha t sandy L o n g B e a c h near Tof ino has wel l defined seasonal behav io r w i t h accret ive profiles i n the s u m m e r and erosive profiles in the win te r . R e v i e w of wave c l ima t e d a t a for the open coast near Tof ino ind ica t e tha t long p e r i o d low steepness waves a r r ive for up to 5 to 6 days con t inuous ly l i ke ly i n i t i a t i n g an episode pf beach b u i l d i n g . T h i s same p h e n o m e n o n has been observed and d o c u m e n t e d ex tens ive ly i n Sou the rn C a l i f o r n i a [42]. Fe t ch res t r ic ted S t ra i t of G e o r g i a has a n upper l i m i t on wave p e r i o d and plots to the left, of the open coast curve . For short p e r i o d waves the curves represent waves of h i g h Chapter 5. DISCUSSION 60 steepness and co r r e spond ing ly for long p e r i o d waves the curves represent low steepness waves, f igure 37. T h e wave c l i m a t e i n the S t ra i t of G e o r g i a has more frequent h i g h steepness and low in tens i ty waves i n c o m p a r i s o n to the open .coast as i n d i c a t e d by the wave steepness a n d in tens i ty d i s t r i b u t i o n s , figures 39 and 40, w h i c h have been der ived f r o m wave sca t te rgrams for the S t r a i t of G e o r g i a a n d the N o r t h Pac i f i c , appendices B and C . Heights and per iods f rom the records were c o m b i n e d to f o r m wave steepnesses a n d intensi t ies and were p lo t t ed against p r o b a b i l i t y of occurance de t e rmined by d i v i d i n g the n u m b e r of occurances of a p a r t i c u l a r height p e r i o d c o m b i n a t i o n by the t o t a l n u m b e r of observat ions i n the record . T i d e s are an i m p o r t a n t factor i n the select ive onshore t r anspo r t of coarse m a t e r i a l observed o n inner coast beaches. M o b i l i z a t i o n of coarse par t ic les occurs i m m e d i a t e l y benea th the p l u n g i n g wave a n d par t ic les have been observed to advance onshore w i t h the advanc ing breaker p o s i t i o n on a r i s ing t ide . T h u s the onshore movement of coarse par t ic les is a ided by the subs t an t i a l t i d a l range on the inner coast . A shoreward advanc ing breaker pos i t i on on a r i s ing t ide mob i l i ze s par t ic les up the beach to the upper foreshore where they r e m a i n or cont inue m o v i n g i n the longshore d i r ec t i on when waves break o b l i q u e l y to the shore. In the absense of t ides coarse par t ic les w o u l d be m o b i l i z e d i n the b r e a k i n g wave swash and t y p i c a l l y move on ly a few metres shoreward . T h e da t a of tab le 1 shows a range of 5 metres for annua l t ides. A s s u m i n g a t y p i c a l beach slope of 1 V : 1 0 H the b r e a k i n g wave p o s i t i o n w i l l shift 50 metres across the profi le on an annua l t ide . D e v e l o p m e n t of a r m o u r e d beaches on the inner coast, is i n par t a func t ion of t ides. O v e r vast, pe r iods of t ime b reak ing waves shi f t ing p o s i t i o n over the profile due to t i d a l fluctuations have removed a l l bu t the largest s table cobble f r o m the beach surface. M o -bi le cobble , g rave l and coarse sands a c c u m u l a t e i n the upper foreshore where they are t r a n s p o r t e d longshore . U n d e r the p r e d o m i n a n t wave c l i m a t e of the inner coast finer sands and s i l ts are Chapter 5. DISCUSSION 61 bel ieved to move offshore a c c u m u l a t i n g on lower foreshores and t i d a l flats. T i d a l flats genera l ly o c c u r at sites where there is a large source of fine sediments often of f l u v i a l or g lac ia l o r i g i n , the fine sediments m o v i n g offshore under steep waves a ided b y . a f a l l ing t ide and re t r ea t ing breaker posi t ion. . U n l i k e the open coast, the inner coast wave c l ima t e lacks l ong p e r i o d , low steepness waves necessary to m o b i l i z e t i d a l flat sands onshore for sandy beaches to accrete. Inves t iga t ion by others [20] have i n d i c a t e d l o c a l beaches exper ience offshore sand loss w i t h depos i t ion t a k i n g p lace onto 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 feature tha t has been associa ted w i t h fetch res t r ic ted water bodies and a s ignif icant t i d a l range; t i d a l flats w i t h steep cobble upper beaches occur i n the G u l f of C a l i f o r n i a w h i c h is a fetch res t r ic ted water b o d y l ike the waters of inner south coas ta l B r i t i s h C o l u m b i a [24]. T h e select ive onshore movement of coarse m a t e r i a l and offshore movement of fine m a t e r i a l can e x p l a i n the gravel and cobble uppe r beaches and sandy t i d a l flats found benea th sandy bluffs o n the inner coast , pho to 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 longshore sediment t r anspo r t i n the upper foreshore such as at D u n d a r a v e , Wes t V a n c o u v e r , pho to 14, i n the absence of sufficient of sand supp ly for t i d a l flats to f o r m . W h e r e coarse m a t e r i a l moves onshore and longshore a n d storage exists steep shingle beaches fo rm, photos 5 to 12. C o b b l e co lon ized by seaweed m a y be ca r r i ed onshore f r o m deep water by intense s t o r m waves. T h e cobble has been found h i g h i n the upper foreshore on seve ra l sh ingle beaches on the inner coast , pho to 7. It is be l ieved tha t intense s t o r m waves tear the seaweed a n d a t t ached cobble f r o m the seabed offshore and w i n d a n d t i d a l l y generated currents car ry i t onshore where the swash f rom b reak ing waves deposit, it h igh i n the upper foreshore. A p o r t i o n of the cobble on inner coast shingle beaches or iginates f r o m this offshore source. C h a p t e r 6 F U R T H E R R E S E A R C H T h e r e is o p p o r t u n i t y for further research o n beaches in b o t h the field and the l abora to ry . Some poss ib le research topics are s u m m a r i z e d : • F i e l d I n v e s t i g a t i o n Some sect ions of coas t l ine w i t h i n the S t ra i t of G e o r g i a are l i n e d w i t h extents ive matresses of f loa t ing logs such, as C a p e M u d g e on Q u a d r a I s land , pho to 18. L i t e r -a ture on the effect the f loa t ing matress of logs has on the b r e a k i n g of waves or the c o n t r i b u t i o n to backshore eros ion by matress of logs has not been found . • L a b o r a t o r y I n v e s t i g a t i o n 1. A theory of layers shou ld exist w h i c h c o u l d descr ibe the s t ab i l i t y of the a r m o u r l ike layers w h i c h exist on some inner coast beaches. H u d s o n ' s fo rmula for r u b b l e m o u n d breakwaters , for example , can not be ex tended to beach slopes. 