Predictions o f the bpaces of Fddal Power W-vePop~nE
on Ice Conditions 2x1 ehe Upper Reaehea of the Bay o f Fundy
Donald C, Cordon, J r ,
Marine Ecology L a b o r a t o r y
Bedford I n s t i t u t e of Oceanography
V,O. Box 1006
B2X 4A2
Dartmouth, N,S,
ABSTRACT
A t i d a l power p r o j e c t i n t h e upper r e a c h e s of t h e Bay of Fundy
would markedly change i c e c o n d i t i o n s by r e d u c i n g t i d a l e n e r g y , h i g h w a t e r
l e v e l s and i n t e r t i d a l a r e a s . S h e e t i c e c o v e r a g e i s e x p e c t e d t o i n c r e a s e
w h i l e t h e e x t e n t and e l e v a t i o n of s h o r e f a s t i c e s h o u l d d e c r e a s e , e s p e c i a l l y along t i d a l rivers.
Sediment s c o u r by d r i f t i c e s h o u l d a l s o d e c r e a s e .
I n t e r a c t i o n s between d r i f t i c e and a t i d a l b a r r a g e ( i n c l u d i n g t u r b i n e s and
s l u i c e s ) must be c l o s e l y examined b e f o r e a f i n a l d e s i g n Ps a d o p t e d ,
Key words:
i c e , Bay of Fundy, Cumberland B a s i n , Cobequid Bay, t i d a l power,
environmental impacts
L1am6nagement d ' u n e u s i n e mar6motrice d a n s l a p a r t i . e amsnt d e l a
b a i e de Fundy m o d i f i e r a i t f o r t e m e n t l e s c o n d i t i o n s g l a e i o l o g i q u e s , e n
r e ' d u i s a n t I V n e r g i e d e s rnarQes, l e n i v e a u de I a hcruce m e r , el: I '6tei1cfue d e s
zones i n t e r t i d a l e s , On p r d v o i t que Pa c o u v e r t u r e de g l a c e unlforme
augmentera, e t q u f e n m&me temps, l a s u p e r f i c i e e t 3a h a u t e u r de l a g l a c e
c 6 t i G r e d i m i n u e r o n t s u r t o u t dans l e s p a r t i e s d e s c o u r s d'eau exposges aux
marees.
L ' a f f o u i l l e m e n t d e s s d d i m e n t s p a r $a glace de d&r-fve d i n i r l u e r a
a u s s i probablement.
On d o i t examiner en d g t a i l l e s i n t e r a c t i o n s p o s s i b l e s
e n t r e l a g l a c e de d 6 r i v e e t l a d i g u e de I 7 u s a " n e mar6motrice ( y c o ~ n p r i sl e s
t u r b i n e s et les v a n n e s ) , a v a n t d ' a d o p t e r l e modPle de c o n s t r u c t i o n f i n a l .
INTRODUCTION
A t t h e Acadia c o n f e r e n c e i n 1976 s e v e r a l s p e a k e r s a d d r e s s e d t h e
t o p i c of ice (Hodd 1979, Greenberg 1971, and G a r r e t t 1 9 7 7 ) - T h e r e seemed
t o a c o n s e n s u s t h a t i c e c o v e r would i n c r e a s e i n the headpond b u t few
d e t a i l e d p r e d i c t i o n s were o f f e r e d because of a l a c k of lcrlowledge a b o u t proc e s s e s c o n t r o l l i n g i c e f o r m a t i o n i n t h e upper r e a c h e s of t h e Bay of Fundy,
S i n c e t h e n two f u r t h e r i c e s t u d i e s have been c o n d u c t e d : Knight and
Dalrymple (1976) i n Cobequid Bay and Gordon a n d Desplanque (1983) i n
Cumberland Basin. The f o l l o w i n g a r e some p r e d i c t i o n s based l a r g e l y on t h e
work i n Cumberland Basin.
These p r e d i c t i o n s s h o u l d be c o n s i d e r e d v e r y
t e n t a t i v e u n t i l reviewed and confirmed by o t h e r s ,
T h e r e a r e b a s i c a l l y f o u r t y p e s of i c e o c c u r r i n g fn t h e upper
r e a c h e s of Fundy:
1,
S h e e t i c e forms a c o n t i n u o u s
-e x c e p t f o r v e r t i c a l movement
along the shoreline.
l a y e r t h a t more o r l e s s s t a y s %n p l a c e
which can produce f r a c t u r i n g , e s p e c i a l l y
I t forms ashere t i d a l energy i s l o w ,
2.
