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Flood risk and hazard assessment on Lulu Island Jacobs, Paul Arthur 1986

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Flood Risk and Hazard Assessment on Lulu Island By Paul Arthur Jacobs B. Sc. Honours, Simon Fraser University, 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of C i v i l Engineering) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA November 1986 © P a u l Arthur Jacobs, 1986 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date a c n w e e - K t, i i ABSTRACT Lulu Island contains most of the Municipality of Richmond. Richmond i s a growing community with 1 0 0 , 0 0 0 population located south of the c i t y of Vancouver in the Fraser River estuary. The flood hazard from both the sea and the Fraser River are well known and to protect against i t , an extensive diking system has been b u i l t . Despite t h i s diking system a s i g n i f i c a n t residual flood hazard has been created by the extensive development on the isl a n d . In addition, concerns have been raised about potential flooding from earthquake damage and a predicted r i s e in sea l e v e l due to global warming. This thesis analyses the extent of the flood hazard from various sources. New techniques of r i s k analysis and findings on risk perception are used to examine the flood r i s k . The role of contingency planning for flood control in conjunction with dikes is examined. F i n a l l y , the role of flood insurance i s discussed as a method of providing information about flood r i s k levels to floodplain users.. Conclusions are drawn about the adequacy of current flood control measures and recommendations are made to improve them. ACKNOWLEDGEMENTS In the course of this study assistance was received from many sources. I am p a r t i c u l a r l y indebted to the people involved in providing flood protection at a l l leve l s of government for their time, access to their documentation, and, most of a l l , for sharing their expertise with me. From the federal government, I would l i k e to thank Dr. Sandy D'Aquino, Jim Leung, N e i l l Lyons, and Jim Oakey of the Water Planning and Management Branch of Inland Waters. From the B r i t i s h Columbia government, I would l i k e to thank Eri c Bonham, Ron Henry, Robin Round, Sandra Smith, and Jake Wester of the Ministry of Environment and Parks. From the Municipality of Richmond, I would l i k e to thank Alex Jamieson, Don Mclver, and Henry Pelzer. In addition, I would l i k e to thank my thesis advisor S. 0. Russell for his guidance, cooperation, and most of a l l for his careful l i s t e n i n g . F i n a l l y , I would l i k e to thank my wife, Maruta Jacobs, for her ca r e f u l e d i t i n g and general support. i v TABLE OF CONTENTS A b s t r a c t i i A c k n o w l e d g e m e n t s i i i L i s t o f T a b l e s v L i s t o f F i g u r e s v i G l o s s a r y v i i I n t r o d u c t i o n 1 L i t e r a t u r e R e v i e w 6 T h e F l o o d H a z a r d 34 R i s k A n a l y s i s a n d P e r c e p t i o n 48 C o n t i n g e n c y P l a n n i n g a n d O t h e r M e a s u r e s t o R e d u c e D a m a g e 59 F l o o d . I n s u r a n c e 65 C o n c l u s i o n s 69 R e c o m m e n d a t i o n s 71 B i b l i o g r a p h y 73 A p p e n d i c e s 78 - A p p e n d i x A - T a b l e s 7 9 - A p p e n d i x B - F i g u r e s 8 5 - A p p e n d i x C - E x p e c t e d F l o o d D a m a g e C a l c u l a t i o n f o r L u l u I s l a n d .... 90 V LIST OF TABLES I . T e r m s f o r C l a s s i f y i n g H a z a r d P o t e n t i a l s 79 I I . U . S. A r m y C o r p s E n g i n e e r s H y d r a u l i c E v a l u a t i o n G u i d e l i n e s : R e c o m m e n d e d S p i l l w a y D e s i g n F l o o d s .. 79 I I I . V a l u e o f C o m m e r c i a l B u i l d i n g P e r m i t s I s s u e d 80 I V . A n n u a l P r o b a b i l i t i e s o f C o m b i n e d F l o o d H a z a r d s .. 80 V . P r e d i c t e d C h a n g e s t o T i d a l L e v e l s 81 V I . F l o o d D a m a g e E s t i m a t e f o r L u l u I s l a n d 81 V I I . F e d e r a l - P r o v i n c i a l F l o o d D a m a g e C o s t S h a r i n g F o r m u l a 82 V I I I . E x a m p l e R u l e o f Thumb F l o o d P r o t e c t i o n L e v e l C h a r t 83 v i L I S T OF F IGURES 1 . M a p o f t h e W e s t e r n E n d o f t h e L o w e r F r a s e r V a l l e y 8 6 2. R i s k - H a z a r d P e r c e p t i o n R a t i n g C h a r t 87 3. M a p o f F u l l T i d a l R e l i e f Z o n e 88 4. R a i s e d R o a d A l i g n m e n t 8 9 v i i GLOSSARY C a p i t a t i o n - A m e t h o d o f p a y m e n t f o r m e d i c a l s e r v i c e s i n w h i c h t h e p h y s i c i a n r e c e i v e s a f i x e d a m o u n t a n n u a l l y p e r p a t i e n t f o r a l l h e a l t h c a r e s e r v i c e s u s e d . C l i m a t o l o g i c a l C h a n g e - A l o n g t e r m , w o r l d - w i d e , w a r m i n g t r e n d t h a t h a s b e e n p o s t u l a t e d b a s e d o n i n c r e a s e d l e v e l s o f c a r b o n d i o x i d e i n t h e a t m o s p h e r e . T h e m o s t s i g n i f i c a n t a s p e c t o f t h i s c h a n g e f r o m t h e p o i n t o f v i e w o f t h i s s t u d y i s t h e m e l t i n g o f p o l a r i c e s h e e t s a n d a s u b s e q u e n t 1m r i s e i n s e a l e v e l . H i g h w a y 99 - T h e f r e e w a y r u n n i n g n o r t h - s o u t h r o u g h l y t h r o u g h t h e c e n t r e o f L u l u I s l a n d . F l o o d H a z a r d - T h e p o t e n t i a l d a m a g e t h a t w o u l d b e d o n e b y f l o o d i n g . F l o o d R i s k - T h e p r o b a b i l i t y t h a t f l o o d i n g w i l l o c c u r . L e v e l o f P r o t e c t i o n - T h e p r o b a b i l i t y o f o c c u r r e n c e o f a f l o o d e v e n t t h a t d i k e s o r o t h e r f l o o d c o n t r o l s t r u c t u r e s a r e d e s i g n e d t o w i t h s t a n d . T h e s e ' p r o b a b i l i t i e s c a n b e e x p r e s s e d a s e i t h e r a n a n n u a l p r o b a b i l i t y o f o c c u r r e n c e o r a r e t u r n p e r i o d . (.005 a n n u a l p r o b a b i l i t y o f o c c u r r e n c e i s e q u i v a l e n t t o a 1 i n 200 y e a r r e t u r n p e r i o d . ) Low P r e s s u r e S y s t e m s - W e a t h e r s y s t e m s c h a r a c t e r i z e d b y l o w b a r o m e t r i c p r e s s u r e s a n d h i g h w i n d s . T h e h i g h e s t t i d a l l e v e l s a r o u n d L u l u I s l a n d r e s u l t f r o m s e v e r e l o w p r e s s u r e s y s t e m s o c c u r r i n g d u r i n g t h e w i n t e r m o n t h s . v i i i N o r m a l H i g h T i d e - A n y h i g h t i d e t h a t o c c u r s f r o m t h e g r a v i t a t i o n a l p u l l o f t h e s u n a n d t h e moon a l o n e , r a t h e r t h a n i n c o n j u n c t i o n w i t h a l o w p r e s s u r e s y s t e m . MCE - M a x i m u m C r e d i b l e E a r t h q u a k e - T h e l a r g e s t e a r t h q u a k e t h a t c a n b e e x p e c t e d t o o c c u r i n a n a r e a . M o r b i d i t y - T h e a v e r a g e n u m b e r o f p e o p l e s i c k a t a n y o n e t i m e . M o r t a l i t y - T h e e x p e c t e d n u m b e r o f d e a t h s p e r t h o u s a n d i n a p o p u l a t i o n . F o r e x a m p l e , t h e m o r t a l i t y o f m a l e s f r o m 45 t o 54 i s t h e n u m b e r o f d e a t h s t h a t c a n b e e x p e c t e d t o o c c u r i n a g r o u p o f 1 0 0 0 m a l e s 45 y e a r s o l d b e f o r e t h e y r e a c h 55 y e a r s o l d . PMF - P r o b a b l e M a x i m u m F l o o d - A h y p o t h e t i c a l f l o o d d e r i v e d f r o m p h y s i c a l c r i t e r i a t h a t i s t h e l a r g e s t f l o o d t h a t c o u l d r e a s o n a b l y b e e x p e c t e d t o o c c u r . P o n d i n g - T h e f i l l i n g o f a d i k e d a r e a t o t h e l e v e l o f w a t e r e n t e r i n g t h r o u g h a d i k e b r e a c h , c h a r a c t e r i z e d b y d e e p e r w a t e r l e v e l s t h a n w o u l d h a v e o c c u r r e d w i t h o u t t h e d i k e s a n d a l o s s o f v e l o c i t y t h r o u g h t h e b r e a c h . I n e f f e c t , t h e d i k e d a r e a b e c o m e s a p o n d w i t h t h e d i k e s a s b a n k s . P r i m a r y C a r e - T h e t y p e o f h e a l t h c a r e f i r s t s o u g h t b y p a t i e n t s a s o p p o s e d t o h e a l t h c a r e d e l i v e r e d a s a r e s u l t o f a r e f e r r a l b y a p h y s i c i a n . T y p i c a l e x a m p l e s o f p r i m a r y c a r e a r e t h e f a m i l y p h y s i c i a n a n d h o s p i t a l e m e r g e n c y w a r d s . R i v e r S t a g e - A r i v e r l e v e l w i t h r e s p e c t t o a k n o w n d a t u m o r e l e v a t i o n . ix Spring Freshet - The high riv e r l e v e l s caused by the spring snowmelt. Tidal Relief - The drop in water l e v e l s around Lulu Island that occurs during low t i d e . F u l l t i d a l r e l i e f occurs when the water l e v e l at low tide i s lower than the land l e v e l inside the dikes. 1 INTRODUCTION This i s a study of the flood hazards and flood risk in the Municipality of Richmond, s p e c i f i c a l l y Lulu Island. The Municipality of Richmond i s located primarily on Lulu Island, south of the City of Vancouver, in the Province of B r i t i s h Columbia. For a flood hazard to e x i s t , two conditions must be met: there must be development that can be damaged by inundation and there must be a path for water to inundate the development. Richmond's location and geology have been excellent for the development of a flood hazard. The Province of B r i t i s h Columbia i s mountainous and contains r e l a t i v e l y l i t t l e f l a t or a g r i c u l t u r a l l y productive land. The e x i s t i n g f l a t land i s concentrated in r i v e r v a l l e y s . Most of the rest of the province i s made up of steep, forested land. As a r e s u l t , most of the land outside of s e t t l e d areas i s uninhabited. The Atlas of B r i t i s h Columbia describes and explains the population d i s t r i b u t i o n t h i s way: "Three features characterize the d i s t r i b u t i o n of population in B r i t i s h Columbia - heavy concentration in the southern coastal lowlands, valley oriented l i n e s of settlement with larger c l u s t e r s along them in the southern and central i n t e r i o r and large areas of unpopulated land. "The e s s e n t i a l l y unpopulated areas are those which by reason of topography, climate, s o i l conditions, vegetative cover, or r e l a t i v e i s o l a t i o n have offered l i t t l e inducement to settlement."(Farley, 1979, p. 4) In a province with t h i s type of topography and population d i s t r i b u t i o n , i t i s no surprise that a f l a t area with a mild climate, prime a g r i c u l t u r a l s o i l , and located within easy 2 c o m m u t i n g d i s t a n c e o f V a n c o u v e r ( m e t r o p o l i t a n p o p u l a t i o n 1.2 m i l l i o n ) h a s a t t r a c t e d d e v e l o p m e n t . B e t w e e n 1 9 5 0 a n d 1960 R i c h m o n d ' s p o p u l a t i o n g r o w t h was m o r e t h a n 5% p e r a n n u m . S i n c e t h e n t h e g r o w t h r a t e h a s s l o w e d , b u t i t i s s t i l l a p p r o x i m a t e l y 4% p e r a n n u m . M o n e t a r y v a l u e o f f l o o d d a m a g e s was l a s t e s t i m a t e d f o r R i c h m o n d i n 1 9 7 1 . A t t h a t t i m e , t h e p o p u l a t i o n was 6 2 , 0 0 0 a n d p o t e n t i a l f l o o d d a m a g e s w e r e e s t i m a t e d a t $ 1 0 0 m i l l i o n . S i n c e 1 9 7 1 , t h e p o p u l a t i o n h a s i n c r e a s e d t o 1 0 4 , 0 0 0 . I n a d d i t i o n , R i c h m o n d h a s b e e n m o r e c l o s e l y i n t e g r a t e d i n t o t h e G r e a t e r V a n c o u v e r R e g i o n a l D i s t r i c t ' s e c o n o m y a n d h a s b e c o m e a m a j o r s h o p p i n g a n d w a r e h o u s i n g a r e a . O v e r $ 5 0 0 m i l l i o n o f b u i l d i n g p e r m i t s f o r c o m m e r c i a l d e v e l o p m e n t s h a v e b e e n i s s u e d s i n c e 1 9 7 1 . A s s u m i n g t h a t f l o o d d a m a g e s w o u l d i n c r e a s e p r o p o r t i o n a t e l y w i t h p o p u l a t i o n a n d i n f l a t i o n , t h e m aximum f l o o d t h a t t h e d i k e s w e r e d e s i g n e d f o r , w o u l d c a u s e a b o u t $ 5 0 0 m i l l i o n i n d a m a g e t o d a y ( 1 9 8 6 ) . S i n c e , a s w a s m e n t i o n e d a b o v e , t h e c h a r a c t e r o f d e v e l o p m e n t h a s c h a n g e d , t h e s e a s s u m p t i o n s a r e p r o b a b l y c o n s e r v a t i v e . L u l u I s l a n d i s a l o w l y i n g i s l a n d l o c a t e d i n t h e m o u t h o f t h e F r a s e r R i v e r e s t u a r y . I t i s s u s c e p t i b l e t o f l o o d i n g f r o m b o t h t h e o c e a n a n d t h e F r a s e r R i v e r . I f t h e r e w e r e n o d i k i n g s y s t e m , f l o o d i n g o v e r t h e w h o l e i s l a n d t o t h e 2 f o o t l e v e l w o u l d o c c u r f r o m a 1 i n 10 y e a r r e c u r r e n c e p e r i o d f l o o d . H i g h t i d e s c o u l d b e e x p e c t e d t o f l o o d p a r t s o f t h e i s l a n d o n s e v e r a l d a y s e a c h m o n t h . 3 T o p r o t e c t a g a i n s t t h i s f l o o d i n g , 30 m i l e s o f d i k i n g h a v e b e e n b u i l t . T h e e a r l i e s t d i k e s o n L u l u I s l a n d w e r e b u i l t i n 1 8 7 6 . S i n c e t h e n t h e d i k e s h a v e b e e n e x p a n d e d t o e n t i r e l y s u r r o u n d L u l u I s l a n d . T h e d i k e s h a v e b e e n p e r i o d i c a l l y r a i s e d a n d w i d e n e d . T h e l a s t t i m e t h e d i k e s w e r e r a i s e d was u n d e r t h e F e d e r a l - P r o v i n c i a l A g r e e m e n t o f 1 9 6 8 . U n d e r t h i s a g r e e m e n t , t h e d i k e s w e r e r a i s e d t o p r o v i d e .6 m e t e r s o f f r e e b o a r d a b o v e t h e l e v e l o f a f l o o d w i t h a 1 i n 2 0 0 y e a r r e c u r r e n c e p e r i o d . T h i s l e v e l o f p r o t e c t i o n was c h o s e n b e c a u s e t h e 1 i n 200 y e a r f l o o d a p p r o x i m a t e s t h e l a r g e s t f l o o d o f r e c o r d . I n c i d e n t a l l y , i n s e v e r a l a r e a s o f t h e F r a s e r V a l l e y , s o i l c o n d i t i o n s m a k e i t t e c h n i c a l l y d i f f i c u l t ( b u t n o t i m p o s s i b l e ) t o b u i l d d i k e s a n y h i g h e r . ( W e s t e r , 1 9 8 6 , p e r s o n a l comm.) A l t h o u g h c o s t b e n e f i t s t u d i e s w e r e d o n e t o d e t e r m i n e w h i c h a r e a s s h o u l d r e c e i v e m o n e y t o u p g r a d e t h e i r d i k e s , t h e d e s i g n s t a n d a r d f o r t h e d i k e s was s e t p r i m a r i l y f o r p o l i t i c a l a n d t e c h n i c a l , r a t h e r t h a n e c o n o m i c , r e a s o n s . T h e d e s i g n s t a n d a r d s e t s t h e r i s k o f f l o o d i n g a t . 0 0 5 p e r y e a r a n d i s now t h e s t a n d a r d f o r f l o o d p r o t e c t i o n t h r o u g h o u t B r i t i s h C o l u m b i a . T h e r e a r e s e v e r a l f a c t o r s t h a t m a k e t h e f l o o d s i t u a t i o n o n L u l u I s l a n d w o r t h y o f s t u d y a t t h i s t i m e . T h e f i r s t h a s a l r e a d y b e e n d i s c u s s e d . T h e r e i s a l a r g e ( a n d g r o w i n g ) f l o o d h a z a r d i n R i c h m o n d . I n f a c t , i t i s t h e l a r g e s t f l o o d h a z a r d i n C a n a d a a n d o n e o f t h e l a r g e s t i n N o r t h A m e r i c a . T h e s e c o n d f a c t o r i s t h a t a new t e c h n o l o g y o f r i s k a s s e s s m e n t h a s b e e n e m e r g i n g o v e r t h e l a s t d e c a d e . T h i s t e c h n o l o g y h a s b e e n d e v e l o p e d m a i n l y t o d e a l w i t h i s s u e s r e l a t e d 4 to the nuclear and hazardous chemicals industries. Spin-offs of th i s research have been applied to dam safety and are applicable to flood c o n t r o l . The main thrust of t h i s research i s to determine "How safe i s safe enough?" This question i s c l e a r l y germane, given the somewhat a r b i t r a r y way in which the current design standards were arrived at. The t h i r d factor i s that there i s concern that the risk of flooding is increasing. This concern arises from the trend toward higher l e v e l s of carbon dioxide in the atmosphere. It i s f e l t that the increased levels of carbon dioxide w i l l cause atmospheric warming, which in turn w i l l melt parts of large ice sheets such as the Greenland ice sheet. It i s predicted that the water thus released could increase sea l e v e l by about 1 metre within the next 50 years. The fourth factor i s that some concern has been expressed that the flood r i s k has been underestimated because of the p o s s i b i l i t y that an earthquake could liquefy, and thus damage, the dikes. This concern was triggered by the earthquake which struck Niigata, Japan. Niigata has similar s o i l structures to those found in Richmond. Both c i t i e s are b u i l t on poorly compacted sands and s i l t y sands. During the Niigata earthquake, widespread s o i l l i q u e f a c t i o n occurred and some dikes f a i l e d as a r e s u l t . The f i n a l factor i s that the B r i t i s h Columbia government i s in the process of revising i t s flood control p o l i c i e s . This makes the timing of this thesis f o r t u i t o u s . 5 In an o v e r a l l sense, the management of the flood situation in Richmond has been successful because no s i g n i f i c a n t flooding has occurred since Lulu Island was developed. The combination of a large and growing hazard and both technical and p o l i t i c a l d i f f i c u l t i e s in reducing the risk make i t worthwhile to study th i s s i t u a t i o n . This thesis reviews the contemporary trends in flood and other hazard protection and examines the flood hazard situation in Richmond in the l i g h t of these trends. 6 L ITERATURE REVIEW T h e l i t e r a t u r e a p p l i c a b l e t o t h i s t h e s i s h a s c o m e f r o m s e v e r a l d i f f e r e n t a r e a s . S i n c e t h e e a r l y 1 9 7 0 ' s , a c o n s i d e r a b l e b o d y o f l i t e r a t u r e h a s g r o w n u p t h a t i s s p e c i f i c a l l y c o n c e r n e d w i t h r i s k a s s e s s m e n t . W o r k s w i l l b e r e v i e w e d f r o m t h i s a r e a o n t h e s u b j e c t s o f r i s k p e r c e p t i o n , r i s k a n a l y s i s i n g e n e r a l , a n d r i s k a n a l y s i s a p p l i e d t o w a t e r r e s o u r c e s p r o j e c t s i n p a r t i c u l a r . A n o t h e r r e l e v a n t a r e a i s t h e c o s t / b e n e f i t a n a l y s i s w h i c h h a s b e e n u s e d t o e v a l u a t e f l o o d c o n t r o l p r o j e c t s i n t h e l o w e r F r a s e r V a l l e y . T h e f i n a l a r e a a p p l i c a b l e t o t h i s t h e s i s i s t h e h y d r o l o g y a n d g e o l o g y o f R i c h m o n d . S p e c i f i c a l l y , w o r k s r e v i e w i n g t h e e a r t h q u a k e h a z a r d , t h e r i v e r f l o o d h a z a r d , a n d t h e o c e a n f l o o d h a z a r d w i l l b e r e v i e w e d . V a n c o u v e r I n t e r n a t i o n a l A i r p o r t Sea Dyke s R e h a b i l i t a t i o n -Hay and Company (1985) T h i s r e p o r t d i s c u s s e s t h e d e s i g n o f d i k e s t o p r o t e c t S e a I s l a n d . S e a I s l a n d i s w i t h i n t h e b o u n d a r i e s o f t h e M u n i c i p a l i t y o f R i c h m o n d , b u t i s n o r t h a n d w e s t o f L u l u I s l a n d , t h e m a i n s u b j e c t o f t h i s t h e s i s . T h e s e c t i o n o n h y d r o l o g i c b a c k g r o u n d o f t h i s r e p o r t g i v e s a g o o d d e s c r i p t i o n o f t h e o c e a n - b a s e d f l o o d h a z a r d f a c e d b y L u l u I s l a n d . T h e r e p o r t s t a t e s t h a t : " W i t h o u t t h e d i k e s a b o u t 8 5 % o f S e a I s l a n d w o u l d b e i n u n d a t e d d u r i n g n o r m a l h i g h t i d e s , a n d w o u l d s u b s e q u e n t l y b e e x p o s e d a t l o w t i d e s . T h e n a t u r a l g r o u n d l e v e l s o f t h e l o w l y i n g a r e a s r a n g e f r o m .9 t o 1.5m G S C , j u s t o v e r a m e t r e a b o v e t h e m i d - t i d e l e v e l o f 0.0m G S C " ( H a y a n d C o m p a n y , 1 9 8 5 , p . 