2. T h e t i m e scale of beach profi le e v o l u t i o n to an e q u i l i b r i u m c o n d i t i o n has been assumed to be a func t ion of the state of the i n i t i a l profi le (ie. how close the prof i le is to the e q u i l i b r i u m profi le for the i m p o s e d wave c o n d i t i o n ) and the wave in tens i ty . These assumpt ions shou ld be exp lo red further . 3. W a v e in tens i ty has been assumed to de te rmine the m a g n i t u d e and rate of movemen t of an ac t ive on-offshore v o l u m e of sediment on a beach; the as-s u m p t i o n shou ld be inves t iga ted fur ther . 62 Chapter 6. FURTHER RESEARCH 63 4. T h e swept area var iab le used to invest igate on-offshore t r anspor t o n l abora -to ry beaches has sucessfully re la ted the movement of beach sediment to wave i pa ramete r s because 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 essent ia l ly a d a t u m requi red to define the swept area var iab le . For na tu r a l beaches where the i n i t i a l profile is not flat the reference profile or d a t u m re-qu i r ed to define a swept area var iab le remains undef ined. 5. T h e concept of an ac t ive v o l u m e of sediment on a beach represented by a swept area var iab le migh t be used 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 t r anspo r t . 6. T h e concept of an ac t ive v o l u m e of sediment represented by a swept area va r i ab le migh t be considered i n the inves t iga t ion of b r idge pier scour problems. C h a p t e r 7 C O N C L U S I O N S 7.1 F i e l d I n v e s t i g a t i v e W o r k T h e s u m m e r / win te r beach profiles k n o w n to occur on open coast beaches due to on-offshore t r anspo r t of sand do not occur on the beaches of inner south coas ta l B r i t i s h C o l u m b i a because the waters are fetch l i m i t e d and thus lack low frequency waves w h i c h generate tu rbu lence at bed level necessary for onshore movement of sand. W a v e c l ima te i nves t i ga t i on has shown deep water waves i n the S t r a i t of G e o r g i a do not have per iods exceed ing a p p r o x i m a t e l y 8 seconds and the waves are p r e d o m i n a n t l y h igh steepness and low in t ens i ty re la t ive to the wave c l i m a t e of the N o r t h Pac i f i c . T h e r e is evidence of m i n o r seasonal morphologic , changes o n inner coast beaches due to seasonal ly v a r y i n g sediment supp ly ; beach sediment of f l uv i a l o r ig in m a y be more preva-lent a long the coas t l ine d u r i n g and i m m e d i a t e l y fo l lowing per iods when source streams and r ivers have h igh runoff, d u r i n g per iods of low runoff l i t t o r a l sediment is t r anspo r t ed away. A t D u n d a r a v e , Wes t V a n c o u v e r , it was observed that beaches were more sandy i n the win te r as opposed to the summer . Coa r se par t ic les such as gravels and cobbles on inner south coas ta l beaches t end to move se lec t ive ly 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 r i s i ng t ide a s . e v i d e n c e d by sediment t r a c i n g exper imen t s and the occurence of steep shingle beach be rms . T h e p l u n g i n g or s p i l l i n g water mass of b r eak ing waves a n d subsequent sheet flow up the beach face mob i l i ze s smal le r less s table gravels and cobbles shoreward 64 Chapter 7. CONCLUSIONS 65 a n d longshore wh i l e larger cobbles and boulders r e m a i n a r m o u r i n g the beach surface. Sediment t r anspor t exper iments conduc ted us ing a range of coarse pa r t i c l e sizes have shown tha t the highest sediment t r anspor t rates occur i n the upper foreshore whi le m i d d l e a n d lower foreshores of inner coast beaches have re la t ive ly low t ranspor t rates due to cobble bou lde r a r m o u r i n g . E v i d e n c e of movement of coarse par t ic les i n the offshore d i r e c t i o n has not been found , however, i t is recognized tha t i n general sediment t r anspor t across a profi le m a y occu r b o t h onshore a n d offshore (shoreward and seaward of the breaker zone respec t ive ly) depend ing u p o n the wave character is t ics i n the nearshore zone. T h e observed p redominan t d i r ec t i on of movement of coarse sediments on inner coast beaches is onshore a n d longshore where waves approach a beach ob l ique ly . F u r t h e r , the occurance of si l t and sand t i d a l flats t h roughou t the inner coast and lack of acc re t ing sand beaches is ev idence tha t fine m a t e r i a l tends to move i n an offshore d i r e c t i o n depos i t i ng on lower foreshore t i d a l flats or offshore. Coa r se sediments i n c l u d i n g cobbles a n d boulders m a y be ac t ive on the inner coast as ev idenced by r o c k y spits such as R e b e c c a Spi t o n Q u a d r a I s land . M o b i l e coarse sediments can accelerate wear and de te r io ra t ion of t i m b e r piles as hourg lass ing of piles at the beach surface has shown. C o b b l e co lon ized by seaweed found i n the upper foreshore of shingle beaches ind ica tes tha t coarse beach sediments m a y or ig ina te f r o m offshore sources. W h e r e shingle beaches have formed the coarse sediments are f requent ly flat i n shape; whether the sediments are n a t u r a l l y flat or have been w o r n to the i r flat shape t h r o u g h shear ing m o t i o n w i t h i n the beach b e r m or o ther forces remains u n k n o w n . Inner coast shingle beaches are steep, slopes up to 26 degrees have been measured ; a r m o u r e d beaches are a l l a p p r o x i m a t e l y the same slope fa l l ing i n the range 5 to 10 degrees. A r m o u r e d beach surface and subsurface g r a i n size d i s t r i bu t i ons ind ica t e tha t the a r m o u r layer forms a n a t u r a l filter i so l a t i ng fine subsurface sediments f r o m erosion a n d en t ra inment . A n inves t iga t ion of a series of shore n o r m a l beach profiles measured at three sites Chapter 7. CONCLUSIONS 66 a n d syn thes ized wave d a t a h indcas t for the p e r i o d of profile survey showed that s t o r m waves i n d u c e d profi le changes p r i m a r i l y in the u p p e r foreshore of beaches. T h e profile changes were found to be due to longshore sediment ac t iv i ty , pe r iod i c i n na ture , o c c u r i n g p r e d o m i n a n t l y i n the upper foreshore i n con junc t i on w i t h h igh tides and wave ac t ion . T h e results of the profi le and h i n d c a s t i n g s tudy are consistent w i t h f ield obse rva t ion and sediment t r a c i n g exper imen t s w h i c h also show uppe r foreshore sediment ac t iv i ty . T h e l i t t o r a l processes o c c u r i n g o n the inner coast are governed by a regime of wave heights , wave pe r iods and t i d a l ranges tha t fa l l w i t h i n a sma l l range of poss ible wave heights , wave per iods and t i d a l ranges k n o w n to occur on coast l ines. T h i s wave c l ima te reg ime i n con junc t i on w i t h a w ide range of na t ive sediments r ang ing f rom silts to cobbles and boulders have lead to the development of inner coas ta l features such as t i d a l flats, c o b b l e / bou lde r a r m o u r e d beaches and steep sh ingle beaches. B l u f f recession is p r i m a r i l y a func t ion of foreshore erosion and e levat ion change. R e -cession m a y be s i m p l y expressed as: R = my where R= bluff recession, ???.