Drift ice
--
forms on t h e s e a w a t e r s u r f a c e where etidal Prlergy I s Ihigh and
r e m a i n s as rounded d i s c r e t e p i e c e s b e c a u s e of a l m o s t c o n t i n u a l movement
It can s t r a n d on i n t e r t i d a l f l a t s .
i n t i d a l currents.
3,
S h o r e f a s t i c e forms when d r i f t i c e s t r a n d s a l o n g t h e s h o r e l l r ~ ebetween
neap and s p r i n g h i g h w a t e r l e v e l s and can d e v e l o p t h i c k accumulatiorls
which remain i n p l a c e u n t i l t h e s p r i n g thaw.
It i s most pronounced
a l o n g t i d a l r i v e r s and c o n t r i b u t e s t o f l o o d i n g by r e s t r i c t i n g c r o s s - "
sectional areas,
P
4.
Frozen c r u s t forms on t h e s u r f a c e of i n t e r t i d a l s e d i m e n t s by t h e downward f r e e z i n g of p o r e w a t e r and t h e upward a c c r e t i o n of precipitation.
I c e c o n d i t i o n s a r e p r o f o u n d l y i n f l u e n c e d by t i d a l p r o p e r t i e s and
marked changes a r e e x p e c t e d i n t h e headpond r e g i o n of a t i d a l power p r o j e c t
as a r e s u l t of reduced h i g h w a t e r l e v e l s , t i d a l e n e r g y , and i o c e r t i d a l
area.
E a r l i e r p r e d i c t i o n s t h a t t h e a r e a l e x t e n t of s h e e t i c e c o v e r a g e
w i l l i n c r e a s e b e c a u s e of reduced t i d a l e n e r g y seem j u s t - l f f e d (Greenberg
1 9 7 7 ) . A t t h e p r e s e n t , s h e e t i c e i s g e n e r a l l y r e s t r i c t e d t o t h e upper
p a r t s of t i d a l r i v e r s but how much f a r t h e r i t would e x t e n d seaward i s d i f f i c u l t t o p r e d i c t , The s t r a t i f i c a t i o n p r e d i c t e d by G a r r e t t e t a l . (1978)
w i l l a l s o promote t h e development of sheer: i c e by producing P r e s h e r s u r f a c e
w a t e r and a f a s t e r c o o l i n g r a t e i n t h e f a l l , 'The exparzded s h e e t i c e zoile
would p r o b a b l y he h e a v i l y f r a c t u r e d from vertical t j d a l movement, e s p e c i a l l y a l o n g t i d a l r i v e r s , and s h o u l d remain i n p l a c e t a n t i 1 s p r i n g b r e a k u p ,
The f o r m a t i o n of s h e e t i c e would be encouraged by I n t e n t i o n a l l y h o l d i n g t h e
headpond w a t e r l e v e l c o n s t a n t ( a t a h i g h e l e v a t i o n ) f o r s e v e r a l d a y s i n
e a r l y w i n t e r under t h e p r o p e r w e a t h e r c o n d i t b o n s , B e f o r e t h i s p r a c t i c e was
c o n s i d e r e d , however, o t h e r e n v i r o n m e n t a l e f F e c t s such a s sediment compact i o n must be examined,
The Annapolis R i v e r causeway, c o n s t r u c t e d i n 1960, p r o v i d e s a usef u l a n a l o g y , B e f o r e c o n s t r u c t i o n , t h e e s t u a l y was s u b j e c t t o c o n s i d e r a b l e
t i d a l e n e r g y (mean t i d a l r a n g e w a s 7 m) and c o n t a i n e d nioving d r i f t i c e d m i n g t h e w i n t e r months. The causeway removed most of t h e t i d a l i n f l u e n c e
and t h e w a t e r became f r e s h e r and s t r a t i f i e d , A s a r e s u l t , a c o n t i n u o u s
l a y e r of s h e e t i c e i s now formed e a c h w i n t e r , up t o 60 cm t h i c k (Sweet,
1 9 6 7 ) , which e x t e n d s r i g h t $ o m t o t h e causeway, i t : w i l l be i n t e r e s t i n g t o
s e e what changes o c c u r once t h e p i l o t t i d a l power p r o j e c t f s i n o p e r a t i o n
and t i d a l e n e r g y i n t h e b a s i n i n c r e a s e s .