1 3 ) . * G S C - G e o d e t i c S u r v e y o f C a n a d a . 7 T h e r e p o r t a l s o c a l c u l a t e s t h e e f f e c t o f a 200m b r e a c h , l a s t i n g 1 t i d a l c y c l e , i n S e a I s l a n d d i k e s . T h e c a l c u l a t i o n , d o n e u n d e r w o r s t c a s e c o n d i t i o n s , s h o w s t h a t 7.4 m i l l i o n c u b i c m e t r e s o f w a t e r w o u l d e n t e r S e a I s l a n d , r e s u l t i n g i n f l o o d i n g t o a d e p t h o f .7m o n a g r i c u l t u r a l l a n d . 8 5 % o f S e a I s l a n d i s a g r i c u l t u r a l l a n d . T h e f i n a l a p p l i c a b l e p a r t o f t h i s s t u d y d i s c u s s e s o c e a n w a v e s . T h e r e p o r t s t a t e s t h a t 2.8 t o 3.4m w a v e s w o u l d b e g e n e r a t e d u n d e r 8 5 k p h w i n d s b l o w i n g a c r o s s t h e S t r a i t o f G e o r g i a f o r a m i n i m u m o f 6 h o u r s . I t t h e n s t a t e s t h a t t h i s m a x i m u m w a v e h e i g h t i s r e d u c e d b y 8 2 % a c r o s s S t u r g e o n B a n k s a s a r e s u l t o f b o t t o m f r i c t i o n . T h i s m e a n s t h a t a 3m w a v e w o u l d b e r e d u c e d t o ,6m b y t h e t i m e i t a p p r o a c h e s t h e d i k e s a c r o s s S t u r g e o n B a n k s . B e c a u s e L u l u I s l a n d i s c l o s e t o S e a I s l a n d , m u c h o f t h e d e s c r i p t i o n i s a p p l i c a b l e . I t s h o u l d b e n o t e d t h a t S e a I s l a n d t i d e s a r e s l i g h t l y h i g h e r . L a r g e p o r t i o n s o f L u l u I s l a n d , i n c l u d i n g a l m o s t a l l h e a v i l y d e v e l o p e d a r e a s , a r e l o c a t e d a t e l e v a t i o n s f r o m .9 t o 2.0m G S C . T h e b u i l d i n g c o d e i n R i c h m o n d r e q u i r e s t h a t a l l u r b a n d e v e l o p m e n t o n L u l u I s l a n d b e b u i l t a t o r a b o v e ,9m G S C . T h e r e p o r t g i v e s m e a n h i g h t i d e l e v e l a s 1.4m G S C a n d l o w t i d e l e v e l a s -3m G S C . T h e M u n i c i p a l i t y o f R i c h m o n d p u t s t h e m e a n h i g h t i d e l e v e l a t t h e s l i g h t l y l o w e r l e v e l o f 1m f o r L u l u I s l a n d . I t s h o u l d a l s o b e n o t e d t h a t t h e t i m e i t w o u l d t a k e t o f l o o d L u l u I s l a n d f r o m a s t o r m - c a u s e d b r e a c h w o u l d b e s o m e w h a t l o n g e r b e c a u s e L u l u I s l a n d i s 8.5 t i m e s a s b i g a s S e a I s l a n d . I f n o p o n d i n g o c c u r r e d , t h e n f l o o d i n g t o a n a v e r a g e d e p t h o f 6cm 8 per t i d a l cycle could be expected from a similar dike breach. Deeper flooding could be expected in the lowest areas nearest the dikes, but i t i s clear that as long as the duration of ocean flooding i s kept to 1 or 2 t i d a l cycles, the flood damage would be kept to acceptable l e v e l s . F i n a l l y , while Lulu Island i s near to Sea Island, i t is. far less exposed to wave action because almost a l l of Lulu Island's western coast i s protected by Sturgeon Banks. In fact, the reduction in wave action caused by Sturgeon Banks has made i t unnecessary to rip-rap Lulu Island sea dikes to protect them against wave action. The R o l e o f P e r c e p t i o n i n F l o o d C o n t r o l - G o r d o n Shanks (1972) This work provides an excellent summary of the rive r hydrology around Lulu Island. It c o r r e c t l y points out that the largest flood hazard facing Richmond i s the one caused by the spring freshet involving a dike breach in the eastern end of Lulu Island. In addition, Shanks provides d e t a i l e d descriptions of the attitudes and perceptions toward the flood hazard of both the government o f f i c i a l s concerned with flood control and the public l i v i n g on Lulu Island. HYDROLOGY OF LULU ISLAND Lulu Island i s located in the Fraser River Estuary. The river branches and forms several channels around Lulu Island. The eastern end of Lulu Island i s t o t a l l y in a r i v e r i n e environment, while the western end, fronting on Georgia S t r a i t , i s in a marine environment. The general east-west dividing l i n e separating areas under r i v e r i n e and t i d a l based flood hazard i s 9 shown. The areas under t i d a l influence are not treated in t h i s work. Flooding from a dike breach during the spring freshet is i d e n t i f i e d as the largest flood hazard. The work c o r r e c t l y states that a major dike break, from th i s cause, would flood the whole isla n d . It also states that flooding would occur to the same l e v e l as i f there were no dikes. The average flooding l e v e l for a 1 in 200 year flood i s given as 4 feet (1.2m). DIFFICULTIES WITH DIKING SYSTEMS Several d i f f i c u l t i e s in the dependence on diking systems to protect urban areas from flooding are described. These include: - The d i f f i c u l t y in building dikes high enough to provide complete protection from overtopping. - The impo s s i b i l i t y of building dikes that are completely safe from extreme flooding events. Problems from b o i l s , undercutting, piping, and underseepage can occur even with well maintained dikes during these extreme events. - The i m p o s s i b i l i t y of maintaining dikes to 100% of standard. Dikes s e t t l e , are damaged by bank erosion and other less obvious factors such as burrowing animals over time. As a r e s u l t , constant repairs are necessary. - The fact that a major break in the dikes would cause flooding of the whole island making the dikes useless. 10 - T h e t e n d e n c y f o r d e v e l o p m e n t t o g r o w u p b e h i n d d i k e s . When d i k e s f a i l , t h e d a m a g e i s g r e a t e r t h a n i t w o u l d h a v e b e e n i f d i k e s h a d n o t b e e n b u i l t . P R O B A B I L I T I E S OF F L O O D I N G When t h i s w o r k w a s w r i t t e n t h e d e s i g n s t a n d a r d f o r R i c h m o n d d i k e s was t h e 1948 f l o o d p l u s t w o f e e t o f f r e e b o a r d . I t i s s t a t e d t h a t t h e p r o b a b i l i t y o f o v e r t o p p i n g i s . 0 0 5 p e r a n n u m . T h e a u t h o r p o i n t s o u t t h a t , o v e r a d e s i g n l i f e o f 50 y e a r s , t h e p r o b a b i l i t y o f o v e r t o p p i n g t h e d i k e s u n d e r t h e s e c o n d i t i o n s i s .2 2 . P E R C E P T I O N OF F L O O D HAZARD T h e d i s c u s s i o n o f f l o o d h a z a r d p e r c e p t i o n i s d i v i d e d i n t o 2 p a r t s : t h e p e r c e p t i o n o f i n v o l v e d g o v e r n m e n t o f f i c i a l s a n d t h e p e r c e p t i o n o f t h e p u b l i c l i v i n g i n R i c h m o n d . I t w a s f o u n d t h a t t h e r e i s a l a r g e v a r i a t i o n i n how s e r i o u s t h e f l o o d h a z a r d w a s p e r c e i v e d t o b e a m o n g g o v e r n m e n t o f f i c i a l s . A g r a d a t i o n i n c o n c e r n w a s n o t e d f r o m f e d e r a l o f f i c i a l s t o m u n i c i p a l o f f i c i a l s . S h a n k s w r i t e s : " F e d e r a l o f f i c i a l s who h a v e t h e l e a s t d i r e c t i n p u t c o n s i d e r t h e p r e s e n t h a z a r d t o b e a s i g n i f i c a n t o n e . On t h e o t h e r h a n d , t h e m u n i c i p a l l e v e l o f f i c i a l s who a r e t h e m o s t d i r e c t l y i n v o l v e d w i t h i m p l e m e n t a t i o n o f f l o o d m a n a g e m e n t p o l i c i e s f a i l t o p e r c e i v e t h e f l o o d h a z a r d a s b e i n g s i g n i f i c a n t . " ( S h a n k s , 1 9 6 8 , p . 9 4 ) O f f i c i a l s p e r c e i v e d d i k i n g a s t h e m o s t s u i t a b l e a d j u s t m e n t t o t h e f l o o d h a z a r d a n d u p s t r e a m s t o r a g e a s t h e n e x t m o s t s u i t a b l e a l t e r n a t i v e . T h e s e m e a s u r e s c o n t r o l t h e f l o o d r i s k , n o t t h e f l o o d h a z a r d . T h e r e was l i t t l e s u p p o r t f o r s o l u t i o n s t h a t c o n t r o l t h e f l o o d h a z a r d s u c h a s f l o o d p r o o f i n g a n d l a n d u s e r e s t r i c t i o n s . 11 T h i s w o r k f o u n d t h a t t h e p u b l i c r e c o g n i z e d t h e p o s s i b i l i t y o f f l o o d d a m a g e ( 5 2 % o f r e s p o n d e n t s ) , b u t d i d n o t e x p e c t t o e x p e r i e n c e f l o o d i n g i n t h e i r l i f e t i m e ( 8 5 % o f r e s p o n d e n t s ) . T h e a u t h o r s t a t e s t h a t t h i s i s a l o w l e v e l o f f l o o d h a z a r d p e r c e p t i o n . T h i s w o r k f o u n d t h a t t h e p u b l i c i s e s s e n t i a l l y i n d i f f e r e n t t o t h e f l o o d h a z a r d a n d t h a t , b y d e f a u l t , p o l i c y i s made b y t h e p r o f e s s i o n a l s i n f l o o d c o n t r o l . A s t h e a u t h o r s t a t e s : " I n d i c a t i o n s a r e t h a t p u b l i c s u p p o r t w o u l d n o t b e a d e c i s i v e f a c t o r i n a f f e c t i n g f l o o d a d j u s t m e n t s . " ( S h a n k s , 1 9 6 8 , p . 1 0 8 ) S i n c e t h i s s t u d y was p e r f o r m e d , t h e d i k e s h a v e b e e n r a i s e d t o t h e 1 i n 200 y e a r l e v e l p l u s 2 f e e t o f f r e e b o a r d . I t i s p r o b a b l e t h a t r a i s i n g t h e d i k e s d e c r e a s e d p u b l i c a w a r e n e s s o f t h e f l o o d h a z a r d . I t s h o u l d b e n o t e d t h a t t h e p r o b a b i l i t y o f n o f l o o d i n g o c c u r r i n g i n t h e n e x t 40 y e a r s i s 8 2 % . * I n v i e w o f t h e l e n g t h o f t i m e p e o p l e c a n b e e x p e c t e d t o l i v e i n o n e p l a c e , t h e p u b l i c ' s l a c k o f c o n c e r n a b o u t t h e f l o o d h a z a r d d o e s n o t s e e m u n r e a s o n a b l e . T h e s e n s e o f t h e a u t h o r ' s a r g u m e n t i s t h a t i f g o v e r n m e n t o f f i c i a l s f i n d t h a t d i f f e r e n t f l o o d c o n t r o l m e t h o d s s u c h a s f l o o d p r o o f i n g o r s t r i c t e r z o n i n g a r e n e c e s s a r y , t h e p u b l i c p r o b a b l y w o u l d n o t o b j e c t . F i n a l l y , S h a n k s wa s u n a b l e t o e x p l a i n why f e d e r a l o f f i c i a l s w e r e t h e m o s t c o n c e r n e d a b o u t t h e f l o o d h a z a r d w h i l e p r o v i n c i a l * T h e p r o b a b i l i t y o f n o f l o o d o c c u r r i n g i n 40 y e a r s g i v e n a n n u a l p r o b a b i l i t y o f f l o o d i n g i s . 0 0 5 i s (1 - . 0 0 5 ) 4 0 = .818 . 12 o f f i c i a l s were less concerned and municipal o f f i c i a l s were the least concerned. No attempt was made to correlate the l e v e l of r e s p o n s i b i l i t y for payment of flood damages with l e v e l of concern about flooding. Earthquake D e sign i n Richmond, B.C. -P e t e r M. Byrne and Donald L. Anderson (1983) This work documents the earthquake hazard faced by Richmond. Richmond i s located in the circumpacific belt well known for i t s earthquake a c t i v i t y . It outlines the role of the underlying s o i l s in creating the potential for high earthquake hazard. It i s stated that water-saturated loose- to medium-dense sands and s i l t s are prone to strength loss through li q u e f a c t i o n when exposed to strong shaking. This paper describes the process of l i q u e f a c t i o n of sand as follows: "If a l l the load i s transferred to the water, the s o i l loses a l l of i t s strength and behaves l i k e a l i q u i d and i s said to have l i q u e f i e d . The high water pressures can lead to expulsion of water and sand at the ground surface in the form of miniature volcanoes and the loss of strength can result in large movements of structures and services founded in or above the l i q u e f i e d zone. Such behaviour has been noted repeatedly during earthquake shaking where the underlying s o i l s are comprised of loose saturated s o i l s (Youd, 1975). Resulting earthquake damage has generally been much more severe in areas underlain by such s o i l s . " (Byrne, 1985, p. 3) The e s s e n t i a l points made in t h i s paper with respect to flooding in Richmond are: - Richmond s o i l s are loose to medium dense sands and s i l t s . - The dikes around Richmond are made of the ..same materials. 13 - The high water table in Richmond ensures that the dike foundations and the lower part of the dikes are constantly saturated. - The s o i l s found in both the surface s o i l layers and the dikes are of the type that i s l i k e l y to liquefy in a strong earthquake. - An earthquake l i k e l y to cause li q u e f a c t i o n would have a return period of 475 years. - The upper portions of the dikes are only saturated during extreme high tides or the spring freshet. Consequently the p r o b a b i l i t y of l i q u e f a c t i o n of the t o t a l height of the dikes is quite small. - Even i f only the base of the dikes and the foundations l i q u e f y , longitudinal and transverse cracks could occur in the dikes. - The flooding that would occur under the most l i k e l y conditions would be from t i d a l sources. The t i d a l r e l i e f during low tide would allow repairs to be made to the dikes under dry conditions. If repairs to the dikes were not completed quickly, serious flooding would r e s u l t . - The p r o b a b i l i t y of an earthquake occurring during the high water levels of the spring freshet i s so small that the p o s s i b i l i t y can be considered n e g l i g i b l e . 1 4 E s t i m a t i n g F l o o d Damages i n the F r a s e r R i v e r B a s i n -A r c h i e N. Book and Romeo P r i n c i c (1975) T h i s work c o n t a i n s the methodology and r e s u l t s of the l a s t comprehensive e s t i m a t e of p o t e n t i a l f l o o d damage i n the F r a s e r R i v e r B a s i n ( i n c l u d i n g Richmond). As t h i s s tudy i s co n c e r n e d o n l y w i t h e s t i m a t i n g p o t e n t i a l f l o o d damages, no gu i d a n c e i s g i v e n i n t h i s r e p o r t as t o what a p p r o p r i a t e l e v e l s of f l o o d p r o t e c t i o n a r e . I t i s n o t e d , however, t h a t f l o o d c o n t r o l s t r u c t u r e s a r e t y p i c a l l y d e s i g n e d t o p r o t e c t a g a i n s t a " d e s i g n f l o o d " and t h a t the s i z e of the d e s i g n f l o o d i s u s u a l l y d e t e r m i n e d by methods o t h e r than e c o n o m i c a l l y r a t i o n a l c r i t e r i a . A major problem w i t h the r e s u l t s of t h i s s tudy i s t h a t i t i s now 15 y e a r s o l d . Much development has o c c u r r e d i n Richmond i n the i n t e r v e n i n g y e a r s . In p a r t i c u l a r , $500 m i l l i o n of b u i l d i n g p e r m i t s f o r commercial uses have been i s s u e d s i n c e 1971. T h i s s t u d y i d e n t i f i e s 4 t y p e s of f l o o d damage: l o s s of p r o p e r t y and income, r i s k - t a k i n g , i n t a n g i b l e s , and r e s t r i c t i o n s on the use of the f l o o d p l a i n . MEASUREMENT OF RISK-TAKING R i s k - t a k i n g i s measured as the d i f f e r e n c e between the l e v e l of p r o t e c t i o n s p e c i f i e d by p o l i t i c a l d ecree and the l e v e l t h a t would be o p t i m a l on the b a s i s of m a r g i n a l a n a l y s i s . I n t a n g i b l e s are g i v e n o n l y minor c o n s i d e r a t i o n . INTANGIBLES T h i s r e p o r t l i s t s i n t a n g i b l e damages as l o s s of l i f e , i n j u r i e s , p s y c h o l o g i c a l d i s t u r b a n c e s , and s o c i a l u p h e a v a l . Loss of l i f e and i n j u r i e s a r e d i s c o u n t e d because deaths and i n j u r i e s n o r m a l l y do not r e s u l t from f l o o d i n g i n the F r a s e r V a l l e y and i t 15 is unclear that structural flood control measures prevent either deaths or i n j u r i e s . Given the slow r i s e in r i v e r l e v e l s that occurs in the Fraser Valley, these observations about the l i k e l i h o o d of deaths and i n j u r i e s are reasonable. Psychological disturbances and s o c i a l upheaval are not considered because they are d i f f i c u l t to determine in monetary terms. COST OF RISK-TAKING The cost of risk-taking i s defined as the premium people are w i l l i n g to pay to avoid very large losses in a catastrophic flood. The report suggests that t h i s premium equals the excess in protection l e v e l s s p e c i f i e d , over what would be s p e c i f i e d by setting marginal costs of protection equal to marginal benefits from protection. PROPERTY AND INCOME LOSSES The main focus of t h i s report i s on property and income losses. Three types of floodplain usage were found to contribute s i g n i f i c a n t l y to potential flood damages: - Residential usage. - Commercial and i n d u s t r i a l usage. - A g r i c u l t u r a l usage. Residential Usage This study found that s l i g h t l y less than half of a l l potential flood damages in the Fraser Valley are from r e s i d e n t i a l losses. For Richmond, i t was s l i g h t l y more than 50%. Given the 2/3 increase in Richmond's population since 1971, the potential for t h i s type of damage has c e r t a i n l y increased. 16 Commercial and Industrial Usage Extensive surveys were performed to determine potential commercial and i n d u s t r i a l flood damage. Commercial a c t i v i t i e s were grouped to f a c i l i t a t e c a l c u l a t i o n of flood damage. Each i n d u s t r i a l a c t i v i t y was surveyed to determine potential flood damage. These a c t i v i t i e s accounted for 16% of potential damages in the Fraser Basin and 23% in Richmond. It i s clear from the value of building permits issued that commercial a c t i v i t y has increased greatly in Richmond since 1971. It would be necessary, however, to repeat the extensive survey reported in t h i s work to determine an accurate figure for these usage types. A g r i c u l t u r a l Usage The report l i s t s the probable a g r i c u l t u r a l flood damages as: "crop and equipment losses, reductions in productive capacity of livestock, premature slaughtering of poultry, and the costs of extra feed to replace that lost during a flood" (Book and P r i n c i c , 1975, p. 62). This type of a c t i v i t y accounted for 16% of potential flood damage in the Fraser Basin, but only 5% in Richmond. SUMMARY Because of the urbanized nature of development on Lulu Island in 1971, a large flood hazard was i d e n t i f i e d . The trend toward urbanization, has i f anything, increased since 1971. The increasing le v e l s of urbanization since then can only have increased the hazard. As a thorough documentation of the size of the Lulu Island flood hazard, the authors' work i s relevant to this thesis. 1 7 The major l i m i t a t i o n of the report i s i t s treatment of intangible and risk-taking costs. By defining risk-taking cost as the premium people are w i l l i n g to pay over what marginal cost analysis would suggest, the report neglects the p o s s i b i l i t y that the aversion f e l t against extremely large losses occurs because these losses would lead to s o c i a l upheaval and disruption. S a f e t y of Dams: F l o o d and Earthquake C r i t e r i a -Committee on S a f e t y C r i t e r i a f o r Dams (1985) This work reviews current practices in designing dams to r e s i s t extreme hydrologic and seismic events. It c l e a r l y i d e n t i f i e s two types of f a i l u r e during extreme flooding events: reservoir f a i l u r e and dam f a i l u r e . Reservoir f a i l u r e occurs when there i s i n s u f f i c i e n t reservoir capacity to store inflow waters behind a dam. To protect the dam and prevent a sudden release of a l l the water stored behind the dam, water i s routed over a spillway. Extreme hydrologic events can cause the release of s u f f i c i e n t flows over the spillway to cause flood damages approaching or even exceeding those that would have occurred i f the dam had not been b u i l t . Dam f a i l u r e occurs when the spillway capacity i s i n s u f f i c i e n t to prevent overtopping and/or breaching of the dam. A dam f a i l u r e can cause flood damages much greater than would have been experienced i f no dam had been present. A rare and large magnitude event can cause either type of f a i l u r e . This work is mainly concerned with dam f a i l u r e rather than reservoir fa i l u r e . 