= beach slope a n d y= foreshore e levat ion change. O n the inner sou th coast, sand bluffs m a y n a t u r a l l y develop aprons of loose eroded sand at the angle of repose a round the bluff toe d u r i n g s u m m e r mon ths when wave a c t i v i t y in the uppe r foreshore is low. W i n t e r s t o r m waves, l i ke ly a c c o m p a n i e d by s t o r m surge, b r e a k i n g i n the uppe r foreshore at h i g h t ide erodes the sand aprons fu r the r ing bluff recession t h r o u g h overs teepening and subsequent erosion as ev idenced at W i l l e m a r Bluf f s , C o m o x . Chapter 7. CONCLUSIONS 67 7.2 L a b o r a t o r y B e a c h e s On-offshore sediment movement on a beach and waves p r o d u c i n g the movement m a y be in te r re la ted us ing the area swept out between an i n i t i a l , reference or d a t u m profi le and a f ina l prof i le evo lv ing as a func t ion of t ime . A var iab le t e rmed act ive v o l u m e , equal to ha l f of the swept area be tween profiles, has been inves t iga ted us ing l a b o r a t o r y beach d a t a and has been corre la ted w i t h wave parameters such as wave height and p e r i o d and t ime . T h e ac t ive v o l u m e of sediment is the amount of sediment tha t has m o v e d on a beach re la t ive to an i n i t i a l profi le as a result of a beach ad jus t ing its profile shape to an i m p o s e d wave c o n d i t i o n . A c t i v e v o l u m e indica tes the p r e d o m i n a n t sediment transport, across the ent i re profile and thus does not r ead i ly ident i fy cond i t i ons where b o t h onshore and offshore t r anspor t m a y occur on a profile shoreward and seaward of the breaker zone respect ively . A d imens ionless erosion pa ramete r Va/(H0Lo), w h i c h is the ac t ive v o l u m e per un i t w i d t h of beach per un i t t i m e d i v i d e d by the p r o d u c t of deep water wave height, and wave l eng th , m a y be defined and used to descr ibe the on-offshore movement of beach sediments . L a b o r a t o r y beach d a t a p l o t t e d us ing the ac t ive v o l u m e var iab le shows that for a given wave height there is a wave p e r i o d w h i c h w i l l p roduce a m a x i m a of sediment, a c t i v i t y subject to sediment size. F i n e sediments such as sands m a y show two m a x i m a i n sediment, a c t i v i t y over a w i d e range of per iods ; one m a x i m a corresponds to onshore sediment movement and one to offshore sediment movement . Coa r se sediments have on ly one m a x i m a of sediment, a c t i v i t y co r re spond ing to onshore movement of gravel . A n e x p o n e n t i a l g r o w t h a n d decay func t ion describes the e v o l u t i o n of a beach to an e q u i l i b r i u m state i n te rms of ac t ive 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 an evo lu t i on of ac t ive v o l u m e as a func t ion of t i m e f r o m an i n i t i a l l y flat profi le to Chapter 7. CONCLUSIONS 68 an e q u i l i b r i u m profile tha t m a y be descr ibed by the equa t ion : Va{t) = Vaeq(l-e-rt) where r is a t i m e cons tan t and Vaeq is the e q u i l i b r i u m act ive vo lume . S i m i l a r l y , sediment ac t iv i ty , w h i c h is the t i m e de r iva t ive of ac t ive v o l u m e , decreases e x p o n e n t i a l l y as a beach approaches e q u i l i b r i u m : Va - d t - vaege T h e concept of ac t ive v o l u m e m a y also be ex tended to n a t u r a l beaches, however, since n a t u r a l beaches have forever chang ing profiles a n d do not have i n i t i a l l y flat reference profiles fur ther cons idera t ions are requi red : • A reference or d a t u m profi le , w h i c h m a y not necessar i ly be flat as i n the l abora to ry , remains undef ined. T h e def in i t ion of a reference profi le w i l l l i ke ly i nvo lve longer t e r m observa t ion and s tudy of the evo lu t i ona ry shapes of n a t u r a l beaches a n d is thus a t o p i c for fur ther research. • A 's ta te ' pa ramete r is r equ i red to ident i fy how close the i n i t i a l profi le is to equi-l i b r i u m . W i t h swept areas measured re la t ive to the reference profi le the state pa ramete r m i g h t be defined as fol lows: where Vaeq is the e q u i l i b r i u m ac t ive v o l u m e for the i m p o s e d wave c o n d i t i o n mea-sured re la t ive to the profi le and Vat is the ac t ive v o l u m e of the i n i t i a l profile mea-sured re la t ive to the reference profi le . 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, pp . 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 Beaches" , Proceedings /jth Conference on Coastal Engineering, A S C E , C h i c a g o , 1954, pp . 163- 180. 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A . , "Tes t of a S i m p l e M o d e l to Forecast S igni f i -cant W a v e He igh t s in G e o r g i a S t r a i t " , Technical Memoranda TEC 75, A t m o s p h e r i c Environment Serv ice , E n v i r o m e n t C a n a d a , 27 O c t o b e r 1977. [17] H a l e , P . B . and M c G i l l v a r y , D . G . , " N u m e r i c a l M o d e l l i n g of Waves and Nearshore D y n a m i c s i n Fe tch L i m i t e d W a t e r B o d i e s " , Discussion Paper No. 15, Department of Geography, H a m i l t o n , O n t a r i o , M a y 1980. [18] H a r p e r , J . R . , "Seasona l Changes i n B e a c h M o r p h o l o g y A l o n g the B . C . C o a s t " , G e -o log i ca l Su rvey of C a n a d a , Pacific. Geoscience Cen t r e , Sydney, Proceedings Canadian Coastal Conference 1980, B u r l i n g t o n , O n t a r i o , p p . 136- 150. [19] H a y and C o m p a n y C o n s u l t a n t s , " T s a w w a s s e n I n d i a n B a n d M a r i n a P ro jec t and Shore l ine P r o t e c t i o n , O c e a n o g r a p h i c and G e o m o r p h i c C o n s i d e r a t i o n s " , O c t o b e r 1986. U n p u b l i s h e d . [20] H a y and C o m p a n y C o n s u l t a n t s , " R e p o r t on Foreshore E r o s i o n and C o n t r o l " , De -cember 1984, u n p u b l i s h e d . [21] Hay , D . , M c C o n n e l l , D . and A p p l e t o n , T . , " H a r b o u r S i t i n g S tudies , C a m p b e l l R i v e r , B . C . " , Proceedings Canadian Coastal Conference 19S5, S t . J o h n ' s , N e w f o u n d l a n d , pp . 