The p r e d i c t e d i n c r e a s e i n s h e e t i c e c o v e r a g e i n t h e t i d a l b a s i n
w i l l r e d u c e t h e open w a t e r a r e a where d r i f t i c e can form, Expanded sllcet-
i c e c o v e r a g e s h o u l d a l s o r e t a r d d r i f t i c e from r e a c h i n g t h e s h o r e l i n e and
forming s h o r e f a s t i c e , e s p e c i a l l y i n t h e lower p a r t s of t i d a l r i v e r s ,
These changes, coupled w i t h t h e lower h i g h w a t e r Bevels ( 0 , 3 , 0 , 7 , and
1.0 m f o r n e a p , mean, and s p r i n g t i d e s , r e s p e c t i v e l y ) , s h o u l d r e d u c e b o t h
t h e e x t e n t and e l e v a t i o n s of s h o r e f a s t i c e i n t i d a l r i v e r s , which i n t u r n
s h o u l d d e c r e a s e t h e l i k e l i h o o d and s e v e r i t y of w $ n t e r f l o o d i n g produced by
d r i f t - i c e j a m s i11 r i v e r s , I f t h i s p r e d i c t i o i a i s a c c u r a t e , i t c o n s t i t u t e s a
p o s i t i v e impact f o r t h e Cobequid Way s i t e (B9) because of c u r r e n t s e r i o u s
Shore East i c e w i l l s t i l l
f l o o d i n g i n t:h@ Salmon R i v e r a t T r u r o , M,S,
d e v e l o p more seaward i n t h e headpond where d r i f t i c e now d o m i n a t e s b u t i t s
e l e v a t i o n and v e r t i c a l e x t e n t w i l l be r e d u c e d ,
The i n t e r t i d a l a r e a of the headpond w 4 1 1 be reduced by a b o u t 65% on
a mean t i d e , T h e r e f o r e , much l e s s i n t e r t i d a l sediment w i l l be exposed t o
s c o u r by d r i f t i c e as t h e t i d e r i s e s and f a l l s , The s c o u r i n g promotes b o t h
t h e r e s u s p e n s i o n of sediment and t h e m o r t a l i t y of b e n t h i c o r g a n i s m s , e s p e c i a l l y Corophium, and any r e d u c t i o n i n i t s magnitude may promote b i o l o g i c a l
productivity.
A s u b s t a n t i a l amount of d r i f t i c e can form seaward o f b o t h p o t e n t i a l b a r r a g e s i t e s (Cumberland B a s i n and Cohequi-d Bay), The p r e s e n c e of
d r i f t i c e on b o t h s i d e s of a b a r r a g e p r e s e n t s s e v e r a l i n t e r e s t i n g q u e s t j o n s
t h a t e n g i n e e r s s h o u l d c o n s i d e r when p r e p a r i n g f i n a l d e s i g n s , For example,
w i l l i c e p a s s t h r o u g h t h e s l u i c e s and t u r b i n e s ? i f s o , i s t h e r e a p o s s f b i l i t y of damage t o equipment o r c l o g g i n g ? What w i l l happen t o t h e i c e
t h a t w i l l ac.cumulate on e i t h e r s i d e of t h e b a r r a g e and c o u l d i t b u i l d up t o
t h e d e g r e e t h a t w a t e r f l o w would be s e r i o u s l y impeded?
I n summary, t h i s b r i e f r e v i e w i d e n t i f i e s a nutnber of p o s s i b l e negat i v e and p o s i t i v e i m p a c t s on i c e development t h a t c o u l d r e s u l t from t i d a l
power development, It a l s o r a i s e s some q u e s t i o n s t h a t s h o u l d he c o n s l d e r e d
by e n g t n e e r s i n f i n a l p r o j e c t desPgn,
G a r r e t t , C,J.R,
1977, T i d a l i n f l u e n c e s on t h e p h y s i c a l oceanography of
I n : Daborn, G . K , , e d , Fundy
t h e Bay of Fundy and G ~ r l f of Maine,
t i d a l power and t h e e n v i r o n m e n t , Acadia U n i v e r s i t y I n s t i t u t e
P u b l i c a t i o n No, 2 8 , pp, 209-115,
G a r r e t t , C , J , R , , J , R , Ree1.y and D,A, Greenberg,
1978, T i d a l mixing v e r s u s
t h e r m a l s t r a t i f i c a t i o n i n t h e Bay of' Pvndy and Gulf of N a i n e ,
Atmosphere-Ocean 16: 403-423,
Gordon, D.C.,
J r , , and C, Desplanque, 1983, Dynamics and e n v i r o n m e n t a l
e f f e c t s of i c e i n t h e Cumberland B a s i n of the Ray of Pundy, Can.