18 This report makes several useful points concerning how much safety should be designed into a dam. It states the design objective as follows: "The objective should be to balance the benefits of making dams safer against the cost of the increased safety and to reduce any risks to acceptable proportions." (Committee on Safety of Dams, 1985, p. 9) It states that government must decide what i s an acceptable l e v e l of risk for involuntary hazards where i t acts as the agent for groups of people. Several factors are c i t e d that have made i t d i f f i c u l t for government to decide what i s an acceptable r i s k . These include a lack of precision and accuracy in the prediction of large magnitude hydrologic events, the i n a b i l i t y to e a s i l y factor in intangibles such as loss of l i f e into c a l c u l a t i o n s , and the p o s s i b i l i t y that future downstream development might s i g n i f i c a n t l y increase the hazard af t e r a dam i s b u i l t . This work, also, suggests that the costs of safety r e l a t i v e to t o t a l project cost are important in making design trade-offs: "For example, i f only a tiny addition to the cost of building the dam would be required to design to a higher standard, t h i s greater standard makes sense. S i m i l a r l y , i f the cost of designing to the PMF and MCE are very large in r e l a t i o n to a s l i g h t l y less stringent design, c a r e f u l consideration must be given to whether the more stringent design i s needed." (Committee on Safety of Dams, 1985, p. 14) The current design practices reviewed by t h i s work show that most j u r i s d i c t i o n s use a r e l a t i v e l y simple hazard c l a s s i f i c a t i o n scheme to decide on appropriate risk l e v e l s . (See Table I at the end of t h i s t h e s i s ) . Minimum discharge *PMF - Probable Maximum Flood. MCE - Maximum Credible Earthquake. 19 capacities, which are usually quite stringent, are set. This work describes several situations under which these conditions might be relaxed to a less stringent discharge capacity. These situations include re-evaluation of exis t i n g high hazard dams and evaluation of low and intermediate hazard dams. It i s suggested that risk analysis techniques be applied to determine required discharge capacity in these situations and two d i s t i n c t types of risk analysis are described. The f i r s t technique involves determining the costs of various spillway designs and the associated long term damages (risk c o s t ) . The spillway capacity chosen would be the one with the lowest t o t a l cost. It was proposed that costs associated with loss of l i f e be translated into monetary amounts based on recent court decisions. This approach has not been widely accepted because: - There i s reluctance to place a monetary value on human l i f e . - The present value calculations in an economic analysis are dependent on the interest rate selected. It i s f e l t that the choice of interest rate i s a r b i t r a r y . - Estimates of average annual risk costs are dependent on the flood frequency curve adopted. Estimates of the frequency of rare flood events are inaccurate. (The frequency for a given size event has been observed to increase over time as more data i s c o l l e c t e d ) . .. The second technique involves choosing the flood flow for which f a i l u r e of the dam would cease to create s i g n i f i c a n t 20 additional damage downstream. This technique i s more in l i n e with current legal and professional practice, in that i t ensures that damage would be no greater than i f the dam had not been b u i l t . One problem mentioned, with t h i s approach, i s the p o s s i b i l i t y that increased downstream development after the dam is b u i l t could make the expected spillway capacity inadequate. This technique i s p a r t i c u l a r l y applicable to the review of exist i n g high hazard dams. For these dams i t i s often found that the spillway i s inadequate to pass the probable maximum flood because the size of the probable maximum flood has been revised upward. For low hazard and intermediate hazard dams t h i s report appears to relax the c r i t e r i a further: "Safety evaluations for intermediate- and low-hazard dams are primarily concerned with the economic effects of thei r potential f a i l u r e s . However, a continuing problem with such evaluations i s the actual or potential development of the area downstream from the dam after the dam i s constructed and the consequent change in the hazard ratings for the project." (Committee on Safety of Dams, 1985, p. 102) The low- and intermediate-hazard dam break evaluations are not very far removed from the natural flood control evaluation. Some differences do exi s t , however. The p r i n c i p a l difference i s that a l l dam breaks involve higher hydraulic head, higher water v e l o c i t i e s , deeper flood waters, and rapid flooding. A l l of these factors make the pr o b a b i l i t y of loss of l i f e high i f any development exists immediately downstream of a dam. This is not the case with most flood s i t u a t i o n s . In p a r t i c u l a r , loss of l i f e i s not probable from the flooding of Lulu Island. A second 21 difference i s that dams are b u i l t and operated by someone. If a dam f a i l s , whoever b u i l t i t can expect to have to account for result i n g flood damage. F i n a l l y , the building of dams does not necessarily act as a catalyst to development on the floodplain. The p o s s i b i l i t y that future development might increase the hazard i s es p e c i a l l y important for flood control because, unlike most dam projects, flood control projects increase the hazard by fostering development. Another important point with respect to flood control i s the high incremental costs when e f f o r t s are made to reduce the risk of flooding to very small p r o b a b i l i t i e s . This i s not true for dams where the cost of a spillway per unit discharge decreases as the capacity of the spillway increases. The d i f f e r i n g cost structures make i t expensive to avoid the task of assessing r i s k s for the flood hazard by making those r i s k s very small. On the other hand, there are many s i m i l a r i t i e s between the two s i t u a t i o n s . Both result in flood damage. In both cases not a l l flood damage can be calculated. In p a r t i c u l a r , the s o c i a l upheaval from a natural flood i s d i f f i c u l t to quantify. Both are subject to the inaccuracies in determining frequencies of rare flooding events. F i n a l l y , although no one i s responsible for natural flooding, governments usually take some r e s p o n s i b i l i t y for aiding flood victims. On the whole, dam breaks are a more serious hazard than natural flooding, but the two hazards are similar enough that 22 the methods used to evaluate dam breaks can be applied, with some modifications, to natural flood hazards. M o d e l l i n g the S o c i e t a l Impact of F a t a l A c c i d e n t s -P a u l S l o v i c , Sarah L i c h t e n s t e i n , and Baruch F i s c h o f f (1984) This a r t i c l e considers two models of how f a t a l accidents are perceived. The f i r s t model suggests that the s o c i a l cost of N l i v e s lost i s a function of N a. It is commonly suggested that a single large accident i s perceived to be more serious than many small accidents producing the same number of f a t a l i t i e s , implying that a > 1. The second model suggests that the seriousness with which an accident i s perceived i s not necessarily related to the number of f a t a l i t i e s . The a r t i c l e instead suggests that the seriousness of an accident can be attributed in part to the fact that accidents are signals of future trouble. It states that: The s o c i e t a l impact of an accident i s determined to an important degree by what i t s i g n i f i e s or portends. An accident that causes l i t t l e d irect harm may have immense consequences i f i t increases the judged pr o b a b i l i t y and seriousness of future accidents." (Slovic et. a l . , 1984, p. 464) To support t h i s model, the authors c i t e several studies in which people were asked to characterize the r i s k s from several sources - including nuclear power. It was found that the results of these studies could be explained by two factors, unknown r i s k and dread r i s k . Unknown ri s k s are those which are: not observable, unknown to those exposed, delayed in their e f f e c t s , new, and unknown to science. Dread risks are those which are: uncontrollable, global catastrophic, f a t a l , not equitable, of 23 high r i s k to future generations, not e a s i l y reduced, increasing, involuntary, and personally af f e c t the respondent. The r i s k s associated with nuclear power were found to be quite high in both of these catagories. This a r t i c l e does not s p e c i f i c a l l y cover the flood hazard, but i t does consider the risk from large dams. Large dams are perceived to be known but dread r i s k s . As the same technology i s used to contain floods as to b u i l d dams, but the p r o b a b i l i t y of f a t a l i t i e s i s less during most flooding than during a dam break, floods should be c l a s s i f i e d as non-dread, known r i s k s . Thus, this model suggests a s l i g h t l y risk-prone attitude toward flooding. Shank's finding that people in Richmond are at most ind i f f e r e n t to the flood hazard supports t h i s view. The federal government's policy that a l l flood control works be s t r i c t l y cost j u s t i f i e d also supports t h i s view. In e f f e c t , t h i s p o licy states that expected flood damages (net benefits) must exceed the amount spent to avoid the damages (expected project costs). In addition, because of the fixed l e v e l of protection provided in B r i t i s h Columbia ( a l l flood protection i s designed to protect up to the 1 in 200 year l e v e l ) , benefit-cost r a t i o s have been higher for urban areas than r u r a l ones. A flood in an urban area such as Richmond would cause far more damage than a flood in a rural area having far less population and development. Current policy spends less for each d o l l a r of damages in areas with higher expected flood damages than in areas with lower potential damages. Current policy i s , in e f f e c t , risk-prone toward larger flood r i s k s . 24 R i s k P e r c e p t i o n : A S y s t e m a t i c R e v i e w o f C o n c e p t s and R e s e a r c h R e s u l t s - O r t w i n R e n n . (From " A v o i d i n g and M a n a g i n g E n v i r o m e n t a l Damage f r o m M a j o r A c c i d e n t s " ) (1985) T h i s paper r e v i e w s the s t a t e of the a r t knowledge i n r i s k p e r c e p t i o n . I t p r e s e n t s a number of c o n c e p t s t h a t a r e u s e f u l i n a s s e s s i n g a t t i t u d e s t o the f l o o d h a z a r d . I t s t a t e s t h a t , g e n e r a l l y , p e o p l e do a good j o b i n a s s e s s i n g r i s k s t h a t a r e f a m i l i a r . Low r i s k s , however, tend t o be u n d e r e s t i m a t e d w h i l e h i g h r i s k s t e n d t o be o v e r e s t i m a t e d . When a r i s k i s o u t s i d e of normal e x p e r i e n c e , few peopl e have the a b i l i t y t o de t e r m i n e even the o r d e r of magnitude of the r i s k s i n v o l v e d . Examples g i v e n i n c l u d e : - The number of l i v e s l i k e l y t o be l o s t i n a c a t a s t r o p h i c event t h a t o c c u r s once i n a l i f e t i m e . E i t h e r a l l r i s k s a r e graded almost u n i f o r m l y or e x o r b i t a n t e s t i m a t e s a r e made. - D i s a s t e r s e x p e c t e d a t l o n g i n t e r v a l s (80 t o 100 y e a r s ) . An i m p o r t a n t f i n d i n g r e p o r t e d i n t h i s paper i s t h a t presumed l o s s r a t e s a r e p r a c t i c a l l y independent of r i s k p e r c e p t i o n . In o t h e r words, p e o p l e do not a s s e s s h a z a r d s a c c o r d i n g t o presumed l o s s e s per y e a r . E x p e c t e d l o s s e s per year have o n l y s l i g h t e x p l a n a t o r y v a l u e i n p r e d i c t i n g r i s k p e r c e p t i o n . The m i n i m a l p r e d i c t i v e v a l u e of ex p e c t e d l o s s e s on r i s k p e r c e p t i o n i s p a r t i a l l y e x p l a i n e d by the f a c t t h a t most p e o p l e a r e not f a m i l i a r w i t h the r a t i o n a l e of p r o b a b i l i t y e s t i m a t e s . When p r o b a b i l i t i e s a r e not i n t u i t i v e l y u n d e r s t a n d a b l e , the p e r c e i v e d r i s k i n e s s i s l i k e l y t o be r e l a t e d t o the worst 25 imagined accident. Media coverage sensationalizes the worst imagined accident: i . e . , tends to make i t seem more probable and more serious than i t i s . Another point made in thi s a r t i c l e i s that people do not perceive risk d i r e c t l y . They see options or p o s s i b i l i t i e s that have benefits and risks attached to them. If an option benefits them d i r e c t l y , people w i l l accept more risk than i f the option d i s t r i b u t e s benefits and ri s k s equally throughout society. If the option does not benefit them, but imposes ri s k s on them, people w i l l perceive the risk very stongly. Hazards that pose a pending danger are perceived as more serious than hazards that come at predictable times. This is so because the dangerous situ a t i o n could occur at any time. Two other factors which influence risk perception, after the debate on a hazard has been p o l i t i c i z e d , are mentioned. A person's value orientation and general a t t i t u d i n a l system w i l l influence risk perception. This i s es p e c i a l l y true i f the debate on the hazard has become p o l i t i c i z e d . In addition, the c r e d i b i l i t y of normal sources of information can be destroyed in a p o l i t i c i z e d s i t u a t i o n . When this happens, people w i l l pay more attention to counter-information highlighting the r i s k s than to reassuring information and w i l l demonstrate risk averse behaviour to be on the "safe side." The f i n a l point made in t h i s a r t i c l e i s that r i s k perception and risk analysis are not the same thing. 26 A n u m b e r o f t h e p o i n t s made i n t h i s a r t i c l e a r e i m p o r t a n t i n a s s e s s i n g t h e p e r c e p t i o n o f t h e f l o o d h a z a r d o n L u l u I s l a n d . F i r s t , p e o p l e c a n n o t b e e x p e c t e d t o h a v e a n a c c u r a t e p e r c e p t i o n o f t h e f l o o d h a z a r d b e c a u s e t h e 1 i n 2 0 0 y e a r r e t u r n p e r i o d u s e d f o r f l o o d p r o t e c t i o n i s o u t s i d e o f t h e r a n g e o f n o r m a l e x p e r i e n c e . S e c o n d , t h e u s e o f a w o r s t i m a g i n e d a c c i d e n t i s i m p o r t a n t i n a n a l y z i n g t h e f l o o d h a z a r d b e c a u s e k n o w l e d g e a b o u t t h e f l o o d h a z a r d i s q u i t e g o o d . T h e w o r s t i m a g i n e d f l o o d i n R i c h m o n d i s s o m e t h i n g p e o p l e w o u l d r a t h e r n o t l i v e t h r o u g h . I t w o u l d c a u s e a l o t o f p r o p e r t y d a m a g e a n d d i s r u p t i o n . H o w e v e r , u n l i k e t h e w o r s t i m a g i n a b l e n u c l e a r a c c i d e n t o r h a z a r d o u s m a t e r i a l s s p i l l , a f l o o d i s n o t l i k e l y t o k i l l l a r g e n u m b e r s o f p e o p l e . A f l o o d i s , t h u s , s o m e t h i n g t h a t p e o p l e a r e n o t e x t r e m e l y a f r a i d o f . P e o p l e a r e e s p e c i a l l y a f r a i d o f r i s k s t h a t a r e n o t w e l l k n o w n a n d w h i c h c o u l d h a v e c a t a s t r o p h i c a n d l o n g l a s t i n g c o n s e q u e n c e s . F l o o d i n g i n R i c h m o n d i s a w e l l k n o w n h a z a r d , a n d w o u l d l i k e l y c a u s e f e w c a s u a l t i e s a n d n o l o n g t e r m e f f e c t s . T h i r d , t h e p o i n t t h a t p e o p l e d o n o t p e r c e i v e r i s k d i r e c t l y , b u t r a t h e r , p e r c e i v e o p t i o n s w i t h r i s k s a n d b e n e f i t s a t t a c h e d i s a l s o i m p o r t a n t . T h e d e c i s i o n t o l o c a t e a n a c t i v i t y i n R i c h m o n d h a s many b e n e f i t s f o r t h e p e o p l e t a k i n g t h e r i s k , i n c l u d i n g f l a t f e r t i l e l a n d , a c c e s s t o a m a j o r m e t r o p o l i t a n a r e a , a n d a c c e s s t o w a t e r t r a n s p o r t a t i o n . F i n a l l y , i t s h o u l d b e n o t e d t h a t t h e f l o o d h a z a r d i n R i c h m o n d d o e s n o t f i t t h e d e f i n i t i o n o f a p e n d i n g d a n g e r . C u r r e n t f l o o d f o r e c a s t i n g s y s t e m s g i v e s e v e r a l d a y s w a r n i n g t h a t 27 a dangerously high r i v e r l e v e l w i l l occur. In addition, 8 to 12 hours would elapse after a dike break before flooding became deep enough to immobilize road transportation. This summary of risk perception gives no indication that risk averse behaviour toward the flood hazard in Richmond can be expected. Who S h a l l L i v e ? - V i c t o r F u c h s ( 1 9 7 4 ) This work analyzes the health care system in the United States in the early 1970s from an economic point of view. It i s important to t h i s thesis because i t i s one of the e a r l i e s t examples of a r i s k - b e n e f i t analysis. The methodology used in t h i s work i s applicable to risk analysis, in general, and flood control, in p a r t i c u l a r . It consists of the following steps: - Identifying the hazards. - Identifying a standard which can be used to judge the effectiveness of money spent to reduce the hazard. - Using economic analysis to examine various options that w i l l not increase hazards. - Choosing the least cost option that does not increase the hazards. The problems i d e n t i f i e d in the U.S. health care system were increasing costs, d i f f i c u l t y in access, and mounting health problems. COST PROBLEMS This work breaks cost problems in health care into average cost problems and unusual cost problems. Average cost problems 28 r e f e r t o t h e f a c t t h a t t h e a v e r a g e c o s t o f h e a l t h c a r e i n t h e U . S . i n c r e a s e d a t a g r e a t e r r a t e t h a n t h e r e s t o f t h e U . S . e c o n o m y f r o m 1 9 6 3 t o 1 9 7 2 . T h e u n u s u a l c o s t p r o b l e m s a r i s e f o r a s m a l l n u m b e r o f p e o p l e who u s e l a r g e a m o u n t s o f m e d i c a l s e r v i c e s b e c a u s e o f m a j o r i l l n e s s . A C C E S S P R O B L E M S Two t y p e s o f a c c e s s p r o b l e m s a r e i d e n t i f i e d : g e n e r a l a c c e s s p r o b l e m s a n d s p e c i a l a c c e s s p r o b l e m s . G e n e r a l a c c e s s p r o b l e m s o c c u r w i t h r e s p e c t t o p r i m a r y c a r e , e m e r g e n c y c a r e , home c a r e , a n d c a r e o u t s i d e o f c u s t o m a r y w o r k i n g h o u r s . T h e s e t y p e s o f c a r e d o n o t r e q u i r e t h e h i g h e r l e v e l s o f s k i l l f o u n d i n m e d i c a l s p e c i a l i s t s . I n many c a s e s , t h e y c o u l d b e p r o v i d e d b y p a r a - m e d i c a l s t a f f w o r k i n g u n d e r t h e g u i d a n c e o f a g e n e r a l p r a c t i t i o n e r . S p e c i a l a c c e s s p r o b l e m s a f f e c t s p e c i f i c g r o u p s o f p e o p l e , s u c h a s t h e p o o r , g h e t t o d w e l l e r s , a n d r u r a l p o p u l a t i o n s . H E A L T H P R O B L E M S T h i s w o r k . p o i n t s o u t c o n c e r n s t h a t h e a l t h l e v e l s a r e n o t a s h i g h i n t h e U . S . a s i n o t h e r d e v e l o p e d c o u n t r i e s a n d t h a t h e a l t h l e v e l s v a r y g r e a t l y a m o n g d i f f e r e n t g r o u p s . A d i s t u r b i n g t r e n d n o t e d i n t h i s w o r k i s t h e d e c l i n e i n h e a l t h l e v e l s a m o n g U . S . m a l e s ( w i t h t h e e x c e p t i o n o f i n f a n t s a n d t h e v e r y o l d ) b e t w e e n 1 9 6 3 a n d 1 9 7 2 . HOW I S H E A L T H J U D G E D ? T h e m e a s u r e o f t h e g e n e r a l l e v e l o f h e a l t h u s e d b y t h i s w o r k i s m o r t a l i t y . ( T h e p e r c e n t a g e o f a p o p u l a t i o n o f a g i v e n 29 a g e w h i c h c a n b e e x p e c t e d t o d i e b e f o r e a l a t e r a g e ) . I t i s a r g u e d t h a t o t h e r m e a s u r e s o f h e a l t h a r e h i g h l y c o r r e l a t e d w i t h m o r t a l i t y . A n i m p l i c i t a s s u m p t i o n t h r o u g h o u t t h e b o o k i s t h a t c h a n g e s t o t h e h e a l t h c a r e s y s t e m w h i c h w o u l d l e a d t o a n i n c r e a s e i n m o r t a l i t y w o u l d n o t b e a c c e p t a b l e . C o n v e r s e l y , c h a n g e s t h a t d o n o t l e a d t o a n i n c r e a s e i n m o r t a l i t y a r e j u d g e d o n t h e i r e c o n o m i c m e r i t s . E C ONOMIC A N A L Y S I S T h e t h r u s t o f t h i s w o r k i s t h a t m o r t a l i t y a n d h e a l t h c a r e c o s t s a r e l o o s e l y c o n n e c t e d . " T h e c o n n e c t i o n b e t w e e n h e a l t h a n d m e d i c a l c a r e i s n o t n e a r l y a s d i r e c t a s m o s t d i s c u s s i o n s w o u l d h a v e u s b e l i e v e . " ( F u c h s , 1 9 7 4 , p . 