427- 447. [22] H a t t o r i , M . and K a w a m a t a , R . , "Onshore -Of f shore T r a n s p o r t and B e a c h Prof i l e C h a n g e " , Proceedings 17th Conference on Coastal Engineering, A S C E , Sydney, 1980, pp . 1175- 1193. [23] Howes , D . E . , a n d H a r p e r , J . 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W . , "Recess ion R a t e of G l a c i a l T i l l B l u f f s " , Journal of Waterway, Port, Coastal and Ocean Engineering, A S C E , V o l . 113, N o . 1, J a n u a r y 1987, pp . 60-73. [28] K e l l e r h a l s , R . and B r a y , D . , " S a m p l i n g P rocedures for Coarse F l u v i a l Sed iments" , Journal of the Hydraulics Division, A S C E , V o l . 97, N o . H Y 8 , A u g u s t , 1971, pp . 1165-1179. [29] K o m a r , P . D . , " B e a c h Processes and S e d i m e n t a t i o n " , P ren t i ce H a l l , E n g l e w o o d Cl i f f s , N e w Jersey, 1976, pp . 303- 305. [30] K o m a r , P . D . , " T h e M e c h a n i c s of S a n d T r a n s p o r t on Beaches" , Journal of Geophys-ical Research, 76, N o . 3: 713- 721. [31] L i t t l e , W . C . and M a y e r , P . G . , " S t a b i l i t y of C h a n n e l Beds by A r m o u r i n g " , Journal of the Hydraulics Division, A S C E , V o l . 102, N o . H Y l l , N o v e m b e r , 1976, pp . 1647-1661. [32] M c C a n n S. B . a n d H a l e , P . B . , "Sed imen t D i s p e r s a l Pa t t e rns and Shore M o r p h o l o g y A l o n g the G e o r g i a S t ra i t C o a s t l i n e of V a n c o u v e r I s l and" , Proceedings Canadian Coastal Conference 1980, B u r l i n g t o n , O n t a r i o , pp . 151- 163. 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 . , Wolff , D . A . , " C o a s t a l Resources Fo l io - E a s t V a n c o u v e r I s l a n d " , L a n d s D i r ec to r a t e , E n v i r o m e n t C a n a d a , V a n c o u v e r , B . C , N o v e m b e r 198.1. [34] N o d a , H . , "Sca 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 ro f i l e s " , Proceedings 16th Coastal Engineering Conference, A S C E , H a m b e r g , 1978, pp . 1531- 1541. [35] Q u i c k , M . C . a n d H a r , B . C , " C r i t e r i a for Onshore- Offshore Sediment M o v e m e n t on Beaches" , Proceedings Canadian Coastal Conference 1985, S t . John ' s , Newfound -l a n d , p p . 257- 269. [36] Q u i c k , M . O , K i n g s t o n , K . , L e i , S., " O n s e t of Sed iment M o t i o n U n d e r Waves and C u r r e n t s " , Proceedings CSCE Annual Conference, Saska toon , Saska tchewan , 1985, pp . 107- 125. [37] R a u d k i v i , A . J . a n d E t t e m a , R . , " S t a b i l i t y of A r m o u r Layers i n R i v e r s " , Journal of the Hydraulics Division, A S C E , V o l . 108, N o . H Y 9 , Sep tember 1982, p p . 1047- 1057. [38] R e c t o r , R . L . , " L a b o r a t o r y S t u d y of the E q u i l i b r i u m Prof i les of Beaches" , Beach Erosion Board. Technical Memo No. J,l, U . S . A r m y C o r p s of Eng ineers , 1954. [39] R i c h m o n d , B . M . and Sal lenger , A . H . , " C r o s s Shore T r a n s p o r t of B i M o d a l Sands" , Proceedings 19th Coastal Engineering Conference, A S C E , H o u s t o n , 1984, pp . 1997-2008. [40] Sayao , 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 of L i t t o r a l D r i f t " , Proceedings Canadian Coastal Conference 1985, St . J o h n ' s , N e w f o u n d l a n d , p p . 241- 255. [41] Sav i l l e , T . J r . , " T h e Effect, of Fe tch W i d t h on 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 of Eng inee r s , 1954. Bibliography 74 [42] S h e p a r d , F . P . , " B e a c h Cyc le 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 Eng ineers , 1950. [43] Shore 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 Research Cen te r , U . S . A r m y C o r p s of Eng inee r s , W a s h i n g t o n , D . C , 1984. [44] Sorensen, 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 Press , 1978. [45] T h o m s o n , R . E . , " O c e a n o g r a p h y of the 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 F i sher ies and Oceans , C a n a d i a n G o v e r n m e n t P u b l i s h i n g Cen t r e , O t t a w a , O n t a r i o , 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 Profi les and O n - Offshore Sediment T r a n s p o r t " , Proceedings 11 th Coastal Engineering Conference, A S C E , Sydney, 1980, pp . 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 Shingle Beaches: T h e S o l u t i o n to Some P r a c t i c a l P r o b l e m s " , Proceedings 12th Conference on Coastal Engineering, A S C E , V a n c o u v e r , 1972, pp . 1059- 1075. f i g u r e s 75 N O R T H P A C I F I C x0 JJi 5* • 1 —O" ,0* A< ?\9 c i s 9l • • .... vi*.-„, \>f> M> Jt*,t 3 «1 V 1 - V , * 5 8»' Q2>* ^ \ ?T\9FA 4 1 .W"" V * ' 1** c* 3? study area S I T E P L A N 1c<" S O U D I N G S I N I M S S C A L E 1 =525, >src lure 2 \ l 6 ft? 0?S GRAIN S I Z E A N D SOIL PERMEABIL ITY CLASSIFICATION British Standards Clay Silt Fine Medium Coarse Sand Fine Medium Coarse Gravel Fine Medium Coarse Cobbles Boulders 0.002 0.006 0.02 0.06 0.2 0.6 0.001 0.01 0.1 20 60 200 10 100 Particle size (mm) Coefficient of permeability (m/s) 1 10 _ 1 10"2 1 0 - 3 10"4 10"s 1 0 - 6 10"7 1 0 - 8 1 0 - 9 10" Clean Clean sands and Very fine sands, Unfissured clays and gravels sand-gravel mixtures silts and clay-silts (>20% clay) clay-silt laminate Dessicated and fissured clays figure 3 S^V HHW B E A C H PROFILE E N V E L O P E S O P E M C O A S T A N b RESTRICTETs F E T C H BEACHES P R O F I L E S P L O T T E D AT T H £ SAME" GEOMETRIC S C A L E UPPER PROFILE ON - O F F S H O R E T R A N S P O R T SANiD B E A C H , S C R A P S P I E R L A J O L L A , C A L I F O R N I A 5 •• 4" 3" 2 -SEPTEMBER \°)A0 TO APfML L L W H O R I Z O N T A L A M D V E R T I C A L S C A L E IM M E T R E S - 4 -25 5 0 7 5 I0O f igure k CHARACTERISTIC HEIGHT IN METRES 2 > X "n M 01 X m z x m M m n cn z < x > M > Z X < a o m z O 2 I n m m m z > cn r > D > z o m CD X n a > > m x rn o tu cn rn X < M > n M z rn a -r\ X O H I m SIGNIFICANT WAVE HEIGHT (metres) O x n o H CD o m CD X m H x cn CD 10 > VJ Z 4i A D n > cn > < m m H CT X H cn o o o i— r>5 c n o c / i o I i | I I I I | I 1 I I | ! I I I | I I I I 1 (V5 O X n o H CD a m CD X m H x cn CD > Z T; m > cn c X m a > m x m cn X cn CHARACTERISTIC HEIGHT IN METRES l O c cn SIGNIFICANT WAVE HEIGHT (rretres) 0 . 0 0 . 5 1.0 1.5 2 . 0 2 . 