6) T h i s w o r k d i s c u s s e s m o r t a l i t y i n d i f f e r e n t a g e g r o u p s t o e x a m i n e t h e p o t e n t i a l * e f f e c t o f i n c r e a s e d m e d i c a l e x p e n d i t u r e s . I n f a n t m o r t a l i t y T h e f i r s t a g e g r o u p d i s c u s s e d i s i n f a n t s -(0 t o 1 y e a r s ) . I t n o t e s t h a t m o s t o f t h e d e c l i n e i n i n f a n t m o r t a l i t y , s i n c e 1 8 0 0 , h a s o c c u r r e d a s a r e s u l t o f h i g h e r l i v i n g s t a n d a r d s . A s n u t r i t i o n , s h e l t e r , q u a l i t y o f d r i n k i n g w a t e r , a n d i m p r o v e d s a n i t a t i o n h a v e b e c o m e a v a i l a b l e t o t h e g e n e r a l p o p u l a t i o n , i n f a n t m o r t a l i t y h a s d r o p p e d f r o m - t h e v e r y h i g h r a t e s ( 2 0 0 - 5 0 0 p e r 1 0 0 0 l i v e b i r t h s ) f o u n d i n 1 8 0 0 . T h i s r i s e i n l i v i n g s t a n d a r d s h a s b e e n v e r y e f f e c t i v e i n r e d u c i n g t h e m o r t a l i t y r a t e i n t h e 2 - m o n t h t o 1 2 - m o n t h a g e g r o u p . I t h a s b e e n s o s u c c e s s f u l t h a t m o s t i n f a n t d e a t h s o c c u r b e t w e e n b i r t h a n d 1 m o n t h o f a g e . R e d u c t i o n o f t h e d e a t h r a t e i n t h i s a g e g r o u p h a s p r o v e d v e r y d i f f i c u l t . I t i s s u g g e s t e d t h a t t h e m o t h e r ' s n u t r i t i o n , s m o k i n g 30 habits, and age (very young or very old) are more important than medical intervention in achieving further reductions in infant mortality. Childhood The tremendous advances in medical care since the 1930's are noted. These advances d r a s t i c a l l y reduced the death rate, from childhood diseases, through the use of drug and immunization therapies. Deaths from childhood diseases are r e l a t i v e l y rare and mortality in children between 1 and 15 i s quite low. There i s l i t t l e more that increased medical expenditures could do to lower mortality in t h i s age group. Young Adulthood For young American males, 3 out of 4 deaths occur by means of violence, including automobile and other accidents, suicide, and homicide. Behaviour-related mortality such as t h i s cannot be reduced by medical care. Early Middle-Age For male Americans in early middle age, the leading causes of death c i t e d are heart disease, cancer, accidents, suicide, c i r r h o s i s of the l i v e r , and homicide. L i f e s t y l e , including d i e t , exercise, tobacco consumption, alcohol consumption, and the propensity for violence are the chief contributors to mortality for t h i s age group. Again, increased medical expenditures w i l l not s i g n i f i c a n t l y decrease the death rate in t h i s age group. Late Middle-Age For males in late middle-age, heart disease and cancer dominate as causes of mortality. As these diseases are l i f e s t y l e 31 related, increased medical expenditures w i l l not s i g n i f i c a n t l y decrease mortality. In summary, this work presents a convincing case that mortality in the United States i s r e l a t i v e l y invariant once a basic l e v e l of health care has been attained. This basic l e v e l of care i s far lower than the l e v e l s normally available for most Americans when the work was written. This finding allows considerable scope to consider a l t e r n a t i v e methods of providing health care that reduce cost and increase access. On this basis the rationale for current expenditure patterns i s examined. This author states: "Although i t i s the patient rather than the physician who has the major influence on his health, the opposite i s true regarding the cost of medical care."(Fuchs, 1974, p. 6) The work goes on to point out that the importance of the physician in determining health costs results from the physician's control of medical procedures, h o s p i t a l i z a t i o n s , and drugs prescribed. The suggestion that overpayment of physicians, because of their monopoly pos i t i o n , i s a s i g n i f i c a n t cause of high health care costs i s rejected. The argument that providing more physicians i s a feasible method of improving access to the health care system i s examined. The problems with t h i s approach are the i m p o s s i b i l i t y of t r a i n i n g s u f f i c i e n t physicians to provide a l l of the primary care access required and the high cost of using highly trained physicians for t h i s purpose. It i s suggested that people want access to the health care system 24 hours per day, 7 days per week for primary and emergency care. Further, they want the person attending them to 32 b e f a m i l i a r w i t h t h e i r c a s e h i s t o r y . I t i s c l e a r t h a t t h e p r o v i s i o n o f m o r e h i g h l y t r a i n e d s p e c i a l i s t s i s n o t t h e w a y t o f i l l t h i s d e m a n d . B y c a r e f u l l y e x a m i n i n g t h e p r o b l e m w i t h a c c e s s t o t h e h e a l t h c a r e s y s t e m , t h i s w o r k m a d e i t c l e a r t h a t l e s s e x p e n s i v e o p t i o n s e x i s t t h a n s i m p l y e x p a n d i n g t h e s y s t e m . S p e c i a l a c c e s s p r o b l e m s a n d u n u s u a l c o s t p r o b l e m s w e r e d i s c u s s e d i n c o n j u n c t i o n w i t h m e t h o d s o f p a y i n g f o r h e a l t h c a r e . T h e p o i n t i s m a d e t h a t , n o m a t t e r how h e a l t h c a r e i s f i n a n c e d , i f m o r e h e a l t h c a r e i s d e s i r e d , t h e c o s t w i l l b e h i g h e r . H o w e v e r , i t i s n o t e d t h a t p a y m e n t o n a f e e f o r s e r v i c e b a s i s b y t h e p a t i e n t e f f e c t i v e l y e x c l u d e s t h e p o o r f r o m t h e h e a l t h c a r e s y s t e m a n d l e a v e s e v e r y o n e o p e n t o t h e p o s s i b i l i t y o f e x t r e m e l y h i g h c o s t s f r o m u n u s u a l d e m a n d s f o r h e a l t h c a r e s e r v i c e s . I t i s a l s o n o t e d t h a t f e e f o r s e r v i c e p a y m e n t p r o v i d e s l i t t l e i n c e n t i v e f o r t h e p h y s i c i a n t o m i n i m i z e t h e u s a g e o f h e a l t h c a r e . F o r t h e s e r e a s o n s , u n i v e r s a l h e a l t h i n s u r a n c e b a s e d o n a f i x e d p a y m e n t p e r p e r s o n i s a d v o c a t e d . I t i s i n t e r e s t i n g t o n o t e t h a t d e s p i t e t h e f a c t t h a t m o s t o f t h e a n a l y s i s i n t h i s w o r k i s e c o n o m i c i n n a t u r e , m a j o r f a c t o r s i n m a k i n g t h i s r e c o m m e n d a t i o n a r e v a l u e j u d g e m e n t s . T h e i m p o r t a n c e o f e q u a l i t y o f a c c e s s a n d p r o t e c t i o n f r o m u n u s u a l f i n a n c i a l r i s k s a r e b o t h v a l u e j u d g e m e n t s . S e v e r a l o t h e r r e c o m m e n d a t i o n s a r e m a d e t o r e d u c e t h e c o s t o f h e a l t h c a r e , w i t h o u t a d v e r s e l y a f f e c t i n g h e a l t h c a r e . T h e s e i n c l u d e : d e c e n t r a l i z e d h e a l t h c a r e d e l i v e r y s y s t e m s , m o r e 33 f l e x i b l e use of health resources/personnel, matching physician supply with demand, and matching hospital capacity with demand. In summary, t h i s work found that, beyond a f a i r l y minimal l e v e l of a v a i l a b i l i t y of health care services, the e f f e c t of the health care system on improving o v e r a l l health i s minimal. Improvements in health w i l l l i k e l y come from medical research or from changes in human behaviour. It also found that considerable scope exists for reducing the costs of the health care system and improving access to the system without endangering health. Major differences exist between the flood control problem and the health care problem. In p a r t i c u l a r , the effectiveness of the health care system can be measured by average numbers of deaths and average amounts of sickness (mortality and morbidity respectively). Because deaths and i l l n e s s happen frequently, t h i s work did not consider the a d v i s a b i l i t y of providing a health care system to handle infrequent events that would a f f e c t large numbers of people. In designing flood control systems, infrequent, catastrophic events must be considered. The amount used to evaluate flood control projects, expected annual flood damages, w i l l probably never occur in any year. Notwithstanding these differences, the methodology presented in t h i s work is extremely useful in evaluating the flood hazard. This work i s relevant because i t presents a method of integrating tangible and intangible factors to evaluate policy options. The methods presented in t h i s work are applicable to a wide range of problems including flood c o n t r o l . 34 THE FLOOD HAZARD Lulu Island i s 12000 hectares of f l a t land in a mountainous province, located within easy commuting distance of the downtown of a major metropolitan area. It i s , also, a low-lying island located in the Fraser River estuary. Lulu Island i s made up of poorly consolidated sandy s o i l s in the most t e c t o n i c a l l y active area of Canada. A l l of these factors have led to the creation of a flood hazard on Lulu Island. Its proximity to the c i t y of Vancouver and f l a t topography have created a s o c i a l and economic opportunity. Flat land i s excellent for the development of r e s i d e n t i a l , a g r i c u l t u r a l , commercial and i n d u s t r i a l properties. The mountainous nature of B r i t i s h Columbia's topography and of the Vancouver area has meant the supply of f l a t land for these purposes i s li m i t e d . The opportunity to f u l f i l l demands for f l a t land for r e s i d e n t i a l , commercial, and l i g h t i n d u s t r i a l development on Lulu Island has been recognized for at least 20 years. In 1966, v i r t u a l l y the whole western half of Lulu Island was zoned for urban uses, despite the fact that large parts of the urban zoned areas were in a g r i c u l t u r a l use. The opportunity has been and i s being realized by the growth of an urban municipality with a population of over 100,000 and property assessed at $6 b i l l i o n . Population has grown by 2/3 since 1971 and i s s t i l l growing. Residential, commercial, and i n d u s t r i a l development have grown with the population. The growth of commercial development has been esp e c i a l l y notable (see table III) since 1971. 35 It i s important to keep in mind the magnitude of the economic and s o c i a l opportunity presented by the development of Lulu Island in evaluating the flood hazard there. The p o s s i b i l i t y of potential flood damages, even extremely large potential flood damages, has not been s u f f i c i e n t to cause any hesitation in r e a l i z i n g t h i s opportunity. The high l e v e l of development that has occurred on Lulu Island i s a necessary prerequisite for a large flood hazard to e x i s t . If Lulu Island were undeveloped, no flood hazard would e x i s t . Conversely, i f there i s development, but no p o s s i b i l i t y of flooding, then there i s no flood hazard. Two sources of flooding exist around Lulu Island: the S t r a i t of Georgia and the Fraser River. To protect against flooding from these sources a system of dikes has been b u i l t around Lulu Island. Several possible mechanisms exist which could cause these dikes to f a i l and result in subsequent flooding. These mechanisms include winter storms, the spring freshet, and earthquake damage to the dikes. Conceivably, combinations of these events could also cause flooding, but as shown in table IV, the p r o b a b i l i t i e s of combined events are small. To understand the nature of these mechanisms and to evaluate the seriousness of a dike f a i l u r e caused by each mechanism, a good understanding of the topography, t i d a l ranges, expected flood depths, expected flood warning, and geology on Lulu Island i s necessary. In addition, an understanding of the 3 6 e a s e o f r e p a i r i n g a d i k e b r e a k u n d e r e a c h o f t h e f a i l u r e m e c h a n i s m s i s n e c e s s a r y . T O P O G R A P H Y L u l u I s l a n d i s e s s e n t i a l l y f l a t . T h e s t a n d a r d m e a s u r e m e n t s c a l e u s e d f o r e l e v a t i o n s i s b a s e d o n g e o d e t i c z e r o e l e v a t i o n ( G S C ) . Z e r o m e t r e s G S C i s s e t a t m e a n s e a l e v e l . F o r t h e r e s t o f t h i s d i s c u s s i o n a l l e l e v a t i o n s c i t e d a r e r e l a t i v e t o z e r o m e t r e s G S C . E l e v a t i o n s o n L u l u I s l a n d v a r y f r o m Om t o 4 . 0 m o v e r a l e n g t h o f 21 k m . E v e n t h i s r e l a t i v e l y n a r r o w r a n g e o v e r s t a t e s t h e e l e v a t i o n d i f f e r e n c e s f o r f l o o d c o n t r o l p u r p o s e s . A l l s t r u c t u r e s o n L u l u I s l a n d m u s t b e o n g r o u n d t h a t h a s b e e n b u i l t u p t o a t l e a s t . 9 m a n d o n l y 10% o f t h e t o t a l a r e a i s a b o v e 2 . 1 m . F u r t h e r , a l m o s t a l l o f t h e m o r e h e a v i l y d e v e l o p e d c o m m e r c i a l a n d r e s i d e n t i a l a r e a s a r e b e t w e e n . 9 a n d 2 . 1 m . S o i t c a n b e s e e n t h a t " f l a t " i s a n a p t d e s c r i p t i o n o f L u l u I s l a n d ' s t o p o g r a p h y . A m a j o r i m p l i c a t i o n o f t h i s f l a t t o p o g r a p h y i s t h a t a m a j o r b r e a k i n t h e d i k e s , a n y w h e r e o n L u l u I s l a n d , c o u l d f l o o d t h e w e s t e r n h a l f o f t h e i s l a n d , w h e r e m o s t u r b a n d e v e l o p m e n t i s c o n c e n t r a t e d , a n d p r o b a b l y w o u l d f l o o d t h e w h o l e i s l a n d . T I D A L R A N G E S T i d a l l e v e l s a r e i n h e r e n t l y v a r i a b l e p h e n o m e n a . T h e m a j o r d e t e r m i n a n t s o f t i d a l l e v e l s a r e t h e g r a v i t a t i o n a l e f f e c t s o f t h e m o o n a n d s u n , a t m o s p h e r i c p r e s s u r e , a n d w i n d s p e e d a n d d i r e c t i o n . T h e g r a v i t a t i o n a l e f f e c t s o f t h e s u n a n d m o o n p r o d u c e h i g h a n d l o w t i d e s t w i c e a d a y . I n a d d i t i o n , t h e g r a v i t a t i o n a l p u l l 37 of the moon produces two t i d a l cycles per month (lunar day). The combined ef f e c t of solar and lunar gravity usually produces a single highest tide for each month and for each year. The highest tide for each year due to g r a v i t a t i o n a l forces i s c a l l e d the highest normal t i d e . Tide l e v e l s vary inversely with atmospheric pressure. In e f f e c t , the S t r a i t of Georgia acts as an inverse barometer. When there i s a high pressure system over the S t r a i t of Georgia, water leve l s are depressed. Conversely, a low pressure system causes increased water l e v e l s . High winds that last over a period of several hours cause large waves. This wave set up adds to any t i d a l e f f e c t s or surge resulting from changing atmospheric pressure. In practice, the highest v e l o c i t y winds and lowest atmospheric pressures occur during winter storms. These storms occur from November to March. Comparing Table V to the land elevation on Lulu Island, i t can be seen that most of the island i s at elevations equal to or greater than the normal high tide l e v e l . This means that only severe tide surges during winter storms present a flood r i s k . A l l of the island i s above low tide l e v e l . CLIMATOLOGICAL CHANGE In recent years, there has been increasing speculation that ocean l e v e l s are not stable. The Atmospheric Environment Service has predicted a r i s e of up to 1m in sea l e v e l in the next 50 years, as a result of a world-wide warming trend. The results of th i s r i s e in sea l e v e l would put most of Lulu Island below 38 n o r m a l h i g h t i d e l e v e l , b u t w o u l d s t i l l l e a v e t h e i s l a n d w e l l a b o v e t h e . l o w t i d e l e v e l . E X P E C T E D F R A S E R R I V E R S T A G E S T h e F r a s e r R i v e r o n l y p o s e s a f l o o d h a z a r d d u r i n g t h e s p r i n g f r e s h e t . T h e s p r i n g f r e s h e t i s c a u s e d b y t h e a n n u a l s n o w m e l t i n t h e m o u n t a i n o u s a r e a s o f t h e F r a s e r R i v e r B a s i n . A n u m b e r o f f a c t o r s d e t e r m i n e t h e s t a g e w h i c h w i l l b e r e a c h e d d u r i n g t h e s p r i n g f r e s h e t . T h e s e i n c l u d e : - T h e a m o u n t o f s n o w o c c u r r i n g d u r i n g t h e c o u r s e o f t h e w i n t e r . H e a v i e r s n o w f a l l p r o d u c e s t h e p o t e n t i a l f o r a h i g h e r p e a k r u n o f f . - T h e s u d d e n n e s s a n d i n t e n s i t y o f s p r i n g w a r m i n g . A s u d d e n h o t s p e l l a f t e r a c o o l s p r i n g i n c r e a s e s t h e c h a n c e o f h i g h w a t e r . - T h e g e o g r a p h i c a l d i s t r i b u t i o n o f s p r i n g w a r m i n g . I f t h e w h o l e b a s i n w a r m s s i m u l t a n e o u s l y , h i g h e r r u n o f f w i l l r e s u l t . - T h e c o - o r d i n a t i o n w i t h w h i c h t h e t r i b u t a r i e s o f t h e F r a s e r R i v e r r e a c h t h e i r p e a k d i s c h a r g e . I f f l o o d p e a k s f r o m t r i b u t a r i e s o c c u r s o t h a t t h e y a r e s u p e r i m p o s e d o n e a c h o t h e r , t h e n t h e p e a k r e a c h e d w i l l b e h i g h e r . - T h e o c c u r r e n c e o f i n t e n s e r a i n f a l l t h a t c o i n c i d e s w i t h p e a k r u n - o f f f r o m s n o w m e l t . I f e n o u g h o f t h e s e f a c t o r s o c c u r i n a g i v e n y e a r , t h e p e a k r i v e r d i s c h a r g e c a n b e v e r y h i g h . T h e n o r m a l p e a k d i s c h a r g e i s 5 6 0 0 t o 8 5 0 0 m 3 / s . T h e h i g h e s t k n o w n d i s c h a r g e i s 1 7 , 0 0 0 m 3 / s . A 39 d i s c h a r g e g r e a t e r t h a n o r e q u a l t o t h i s o n e h a s a .005 p r o b a b i l i t y o f b e i n g e x c e e d e d i n a n y o n e y e a r . A c c u r a t e r i v e r s t a g e s h a v e n o t b e e n c a l c u l a t e d f o r r i v e r d i s c h a r g e s h i g h e r t h a n 1 7 , 0 0 0 m^/s. R i v e r s t a g e s f o r t h i s d i s c h a r g e s l o p e d o w n w a r d f r o m 3.7m a t t h e e a s t e r n e n d o f L u l u I s l a n d t o 2.5m a t t h e w e s t e r n e n d . A t t h e l o w e r ( w e s t e r n ) e n d o f L u l u I s l a n d t h e s e l e v e l s a r e .4 t o 1.6m a b o v e 9 0 % o f t h e i s l a n d . A t t h e u p p e r ( e a s t e r n ) e n d t h e y a r e a b o v e v i r t u a l l y t h e w h o l e i s l a n d . G E O L O G Y L u l u I s l a n d i s l o c a t e d i n t h e a r e a o f g r e a t e s t t e c t o n i c a c t i v i t y i n C a n a d a . I t i s c o m p o s e d o f l o o s e l y c o m p a c t e d s i l t y s a n d s a n d s a n d y s i l t s . T h e d e s i g n e a r t h q u a k e a c c e l e r a t i o n h a s a .0021 a n n u a l p r o b a b i l i t y o f o c c u r r e n c e . When L u l u I s l a n d ' s s o i l s a r e d r y t h e y a r e s t a b l e u n d e r t h e d e s i g n e a r t h q u a k e a c c e l e r a t i o n . H o w e v e r , b e c a u s e L u l u I s l a n d i s a l o w - l y i n g a r e a , t h e w a t e r t a b l e i s a l w a y s h i g h , e n s u r i n g t h a t s o i l s a r e s a t u r a t e d . U n d e r t h e s e c o n d i t i o n s , L u l u I s l a n d ' s l o o s e l y c o n s o l i d a t e d s o i l s a r e l i k e l y t o l i q u e f y t o a d e p t h o f 6-9m. T h e i n c r e a s e d p o r e p r e s s u r e t h a t r e s u l t s w h e n l i q u e f a c t i o n o c c u r s , l e a d s t o t h e e x p u l s i o n o f s a n d a n d w a t e r f r o m t h e g r o u n d . T h e e x p u l s i o n o f s a n d a n d w a t e r c a n l e a d t o d i f f e r e n t i a l s e t t l e m e n t , c a u s i n g c r a c k i n g i n f l a t a r e a s a n d s l u m p i n g i n a r e a s l o a d e d w i t h f i l l a n d o n s t e e p e r s l o p e s . A s t h e d i k e s f i t t h e s e c r i t e r i a , s i g n i f i c a n t d a m a g e t o t h e m w o u l d o c c u r . A c o m p a r i s o n o f n o r m a l t i d e a n d r i v e r l e v e l s w i t h e l e v a t i o n o n L u l u I s l a n d s h o w s t h a t m o s t a r e a s o f t h e i s l a n d w o u l d b e a t 40 or above high tide or r i v e r l e v e l s as long as the earthquake did not occur during the spring freshet or an extreme high t i d e . It should be noted that the predicted 1m r i s e in sea l e v e l from c l i m a t o l o g i c a l change a l t e r s t h i s s i t u a t i o n . Under the assumption of a 1m r i s e in sea l e v e l , t i d a l l e v e l s would be higher than most of Lulu Island during any high t i d e . The dikes surrounding Lulu Island are made of the same types of s o i l s as the rest of the island. During extreme events, the dikes are saturated and could be expected to l i q u e f y . Greater damage could be expected to the dikes i f they, rather than just the underlying s o i l s , are saturated. During extreme events, r i v e r and tide levels are higher than most of Lulu Island. For both of these reasons, the combined event (which is extremely unlikely) of earthquake and high tide or high river flows could produce severe flooding. DIKE REPAIR A key consideration in assessing the seriousness of any of the foregoing flood hazards, i s the ease with which a breach in the dikes can be repaired. Many organizational issues a f f e c t the c a p a b i l i t y to repair dikes under emergency conditions. At t h i s point, adequate organizational preparations w i l l be assumed. Given adequate flood fighting c a p a b i l i t i e s , the most important determinant of the ease of dike repair i s the v e l o c i t y with which water moves through a breach. If the water i s moving very slowly (or preferably not at a l l ) , dike repair i s r e l a t i v e l y straight forward. If the area behind the dikes i s dry enough that equipment can work in the 41 breach, dike repair i s even easier. On the other hand, i f water is pouring through the dike at 2 m/s dike repair can be a very d i f f i c u l t task. The easiest conditions for the repair of dikes are those in which i t i s dry behind the dikes and in the dike breach. Under these conditions, i t i s possible to work along the f u l l length of the breach simultaneously and any e a s i l y accessible, reasonably suitable material can be used to make the necessary repairs. Under these conditions, access to s u f f i c i e n t quantities of sand and earth moving equipment would be the l i m i t i n g factors in e f f e c t i n g repairs. Repairs made after an earthquake could probably be made under these conditions. Somewhat more d i f f i c u l t conditions occur when there i s water in the dike breach, but i t i s moving at extremely low ve l o c i t y . Under these conditions i t would not be possible to work behind the dikes because wet and/or muddy conditions would prevent access. Any reasonably suitable material could be used in repairing the breach, but i t would be necessary to end dump material into the dike breach from on top of the dike at either end of the breach. The l i m i t i n g factor in making repairs would be the l o g i s t i c s of maneouvering trucks to and from the ends of the dike breach along the top of the r e l a t i v e l y narrow dikes. Repairs made after a severe winter storm would probably require t h i s technique. The most d i f f i c u l t conditions occur when water pours through a breach at appreciable v e l o c i t i e s . A breach during the spring freshet could result in v e l o c i t i e s of 2 m/s. Water moving 42 a t t h i s v e l o c i t y i s c a p a b l e o f m o v i n g 5 cm d i a m e t e r r o c k . L a r g e r r o c k w o u l d b e d e s i r a b l e f o r r e p a i r w o r k ; a n d w o u l d b e n e c e s s a r y f o r t h e f i n a l s t a g e s o f c l o s u r e . T h e e n d s o f t h e b r e a c h w o u l d b e u n s t a b l e a n d a n y s m a l l e r m a t e r i a l s ( s u c h a s s a n d ) d u m p e d i n t o t h e b r e a c h w o u l d b e s w e p t a w a y b y t h e w a t e r p o u r i n g t h r o u g h t h e b r e a c h . S e v e r a l s t r a t e g i e s h a v e b e e n s u g g e s t e d t o d e a l w i t h t h i s s i t u a t i o n . T h e y i n c l u d e : - C a t c h t h e b r e a c h e a r l y b e f o r e i t h a s a c h a n c e t o e n l a r g e . E n d dump r o c k i n t o t h e b r e a c h t o c l o s e i t . T h i s s t r a t e g y was s u c c e s s f u l l y a p p l i e d i n C h i l l i w a c k f o r a s m a l l b r e a c h i n 1 9 4 8 . O t h e r b r e a c h e s o p e n e d t o o v e r 100m i n o n l y a f e w m i n u t e s d u r i n g t h e s a m e f l o o d . T h i s s t r a t e g y c a n o n l y b e e x p e c t e d t o w o r k f o r a l i m i t e d n u m b e r o f b r e a c h e s . - B u i l d a r i n g d i k e a r o u n d t h e b r e a c h . T h i s a p p r o a c h w i l l w o r k a s l o n g t h e r e a r e n ' t m u l t i p l e b r e a c h e s . I t i s , h o w e v e r , s l o w b e c a u s e b e c a u s e i t r e q u i r e s s e v e r a l t i m e s a s m u c h d i k e t o b e b u i l t a s t h e l e n g t h o f t h e b r e a c h . A c o n s i d e r a b l e a m o u n t o f f l o o d i n g c a n o c c u r w h i l e t h e r i n g d i k e i s b e i n g b u i l t . - L e t t h e w a t e r i n s i d e t h e d i k e s p o n d u p t o t h e l e v e l o f t h e r i v e r o u t s i d e o f t h e b r e a c h . When t h i s h a p p e n s t h e v e l o c i t y t h r o u g h t h e b r e a c h w i l l d r o p t o n e a r z e r o a n d t h e b r e a c h c a n b e d i r e c t l y r e p a i r e d . A s f l o o d d a m a g e i s l a r g e l y d e t e r m i n e d b y d e p t h o f f l o o d i n g , p o n d i n g o n 43 L u l u I s l a n d would r e s u l t i n g r e a t e r damage than i f no d i k e s e x i s t e d . - D e l i b e r a t e l y breach the di k e s on the downstream end of the i s l a n d to l e t the water d r a i n o f f the i s l a n d . T h i s approach would prevent ponding. The use of t h i s s t r a t e g y would probably mean that f l o o d i n g would l a s t u n t i l the r i v e r l e v e l dropped c l o s e to the bankf u l l e v e l . From the fo r e g o i n g d i s c u s s i o n , i t i s c l e a r that a breach with water c o n t i n u o u s l y f l o w i n g through i t i s the most d i f f i c u l t type to r e p a i r . TIDAL RELIEF I m p l i c i t i n the f o r e g o i n g d i s c u s s i o n of dike r e p a i r i s the concept of t i d a l r e l i e f . During low t i d e , there i s a r e d u c t i o n i n the v e l o c i t y of water f l o w i n g through a breach. T h i s p r o v i d e s an o p p o r t u n i t y to r e p a i r d i k e s under much l e s s d i f f i c u l t c o n d i t i o n s . These c o n d i t i o n s make dik e r e p a i r much f a s t e r and, hence, l i m i t the amount of the r e s u l t i n g f l o o d i n g . While i t i s true t h a t any t i d a l r e l i e f i s welcome i n a f l o o d s i t u a t i o n , to provide a r e a l o p p o r t u n i t y to r e p a i r the d i k e s , low t i d e must reduce water l e v e l s to l e v e l with or below the bottom of the breach f o r s e v e r a l hours d u r i n g each t i d a l c y c l e . As can be seen from F i g . 3, s i g n i f i c a n t t i d a l r e l i e f occurs f o r the western h a l f of L u l u I s l a n d . T i d a l r e l i e f from the s p r i n g f r e s h e t i s not great enough to f i t t h i s c o n d i t i o n i n the eastern h a l f of L u l u I s l a n d . 44 It i s reasonable to assume that a l l dike breaks on the western half of Lulu Island, from any source, can be repaired in. under 24 hours. On the other hand, the least that could be expected from a major dike break on the eastern end of the island from the spring freshet i s several days of flooding. FLOOD DEPTHS Predicted flood depths vary for the d i f f e r e n t types of hazard. The major determinants of flood depth are the length of time to repair the dikes, the difference in elevation between the water outside the dikes and the ground inside, and the size of any dike breaches. The length of time to repair a breach i s determined by the size of the breach and the techniques that can be applied to eff e c t repairs. An extremely large breach would take longer to f i x because more material would be required. The techniques that could be applied to repair, a breach depend mainly on the presence or absence of t i d a l r e l i e f . Without t i d a l r e l i e f , water is constantly moving across a breach, making the task more d i f f i c u l t . The elevation difference across a breach determines the volumetric flow rate through the breach. The elevation difference can be expected to be greatest for a breach on the eastern end of Lulu Island. A breach from earthquake damage not associated with an extreme hydrological event would have a much smaller elevation difference. 45 The width of a dike breach i s e s s e n t i a l l y random. One thing is c l e a r , a wider breach w i l l allow more water through than a narrower one. The deepest flood depths would result from a breach on the eastern end of Lulu Island from which the water ponded to either the l e v e l of the inflow water or the l e v e l of the dikes (whichever i s lower). Expected flood depths under these conditions would be 2.3m. If no dikes existed or deliberate breaches were made in the dikes in the western end of Lulu Island to prevent ponding, expected flood depths would be 1.2m. It should be noted that for a major breach in the dikes in eastern Lulu Island, a similar length breach would have to be opened downstream to prevent ponding above the 1.2m l e v e l . Flooding from a winter storm could be expected to increase by 6 cm per t i d a l c ycle. As thi s sort of flooding would be subject to t i d a l r e l i e f i t should be possible to repair any damage within 24 hours. Damage from th i s l e v e l of flooding would probably remain within acceptable bounds. Flooding from earthquake damage in the absence of an extreme hydrologic event would be limited in extent because most of Lulu Island i s above normal high t i d e . However, i f sea l e v e l r i s e s over the next 50 years due to clima t o l o g i c a l change, serious flooding would result i f repairs were not made quickly. Potential damage from t h i s source i s not a serious risk and may not materialize unless the predicted r i s e in sea l e v e l does, in fact, take place. 46 F L O O D WARNING O f t h e v a r i o u s t y p e s o f f l o o d i n g , t h e s p r i n g f r e s h e t i s t h e o n l y o n e f o r w h i c h a c c u r a t e w a r n i n g s c o u l d b e i s s u e d b e f o r e a b r e a c h o c c u r s . A p p r o x i m a t e l y f o u r d a y s w a r n i n g c o u l d b e e x p e c t e d f o r t h i s t y p e o f f l o o d i n g . T h e s e w a r n i n g s w o u l d o n l y p r e d i c t h i g h w a t e r l e v e l s a n d t h e d a n g e r o f f l o o d i n g . T h e y w o u l d a l l o w s u f f i c i e n t t i m e t o s e t u p d i k e p a t r o l s , f l o o d f i g h t i n g c r e w s , a n d t o move some p r o p e r t y t o h i g h e r l e v e l s . I t i s d o u b t f u l t h a t a f u l l s c a l e e v a c u a t i o n w o u l d b e o r d e r e d o n t h i s b a s i s . F r o m t h e d e s c r i p t i o n o f t i d a l f l o o d i n g , i t i s c l e a r t h a t a m p l e o p p o r t u n i t y w o u l d e x i s t t o e v a c u a t e L u l u I s l a n d ( s h o u l d i t b e n e c e s s a r y ) b e f o r e f l o o d d e p t h s w e r e s u f f i c i e n t t o c r i p p l e r o a d t r a n s p o r t a t i o n . F l o o d i n g f r o m t h e s p r i n g f r e s h e t i n t h e e a s t e r n e n d o f L u l u I s l a n d w o u l d a l m o s t c e r t a i n l y r e q u i r e t h e e v a c u a t i o n o f L u l u I s l a n d f o r a l l e x c e p t t h e s m a l l e s t o f b r e a c h e s . W a t e r l e v e l s w o u l d b e l e s s t h a n .3m f o r 12 h o u r s a f t e r a 200m b r e a c h . F o r a 400m b r e a c h , o n l y 8 h o u r s w o u l d e l a p s e b e f o r e t h e .3m l e v e l was r e a c h e d . A s e v a c u a t i o n w o u l d b e m u c h m o r e d i f f i c u l t a t f l o o d d e p t h s a b o v e .3m, 8 t o 12 h o u r s p r o v i d e s a n o u t s i d e l i m i t t o t h e t i m e a v a i l a b l e f o r o r d e r l y e v a c u a t i o n . B e y o n d t h i s t i m e , t h e h i g h w a y s y s t e m w o u l d b e i m p a s s a b l e a n d e v a c u a t i o n w o u l d h a v e t o b e c a r r i e d o u t b y b o a t o r h e l i c o p t e r . R A T I N G OF F L O O D H A Z A R D S T h r e e m e c h a n i s m s w e r e i d e n t i f i e d w h i c h c o u l d c a u s e t h e d i k e s t o f a i l : w i n t e r s t o r m s , t h e s p r i n g f r e s h e t , a n d e a r t h q u a k e d a m a g e . I t i s c l e a r f r o m t h e f o r e g o i n g d i s c u s s i o n t h a t t h e d e p t h 47 a n d d u r a t i o n o f f l o o d i n g f r o m t h e s e m e c h a n i s m s m a k e s t h e s p r i n g f r e s h e t t h e m o s t s e r i o u s h a z a r d . F l o o d i n g c a u s e d b y w i n t e r s t o r m s i s a s e r i o u s h a z a r d o n l y i f n o e f f o r t s a r e m ade t o r e p a i r t h e d i k e s . F l o o d i n g f r o m e a r t h q u a k e h a z a r d i s m o r e a m a t t e r o f c o n c e r n t h a n a d a n g e r a t c u r r e n t s e a l e v e l . I f s e a l e v e l r i s e s , f l o o d i n g f r o m e a r t h q u a k e d a m a g e w o u l d b e a h a z a r d o n t h e same o r d e r a s f l o o d i n g f r o m w i n t e r s t o r m s . No s t u d i e s h a v e b e e n d o n e t o d e t e r m i n e t h e e c o n o m i c c o s t o f t i d a l b a s e d f l o o d i n g . T h e l o w d e p t h o f f l o o d i n g , h o w e v e r , p r e c l u d e s l a r g e s c a l e e c o n o m i c d a m a g e . E x t e n s i v e s t u d i e s w e r e d o n e o n t h e f l o o d d a m a g e f r o m t h e s p r i n g f r e s h e t a s p a r t o f t h e F r a s e r R i v e r U p s t r e a m S t o r a g e R e p o r t ( 1 9 7 6 ) . By u p d a t i n g t h e s e s t u d i e s t o a c c o u n t f o r i n f l a t i o n a n d p o p u l a t i o n i n c r e a s e , f l o o d d a m a g e h a s b e e n e s t i m a t e d a t r o u g h l y $ 5 0 0 m i l l i o n ( s e e T a b l e V I ) F a c t o r s not-t a k e n i n t o a c c o u n t i n t h i s e s t i m a t e i n c l u d e : t h e l a r g e i n c r e a s e i n c o m m e r c i a l d e v e l o p m e n t t h a t h a s t a k e n p l a c e o n L u l u I s l a n d s i n c e t h e s t u d y w a s d o n e , t h e t r e n d t o w a r d b u i l d i n g b e t t e r q u a l i t y h o u s e s , a n d t h e t r e n d t o w a r d d e v e l o p i n g b a s e m e n t s . T h e s e f a c t o r s c o u l d m a k e t h e a c t u a l f l o o d d a m a g e c o n s i d e r a b l y h i g h e r t h a n t h e a b o v e e s t i m a t e . F i n a l l y , t h i s e s t i m a t e d o e s n o t i n c l u d e i n t a n g i b l e c o s t s f r o m f l o o d d a m a g e . T h e s o c i a l u p h e a v a l o f s h u t t i n g d o w n a c o m m u n i t y , o f 1 0 0 , 0 0 0 p o p u l a t i o n , f o r o v e r a m o n t h a n d d i s r u p t i n g t h e l i f e o f t h a t c o m m u n i t y f o r t h e n e x t 6 m o n t h s w h i l e r e p a i r s a r e m a d e , i s d i f f i c u l t t o q u a n t i f y , b u t s h o u l d n o t b e n e g l e c t e d i n d e t e r m i n i n g f l o o d p r o t e c t i o n l e v e l s . 48 RISK ANALYS IS AND PERCEPTION In addition to knowledge of the extent of a hazard, knowledge of the l i k e l i h o o d of occurrence i s necessary to judge what constitutes an appropriate response. The o v e r a l l response to a hazard can be determined i n t u i t i v e l y or by the use of s t a t i s t i c a l modelling. If the response to a hazard i s judged i n t u i t i v e l y , the process i s c a l l e d risk perception. If s t a t i s t i c a l modelling i s combined with quantitative measures of the extent of a hazard to determine an appropriate response, the process i s c a l l e d risk analysis. Both risk analysis and risk perception can be used to determine the appropriate l e v e l of protection against flooding in B r i t i s h Columbia. In essence, both methods try to answer the question "How safe i s safe enough?". There i s , however, no guarantee that both methods w i l l arrive at the same answer. The judgement of what constitutes an appropriate l e v e l of protection i s a problem that has no calculable solution. A l l costs of flooding are not economically q u a n t i f i a b l e . The following description of the Pearl River flood in Jackson, M i s s i s s i p p i in A p r i l of 1979 describes the s o c i a l upheaval from a flood. "As the flood waters receded the dimensions of the r e s i d e n t i a l property damage became apparent. Flood damages are p a r t i c u l a r l y depressing. Not only have people suffered losses, but they also must endure an excruciating clean up process. The house i s normally a mess. It smells. The water may be contaminated. The e l e c t r i c i t y is usually damaged meaning one must t o i l in the dark. Snakes can be present. Cherished family belongings have to be discarded into a growing trash pile."(Anderson and Weinrobe, 1979, p. 5) More d e t a i l i s provided on the next page. 49 " T h e l o s s o f f u r n i t u r e , f i x t u r e s , a n d p e r s o n a l b e l o n g i n g s p r o d u c e d t h e m o s t t o r t u o u s l o s s e s . W a l l b o a r d a n d c a r p e t i n g a r e i m p e r s o n a l a n d c a n b e r e p l a c e d . T h e l o s s o f f a m i l y p h o t o g r a p h s , a f a v o r i t e t a b l e , t h e d i n i n g r o o m s e t o r p i a n o g o e s w e l l b e y o n d t h e m o n e t a r y v a l u e o f t h e s e i t e m s . T h e p i l e s o f t h e s e a n d o t h e r o b j e c t s t h a t a c c u m u l a t e d i n f r o n t o f d a m a g e d h o u s e s was o n e o f t h e s a d d e r s i g h t s o b s e r v e d i n J a c k s o n . " ( A n d e r s o n a n d W e i n r o b e , 1 9 7 9 , p . 