5 X o SIGNIFICANT WAVE HEIGHT (metres) C_ X C o Z M m z CD CD Nl x CD m -< • n > cn > < m x m i—i CD X H cn > m -< cn CD CJ o n > cn H > < m x m M CD X H cn CHARACTERISTIC HEIGHT IN METRES 82 EFFECT ON PROFILE SHAPE OF VARYING H„/ i_ . BY VARYING L . EFFECT ON PROFILE SHAPE OF VARYING H./L BY VARYING L. 20 25 30 Distance , In Feet, From 8«och Crist (i) Distance,In Feet, From Beach Crest {*) E F F E C T O N P R O F I L E S H A P E OF V A R Y I N G H „ / L „ B Y V A R Y I N G L . EFFECT ON PROFILE SHAPE OF VARYING H „ / L < ] BY VARYING L„ Oistance,In Feet, From Beoch Crest (x) 10 15 20 25 Distance, tn Feet, From Beach Crest (s) L A B O R A T O R Y B E A C H P R O F I L E S - DATA SET 2 f i gu re 7 SOURCE: R e c t o r , R. L . , " L a b o r a t o r y S tudy 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 B e a c h e s " , Beach E r o s i o n Board T e c h n i c a l Memo No. 41 , U.S. Army Co rp s o f E n g i n e e r s , 1954. LABORATORY BEACH PROFILES - DATA SET 14 I I P r o f i l e changes of erosive beach (sand) . 0 1 2 3 Distance (m) P r o f i l e changes of a c c r e t i v e beach (sand). SOURCE: H a t t o r i , M . and Kawamata, R . , " O n s h o r e - O f f s h o r e T r a n s p o r t and Beach P r o f i l e C h a n g e " , P r o c e e d i n g s 17th C o n f e r e n c e on C o a s t a l E n g i n e e r i n g , ASCE, Sydney, 1980, pp . 1175- 1193. f igure 8 84 2 w a >-pa < o K a-DISTRIBUTION OF WAVE HEIGHTS STRAIT OF GEORGIA AND NORTH PACIFIC ' — I ' 2 4 6 SIGNIFICANT WAVE HEIGHT - (metres) STRAIT OF GEORGIA + NORTH PACIFIC to Z w a >* E-3 5 < ca o 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 -0.1 -0 DISTRIBUTION OF WAVE PERIODS STRAIT OF GEORGIA AND NORTH PACIFIC "l 1— 18 SIGNIFICANT WAVE PERIOD - (seconds) STRAIT OF GEORGIA + NORTH PACIFIC f igure 9 20 FREQUENCY OF WIND AND W A V E S F R E Q U E N C Y O F W I N D S P E E D B Y D I R E C T I O N J A N 1 - D E C 3 1 1 8 5 7 - 1 9 7 9 GEORGIA S T R A I T - 50.3N 48.5 N 07. 20V. 407. 60 7. 1007. (a) figure 10 S T R A I T OF GEORGIA ( b ) 86 figure 11 87 N LLW 6 TRA IT G£ORa/A W A V E S TOWER BEACH/' P R O R L E B PROFILE A / P O I N T G ^ E Y A TOWER B E A C H -POINT GREY S I T E 3 - 1 - 1 5 O O O figure 12 figure 13 BEACH FACE SLOPE V E R S U S GRAIN SIZE LO o LO • ro L O • o ^— a • (Si M CD (D a L CD (D "O ^ a a • LLJ r\i 0_ CO LO a a o L O ' a o . • • • SHINGLE BEACHES • ARMOURED BEACHES 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 igure 14 o o SHINGLE B E A C H - T Y P I C A L CROSS SECTION BERWCRE&T HOMOGENEOUS 6 0 A £ £ E MATERIAL BERIA FiKje/ COARSE M A T E R I A L NAATFU X L L W f igure 15 U3 O A R M O U R E D B E A C H - T Y P I C A L C R O S S S E C T I O N UPPER I SArJc* AUJ> -:::6vv-r/!x M S L FoRtCHoRET F i n e / COARSE. lAATERlAL. f M T f c l * C E j J S o f i E b C O B B l X L A Y E R . L L W f igure 16 TSAWWASSEN BEACH - PROFILE SURVEY A z o < > w w E-t W o o w o LAT. 49 01' 12" - LNG. 123 05' 48 HORIZONTAL DISTANCE (metres) * MAR 06/ 87 o APR 17/ 87 A JUN 13/ 87 JUL 21/ 87 TSAWWASSEN B E ACH - PROFILE SURVEY A UPPER FORESHORE PROFILE VARIATIONS z o > W _) W E-W O o w o HORIZONTAL DISTANCE (metres) + MAR 06/ 87 o APR 17/87 A JUN 13/ 87 JUL 21/ 87 f i g u r e TSAWWASSEN B E A C H - PROFILE S U R V E Y B LAT. 49 01' 12" - LNG. 123 05' 48" 4 3 numbers show sieve sampling locations L 2 -i I . I i i l 1 HORIZONTAL DISTANCE (metres) OCT 19/ 86 + NOV 01/ 86 0 NOV 28/ 86 4 JAN 13/ 87 X MAR 06/ 87 V APR 17/ 87 TSAWWASSEN B E A C H - PROFILE SURVEY B UPPER FORESHORE PROFILE VARIATIONS J -2.8 -numbers show sieve sampling locations 2.6 -2.4 -2.2 -2 -1.8 -1.6 - ^ O v ^ 2 1.4 -1.2 -1 -0.8 -0.6 - 4 0.4 -0.2 -0 - • i i i " I I I I I I I I I I I I - • • I 1 I 1 -10 -6 -2 2 6 10 14 18 HORIZONTAL DISTANCE (metres) OCT 19/ 86 + NOV 01/ 86 0 NOV 28/ 86 A JAN 13/ 87 X MAR 06/ 87 V APR 17/ 87 93 TOWER BEACH - PROFILE SURVEY A LAT. 49 19' 13" - LNG. 123 15' 37 HORIZONTAL DISTANCE (metres) JAN 13/ 87 -t- FEB 14/87 o MAR 15/ 87 60 A JUN 10/ 87 TOWER B E A C H - PROFILE SURVEY A UPPER FORESHORE PROFILE VARIATIONS HORIZONTAL DISTANCE (metres) JAN 13/ 87 + FEB 14/ 87 o MAR 15/ 87 A JUN 10/ 87 TOWER B E A C H - PROFILE S U R V E Y B LAT. 49 19' 15" - LNG. 123 15' 30" o > W Q O w o HORIZONTAL DISTANCE (metres) OCT 26/ 86 + NOV 14/ 86 0 DEC 16/ 86 4 JAN 13/ 87 X FEB 02/ 87 V MAR 07/ 87 TOWER B E A C H - PROFILE SURVEY B UPPER FORESHORE PROFILE VARIATION 2 o > W Q O W O r 2 6 10 HORIZONTAL DISTANCE (metres) 14 OCT 26/ 86 + NOV 14/ 86 0 DEC 16/ 86 4 JAN 13/ 87 X FEB 02/ 87 V MAR 07/ 87 f igure 18 DUNDARAVE - PROFILE SURVEY A LAT. 49 20' 02" - LNG. 123 11' 02 -20 FEB 02/ 87 HORIZONTAL DISTANCE (metres) MAR 07/ 87 o APR 17/87 A JUN 13/ 87 60 X JUL 21/ 87 DUNDARAVE - PROFILE S U R V E Y A UPPER FORESHORE PROFILE VARIATION HORIZONTAL DISTANCE (metres) FEB 02/ 87 4- MAR 07/ 87 o APR 17/ 87 a JUN 13/ 87 X JUL 21/ 87 f i g u r e DUNDARAVE - PROFILE SURVEY B LAT. 49 20' 00" LNG. 123 10' 57" z o H > w J' w L) P w a o w o z o > < > W td E-a o u o HORIZONTAL DISTANCE (metres) OCT 19/ 86 + NOV 02/ 86 o DEC 01/ 86 A DEC 30/ 86 x FEB 02/ 87 f MAR 07/ 87 DUNDARAVE - PROFILE SURVEY B UPPER FORESHORE PROFILE VARIATIONS OCT 19/ HORIZONTAL DISTANCE (metres) 86 + NOV 02/ 86 0 DEC 01/ 86 A DEC 30/ 86 X FEB 02/ 87 V MAR 07/ 87 CROSS S H O R E SEDIMENT SIZE DISTRIBUTION PROFILE B - DUNDARAVE 200 190 -180 -170 -160 -150 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 -0 —i upper foreshore lower foreshore 0 20 HORIZONTAL DISTANCE (metres) 40 60 f i g u r e 20 96 G R A I N S I Z E DISTRIBUTIONS TSAWWASSEN BEACH PROFILE SURVEY B o o 0.1 0.5 1 5 10 50 100 g r a i n s i z e (mm) DUNDARAVE, WEST VANCOUVER PROFILE SURVEY B o o L -P C ° 1 . l ower f o r e s h o r e 2. m i d d l e f o r e s h o r e . 3. upper f o r e s h o r e 4. s u b s u r f a c e 9 i!i' I], i ' 11 _ . . JL = , i 'ii' % iiii .iii III •Tii El n" I ' M •.(!..• ••J*sZZ^-I i i ; i , i : .!:. i I j I I ^ —rr-?' , 11' ilif ill ii" .... . ._ ! ! 1 ! i i 1 I III! • : | - f, . I I "l is \ ii" . . . . ! ' 1 1 i n ij 1111 ,:i •hi M M M i y i l l ! i i 1 ! 1 M i l TTTTiii i I j I / • ! JJ 1 J. Jli M M i y THT T[TT IjM jTlj iiii Mi llli iii' iir iiii iii1 Iiii f:;: "ii M ; ijZ* •TT i III! iiii i l l! 111' TiTi 'Ii ,. .-. ,i' i i i ! /11 1 ii : ; 1 L ' i ' |.i< M M /3r LY>> i I i i i j 111 ,, • 1 • I! • i • M 1 i / i i i i ill V/\ j M 4 rf I'M 1 II '4 •: : 1!'. ; .; " | ! ! i 1 / i i i i | M ill! :li ><i. r, 'i. 1 • • •!' • j 1 : / Alii ' M l 1 4 iii: ~ nn. E iii! M i l i1 ' .L:.li. llji ii' Mi . i • 'i - M M 1 ! ; '- . ; ; • " 1 ,.• .1.-.. • / [ i i i Mil 'r 1 -Mi.., ii.:l 'j •i'i ; • : ' j n i i 1 / V i i j i i i r | | | : , l IIII m i I i ! I ; • : ! • : / 2 1 < 1 •';'i 7 = i' 1 ; ' . ... / " • 1 1 i '. • ~i " i / M — •H II.. -JJL • ! I 1111 Titr Hr v.