6) I n a d d i t i o n , n o t a l l c o s t s o f f l o o d p r o t e c t i o n a r e q u a n t i f i a b l e . I n p a r t i c u l a r t h e e n v i r o n m e n t a l c o s t s o f f l o o d c o n t r o l m e a s u r e s a r e o f t e n q u i t e d i f f i c u l t t o d e t e r m i n e . I t h a s , a l s o , b e e n made c l e a r o v e r t h e y e a r s t h a t n o t a l l d e c i s i o n s c o n c e r n i n g f l o o d c o n t r o l a r e made o n a p u r e l y e c o n o m i c b a s i s . T h e e c o n o m i c s o f d a m m i n g t h e F r a s e r a t L i l l o o e t ( 2 5 0 k i l o m e t e r s n o r t h e a s t o f V a n c o u v e r ) w e r e n e v e r c o n s i d e r e d i n d e t a i l b e c a u s e o f t h e n e g a t i v e i m p a c t s o f t h e dam o n t h e s a l m o n f i s h e r y . R I S K P E R C E P T I O N R e c e n t r e s e a r c h i n t o r i s k p e r c e p t i o n h a s s h e d some l i g h t o n a n i m p o r t a n t c o m p o n e n t o f t h e d e t e r m i n a n t o f a p p r o p r i a t e p r o t e c t i o n l e v e l s . T h e p e r c e p t i o n o f r i s k i s i m p o r t a n t b e c a u s e t h e i n t u i t i v e a s s e s s m e n t o f a h a z a r d i n f l u e n c e s b o t h i n d i v i d u a l a n d c o l l e c t i v e r e a c t i o n t o r i s k . B e h a v i o u r w i t h r e s p e c t t o r i s k c a n b e c l a s s i f i e d a s r i s k p r o n e , r i s k n e u t r a l , o r r i s k a v e r s e . ( S l o v i c e t . a l . , 1 9 8 4 ) . - R i s k p r o n e b e h a v i o u r w o u l d p a y m o r e t o a v o i d many s m a l l a c c i d e n t s t h a n t o a v o i d o n e l a r g e o n e c a u s i n g t h e s a m e a m o u n t o f d a m a g e . 50 - Risk neutral behaviour would pay the same amount to avoid many small accidents as to avoid one large one causing the same amount of damage. - Risk averse behaviour would pay more to avoid one large accident than many small accidents causing the same amount of damage.* Research into risk perception has shown that people determine their response to risk based on a number of q u a l i t i e s of the r i s k . These q u a l i t i e s have been resolved into two factors: dread ri s k and unknown risk as shown in F i g . 2. Flood risk has been drawn onto F i g . 2 as an open c i r c l e based on the fact that the same technology i s used to predict dam f a i l u r e s as dike f a i l u r e s , but dam f a i l u r e s are more serious hazards. Dam f a i l u r e s involve deeper water moving at much higher v e l o c i t i e s , and carrying larger debris. For these reasons dam f a i l u r e s are more l i k e l y to cause f a t a l i t i e s than the slow r i s i n g flood waters t y p i c a l of the Fraser River. The position of the flood hazard in the lower l e f t quadrant of F i g . 2 leads to the hypothesis, based on ris k perception, that response to the flood hazard i s ris k prone. *I t should be noted that t h i s d e f i n i t i o n of risk averse behaviour d i f f e r s from the d e f i n i t i o n of ris k averse behaviour put forward in Book and Pr i n c i c during the Fraser River Upstream Storage Report. In that work, risk averse behaviour was defined as the d i r e c t i o n of more resources toward avoiding a hazard than the optimum l e v e l of expenditures derived from cost benefit analysis using expected costs and benefits would warrant. This is similar to the conventional d e f i n i t i o n from decision theory. P r a c t i c a l problems occur with th i s l a t t e r d e f i n i t i o n because i t i s impossible to separate unmeasured intangibles from the amount that can be assigned to risk aversion. 51 T h e c u r r e n t f l o o d c o n t r o l p o l i c y was n o t j u s t i f i e d o n e c o n o m i c g r o u n d s . T h i s f a c t was r e c o g n i z e d i n t h e l a s t e c o n o m i c a n a l y s i s o f t h e f l o o d h a z a r d o n L u l u I s l a n d : " T h e m o s t common p r a c t i c e i s t o b u i l d a s t r u c t u r e s o a s t o p r o t e c t a g a i n s t some l a r g e " d e s i g n " f l o o d d e t e r m i n e d m o r e b y p o l i t i c a l d e c r e e o r a r b i t r a r y s e l e c t i o n t h a n b y a n y s t a t e d e c o n o m i c a l l y r a t i o n a l c r i t e r i o n . " ( B o o k a n d P r i n c i c , 1 9 7 5 , p . 5) T h e d e s i g n f l o o d f o r a l l f l o o d p r o t e c t i o n w o r k s i n B r i t i s h C o l u m b i a i s a f l o o d t h a t h a s a . 0 0 5 a n n u a l p r o b a b i l i t y o f o c c u r r i n g . T h i s f l o o d i s a l s o r e f e r r e d t o a s t h e 1 i n 2 0 0 y e a r f l o o d . S e t t i n g a l l h a z a r d s t o t h e s a m e p r o b a b i l i t y o f o c c u r r e n c e i s , h o w e v e r , a r i s k p r o n e s t r a t e g y . T h e l e v e l o f p r o t e c t i o n f o r b o t h L u l u I s l a n d a n d D e w d n e y D i k i n g A r e a , a s m a l l a g r i c u l t u r a l a r e a 80 k i l o m e t e r s e a s t o f V a n c o u v e r , h a s b e e n s e t t o t h e same l e v e l . D e w d n e y D i k i n g A r e a , a s m a l l a n d l i g h t l y p o p u l a t e d a r e a , i s a s m a l l e r f l o o d h a z a r d t h a n L u l u I s l a n d . B e c a u s e t h e l e v e l o f p r o t e c t i o n i s t h e same f o r t h e t w o a r e a s , m o r e i s s p e n t t o a v o i d e a c h d o l l a r o f f l o o d d a m a g e f o r t h e s m a l l e r h a z a r d i n t h e D e w d n e y D i k i n g A r e a , t h a n f o r t h e l a r g e r h a z a r d , L u l u I s l a n d . T h u s i t c a n b e s e e n t h a t t h i s m e t h o d o f d e t e r m i n i n g l e v e l s o f p r o t e c t i o n i s r i s k p r o n e . P r e s e n t l y , t h e e x p e c t e d f l o o d d a m a g e f o r L u l u I s l a n d , a f t e r a l l o w a n c e h a s b e e n made f o r t h e p r o t e c t i o n a f f o r d e d b y t h e d i k e s , i s $ 1 5 m i l l i o n a n n u a l l y ( s e e A p p e n d i x C ) . F u n d i n g was r e f u s e d f o r W e s t h a m I s l a n d u n d e r t h e f e d e r a l p r o v i n c i a l c o s t s h a r i n g p r o g r a m b e c a u s e p r o t e c t i o n w o u l d n o t h a v e b e e n c o s t 52 j u s t i f i e d at the 1 in 200 year l e v e l . * More f l e x i b i l i t y in setting the l e v e l of protection i s necessary. The gap between the current l e v e l of protection, based on c o l l e c t i v e r i s k preception and the expected costs of flooding Lulu Island i s p a r t i c u l a r l y serious. It should be e s p e c i a l l y worrisome to the federal government because the federal-p r o v i n c i a l cost sharing formula for flood damage allocates 90% of the costs of flood damage in B r i t i s h Columbia over $10 m i l l i o n to the federal government. RISK ANALYSIS The other methods suggested in the l i t e r a t u r e for determining lev e l s of protection are based on risk analysis. They are: - Set l e v e l s of protection to minimize the expected costs of flood damage plus the costs of flood prevention measures. - Use a rule of thumb system to match flood protection with the size of the flood hazard. Setting protection to minimize costs i s a variant of the ris k - b e n e f i t analysis applied to the provision of health care services. The analysis applied to health care suggested ways to minimize the costs of providing health care without increasing the expected number of deaths. A similar method of setting flood protection l e v e l s i s also limited by the r e s t r i c t i o n that the chance of loss of l i f e not * The p r o v i n c i a l government has subsequently provided protection for Westham Island to a lower standard than the 1 in 200 year l e v e l . 53 b e i n c r e a s e d i n o r d e r t o m i n i m i z e c o s t s . F o r f l o o d c o n t r o l o n L u l u I s l a n d t h i s l i m i t a t i o n i s n o t v e r y s e v e r e b e c a u s e t h e r e w o u l d b e a d e q u a t e t i m e t o e v a c u a t e t h e i s l a n d b e f o r e o r a f t e r a b r e a c h i n t h e d i k e s o c c u r r e d . T h i s m e t h o d i s t h e o r e t i c a l l y a t t r a c t i v e b e c a u s e i t p r o v i d e s a n o p t i m u m l e v e l o f p r o t e c t i o n t h a t c a n b e u s e d . H o w e v e r , s o m e p r a c t i c a l p r o b l e m s e x i s t i n a p p l y i n g t h i s m e t h o d . I t d o e s n o t t a k e i n t o a c c o u n t i n t a n g i b l e s . I n t a n g i b l e s e x i s t i n d e t e r m i n i n g t h e c o s t s o f f l o o d p r o t e c t i o n w o r k s a n d t h e c o s t s o f f l o o d d a m a g e . T h e e n v i r o n m e n t a l d a m a g e t h a t c a n b e d o n e w h e n c o n s t r u c t i n g f l o o d c o n t r o l w o r k s c a n b e b o t h g r e a t a n d d i f f i c u l t t o m e a s u r e . S i m i l a r l y , t h e c o s t s o f d e v e l o p m e n t t h a t d o e s n ' t o c c u r b e c a u s e o f z o n i n g o r f l o o d p r o o f i n g r e q u i r e m e n t s a n d t h e c o s t s o f s o c i a l u p h e a v a l r e s u l t i n g f r o m a m a j o r f l o o d a r e d i f f i c u l t t o m e a s u r e . E v e n w h e r e i t i s p o s s i b l e t o q u a n t i f y t h e c o s t s a n d b e n e f i t s , t h e a n a l y s i s t o d e t e r m i n e t h e m i s d i f f i c u l t a n d e x p e n s i v e . F i e l d s u r v e y s a r e r e q u i r e d f o r i n d u s t r i a l , c o m m e r c i a l a n d r e s i d e n t i a l p r o p e r t i e s . E n g i n e e r i n g w o r k m u s t b e d o n e t o d e t e r m i n e c o s t s o f f l o o d p r o t e c t i o n a t v a r y i n g l e v e l s o f p r o t e c t i o n . T h e e x t r a c a s e s t h a t m u s t b e c o n s i d e r e d , m a k e t h e a n a l y s i s o f a f l o o d c o n t r o l p r o j e c t m o r e d i f f i c u l t a n d r e q u i r e m o r e t i m e . T h e f i n a l p r o b l e m w i t h t h i s a p p r o a c h i s t h a t i t i s h e a v i l y d e p e n d e n t o n t h e a s s u m p t i o n s m a d e a b o u t t h e c o u r s e o f f u t u r e d e v e l o p m e n t i n t h e a r e a t o b e p r o t e c t e d . P r e d i c t i n g g r o w t h o v e r a 50 y e a r p e r i o d i s a n i n h e r e n t l y i n e x a c t p r o c e s s . 54 This approach i s t h e o r e t i c a l l y optimal, but, e s p e c i a l l y for smaller diking d i s t r i c t s , i s expensive and cumbersome to apply. The r e s u l t s for a large diking d i s t r i c t such as Lulu Island would be worthwhile and probably enlightening. Another approach that has been widely applied to the evaluation of dam safety i s to use a rule of thumb system to roughly match the protection l e v e l to the hazard l e v e l . An example rule of thumb system has been derived from the one used by the United States Army Corps of Engineers, and i s presented in Table VIII. There are several disadvantages to the use of a rule of thumb chart. It does not attempt to i d e n t i f y an optimal l e v e l of protection and i t does not take into account d i f f e r i n g costs to provide protection to given l e v e l . In terms of the second point, the costs of flood protection are affected by expected water l e v e l s , the shape and size of the diking area, and the method used to achieve flood protection. C i r c u l a r diking areas are less expensive per hectare enclosed than long, t h i n , banana-shaped diking areas. The costs of building dams for flood protection have proven extremely high in B r i t i s h Columbia. Notwithstanding these problems, t h i s method should not be dismissed out of hand. This method provides a better f i t in assigning protection l e v e l s to areas with d i f f e r e n t hazard leve l s than i s provided by the single province-wide l e v e l of protection in use today. 5 5 It i s easy to implement from a procedural point of view. The table f i t s on one piece of paper and can be e a s i l y memorized. Combined with professional judgement, i t can take intangibles and future growth patterns into account. Where appropriate and j u s t i f i e d , economic modelling and detailed engineering design could be used to adjust these guidelines. The advantages of t h i s method are that i t i s easy to implement and allows the f l e x i b i l i t y of professional judgement to be applied in resolving issues involving uncertainty and d i f f i c u l t i e s in q u a n t i f i c a t i o n . It cannot, however, be applied without taking the i m p l i c i t cost base into account. From the foregoing discussion, each of the methods suggested has drawbacks. The following method draws on the strengths of a l l three methods that have "been discussed: - A minimum l e v e l of protection be set for extremely low hazard areas. An event with .02 annual p r o b a b i l i t y of exceedence seems reasonable. - A rule of thumb chart be used for a l l but the largest diking areas or areas in which there is a clear p r o b a b i l i t y of loss of l i f e . - Formal r i s k benefit analysis be done for the largest areas and those in which loss of l i f e i s a factor. The problems with the current method of setting protection l e v e l s for Lulu Island have increased with the amount of development on Lulu Island. The expected damage increases with development and decreases as le v e l s of protection are increased. Since the last upgrade to the dikes, development has increased 56 t h e f l o o d h a z a r d o n L u l u I s l a n d , b u t p o l i t i c a l d e c r e e h a s h e l d t h e l e v e l o f p r o t e c t i o n , a n d h e n c e t h e r i s k , c o n s t a n t . T h e r e s u l t h a s b e e n i n c r e a s e d e x p e c t e d f l o o d d a m a g e . A s d e v e l o p m e n t o n L u l u I s l a n d i s c o n t i n u i n g a n d t h e p o l i c y f o r d e t e r m i n i n g t h e l e v e l o f p r o t e c t i o n h a s n o t c h a n g e d , t h e t r e n d w i l l b e f o r e x p e c t e d f l o o d d a m a g e t o c o n t i n u e t o i n c r e a s e . E v e n t u a l l y , i t w i l l b e n e c e s s a r y t o i n c r e a s e t h e l e v e l o f p r o t e c t i o n . A C C U R A C Y OF H Y D R O L O G I C A L P R E D I C T I O N S T h r o u g h o u t t h i s p a p e r , t h e s t a t i s t i c a l p r e d i c t i o n s o f t h e p r o b a b i l i t i e s o f h y d r o l o g i c a l e v e n t s h a v e b e e n t a k e n a s a g i v e n . F o r t h e F r a s e r R i v e r B a s i n , p r e d i c t i o n s o f e v e n t s w i t h a n n u a l p r o b a b i l i t i e s a s l o w a s t h e d e s i g n s t a n d a r d o f . 0 0 5 a r e r e a s o n a b l y w e l l s u p p o r t e d . A t t e m p t s t o p r e d i c t p r o b a b i l i t i e s o f e v e n t s t h a t h a p p e n l e s s f r e q u e n t l y t h a n t h e d e s i g n e v e n t s a r e l e s s w e l l s u p p o r t e d . T h e l o w e r t h e p r o b a b i l i t y o f o c c u r r e n c e , t h e g r e a t e r t h e u n c e r t a i n t y t h a t m u s t b e a t t a c h e d t o e s t i m a t e s o f t h e p r o b a b i l i t y o f o c c u r r e n c e . T h i s u n c e r t a i n t y c o m e s f r o m t w o s o u r c e s . F i r s t , g i v e n a s e t o f v a l u e s f r o m w h i c h a p r o b a b i l i t y d i s t r i b u t i o n i s e s t i m a t e d , o n l y o n e o f a w i d e r a n g e o f d i s t r i b u t i o n s c o u l d p l a u s i b l y b e t h e c o r r e c t d i s t r i b u t i o n . S e c o n d , i t i s p o s s i b l e t h a t e v e n t s w i t h e x t r e m e l y l o w p r o b a b i l i t i e s o f o c c u r r e n c e d o n o t f i t t h e d i s t r i b u t i o n d e r i v e d f r o m a v a i l a b l e d a t a b e c a u s e t h e y a r e c a u s e d b y d i f f e r e n t p r o c e s s e s t h a n t h o s e t h a t c a u s e d k n o w n e v e n t s . 57 The use of p r o b a b i l i t i e s with t h i s l e v e l of uncertainty in conjunction with accurate cost estimates to produce a single expected flood damage amount i s methodologically unsound. A second area of uncertainty i s the prob a b i l i t y that a dike w i l l f a i l at a given water l e v e l . It i s unreasonable to expect dikes to be safe up to the design l e v e l and f a i l as soon as the water l e v e l passes the design l e v e l . Whether a dike withstands water leve l s below, up to, or above design l e v e l s depends on many factors including flood duration, underseepage, piping, b o i l s , vegetation and animal burrows in the dike, and the effectiveness of flood f i g h t i n g e f f o r t s . From t h i s l i s t , the l e v e l of maintenance i s an important determinant of dike s t a b i l i t y . The l e v e l of maintenance that a dike w i l l receive i s extremely d i f f i c u l t to predict before the dike i s b u i l t . I n s t i t u t i n g a nominal higher levei-of protection by r a i s i n g the dikes w i l l do nothing to ensure adequate maintenance. It i s , in fact, possible that the maintenance of higher dikes w i l l be worse because flooding w i l l be less frequent. OTHER STRATEGIES The above discussion suggests that other strategies to reduce the ris k than r a i s i n g the dikes be pursued. The strategies that w i l l be proposed w i l l be aimed at reducing or providing for the hazard rather than reducing the risk l e v e l s . The f i r s t strategy involves sectioning Lulu Island by rai s i n g key parts of the road system above flood l e v e l s . In many 58 ways t h i s suggestion i s an adjunct of contingency planning and w i l l be discussed in the next chapter. The second strategy is to accept that flooding w i l l occur on an infrequent basis and to set up a contingency fund to defray the costs of such flooding. In e f f e c t , t h i s i s a flood insurance program and w i l l be discussed in the chapter on flood insurance. 59 CONTINGENCY PLANNING AND OTHER MEASURES TO REDUCE DAMAGE While much has been written about how to prevent flooding and how to design dikes to prevent breaches from occurring, almost a l l information on repairing breaches i s contained in engineering l o r e . It has always been assumed that a dike breach resu l t i n g from the spring freshet would be impossible to contain. For t h i s reason, e f f o r t s have always been directed toward ensuring that no dike breaches occur. This approach has i t s drawbacks. Past experience has shown that techniques to reduce the flood risk below current levels are expensive to implement and c o n f l i c t with other uses of the ri v e r basin. In pa r t i c u l a r , these techniques c o n f l i c t with fishery and recreational uses. Some p o l i c i e s have been suggested that would diminish the flood hazard by l i m i t i n g development on the floodplain or designing floodplain structures to r e s i s t flooding. These p o l i c i e s have not been p a r t i c u l a r l y e f f e c t i v e in c o n t r o l l i n g the flood hazard. The opportunity to develop Lulu Island as an urban community has far outweighed any pressures to l i m i t development to the low density a g r i c u l t u r a l and recreational uses that would l i m i t the amount of potential flood damage. Designing structures to withstand flooding has proved to be too expensive for widespread acceptance. A " s a f e - f a i l " p o l i cy that would allow some flooding without causing catastrophic losses and would be economically feasible would be a t t r a c t i v e . 60 C U R R E N T P O L I C Y B e f o r e s u g g e s t i n g " s a f e - f a i l " p o l i c y , i t i s n e c e s s a r y t o r e v i e w c u r r e n t p l a n n i n g f o r l i m i t i n g f l o o d d a m a g e a f t e r a d i k e b r e a k o c c u r s . C u r r e n t p l a n n i n g i s t o r e q u i s i t i o n p e r s o n n e l , e a r t h m o v i n g e q u i p m e n t , a n d r e p a i r m a t e r i a l s t o r e p a i r t h e b r e a c h a s q u i c k l y a s p o s s i b l e . I n a d d i t i o n i t i s r e c o g n i z e d t h a t a m a j o r b r e a c h f r o m t h e s p r i n g f r e s h e t w o u l d r e q u i r e e v a c u a t i o n o f t h e e n t i r e p o p u l a t i o n o f L u l u I s l a n d . F L O O D F I G H T I N G M A T E R I A L S N o s p e c i f i c s t o c k p i l e s o f r o c k a n d o t h e r m a t e r i a l s a r e k e p t f o r d i k e r e p a i r . H o w e v e r , s e v e r a l b u i l d i n g m a t e r i a l s s u p p l i e r s o p e r a t e o n L u l u I s l a n d . T h e s e s u p p l i e r s s h o u l d h a v e s u f f i c i e n t m a t e r i a l s o n h a n d f o r d i k e r e p a i r . A t l e a s t s o m e o f t h i s m a t e r i a l i s a c c e s s i b l e f r o m t h e d i k e a n d s o c o u l d b e u s e d t o r e p a i r d i k e s a f t e r f l o o d i n g h a s o c c u r r e d . F L O O D F I G H T I N G E Q U I P M E N T E q u i p m e n t f o r d i k e r e p a i r c a n b e r e q u i s i t i o n e d f r o m t h e m u n i c i p a l i t y o r p r i v a t e c o n t r a c t o r s . O n s h o r t n o t i c e i t h a s b e e n f o u n d t h a t l e s s t r u c k s w e r e a v a i l a b l e t h a n w e r e n e e d e d . F o r a f r e s h e t b a s e d f l o o d t h e r e w o u l d b e s e v e r a l d a y s n o t i c e o f t h e e x i s t e n c e o f f l o o d d a n g e r . A d v a n t a g e s h o u l d b e t a k e n o f t h i s n o t i c e t o p r o c u r e a n y n e e d e d e q u i p m e n t a n d p e r s o n n e l . F o r m a l a g r e e m e n t s w i t h e q u i p m e n t s u p p l i e r s o r e v e n a m u n i c i p a l b y - l a w t o g i v e p r i o r i t y t o e m e r g e n c y f l o o d f i g h t i n g e q u i p m e n t d e m a n d s o v e r o t h e r d e m a n d s w o u l d a l s o b e g o o d p r a c t i c e . 61 E V A C U A T I O N P L A N N I N G T o t a l e v a c u a t i o n o f L u l u I s l a n d c o u l d b e a c c o m p l i s h e d i n 6-8 h o u r s . T h i s e s t i m a t e d e p e n d s o n t h e h i g h w a y s y s t e m r e m a i n i n g o p e n . M o d e l i n g d o n e i n t h e c o u r s e o f t h i s s t u d y s u g g e s t s t h a t i t w o u l d t a k e 8-12 h o u r s f o r f l o o d l e v e l s t o r e a c h t h e .3m l e v e l f r o m a m o d e r a t e t o l a r g e d i k e b r e a c h . Low l y i n g a r e a s w o u l d r e a c h t h i s l e v e l m o r e q u i c k l y t h a n h i g h e r a r e a s . A s ,3m o r 1 f o o t o f w a t e r w o u l d make t h e r o a d s y s t e m i m p a s s a b l e , t h e s e a r e a s s h o u l d b e i d e n t i f i e d a n d e v a c u a t e d f i r s t . A C C E S S TO L U L U I S L A N D T h e r e a r e n o s p e c i a l p r o v i s i o n s t o k e e p a c c e s s r o u t e s o p e n . T h e G e o r g e M a s s e y T u n n e l w o u l d c o l l e c t w a t e r v e r y q u i c k l y b e c a u s e i t i s b e l o w t h e l e v e l o f t h e i s l a n d . A l l b r i d g e s a r e a b o v e f l o o d l e v e l s , b u t a c c e s s r o a d s a r e n o t . I t i s r e a s o n a b l e t o e x p e c t t h a t t h e a p p r o a c h e s w o u l d s t a y o p e n a s l o n g a s t h e r e s t o f t h e r o a d s y s t e m . SUMMARY OF C U R R E N T C O N T I N G E N C Y P L A N S T h e c u r r e n t a p p r o a c h s h o w s a g o o d p r a c t i c a l g r a s p o f t h e s i t u a t i o n a n d i s c e r t a i n l y a d e q u a t e f o r t i d a l b a s e d f l o o d i n g . F l o o d i n g f r o m t h e s p r i n g f r e s h e t i s a m o r e d i f f i c u l t p r o b l e m . F r o m t h e p r e v i o u s d i s c u s s i o n o f d i k e r e p a i r t e c h n i q u e s , i t s h o u l d b e c l e a r t h a t f o r a l l b u t t h e s m a l l e s t o f b r e a c h e s , t h e f e a s i b l e t e c h n i q u e s a v a i l a b l e a r e : b u i l d a r i n g d i k e , l e t t h e f l o o d w a t e r s p o n d b e f o r e r e p a i r , o r b r e a c h t h e d o w n s t r e a m d i k e s t o p r e v e n t p o n d i n g . T h e o p t i o n t h a t w o u l d e f f e c t d i k e r e p a i r s t h e m o s t q u i c k l y , b u i l d i n g a r i n g d i k e , w o u l d p r o b a b l y t a k e a m i n i m u m o f 48 h o u r s t o c o m p l e t e . A f t e r 48 h o u r s o f f l o o d i n g , 62 flood l e v e l s could be 1.2 to 1.8m. Large amounts of property damage would r e s u l t . It i s clear that current contingency plans would not be p a r t i c u l a r l y e f f e c t i v e in reducing flood damage after a dike breach occurring during the spring freshet. SUGGESTIONS FOR CONTINGENCY PLANNING An option, that has been alluded to but has never been pursued, consists of segmenting the island to prevent a single breach from causing flooding throughout the is l a n d . Probably, the most feasible way to approach segmentation would be to raise parts of the road system so that they are e f f e c t i v e l y out of the flood p l a i n . If designed co r r e c t l y , t h i s approach could be e f f e c t i v e in cutting the ris k of a catastrophic flood. The pr o b a b i l i t y of both the dikes and the raised portion of the road system f a i l i n g would be extremely small. The areas that would be flooded would be l i g h t l y populated and have a g r i c u l t u r a l development. By allowing flood waters to pond against the raised roads, dike repairs could be made more quickly. It would ensure access to the island was maintained, both for evacuation purposes and to move flood f i g h t i n g equipment and materials. One alignment that appears promising i s shown in F i g . 4. If a dike breach occurred west of the proposed alignment, t i d a l r e l i e f would be available to l i m i t repair time. Development i s r e l a t i v e l y l i g h t east of the alignment so that flooding from a breach there would cause r e l a t i v e l y l i t t l e damage. The rapid ponding that would occur in t h i s case would make i t possible to repair the dikes quickly. 63 The one disadvantage of segmenting the island that should be noted i s that segmetation would make flooding worse in the areas flooded. The preponderance of development on the western end of Lulu Island makes segmentation a good trade-off because worse flooding in l i g h t l y populated areas would be more than offset by protection of large amounts of urban development. OTHER RECOMMENDATIONS In addition to ra i s i n g road lev e l s on Lulu Island, provision should be made to ensure bridge and tunnel access routes remain passable. The entrances to the George Massey Tunnel should be diked on both ends or the tunnel w i l l f i l l with water. A l l bridges are above flood l e v e l but access roads are not. The l e v e l of bridge access roads should be raised above flood l e v e l . Ensuring access routes to the island are passable w i l l a i d in evacuation and rescue operations and w i l l allow personnel, equipment, and material to be brought onto the island for dike repairs. Another consideration i s to make provision to rapidly close off any underpasses, culverts, or other holes in the raised portions of the road system. Failure to do this would resu l t in flooding in the developed areas. As evacuation times w i l l be ti g h t , the lowest areas should be i d e n t i f i e d and evacuated f i r s t . Low ly i n g portions of the road system (below .3m geodetic) should be i d e n t i f i e d to ensure that they do not block any evacuation routes. People not involved in flood fig h t i n g should be encouraged to leave Lulu 64 Island and to store their possessions above flood levels when i t becomes apparent that high flood stages w i l l be reached. Care should be taken that adequate supplies of materials be stockpiled and accessible from the dikes. Alternate supplies of materials should be located off Lulu Island as a back up. Formal agreements should be made with trucking companies or a municipal by-law should be drawn up to ensure adequate equipment i s available for flood f i g h t i n g . On the whole, contingency planning i s adequate as long as large amounts of flood damage are acceptable from flooding caused by the spring freshet on an infrequent basis. On the other hand, r a i s i n g the l e v e l of selected parts of the road system would be an e f f e c t i v e method of reducing t h i s hazard and should be considered. 65 FLOOD INSURANCE At the present, time flood insurance i s not available in Canada. Several factors make i t an a t t r a c t i v e idea at t h i s time. The large but infrequent nature of flood costs make some sort of f i n a n c i a l protection worthwhile for a l l floodplain users. The senior governments, both federal and p r o v i n c i a l , already provide what amounts to flood insurance in that damages have t r a d i t i o n a l l y been compensated. The large, and growing, expected damage from a major flood represents a deferred, but real income transfer from outside of the floodplain to floodplain users. The current p o l i c i e s do not provide l o c a l o f f i c i a l s in the Municipality of Richmond s u f f i c i e n t feedback to make ra t i o n a l decisions about what leve l s of protection to request, what design measures are appropriate for .flood p l a i n structures, what zoning measures are appropriate, and what residual amounts of expected damage should be l e f t to be paid as flood insurance premiums. THE NEED FOR FLOOD INSURANCE A major flood on Lulu Island would cause a great deal of damage. Repair costs for a t y p i c a l residence would range from 1/5 to 1/3 of the value of the residence. A burden such as t h i s would cause f i n a n c i a l hardship. On the surface i t seems l i k e a natural area for the private insurance industry to s e l l insurance to spread the r i s k of flooding. The s i t u a t i o n , however, d i f f e r s from a normal insurance s i t u a t i o n . Usually insurance i s issued when i t can be expected that only a small proportion of those covered w i l l claim in any 66 one year, but that claims w i l l come in continuously. This enables the insurance company to offset a continuous stream of claims against a continuous stream of premiums. The s i t u a t i o n with flood insurance i s that for any given ri v e r basin, claims can be expected to come only rarel y . When there i s a flood, however, everyone covered by the flood insurance can be expected to claim at once. From the insurers' point of view, flood insurance spreads the risk over time, not over a group of policy holders at any one time. GOVERNMENT INVOLVEMENT IN FLOOD INSURANCE Because of the damages caused by flooding and the lack of involvement on the part of the private insurance industry, the pr o v i n c i a l and federal governments have agreed to share the costs of flood damages. For large flood damages (above $4 per capita) the federal government pays 90% of e l i g i b l e flood damages (See Table VII).* Therefore in the primitive sense of sharing a risk among many, the p r o v i n c i a l and federal governments do provide flood insurance. * It should be noted that there i s no legal requirement for either the federal or p r o v i n c i a l governments to pay flood compensation and that not a l l types of damage are e l i g i b l e for compensation under the federal p r o v i n c i a l flood damage cost sharing formula. Normal practice i s to set up a board of inquiry to determine whether flood damages are e l i g i b l e for compensation and to set a deductible amount. Notwithstanding these l i m i t a t i o n s on flood compensation, the type and extent of potential flood damages on Lulu Island make the approval of compensation a near certainty. 67 OTHER FUNCTIONS OF INSURANCE Insurance i s not just a primitive risk-sharing t o o l . It also provides feedback on how well a hazard i s being managed and provides a powerful way of modifying behaviour toward a hazard. It has been shown that residual expected flood damages on Lulu Island i s $15 m i l l i o n per annum. Recent costs of building dikes on Sea Island were estimated at about $1 m i l l i o n per kilometer. As Lulu Island has 56 kilometers of dikes, i t is clear that some improvement in protection l e v e l s could be j u s t i f ied. This discrepancy between the expected damage, as calculated on economic c r i t e r i a , and current policy based on ris k perception represents an income transfer to the floodplain users. If the whole burden of the residual excess value of flood damages was added to Richmond municipal taxes i t would add approximately 2.5 m i l l s to property taxes. As was pointed out above, i t would be economically e f f i c i e n t to reduce t h i s burden by increasing s t r u c t u r a l flood protection. The point i s not, however, that the Municipality of Richmond should be forced to upgrade st r u c t u r a l protection, but that information should be given to the municipality so that their perception of the costs of expected flood damage matches the actual expected costs. It i s not f a i r for p o l i c i e s to be pursued which create higher expected flood damage than i s economically j u s t i f i a b l e and to expect an income transfer from society to cover that damage. 68 IMPLEMENTATION OF FLOOD INSURANCE Because of the p o s s i b i l i t y of a catastrophic flood occurring before enough premiums have been c o l l e c t e d to cover i t , flood insurance would have to be implemented as a government program. Because costs are averaged over time rather than over a risk group, coverage should be mandatory and premiums should be segregated from general revenues in a sinking fund. It i s suggested that premiums be co l l e c t e d as part of municipal taxes based on the assessed value of property, type of property, l e v e l of flood r i s k , s p e c i f i c design measures to re s i s t flooding, and an i n i t i a l study to determine expected flood damage. Tying premiums to assessed value would provide a deferent to inappropriate development. As the character of the flood hazard may change over time the flood damage"study should be repeated p e r i o d i c a l l y . SUMMARY In summary, adoption of a flood insurance plan along these lines w i l l allow diking d i s t i c t s to make rat i o n a l decisions about development, building design, and flood protection l e v e l s to request. It w i l l provide senior governments with information about the p r i o r i t y with which to implement flood control projects. It w i l l make e x p l i c i t what subsidy, i f any, i s provided to flood plain users. F i n a l l y , i t w i l l provide resources to repair the massive amounts of flood damage that would occur i f Lulu Island were flooded. 69 CONCLUSIONS In the course of t h i s thesis, several conclusions were reached. They are: - There i s an increasing flood hazard on Lulu Island because i t s location and topography make i t highly desirable for development as an integral part of the greater Vancouver Regional D i s t r i c t . Property on Lulu Island i s assessed at $6 b i l l i o n . - The three mechanisms that could cause flooding, in order of seriousness of the hazard, are the spring freshet, winter storms, and earthquake damage to the dikes. - The p r o b a b i l i t y of coincidental occurrence of combined events i s too small to require consideration in planning flood protection for Lulu Island at current protection l e v e l s . If future policy decisions raise protection le v e l s s i g n i f i c a n t l y , consideration of combined ri s k s may be required. - The current method of setting le v e l s of protection i s risk prone. It spends more per d o l l a r of expected flood damage to protect against small flood hazards than for large flood hazards. - Expected costs of flooding on Lulu Island can be expected to increase as long as the current policy of a fixed level of protection i s followed and development on Lulu Island continues. - The accuracy of prediction of the size of hydrological events greater than the current design events is not 70 s u f f i c i e n t to be used with confidence in ris k benefit analysis. - Current contingency plans are adequate for storm based flooding. However, these plans would not be e f f e c t i v e in reducing flood damage should there be a breach near the eastern end of the island during the spring freshet. - An i m p l i c i t income transfer to floodplain users on Lulu Island i s currently taking place as a result of the expected flood damage, residual, after current protection levels are taken into account. - While the earthquake hazard i s a danger that should not be minimized, i t should not cause s i g n i f i c a n t flooding i f earthquake damage to the dikes were repaired quickly. - As the t o t a l pumping capacity on Lulu Island i s 1 m i l l i o n U.S. gallons per minute or less than 100 m3/s the pumping system would be of l i t t l e use in pumping out water from a dike breach. The pumps are there to maintain drainage and pump out water resu l t i n g from rain with the dikes i n t a c t . 71 RECOMMENDATIONS The following recommendations follow from t h i s study: - Flood r i s k levels should be set to be roughly risk neutral. Methods of setting risk l e v e l s include a rule of thumb hazard chart and risk benefit analysis. - The option of segmenting Lulu Island by r a i s i n g selected parts of the road system should be considered as an ef f e c t i v e method for reducing the flood hazard from the spring freshet. - A government sponsored flood insurance program that i s mandatory should be set up to defray the costs of flood compensation and to encourage r a t i o n a l decision making about the flood hazard. Premiums should be set based on assessed value and the le v e l of risk of flooding. - The flood hazard on Lulu Island i s not s t a t i c . As long as development continues, periodic review of the size of the hazard should be undertaken to ensure that the residual expected damage i s not excessive. A complete flood damage study should be undertaken once per decade. - Rising sea levels w i l l necessitate r a i s i n g the l e v e l of the sea dikes to accomodate higher tide l e v e l s , but w i l l not change the character of the storm based flooding hazard. They w i l l change the character of the hazard from earthquake damage to.the dikes because flooding would result from a normal high t i d e . For 7 2 t h i s r e a s o n , b e f o r e t h e d i k e s a r e r e b u i l t , t h e b e s t a v a i l a b l e e v i d e n c e r e g a r d i n g a r i s e i n s e a l e v e l s h o u l d b e c o n s i d e r e d . I f a r i s e i n s e a l e v e l i s c o n f i r m e d t h e d i k e s s h o u l d b e b u i l t t o w i t h s t a n d e a r t h q u a k e s . - A c t i o n s h o u l d b e t a k e n t o e n s u r e t h a t b r i d g e a n d t u n n e l a c c e s s t o L u l u I s l a n d w o u l d n o t b e c u t d u r i n g a f l o o d . - A p r i o r i t y , s h o u l d a s e v e r e e a r t h q u a k e o c c u r , s h o u l d b e t o p e r f o r m a c a r e f u l s u r v e y o f t h e d i k e s t o l o c a t e a n y d a m a g e d a r e a s . A s t i m e w o u l d b e l i m i t e d a n d s u r f a c e t r a n s p o r t a t i o n w o u l d b e d i s r u p t e d b y a n e a r t h q u a k e , t h e m o s t f e a s i b l e w a y t o p e r f o r m t h i s s u r v e y i s b y a i r . 73 BIBLIOGRAPHY A i r P o l l u t i o n C o n t r o l A s s o c i a t i o n . A v o i d i n g a n d M a n a g i n g E n v i r o n m e n t a l D a m a g e f r o m M a j o r I n d u s t r i a l A c c i d e n t s :  P r o c e e d i n g s o f a n I n t e r n a t i o n a l C o n f e r e n c e H e l d i n  V a n c o u v e r , B . C . N o v e m b e r , 1 9 8 5 . A i r P o l l u t i o n C o n t r o l A s s o c i a t i o n . P i t t s b u r g h , 1 9 8 5 . A l g e r m i s s e n , S. T . a n d T . H a r d i n g s . T h e P u g e t S o u n d W a s h i n g t o n  E a r t h q u a k e o f A p r i l 2 9 , 1 9 6 5 : P r e l i m i n a r y S e i s m o l o g i c a l  R e p o r t . U . S. C o a s t a n d G e o d e t i c S u r v e y . R o c k e v i l l e , M a r y l a n d . 1 9 6 5 . A n d e r s o n , D a n R. a n d M a u r i c e W e i n r o b e . E f f e c t s o f a N a t u r a l  D i s a s t e r o n L o c a l M o r t g a g e M a r k e t s : T h e P e a r l F l o o d i n  J a c k s o n , M i s s i s s i p p i - A p r i l , 1 9 7 9 . N a t u r a l H a z a r d R e s e a r c h S e r i e s I n s t i t u t e o f B e h a v i o u r a l S c i e n c e #6. U n i v e r s i t y o f C o l o r a d o . 1 9 7 9 . B e a k C o n s u l t a n t s ( K 4 3 5 0 ) . P r o p o s e d I m p r o v e m e n t s t o t h e F r a s e r R i v e r S h i p p i n g C h a n n e l : P r e l i m i n a r y R e p o r t f o r P u b l i c W o r k s  C a n a d a . V a n c o u v e r , B . C . 1 9 7 9 . B o o k , A . N . P r o b l e m s A r i s i n g F r o m F l o o d C o n t r o l B e n e f i t S t u d i e s . E n v i r o n m e n t C a n a d a , P l a n n i n g D i v i s i o n , W a t e r P l a n n i n g a n d O p e r a t i o n s B r a n c h . 1 9 7 1 . B o o k , A . N . a n d R. P r i n c i c . E s t i m a t i n g F l o o d D a m a g e s i n t h e  F r a s e r R i v e r B a s i n . E n v i r o n m e n t C a n a d a , I n l a n d W a t e r s D i r e c t o r a t e , W a t e r P l a n n i n g a n d M a n a g e m e n t B r a n c h . 