-i 7; M I : • ._. ; 1 • ' • I 1 •' M M • I i nh ''!' "i ' i : i = i • / . . . . . M M | i 1 / (\ i i • ! i • ] T .. M i > i M i l i i •Hi i, i i; 1 • : i • | i M. M M M I . i l i ; i' . / ! : : : :IM ':' 'i. i ' i. ! : ; ; /A is* '!: T i 1 4iJM:r- i . 1 i ! i " 1 ! • i I M i I 1 i y : 1 ' ! : M< !.; • : i i 1 'jr i :_.|..:. • I1 i.. . |j 1 ' / |, .,. M" I ! 1 : F • ><r MI • ' 0.1 0.5 1 5 10 50 100 g r a i n s i z e (mm) f igure 21 i B E A C H ELEVATION AND TIDE LEVEL © © © © d 5.0 > h ct < I o 3.0 2.0-0.0. TRACER OftJ&IKJ TRACER. 75 mm TRACER. -2.0 -3.0 TIMECPt>T)o4 08 IZ lb Zo 24 04 08 IZ lb 2.0 24 04 08 / 6 /6 DATE AU&. 7 / 8 7 AUG- 8 / 8 7 AUG °> /87 f igure 22 NUMBER OF 38mm PARTICLES PER SQUARE METRE OF BEACH SURFACE August 8, 1987 11=00 PDT © © © TRACES. ORl&IM © ® © ® © © © © ® © © © © I 0 0 0 0 1 2 1 z 7 3 1 Z i 7 8 8 5 3 4 2 / / 1 4o 1 37 '24 73 / / 10 256 8 /S7 110 27 30Z 395 20 230 110 /a 6 1 3 6 ) 1 IZ O O 0 0 29 434J366J/27 26 is- S 4 0 0 0 0 3 / / 0 / 0 0 o 0 0 0 1 o 0 0 0 o o o o o O 0 0 0 0 0 0 0 L.OM&'S'HofcEr DI-SPEj?SloW S H O R E N O R M A L 210* WAVE ORIGIN 9=250° LOCATIOM: CHASTE ft. CteeK, GIBSONS, &.C. LATITUDE: 41' 24' 03" Sj LONGITUDE: 123*33' 54" W OF PARTICLE'S "• 1100 &ftib SPACING • 4 ft. SLOPE- I -10 figure 23 W A V E O B S E R V A T I O N S T I M E : ( P D T ) D A T E : H s N T (s^ 9 o< B R E A K C R 12 :oo AUG.. 7 / 8 7 0.5 3.9 • 10' S P I L L . 17: 40 AU<J- 7 / 8 7 O.b 3.7 2 G 0 • jo- PL.UN&-Zl : OO Al>6. 7 / S 7 0-3 3.8 2S0- 10- SPILL-|| : OO All 6. 8 / S 7 O.b 4-2 2SU " 10' PLUNG. : 3o AUS. 8 / 8 7 OS 3.1 2S0' io- PLUMS- + S P L . |0:SO A u6- 9 / 8 7 o.s 4.2. 2.50 ' 10' LO 0 3 NUMBER OF 38mm PARTICLES PER SQUARE METRE OF BEACH SURFACE August 9.1987 11=30 PDT © © © © © © © © © © © © © © TRACER OAlGIO © © m 0 1 1 1 4 l 1 1 3 1 / • 0 i Z 1 1 6 1 1 1 1 1 5 3 5 18 10 A 2 1 1 44 / 24 107 HQ IA A 3 I / 273 5 i '32 lib 38 A i 296 : n t (80 134 33 IZ i 383 i <? 25 13 1 49 1 1 0 0 0 I2* 348|3e7|226 43 10 5 2 i i i / l 2 0 0 0 0 1 2 1 0 0 0 / / 0 0 0 o 3 O 0 o i o o ; 0 1 <*= 10' LONGSHORE DISPERSION) 5H0RE NORMAL EIO* WAVE-ORIGIN 6 = 2 5 0 * LOWlOfvJ: CHASTER, CREEK., G<6SOOSTB.C. LATITUDE-' 4*r24*01" N LOKlCrlTOOE'- |23" 33 ' SA" W NUMBER OF PARTICLES'- 1100 GRID SPACINJ& '• 4m SLOPE- l : 10 f igure 24 W A V E O B S E R V A T I O N S TIME (POT) DATE Hs(m) T (s | e «. BREAKER I2--00 AUG. 7/87 0.5 3-9 2so' 10' SPILL. 17:40 AUG- 7/87 o.fe 3.-7 250 • io- PLUNI6 • 21= 00 AO6. 7/87 0.3 3.8 2 S O ' 10 • SPILL. II : 00 AUG.. 8/87 O.fe 4.2 2S0- 10' PLl/NlG. I°l-i0 AUG.. 8 /87 o.s 3.1 2 SO' 10' PUIIOG^ SPL-10 = 50 AO6. V 8 7 0.5 4.2. 2 5 0 ' io- PLUU6. *SPL. L D L D NUMBER OF 75mm PARTICLES PER SQUARE METRE OF BEACH SURFACE August 8, 1987 11=00 PDT 0 ® © ® © © © © © © © © © © ORIGIN © I 0 0 0 0 0 0 0 0 I 0 0 1 lb 2 fc b a 13 17 14 AA 27 86 c 68 A 72 0 I42. |54 |2 | 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 0 0 0 o o o o 10 L0N6 SHORE DlSPERSIOM SHORE NORMAL 210' WAVE 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 W A V E O B S E R V A T I O N S TIME (,PD"0 D A T E mo T C«) 9 ot BREAKER 12 oo AUG.. 7 /87 0-5 3.^  250' to • SPILL-17 AO AU&. 7 / 8 7 o-b 3.7 250" IO" PLuMG-00 AUG. 7 / 8 7 03 3.8 250- 10' SPILL. 11 -00 AU6. B /87 O-fe 4.2 250- 10' PLUKJG. \°i 30 AU6. 8 / 8 7 0.5 3.1 250' 10' PLUMG.4 SPL 10 • 50 Auc °)/Bl 0.5 4.2 2S0' 10 ' PLuW6.-»SPL. o NUMBER OF 75mm PARTICLES PER SQUARE METRE OF BEACH SURFACE August 9, 1987 11=00 PDT © © © © © © © © © © 0 © © © -T R A C E R ORIGIN) © I 15 41 ZO 34 10 ll \0 l\z\l3\24 SI O O O O 0 0 0 O O O O O O 0 © 0 3o LONGSHORE D15PERSI0NJ S H O R E NJORMAL 2i<r WAVE 9= 250" L O C A T I O N ) : CHASTER. CREEK , 6 I 8 S 0 U S LAT ITUDE: 49' 24,' 0 3 " N L O M G I T O D E : : 123' 3 ^ S 4 ' W MUrABER. OF P A R T I C L E S : 21*5 SP/SC/NKS : A(A •SLOPE" = 11 10 figure 26 W A V E O B S E R V A T I O N ) S TIME" (POT) D A T E T O ) 0 c< B R E A K E R . 1 2 = 00 AUG. 7 /87 0.5 •3-*? 2 5 0 " / « • 6 P I U . 1 7 •• 4 0 A U G - 7 / 8 7 O.fc 3-7 2 5 0 " / o - P L U N 6 -*2-|: OO AL>6. 7 /87 o-3 3.8 25-0- /o ' SPILL-IP 00 A U G - 8 / « 7 O.fo 4-2. 2 S - 0 - to- PLutOt. 19 = 3 0 AUG.. 8 A 7 0.5" 3.1 25T> • to- PLOKJG. +SPL 1 0 = 50 AUG.. 9 / 8 7 0-5 4.2. 2 S O - to • PLUtJG--+SPL-B E A C H C L I F F T Y P I C A L C R O S S SECTION COBBLE: LAYER TKA(JSlEMT SAMb LEWS STEEP £oBBUT UPPER B£ACH SAMb APRONJ LAS BOULPE-RS--/ \ _ MSL LLIV TIDAL FLAT CLIFF FACE figure 27 o h o B L U F F R E C E S S I O N GEOMETRY OTHER EROSION) PROCESSES; 1. WINJD 2. RAIM 3. Ff2E.E2E"/T»AW 4. GROUhJD WATER SEEPAGE 5- FLOATING DEBRIS IMPACTS B L U F F F A C E COBBLE FORE5HORE MSL ' ^ P . & g y C O B & L E L A Y E R , ( I I NEW BLUFF FACE AFTER ' WAVE INITIATED RECESS I OlO CAU5EB BY , FORESHORE LOIA/ERIM& WAVE INITIATED BLUFF RECESSION] (R.) IS A FUMCTIOW OF FORESHORE" ELEVATION. figure 28 o CO 104 O N - O F F S H O R E TRANSPORT sign convention and volume definitions I. SIGN CONVENTIONS Z. VOLUME ACCRETED AND ERODED V + = V O L U M E ACCRETED V - = V O L U M E ERODED IV+l = I V - ] (y+) + ( y o = o 3. GROSS VOLUME" Vg |V3I= IV* I + IV-1 ~ A A - A R E A S W E P T 3ETWEENJ P R O F I L E S 4. NET VOLUME Va V n = (.VO + ( V - ) - O 5. ACTIVE VOLUME V A IWhlVj l /2 =|V+| = |V-[ f igure 29 105 W A V E S , A C T I V E VOLUME & TIME D E R I V A T I V E S + = A66RET10M, - = EROSlONi , D S 0 COMSTAfOT L A B O R A T O R Y F I E L D ( H Y P O T H E T I C A L ) -4 0-32 T LU <J*> 2 £ 0 JJJ V a r ACTIVE VOLUME Vaetj,-Qa. = dVa = SEDIMEtOT ACTIVITY , aQa at T t o t o Va = ACTIVE VOLUME Qo - JVo- = SEDIMEUT ACT/VITY f igure 30 I l/i s a a • J m O 3 > o >£, O < V a VERSUS H Q D 5 0= 0.7mm, m; = 0.10, t= lhr beach 1 14 16 ca W < Z o 55 o a w D E E P W A T E R W A V E H E I G H T - H Q (cm) T = 1.0s + T = 1.5s o T=2.0s V A / ( H 0 L 0 ) V E R S U S H Q / L Q D 5 0 = 0.7mm, m t = 0.1, t= lhr  beach 1 0.04 0.06 0.08 T = 1.0s W A V E S T E E P N E S S - H 0 / L 0 + T = 1.5s T=2.0s f igure 31 107 i _^ 5 o O 3 > o PJ W H « « CL, 2 O So o « 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 V a VERSUS H 0 D50= 0.7mm, mj = 0.05, t= lhr accretion beach 2 1 1 1 r 4 6 ~\ 1 r — ~ i ~i T — ~ — i r 8 10 12 14 16 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 DEEPWATER WAVE HEIGHT - H 0 (cm) T= 1.0s + T= 1.5s o T=2.0s • V ^ L , , ) VERSUS H o / L 0 D50= 0.7mm, m; = 0.05, t= lhr  accretion beach 2 T= 1.0s 0.02 0.04 WAVE STEEPNESS -+ T= 1.5s 0.06 0.08 H Q / L Q T=2.0s f igure 32 to D a O 3 > o O 3 K Ed H S CH < 2 o So o Cd w 108 V a VERSUS H 0 D 5 0= 0.2mm, 0.10, t= lhr accretion beach 3 2 points ~i r~ 14 16 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 DEEPWATER WAVE HEIGHT - H 0 (cm) T= 1.0s + T= 1.5s o T=2.0s V a / ( H 0 L 0 ) VERSUS H 0 / L G D 5 0= 0.2mm, m, = 0.10, t= lhr accretion beach 3 0 0.02 ii T= 1.0s 0.04 WAVE STEEPNESS - Ho/L 0 + T= 1.5s 0.06 0.08 T=2.0s