1 9 7 5 . B. C . M i n i s t r y o f E n v i r o n m e n t , R i v e r s B r a n c h . L i q u e f a c t i o n  P r o g r a m C o m m i t t e e P a p e r s . U n p u b l i s h e d . B y r n e , P. M. a n d D. M. A n d e r s o n . E a r t h q u a k e D e s i g n i n R i c h m o n d ,  B . C . S o i l M e c h a n i c s S e r i e s N o . 7 5 , D e p a r t m e n t o f C i v i l E n g i n e e r i n g . 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 . V a n c o u v e r . 1 9 8 3 . C l a r k , E . M. L o w e r F r a s e r R i v e r D y k e S u r v e y : L i q u e f a c t i o n . C a n a d a D e p a r t m e n t o f N o r t h e r n A f f a i r s a n d N a t i o n a l R e s o u r c e s , W a t e r R e s o u r c e s B r a n c h . V a n c o u v e r , B . C . 1 9 6 3 . C l a r k , E . M. R e p o r t o n F l o o d F r e q u e n c i e s , E l e v a t i o n s , a n d  D u r a t i o n s i n t h e S u m a s L a k e A r e a . E n v i r o n m e n t C a n a d a , E n g i n e e r i n g D i v i s i o n , W a t e r P l a n n i n g B r a n c h . 1 9 7 2 . C o m m i t t e e o n S a f e t y o f D ams. S a f e t y o f Dams: F l o o d a n d  E a r t h q u a k e C r i t e r i a . N a t i o n a l A c a d e m y P r e s s . W a s h i n g t o n , D. C . 1 9 8 5 . C r i p p e n a n d A s s o c i a t e s L t d . E s t i m a t e o f C a p i t a l C o s t s , F r a s e r  R i v e r S t o r a g e , S y s t e m ' E ' P r o j e c t s . U n p u b l i s h e d . 1 9 7 1 . 74 C r o s s o n , R o b e r t S . E a r t h q u a k e H a z a r d E v a l u a t i o n i n t h e P a c i f i c  N o r t h w e s t : O p e n F i l e R e p o r t . F i l e 8 1 - 9 6 5 . U . S . G e o l o g i c a l S u r v e y . 1 9 8 1 . D e a l , T e r r e n c e E . a n d A l l a n A . K e n n e d y . C o r p o r a t e C u l t u r e s : T h e  R i t e s a n d R i t u a l s o f C o r p o r a t e L i f e . A d d i s o n - W e s l e y . R e a d i n g , M a s s a c h u s e t t s . 1 9 8 2 . F a r l e y , A . L . A t l a s o f B r i t i s h C o l u m b i a . 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 P r e s s . 1 9 7 9 . F i n n , L i a m . B e h a v i o u r o f E a r t h D a m s D u r i n g E a r t h q u a k e s . C o m m i s s i o n I n t e r n a t i o n a l e d e s G r a n d s B a r r a g e s . N e u v i e m e C o n g r e s d e s G r a n d B a r r a g e s . I s t a n b u l . 1 9 6 7 . F i n n , L i a m , R . G . C a p a n e l l a , a n d Y . A o k i . S e i s m i c T e s t i n g o f  S o i l M o d e l s . D e p a r t m e n t o f C i v i l E n g i n e e r i n g , S o i l M e c h a n i c s S e r i e s N o . 8 , 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 . 1 9 6 9 . F i n n , L i a m a n d B y r n e , P e t e r M . T h e L i q u e f a c t i o n P o t e n t i a l o f t h e  V e d d e r C a n a l D y k e s . U n p u b l i s h e d . 1 9 7 0 . F l a v e l l , D . R . a n d R . 0 . 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S e i s m i c D e s i g n o f E m b a n k m e n t s a n d C a v e r n s . P r o c e e d i n g s o f a s y m p o s i u m s p o n s o r e d b y t h e A S C E G e o t e c h i n c a l E n g i n e e r i n g D i v i s i o n . A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s . New Y o r k . 1 9 8 3 . I n l a n d W a t e r s B r a n c h , E n g i n e e r i n g D i v s i o n , P a c i f i c R e g i o n . L i q u e f a c t i o n P r o b l e m s o f t h e V e d d e r C a n a l D y k e s . U n p u b l i s h e d . 1 9 7 0 . I n l a n d W a t e r s D i r e c t o r a t e , P a c i f i c a n d Y u k o n R e g i o n . E c o n o m i c  A n a l y s i s o f D y k e I m p r o v e m e n t f o r W e s t h a m a n d R e i f e l  I s l a n d s . 1 9 8 2 . I n s p e c t o r o f D y k e s . C o r r e s p o n d e n c e o n E a r t h q u a k e S t u d i e s  F e b r u a r y 1 9 7 0 t o A u g u s t 1 9 8 5 . U n p u b l i s h e d . J o n e s , W. C . 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A p r i l , 1 9 8 6 . P r i n c i c , R . E c o n o m i c A n a l y s i s o f F l o o d C o n t r o l M e a s u r e s o n t h e  V e d d e r R i v e r . I n l a n d W a t e r s D i r e c t o r a t e , P a c i f i c a n d Y u k o n R e g i o n , V a n c o u v e r , B . C . 1 9 7 7 . R i p l e y , K l o h n a n d L e o n o f f I n t e r n a t i o n a l L t d . R i c h m o n d D y k e s - R e m e d i a l T r e a t m e n t f o r F r a s e r R i v e r J o i n t P r o g r a m  C o m m i t t e e . U n p u b l i s h e d . 1 9 6 9 . R i p l e y , K l o h n a n d L e o n o f f I n t e r n a t i o n a l L t d . V e d d e r C a n a l D y k e s ;  P r e l i m i n a r y L i q u e f a c t i o n S t u d i e s . F r a s e r R i v e r J o i n t P r o g r a m C o m m i t t e e . 1 9 7 0 . S e e d , H . B . a n d I. M . I d r i s s . G r o u n d M o t i o n s a n d S o i l L i q u e f a c t i o n s D u r i n g E a r t h q u a k e s . E a r t h q u a k e E n g i n e e r i n g R e s e a r c h I n s t i t u t e . B e r k e l e y , C a l i f o r n i a . 1 9 8 2 . S e e d , H . B . L a n d s l i d e s D u r i n g E a r t h q u a k e s D u e t o S o i l L i q u e f a c t i o n . A S C E J o u r n a l o f t h e S o i l M e c h a n i c s a n d F o u n d a t i o n s D i v i s i o n . S e p t e m b e r , 1 9 6 8 . S e e d , H . B . T u r n a q a i n H e i g h t s L a n d s l i d e , A n c h o r a g e , A l a s k a . J o u r n a l o f t h e S o i l M e c h a n i c s a n d F o u n d a t i o n D i v i s i o n . A S C E . V o l . 9 3 , N o . 5 . J u l y , 1 9 6 7 . p p . 3 2 5 - 3 5 3 . S h e p a r d , F . P . a n d W. H . M a t h e w s . S e d i m e n t a t i o n o f F r a s e r R i v e r  D e l t a . T h e A m e r i c a n A s s o c i a t i o n s o f P e t r o l e u m G e o l o g i s t s , A u g u s t , 1 9 6 2 . 7 7 S h a n k s , G o r d o n R o s s . T h e R o l e o f P e r c e p t i o n i n F l o o d P l a i n  M a n a g e m e n t . U B C M a s t e r ' s T h e s i s . 1 9 7 2 . S l o v i c , P a u l , S a r a h L i c h t e n s t e i n , a n d B a r u c h F i s c h o f f . M o d e l i n g  t h e S o c i e t a l I m p a c t o f F a t a l A c c i d e n t s . M a n a g e m e n t S c i e n c e , V o l . 3 0 , p p . 4 6 4 - 4 7 5 . 1 9 8 4 . S t a t i s t i c s C a n a d a . T a b l e 5 - P o p u l a t i o n b y S e x , a n d P r o p o r t i o n  o f M a l e s t o F e m a l e s , f o r C e n s u s M e t r o p o l i t a n A r e a s W i t h  C o m p o n e n t s . 1 9 7 1 - 1 9 8 5 . S t a t i s t i c s C a n a d a . T i m e S e r i e s R e t r e i v a l o f C o n s u m e r P r i c e  I n d e x e s f o r V a n c o u v e r a n d C a n a d a . J a n . 2 2 , 1 9 8 6 . S t a t i s t i c s C a n a d a . T a b l e 10 - B u i l d i n g P e r m i t s I s s u e d i n  M e t r o p o l i t a n A r e a s . 1 9 7 1 - 1 9 8 5 . T o g a s h i , H i r o s h o y o s h i . S t u d y o n T s u n a m i R u n - u p a n d C o u n t e r m e a s u r e s . D o c t o r o f E n g i n e e r i n g T h e s i s , T o h o k u U n i v e r s i t y , S e n d a i , J a p a n , 1 9 7 6 . ( t r a n s . 1 9 8 1 ) . V a r z e l i o t e s , A . N . T . F r a s e r R i v e r U p s t r e a m S t o r a g e S t u d y : R i v e r  R e g i m e a n d S e d i m e n t S t u d i e s . I n l a n d W a t e r s D i r e c t o r a t e . V a n c o u v e r , B . C . 1 9 7 4 . W a l l i s , D o u g l a s . G r o u n d S u r f a c e M o v e m e n t s D u e t o E a r t h q u a k e s . M a s t e r ' s T h e s i s , 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 . 1 9 7 9 . W e s t e r n C a n a d a H y d r a u l i c L a b o r a t o r i e s L i m i t e d . F e a s i b i l i t y S t u d y : D e v e l o p m e n t o f a F o r t y - F o o t D r a f t N a v i g a t i o n C h a n n e l  New W e s t m i n i s t e r t o S a n d h e a d s . F i n a l R e p o r t H y d r a u l i c M o d e l  S t u d i e s f o r P u b l i c W o r k s C a n a d a A p r i l , 1 9 7 7 . 1 9 7 7 . W e s t e r n C a n a d a H y d r a u l i c L a b o r a t o r i e s . H y d r a u l i c a n d R e l a t e d S t u d i e s a n d R e v i e w o f E x i s t i n g O c e a n o g r a p h i c , H y d r a u l i c a n d  G e o t e c h n i c a l I n f o r m a t i o n o n S t u r g e o n B a n k s f o r B . C . H y d r o  a n d P o w e r A u t h o r i t y . U n p u b l i s h e d . 1 9 8 0 . Y a m a d a , G . D a m a g e t o E a r t h S t r u c t u r e s a n d F o u n d a t i o n s b y t h e ( N i i g a t a E a r t h q u a k e , J u n e 1 6 , 1 9 6 4 ) . S o i l s a n d F o u n d a t i o n s . V o l . V I N o . 1 . J a n , 1 9 6 6 . p p . 1 - 1 3 . APPENDICES A p p e n d i x A - T a b l e s A p p e n d i x B - F i g u r e s A p p e n d i x C - C a l c u l a t i o n o f E x p e c t e d F l o o d D a m a g e s 7 9 A p p e n d i x A - T a b l e s T a b l e I - T e r m s f o r C l a s s i f y i n g H a z a r d P o t e n t i a l s ( C o m m i t t e e o n S a f e t y o f D a m s , 1 9 8 5 , p . 1 3 0 ) L o s s o f L i f e C a t e g o r y L o w S i g n i f i c a n t ( E x t e n t o f D e v e l o p m e n t ) E c o n o m i c L o s s N o n e e x p e c t e d ( n o p e r m a n e n t s t r u c t u r e s f o r h u m a n h a b i t a t i o n ) F e w ( n o u r b a n d e v e l o p m e n t s a n d n o m o r e t h a n a s m a l l n u m b e r o f i n h a b i t a b l e s t r u c t u r e s ) M i n i m a l ( u n d e v e l o p e d t o o c c a s i o n a l s t r u c t u r e s o r a g r i c u l t u r e ) A p p r e c i a b l e ( n o t a b l e a g r i c u l t u r e , i n d u s t r y , o r s t r u c t u r e s ) H i g h M o r e t h a n f e w e x p e c t e d c a s u a l t i e s E x c e s s i v e ( e x t e n s i v e c o m m u n i t y , i n d u s t r y , a g r i c u l t u r e ) o r T a b l e I I - U . S . A r m y C o r p s E n g i n e e r s H y d r a u l i c E v a l u a t i o n  G u i d e l i n e s : R e c o m m e n d e d S p i l l w a y D e s i g n F l o o d s ( C o m m i t t e e o n S a f e t y o f D a m s , 1 9 8 5 , p . 1 3 2 ) H a z a r d S i z e o f Dam S p i l l w a y D e s i g n F l o o d L o w S m a l l 5 0 - t o 1 0 0 - y r f r e q u e n c y I n t e r m e d i a t e 1 0 0 - y r t o 1 / 2 PMF L a r g e 1 / 2 PMF t o PMF S i g n i f i c a n t S m a l l 1 0 0 - y r t o 1 / 2 PMF I n t e r m e d i a t e 1 / 2 PMF t o PMF L a r g e PMF H i g h S m a l l I n t e r m e d i a t e L a r g e 1 / 2 PMF PMF PMF 8 0 1^1 f ! . g u l l d i n q P e r m i t s f o r C o m m e r c i a l P u r p o s e s ( S t a t i s t i c s C a n a d a T a b l e 10 - B u i l d i n g P e r m i t s I s s u e d i n M e t r o p o l i t a n A r e a s , 1 9 7 1 - 1 9 8 5 ) Y e a r 1 971 1 9 7 2 1 9 7 3 1 9 7 4 1 9 7 5 1 9 7 6 1 9 7 7 1 9 7 8 1 9 7 9 1 9 8 0 1 981 1 9 8 2 1 9 8 3 1 9 8 4 1 9 8 5 T o t a l V a l u e ( O O P ' s ) 8 , 1 7 4 1 7 , 3 8 0 1 5 , 7 0 0 2 3 , 3 5 2 2 5 , 9 9 7 3 7 , 4 5 5 3 4 , 2 1 9 1 7 , 8 9 1 1 4 5 , 4 4 7 3 8 , 5 1 8 5 2 , 0 7 1 3 4 , 2 5 5 2 1 , 3 1 1 2 2 , 0 9 6 3 8 , 4 5 2 5 3 2 , 3 1 8 T a b l e I V - — A n n u a l P r o b a b i l i t i e s o f C o m b i n e d F l o o d H a z a r d s F r e s h e t W i n t e r S t o r m E a r t h q u a k e F r e s h e t . 0 0 5 0 . 0 l e s s t h a n . 0 0 8 3 W i n t e r S t o r m 0 . 0 • . 0 0 5 . 0 0 0 1 4 E a r t h q u a k e l e s s t h a n . 0 0 0 8 3 . 0 0 0 1 4 . 0 0 2 1 81 T a b l e V - P r e d i c t e d C h a n g e s t o T i d a l L e v e l s ( L e v e l s G i v e n i n M e t e r s G S C ) C u r r e n t L e v e l s P r e d i c t e d L e v e l s N o r m a l L o w t i d e - 2 . 6 -1 . 6 M e a n T i d e 0 . 0 1 . 0 N o r m a l H i g h T i d e 1 . 0 2 . 0 D e s i g n T i d e 2 . 7 3 . 7 Y e a r l y H i g h T i d e 2 . 2 3 . 2 M i n i m u m D i k e H e i g h t 3 . 0 4 . 0 T a b l e V I - F l o o d D a m a g e E s t i m a t e f o r L u l u I s l a n d 1971 E s t i m a t e b y C a t e g o r y ( B o o k a n d P r i n c i c , 1 9 7 5 ) ( 0 0 0 ' s ) R e s i d e n t i a l 6 1 , 8 3 1 C o m m e r c i a l 1 7 , 9 0 5 I n d u s t r i a l 8 , 8 8 8 A g r i c u l t u r a l - C r o p 5 , 6 6 1 - O t h e r 561 I n d u s t r i a l 2 , 3 7 8 T r a n s f e r C o s t s a n d S e c o n d a r y I n c o m e L o s s e s 2 , 4 0 8 M i s c e l l a n e o u s 1 5 , 0 3 4 T o t a l 1 1 4 , 6 6 6 C h a n g e i n C o n s u m e r P r i c e I n d e x ( S t a t i s t i c s C a n a d a , 1 9 8 6 ) - H i g h 2 . 9 8 - L o w 2 . 6 8 P o p u l a t i o n G r o w t h 1 . 6 7 ( S t a t i s t i c s C a n a d a . T a b l e 5 - P o p u l a t i o n e t c . , 1 9 7 1 - 1 9 8 5 ) C o m b i n e d I n f l a t i o n / P o p u l a t i o n F a c t o r s - H i g h 4 . 9 7 - L o w 4 . 4 7 F l o o d D a m a g e E s t i m a t e s - H i g h $ 5 7 0 , 6 4 6 - L o w 51 3 , 1 9 9 82 T a b l e V I I - F e d e r a l - P r o v i n c i a l F l o o d D a m a g e C o s t S h a r i n g F o r m u l a D a m a g e p e r C a p i t a F e d e r a l S h a r e P r o v i n c i a l S h a r e L e s s t h a n $1 0% 100% $ 1 . 0 0 t o 2 . 0 0 50% 50% $ 2 . 0 0 t o 4 . 0 0 75% 25% A b o v e $ 4 . 0 0 90% 10% 83 T a b l e V I I I - E x a m p l e R u l e o f T h u m b F l o o d P r o t e c t i o n L e v e l C h a r t  F l o o d H a z a r d C l a s s i f i c a t i o n L o w M e d i u m H i g h F l o o d D e p t h < . 3 m , 3 m t o 1 . 4 m > 1 . 4 m F l o o d D u r a t i o n < 1 d a y 1 t o 5 d a y s > 5 d a y s F l o o d W a r n i n g > 48 h r s > 12 h r s N o n e F l o o d D a m a g e E x p o s u r e P o t e n t i a l V e r y L o w U n i n h a b i t e d o r s t r i c t l y r u r a l w i t h l i t t l e r u r a l d e v e l o p m e n t . L o w R u r a l w i t h s o m e s m a l l c o m m u n i t i e s . M o d e r a t e M e d i u m s i z e d c o m m u n i t i e s . P a r t s o f l a r g e c o m m u n i t i e s w h e r e t h e p a r t s a t r i s k a r e c o m p a r a b l e i n p o p u l a t i o n t o a m e d i u m s i z e d c o m m u n i t y . H i g h L a r g e u r b a n c o m m u n i t i e s o r p o s s i b i l i t y o f l o s s o f l i f e . V e r y H i g h P o s s i b i l i t y o f l o s s o f l a r g e n u m b e r s o f l i v e s . \ 84 T a b l e V I I I ( c o n t . ) - R e c o m m e n d e d L e v e l s o f F l o o d P r o t e c t i o n H a z a r d L e v e l D e s c r i p t i o n P r o t e c t i o n L e v e l V e r y L o w L o w M o d e r a t e V e r y l o w d a m a g e p o t e n t i a l o r L o w d a m a g e p o t e n t i a l a n d l o w d e p t h , d u r a t i o n a n d w a r n i n g N o n e L o w d a m a g e p o t e n t i a l , m e d i u m d e p t h , d u r a t i o n , w a r n i n g o r M o d e r a t e d a m a g e p o t e n t i a l , l o w d e p t h , l o w d u r a t i o n , m e d i u m w a r n i n g 1 / 1 0 0 M o d e r a t e d a m a g e p o t e n t i a l , 1 / 1 0 0 t o d e p t h , d u r a t i o n , w a r n i n g 1 / 2 PMF H i g h H i g h d a m a g e p o t e n t i a l , m e d i u m d e p t h , h i g h d u r a t i o n , m e d i u m w a r n i n g o r l o w d a m a g e p o t e n t i a l , h i g h d e p t h , h i g h w a r n i n g 1 / 2 PMF t o PMF V e r y H i g h M o d e r a t e d a m a g e p o t e n t i a l , h i g h d e p t h , h i g h w a r n i n g PMF 8 5 A p p e n d i x B - F i g u r e s L i s t o f F i g u r e s 1 . 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Figure 4= RICHMOND - ROADS WHICH COULD BE RAISED TO S E G M E N T AREA S U B J E C T TO FLOODING. 90 A p p e n d i x C - E x p e c t e d F l o o d D a m a g e C a l c u l a t i o n f o r L u l u I s l a n d A u g u s t 1 2 , 1 9 8 6 A s s u m e d R a t e o f D a m a g e I n c r e a s e 0 . 0 4 E f f e c t i v e I n t e r e s t R a t e 0 . 0 8 F l o o d S t a g e a t M i s s i o n ( f e e t ) 24 25 26 E s t . F l o o d D a m a g e ( 0 0 0 ' s ) $ 2 7 5 , 0 0 0 $ 5 0 0 , 0 0 0 $ 5 1 0 , 0 0 0 P r o b a b i l i t y o f F l o o d i n g . 0 0 5 .01 . 0 0 5 G r o w t h E x p e c t e d P r e s e n t Y e a r F a c t o r D a m a g e V a l u e 1 1 . 0 0 0 0 8 9 2 5 0 0 0 8 9 2 5 0 0 0 2 1 . 0 4 0 0 9 2 8 2 0 0 0 8 5 9 4 4 4 4 3 1 . 0 8 1 6 9 6 5 3 2 8 0 8 2 7 6 1 3 2 4 1 . 1 2 4 9 1 0 0 3 9 4 1 1 7 9 6 9 6 0 8 5 1 . 1 6 9 9 1 0 4 4 0 9 8 8 7 6 7 4 4 3 8 6 1 . 2 1 6 7 1 0 8 5 8 6 2 7 7 3 9 0 1 9 9 7 1 . 2 6 5 3 1 1 2 9 2 9 7 2 7 1 1 6 4 8 8 8 1 . 3 1 5 9 1 1 7 4 4 6 9 1 6 8 5 2 9 1 4 9 1 . 3 6 8 6 1 2 2 1 4 4 7 9 6 5 9 9 1 0 3 10 1 . 4 2 3 3 1 2 7 0 3 0 5 8 6 3 5 4 6 9 2 1 1 1 . 4 8 0 2 1 3 2 1 1 1 8 0 6 1 1 9 3 3 3 1 2 1 . 5 3 9 5 - 1 3 7 3 9 6 2 7 5 8 9 2 6 9 1 1 3 1 . 6 0 1 0 1 4 2 8 9 2 1 3 5 6 7 4 4 4 3 1 4 1 . 6 6 5 1 1 4 8 6 0 7 8 1 5 4 6 4 2 7 8 15 1 . 7 3 1 7 1 5 4 5 5 2 1 2 5 2 6 1 8 9 8 1 6 1 . 8 0 0 9 1 6 0 7 3 4 2 1 5 0 6 7 0 1 3 1 7 1 . 8 7 3 0 1 6 7 1 6 3 5 8 4 8 7 9 3 4 5 18 1 . 9 4 7 9 1 7 3 8 5 0 1 2 4 6 9 8 6 2 9 19 2 . 0 2 5 8 1 8 0 8 0 4 1 2 4 5 2 4 6 0 6 20 2 . 1 0 6 8 1 8 8 0 3 6 2 9 4 3 5 7 0 2 8 21 2 . 1 9 1 1 1 9 5 5 5 7 7 4 4 1 9 5 6 5 6 22 2 . 2 7 8 8 2 0 3 3 8 0 0 5 4 0 4 0 2 6 2 23 2 . 3 6 9 9 2 1 1 5 1 5 2 5 3 8 9 0 6 2 2 24 2 . 4 6 4 7 2 1 9 9 7 5 8 6 3 7 4 6 5 2 5 2 5 2 . 5 6 3 3 2 2 8 7 7 4 9 0 3 6 0 7 7 6 5 26 2 . 6 6 5 8 2 3 7 9 2 5 8 9 3 4 7 4 1 4 4 27 2 . 7 7 2 5 2 4 7 4 4 2 9 3 3 3 4 5 4 7 2 28 2 . 8 8 3 4 2 5 7 3 4 0 6 5 3 2 2 1 5 6 6 2 9 2 . 9 9 8 7 2 6 7 6 3 4 2 7 3 1 0 2 2 4 8 30 3 . 1 1 8 7 2 7 8 3 3 9 6 4 2 9 8 7 3 5 0 31 3 . 2 4 3 4 2 8 9 4 7 3 2 3 2 8 7 6 7 0 8 32 3 . 3 7 3 1 3 0 1 0 5 2 1 6 2 7 7 0 1 6 3 33 3 . 5 0 8 1 3 1 3 0 9 4 2 4 2 6 6 7 5 6 4 34 3 . 6 4 8 4 3 2 5 6 1 8 0 1 2 5 6 8 7 6 6 35 3 . 7 9 4 3 3 3 8 6 4 2 7 3 2 4 7 3 6 2 6 36 3 . 9 4 6 1 3 5 2 1 8 8 4 4 2 3 8 2 0 1 0 37 4 . 1 0 3 9 3 6 6 2 7 5 9 8 2 2 9 3 7 8 8 38 4 . 2 6 8 1 3 8 0 9 2 7 0 2 2 2 0 8 8 3 3 3 9 4 . 4 3 8 8 3 9 6 1 6 4 1 0 2 1 2 7 0 2 4 40 4 . 6 1 6 4 4 1 2 0 1 0 6 6 2 0 4 8 2 4 5 41 4 . 8 0 1 0 4 2 8 4 9 1 0 9 1 9 7 2 3 8 4 42 4 . 9 9 3 1 4 4 5 6 3 0 7 3 1 8 9 9 3 3 3 43 5 . 1 9 2 8 4 6 3 4 5 5 9 6 1 8 2 8 9 8 8 ( c o n t i n u e d n e x t p a g e ) 91 G r o w t h Y e a r F a c t o r 44 5 . 4 0 0 5 45 5 . 6 1 6 5 46 5 . 8 4 1 2 47 6 . 0 7 4 8 48 6 . 3 1 7 8 49 6 . 5 7 0 5 50 6 . 8 3 3 3 C u m u l a t i v e P r e s e n t V a l u e Y e a r l y B u d g e t E x p e c t e d P r e s e n t D a m a g e V a l u e 4 8 1 9 9 4 2 0 1 7 6 1 2 4 7 5 0 1 2 7 3 9 7 1 6 9 6 0 1 6 5 2 1 3 2 4 9 3 1 6 3 3 2 0 0 5 4 2 1 7 7 9 3 1 5 7 2 7 1 2 5 6 3 8 6 5 0 4 1 5 1 4 4 6 3 5 8 6 4 1 9 6 5 1 4 5 8 3 7 2 6 0 9 8 7 6 4 3 1 4 0 4 3 5 8 2 0 4 4 6 1 6 9 2 $ 1 5 , 4 7 5 , 2 6 2 92 C a l c u l a t i o n o f E x p e c t e d F l o o d D a m a g e s F l o o d D a m a g e E s t i m a t e s f r o m B o o k a n d P r i n c i c ( 1 9 7 5 ) F l o o d l e v e l a t M i s s i o n 24 25 26 ( 0 0 0 ' s ) ( 0 0 0 ' s ) ( 0 0 0 ' s ) D a m a g e E s t i m a t e s b y C a t e g o r y R e s i d e n t i a l 3 2 6 4 7 6 1 8 3 1 6 1 8 3 1 C o m m e r c i a l 881 4 1 7 9 0 5 1 7 9 0 5 I n d u s t r i a l 5 1 0 9 6 9 4 6 8 8 8 8 A g r i c u l t u r a l - c r o p 4 2 2 8 5 6 0 3 5661 A g r i c u l t u r a l - o t h e r 4 0 4 5 4 8 561 P r i m a r y I n d u s t r i a l 1401 21 44 2 3 7 8 T r a n s f e r c o s t s 1 4 8 6 2 2 0 7 2 4 0 8 M i s c e l l a n e o u s D a m a g e s 7 3 6 5 1 4 4 6 5 1 5 0 3 4 T o t a l 61 4 5 4 1 1 1 6 4 9 1 1 4 6 6 6 P o p u l a t i o n G r o w t h F a c t o r 1 . 6 7 1 . 6 7 1 . 6 7 T o t a l A d j u s t e d f o r P o p . G r o w t h 1 0 2 6 2 8 1 8 6 4 5 3 1 9 1 4 9 2 I n f l a t i o n F a c t o r s - l o w 2 . 6 8 2 . 6 8 2 . 6 8 - h i g h 2 . 9 8 2 .9 '8 2 . 9 8 L o w e s t i m a t e $ 2 7 5 , 0 4 4 $ 4 9 9 , 6 9 6 $ 5 1 3 , 1 9 9 H i g h e s t i m a t e $ 3 0 5 , 8 3 2 $ 5 5 5 , 6 3 2 $ 5 7 0 , 6 4 7 A n n u a l P r o b a b i l i t y o f s t a g e 0 . 0 5 0 . 0 2 0 . 0 0 5 P r o b . o f F a i l u r e g i v e n s t a g e 0 .1 0 . 5 1 C o m b i n e d P r o b . o f F a i l u r e 0 . 0 0 5 0 . 0 1 0 . 0 0 5 E x p e c t e d A n n u a l C o s t i n 1 9 8 6 D o l l a r s - l o w $ 1 1 , 5 0 4 - h i g h $ 1 2 , 7 9 2 93 F o r m u l a s U s e d i n C a l c u l a t i n g E x p e c t e d F l o o d D a m a g e T h e f o r m u l a s u s e d t o c a l c u l a t e e x p e c t e d f l o o d d a m a g e a r e a s f o l l o w s : G r o w t h F a c t o r = (1 + R a t e o f D a m a g e I n c r e a s e ) Y e a r E x p e c t e d D a m a g e = G r o w t h F a c t o r * ( F l o o d D a m a g e a t 24 f e e t * P r o b F l o o d a t 24 f e e t + F l o o d D a m a g e a t 2 5 f e e t * P r o b F l o o d a t 2 5 f e e t + F l o o d D a m a g e a t 26 f e e t * P r o b F l o o d a t 26 f e e t ) P r e s e n t V a l u e = ( E x p e c t e d D a m a g e ) * ( ! / ( 1 + I n t e r e s t r a t e ) < Y e a r ~ 1 > ) 

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