f igure 33 109 D is O 3 > o > ~ O 5> 5 OS a E-> w <: < Z o oo o ca w 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 V a VERSUS H 0 D5o= 0.2mm, m; = 0.05, t= lhr accretion beach 4 i— 10 12 14 16 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 DEEPWATER WAVE HEIGHT - H Q (cm) T= 1.0s + T= 1.5s o T=2.0s V d ^ L o ) VERSUS H 0 / L Q D5Q= 0.2mm, m;= 0.05, t= lhr accretion beach 4 T= 1.0s 0.02 0.04 WAVE STEEPNESS - H 0 / L Q + T= 1.5s 1 0.06 o T=2.0s 0.08 f i gure 34 110 o > 01 o < O w fr-E-CO w E-W < ca < 2 o 55 o as « V a V E R S U S T FOR EQUILIBRIUM PROFILES CONSTANT HQ= 12cm AND VARIOUS D 5 0 WAVE PERIOD - T (seconds) • D 5 0 = 0.22mm + Da0= 0.47mm o 1)50= 0.90mm V a / ( H o ^ ) V E R S U S g T 2 / D 5 0 CONSTANT H0= 12cm FOR VARIOUS Ds0 4 D5Q= 3.44mm 1.5 H 1 H 0.5 H -0.5 -1 -1.5 H accretion • D5Q= 0.22mm 200 400 (Thousands) „ DIMENSIONLESS PERIOD - g T V D 5 0 + D5Q= 0.47mm 0 D5o= 0.90mm A Dso= 3.44mm f i g u r e 35 111 r . tn i-J (A u J 5 a? as H W < ca < a. z o 55 o ca 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 -1.4 -1.6 V a VERSUS t SAND BEACHES: D 5 0 = 0.22mm, m; = 0.05 accretion 8 10 12 14 16 18 20 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 -1.4 -1.6 DURATION OF WAVE ATTACK - t (hours) Ho/lo= 0.006 + Ho/Lo= 0.035 V a / ( H o L 0 ) VERSUS t / T SAND BEACHES: D5CF 0.22mm, m; = 0.05 accretion erosion r—-1 1 1 1 1 1 1 1 r — 2 4 6 8 10 1 1 1 r 12 14 16 \ 1 r 18 20 DURATION OF WAVE ATTACK - t /T H 0 /1 D = 0.006 + Ho/Lo= 0.035 f i g u r e 36 UJ M a Ld cn LL o UJ D _I a > > M H O < o 2 n m ID IN CO 0) (VI 112 B E A C H SEDIMENT ACTIV ITY N N E R A N D O P E N COASTS LINES OF CONSTANT WAVE HEIGHT FOR COARSE AND FINE MATERIAL + 1 ACCRETION ONSHORE MOVEMENT COARSE MATERIAL V HIGH STEEPNESS WAVES LOW STEEPNESS WAVES WAVE PERIOD FINE MATERIAL OFFSHORE MOVEMENT EROSION MONTHLY VARIATION OF WAVE PERIOD WINTER INNER COAST WAVE PERIOD OPEN COAST WINTER f igure 37 113 O P E N C O A S T W A V E P E R I O D D I S T R I B U T I O N NEAR TOFINO, BRITISH COLUMBIA 0.26 -i 0.24 -0.22 -0.2 H WAVE PERIOD - (seconds) • JANUARY 1982 + AUGUST 1982 f i gu re 38 w o 2 Ed OS D u u o EL. O >• "3 5 < a o K CL, DISTRIBUTION OF WAVE S T E E P N E S S 0.15 NORTH PACIFIC NEAR TOFINO 0.00 0.01 0.02 0.03 0.04 0.05 WAVE STEEPNESS - H 0 / L 0 0.06 0.07 0.08 Ed o z Ed ca p o o EK o P3 <! CO O ca cl, 0.35 -0.25 0.15 -0.05 -DISTRIBUTION OF WAVE INTENSITY NORTH PACIFIC NEAR TOFINO 1.0 2.0 3.0 4.0 WAVE INTENSITY (E/T) - k J / m 2 / s 6.0 figure 39 H U td DJ D o o o o a o es Cd z Cd CK D o u o b O >-ra o « OH 0.15 DISTRIBUTION OF WAVE S T E E P N E S S STRAIT OF GEORGIA NEAR ROBERTS BANK IIIIII 0.00 0.01 0.02 0.03 0.04 0.05 WAVE STEEPNESS - H 0 / L 0 0.06 0.07 0.08 0.4 0.35 DISTRIBUTION OF WAVE INTENSITY STRAIT OF GEORGIA NEAR ROBERTS BANK 0.25 0.15 0.05 0.00 1.00 2.00 3.00 4.00 WAVE INTENSITY (E/T) - k J / m 2 / s 6.00 f igure AO 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 a f t e r i n i t i a l p l a c e m e n t . PHOTO 4 - AUGUST 1987 T y p i c a l p l u n g i n g b r e a k i n g wave d u r i n g 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 , h e i g h t 0.5m and p e r i o d 4 s . PHOTO 5 - MAY 1987 S t e e p s h i n g l e beach a t Camp Byng, R o b e r t s C r e e k . The upper f o r e s h o r e s l o p e i s 1V:3.5H, median s h i n g l e s i z e i s 20mm. PHOTO 7 - JUNE 1987 Cobb le c o l o n i z e d by seaweed, F r e n c h Beach , Sooke . The c o b b l e was Found h i g h i n t he upper f o r e s h o r e , c a r r i e d o n s h o r e f rom deep water by s t o rm waves. 118 PHOTO 8 - MAY 1987 F l a t s t o n e s a r e t y p i c a l o f i n n e r c o a s t s h i n g l e b e a c h e s . PHOTO 9 - JUNE 1987 Gordons Beach , Sooke. A s h i n g l e beach w i t h c u s p a t e F o r m a t i o n s p a c e d a t 15m. PHOTO 11 - MAY 1987 S h i n g l e b e a c h , Lock Bay, G a b r i o l a I s l a n d . The sed imen t i s a g r a v e l oF 15mm median d i a m e t e r . PHOTO 12 - MAY 1987 S h i n g l e beach s u b s u r f a c e , Lock Bay, G a b r i o l a I s l a n d . The beach i s a p r i s m oF g r a v e l i n the upper F o r e s h o r e . PHOTO 13 - MAY 1987 G r a v e l 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 , 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 . The d i s t i n c t change i n s l o p e From the t i d a l F l a t t o t he upper beach i s t y p i c a l o f t h e i n n e r c o a s t . PHOTO 15 - MAY 1987 H e a v i l y a rmoured c o b b l e beach nea r Q u a l i c u m , Vancouver 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 s t o n e s t h i c k . PHOTO 14 - MAY 1987 Dundarave F o r e s h o r e , West Vancouver . The l ower F o r e s h o r e i s c o b b l e armoured and t h e upper f o r e s h o r e i s m o b i l e sand and g r a v e l . PHOTO 16 - JULY 1988 T imber p i l e , W i f f e n S p i t , Sooke. H o u r g l a s s i n g o f t h e p i l e a t beach l e v e l i s due t o wear by m o b i l e g r a v e l and c o b b l e . PHOTO 17 - MAY 1987 Cape Mudge, Quadra 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 , wh ich i s t y p i c a l o f many i n n e r c o a s t b l u f f s , i s a s o u r c e o f f o r e s h o r e c o b b l e . PHOTO 19 - MAY 1987 Rebecca S p i t , Quadra I s l a n d . The median c o b b l e s i z e i s 70mm. 121 PHOTO 18 - MAY 1987 Cobb le and b o u l d e r f o r e s h o r e , Cape Mudge, Quadra I s l a n d . The upper f o r e s h o r e c o b b l e a r e mob i l e as i n d i c a t e d by t h e i r c l e a n , abraded a p p e a r a n c e . PHOTO 20 - MAY 1987 Rebecca S p i t , Quadra I s l a n d . Longshore t r a n s p o r t has b r o u g h t c o b b l e t o t h e s p i t f rom as f a r as Cape Mudge, 5km away. PHOTO 21 - MAY 1987 W i l l e m a r B l u f f s , Comox. Westward d r i f t o f s and i n t h e upper f o r e s h o r e . 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 t he upper 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 W i l l e m a r B l u f f s , Comox. Sand a p r o n s a r e a b l e t o d e v e l o p a r o u n d the b l u f f t o e d u r i n g summer months because o f r e l a t i v e l y low wave a c t i o n i n t h e upper f o r e s h o r e . 122 PHOTO 22 - JANUARY 1988 W i l l e m a r B l u f f s , Comox. Recent s torm waves have t r a n s p o r t e d sand away f rom t h e b l u f f t o e , note t h e f a i l u r e o f t h e c o n c r e t e g r o y n e s . PHOTO 24 - JANUARY 1988 W i l l e m a r B l u f f s , Comox. The p h o t o , t a k e n 9 months a f t e r photo 23, shows e r o s i o n o f t he sand ap ron and b l u f f r e c e s s i o n . PHOTO 25 - MAY 1987 W i l l e m a r B l u f f s , Comox. Sand c o n t i n u a l l y e r o d e s f rom the b l u f f f a c e a c c u m u l a t i n g a round the b l u f f t o e d u r i n g p e r i o d s o f low upper f o r e s h o r e wave a c t i v i t y . PHOTO 27 - MAY 1987 W i l l e m a r B l u f f s , Comox. Sand a p r o n d e v e l o p i n g a round b l u f f t o e . 123 PHOTO 26 - JANUARY 1988 W i l l e m a r B l u f f s , Comox. The e r o d e d sand i s b e l i e v e d t o have 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 t i d a l f l a t s . PHOTO 28 - JANUARY 1988 W i l l e m a r B l u f f s , Comox. The s and i s e a s i l y e r o d e d by w i n t e r s t o r m wave a c t i o n i n t he upper f o r e s h o r e which l e a d s t o 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 s i o n . a p p e n d i c e s 124 1010 458 WIND 5UHHARY /HR) S»HO HEIOS LICHTSTITIOO BC IQf 1986 PST 0« 02 03 0 4 OS 06 07 08 09 10 11 12 13 14 15 16 17 18 iv 02 03 04 05 06 07 08 09 10 11 12 SE SE E SE E X E W w NW NW NW 3 5 2 3 ] 2 3 2 3 5 6 6 H W NW Ntf NW W NW N N N N N N 18 16 16 13 13 13 11 6 10 10 8 10 NW H HE ME E E NW W SE S S SW 16 .11 8 5 5 3 3 3 3 2 3 3 E E E E E E E SE E E E E 10 11 10 8 6 6 6 6 8 13 13 13 SE H SE W w W NW W W NW NW NW 5 2 5 24 34 37 43 45 50 45 43 42 NW *w NW NW N NE N E NW W W W 43 39 34 32 23 6 6 5 10 10 13 10 N SE SU NW NW NW NW N> NW NW NW NW 21 13 13 21 29 31 31 -27 26 23 23 19 E SE SE SE SE SE E E E E E E 18 31 34 29 24 24 23 19 27 29 23 16 E E E E E E E E E E E E 18 16 13 19 18 24 24 23 19 27 29 24 E E E E E E E E E E E E 26 23 21 23 24 19 21 18 21 19 16 11 E E E E E E E E E E E E 24 24 21 23 19 19 14 14 14 11 10 6 E E e E ME E £ E E E E E 11 10 e 3 6 11 11 13 13 13 10 5 E E SE S SE C SE SW SW N NW HW 5 6 5 3 5 2 2 S 11 10 11 E E E E H N NW N N NE H N e 3 5 3 3 2 6 6 10 6 11 10 E E E E S S S S 5 S S S 19 19 19 14 14 11 14 18 24 24 24 31" V V I SE SE s S S S S S S 6 6 10 14 19 19 31 31 35 35 29 24 W W V W W W W W NW E E e 34 39 34 31 27 21 18 14 10 13 IB 16 E E E E E S S S S S S S 51 47 42 48 48 47 40 32 31 29 32 31 V W V W SW SW W SE SE S S SE "23 23" ~2t "27 16 "H ' 6 ' 5 " U TI" ' 26" "26 NW 10 NW 10 14 W NW 13 13 16 17 18 19 NW 14 18 19 W NW NW NW NW 8 11 14 16 18 19 NW 21 SW 3 SE SE SE SE SE SE SE 10 13 14 14 NW NW 40 39 W 40 W 11 SW SW 10 8 W 40 SE 8 W NW 42 55" SE 10 W NW NW 31 27 19 £ E 1) 10 E E 14 18 SE 13 E 31 E 23 E I 16 21 SE E 23 N "26" SE 5 E E E E 27 34 H ~iV E E 23 21 NW NW 13 11 NE SE SE SE 8 3 5 5 NW NW NW 13 18 23" >w 11 SW 39 E "23 SE NW NW 13 19 NW 16 IW 19" •w 16 E 19 SE 13 E 21 w w B 11 S S SE 27 26' "26-W W 10 11 w 11 SE SE "76—2T" HW W 13 13" E E E 24 21—2r E T T 11 E 20 21 22 23 24 PRE* DIR MEIH SPD M i l TEL NW 16 NW 21 NW 19 NW 16 NW 16 HW 9.8 21 Ntf 21 NW 13 W 14 HW 11 NW 14 NW 13.1 21 SW " 3" N "5" w " 5 HE ""5 E 5 W 4.7 16 E 13 E 16 E 13 E 6 E 6 E 11.2 19 WW "2T NW 47 " HW «S HW "42 HW 42 NW 35.7 55 W 13 w 27 WW 39 NW 42 NW 43 HW 19.0 41 NW -29" E •16" E "19 E "19 E 18 HW 24.5 40 E 27 E 27 E 24 E 18 E IB E 22.2 34 E 26 E 31 E 27 E 27 E 26 E 24.0 32 E 19 e 21 e 26 E 27 E 24 E 20.8 27 HW 21" N 16 N 11 SE " 6 SE 10 E 13.6 24 SE 13 E 13 E 8 e 10 8 10 E 9.2 13 SE "14 E "14 E " 13 E 14" E "11 " HW 9.6 23 w 6 W 5 S 6 S B SE 13 S V l B.5 19 S SW W MW SW S 18.6 31 1* 8 3 6 " B NW W w H NW w 27 I 32 35 39 40 E E E E 34" 47" 45 SO St SE S 43 47 53 3 S S S 55 53 47 45 SW SW SW SW 35 40 37 32 SE SE SE "3"9—39—4T" SE SE SB SE TI—5TS—51—5T" SE S S SE T 5 — J 2 — 3 9 — 3 T SE 22.1 40 27.0 80 41.8 S3 30.6" SI > z: v > "1 01 4 S B WIND SUMMARY /MR) SIS0 KtlDS L I C M T S T 1 T I 0 K BC M l 1986 PST OY HR OL 02 03 04 05 06 07 08 09 10 11 12 13 14 13 16 17 18 19 20 21 22 23 24 PREY OIR MEAN SPO m i TEL 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 30. 4 40 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 29.2 43 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 32" SE "34 ' SE ~35 SE ~37 SE "42 SE "45 SE '42 SVL 22.6 45 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 S 18 S 19 S 19 S 16 SE 21 SE 19 S 31.6 56 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 51 W "50 W 42 w W NW W SW S E E E w 42 35 2J 11 10 13 14 "23 19 3 0.0 51 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 SE 35 SE SO SE 51 SS 58 SE 66 S 56 S 50 SW 40 SE 4 4.4 46 26 SW 35 SW 32 W 16 W 21 W 23 W 14 V 11 W 6 E 11 SE 14 E 19 SE 29 SE 31 SE 31 E 26 E 23 E '29 E "39" SE E 48 53" e ""37 E 39 E 37 S 37 E 27.5 53 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 S 32 S 21 S 24 SE 26 S 19 S 11 SW 8 NE 8 NE 10 NE 10 « 6 S 20.4 39 28 NE 3 N 14 N 24 N 24 N 23 NU 24 NW 27 NW 19 NW 21 NW 18 NW 19 NW 23 NW 23 HW 21 NW 24 NW 21 MW 23 NW "23 NW 2 r N 19 M "21 WE "10 E " 8 NE 6 NW 19.1 27 29 E 11 E 13 E 19 E ie E 16 E 13 E 14 E 16 E 21 E 21 E 19 E 23 E 23 E 24 E 23 E 21 E 23 E 24 E 24 e 27 E 27 E 27 E 24 E 26 E 20.7 27 30 E 26 E 24 E 24 E 26 E 26 E 26 E 29 E 26 E 26 E 27 E 27 E 27 E 29 E 31 E 31 E 26 E "37 E "31 E "32 E "34 E "35 E '34 E "37 E 40 E 29.2 40 HI 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 - PUBLISHED "SPEED % TOT 00 • 1 01-05 9 62 06-11 16 115 12-19 22 159 20-28 24 171 "29-38 15 108 39-49 11 78 50-61 3 25 63* • 1 TOTAL 720 PRCNT ME1H 22.4 5 17 4 7 33 5 .9 11. MAXIMUM WIND MAXIMUM GUST NE ENE E ES E SE SSE 5 3 17 IS 5 12 31 8 4 67 18 17 83 10 30 25 25 30 10 24 13 3 10 7 1 15 238 111 106 2 33 15 15 7.1 20.3 27.9 28.1 "SSW ""SW" 5 "8 7 4 8"" ~V5F~ ~ V — W W W 10 16 12 11 •HW 66 M DY 25 DY 3S 5 "19.2 YECTOR MEAN OIR(DECS) 136 ( SE) SPO 7 PREVAILINC DIRECTION E OIR CRT 720 — r 2 9 3 73 10 ""21V2" 2 17 34 26 8"" 19 2 108 15 23.0 CALM 1 MEA1 SPEED 22.4 SPO CUT 720 M i l * CRT > "0 Z O X > 04/16/17 APPESJDIX B P A C - E 127 STATION 108 ROBERTS B A N K , B . C . FEB 7.1974 TO APRIL 3,1976 NUMBER OF OBSERVATIONS 3880 OCCURRENCES OF CALM 1191 4.0 -L U QC I — U J 3.5 -3.0 L U cx 2.5 2 .0 -<x o ± I .5 o , — i I -0 -0 .5 0,0 1 2 2 7 1 1 1 13 28 1 2 44 40 36 134 32 32 229 176 9 1 1377 517119 9 13 8 1 413 287 60 53 28 11 1 ~1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 L7 20 PEAK PERIOD IN SECONDS 10 -. STATION 103 TOFINO B C JANUARY 1,1982 TO DECEMBER 31 .1982 NUMBER OF OBSERVATIONS 2880 OCCURRENCES OF CALM 0 PAGE iZS CO UJ DC t— UJ o t x ' ex o o CO 8 -7 -6 -5 -h 3 -2 -4 5 9 1 1 3 5 1 1 1 4 1 2 1 2 5 9 1 2 2 2 2 3 6 6 1  11 10 1 10 14 19 25 19 12 3 4 26 28 24 20 16 30 2 5 24 47 23 33 37 40 3 13 21 28 44 46 57 48 43 1 4 41 60 70 90 89 58 71 43 1 38 62 58 86 138 92 69 68 81 8 10 9 14 48 48 20 18 24 95 1 ~ i — i — r 2 3 4 5 T T 1 1 1 1 4 5 12 10 7 19 29 86 100 2 2 3 4 2 3 1 11 17 90 87 "i 1 1 1 1 1 1 1 1 1 6 7 8 9 10 11 12 13 14 15 16 17 20 PEAK PERIOD IN SECONDS FORECAST POINT: TSflWHflSSEN LATITUDE: 49 OO 20 N LONGITUDE: 123 07 24 U H I N D C R S T W A V E H E I G H T S N O V E M B E R 1 9 8 6 LD 360 TIME IN HOURS 480 600 720 > rn c; > m 

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