J, F i s h . Aquat, Sci, 4 8 : 1331-1342,
Greenberg, D , A ,
2877, E f f e c t s of t i d a l
oceanography of t h e Bay of Pundy
G.R,, ed,
Fundy t i d a l power and
U n i v e r s i t y f n s t i t t a t e Publf c a t i o n
power development on t h e p h y s i c a l
and Gulf of Naine,
I n : Daborn,
t h e e n v i r o n m e n t . Aeadia
No, 2 8 , pp, 2110--232,
Hodd, S.L.
1977, E n v i r o n m e n t a l c o n s i d e r a t i o n s of a Fundy t i d a l power project.
I n : Daborn, G,R., e d , Fundy t i d a l power and t h e e n v i r o n ment. Acadia U n i v e r s i t y S n s t f t u t e P u b l i c a t i o n No. 2 8 , pp. 72-81.
K n i g h t , R . J . and K,W. Dalrymple,
1976. Winter c o n d i t i o n s i n a m a c r o t l d a l
e n v i r o n m e n t , Cobequid Ray, Nova S c o t i a . Revue d e Geographie d e
M o n t r e a l 30: 65-85,
Sweet, C.E,
1967. P r e l i m i n a r y r e p o r t on i c e c o n d i t i o n s i n Mlaas B a s i n ,
C h i g n e c t o Bay and t h e Annapolis Wasin a r e a of t h e Bay of Pundy.
Unpublished r e p o r t srlbmitted t o t h e A t l a n t i c T i d a l Power programmi n g Board, 22 pp,
QUESTIONS aPaD COMMENTS
K. Mann:
With a b a r r a g e i n p l a c e do you t h i n k f a s t i c e c o v e r a g e w i l l ext e n d o v e r t h e e n t i r e Basin and what w i l l v a r i a b l e w a t e r l e v e l s do t o t h i s
ice?
D. Gordon: I t h i n k t h e E a s t i c e c o v e r a g e w i l l be c o n f i n e d t o t ? ~ ei n n e r
p a r t s of t h e Basin and I t sinould more o r l e s s s t a y i n p l a c e and j u s t d r o p
when t h e t i d e r e c e d e s .
I d o u b t i f f a s t i c e c o v e r a g e would e x t e n d seaward
t o the barrage.
T h e r e p r o b a b l y would s t i l l be a l a r g e zone of d r i f t i c e .
T h i s i c e would move w i t h t h e w a t e r and b u l l d up on t h e i n s i d e , T h e r e might
be much Inore of a problem w i t h b u i l d up of d r i f t : Ece on t h e seavanrd f a c e of
the barrage,
K , Mann:
Do you know whether i c e forms on t h e s a l t ~ n a r s i l c s and where?
D , Gordon: T h e r e a r e
dominated by S p a r t i n a
two t y p e s of s a l t marsh, t h e low marsh which i s
a l t e r n i f l o r a and t h e h i g h marsh composed p r i m a r i l y of
S . p a t e n s found a t a h i g h e r e l e v a t i o n , Under p r e s e n t c o n d i t i o n s s h o r e F a s t
i c e b u i l d s up a t o r j u s t above t h e %ow martsii zorae and e x t e n d s orst o v e r t h e
low marsh, C o n s i d e r a b l e i c e b u i l d s up and a Barge a r e a of t h e zone can be
ice-covered f o r a l a r g e p o r t i o n of t h e w i n t e r , I c e forrnatjeon i n t h e hdgh
marsh i s l a r g e l y f r e s h w a t e r I c e i n t h e t i d e p o o l s . The o n l y t i m e s e a i c e
o c c u r s on t h e h i g h marsh i s i n t h o s e w i n t e r s when extreme s p r i n g t i d e s
o c c u r t h a t push t h e d r i f t i c e up o n t o t h e marsh s u r f a c e . The y e a r b e f o r e
l a s t when we made o u r o b s e r v a t t o n s we had a w l n t e r of small s p r i n g t i d e s
and no s e a i c e reached t h e h i g h marsh, The h i g h marshes were c o v e r e d w i t h
snow and l o c a l l y - f o r m e d i c e on t o p of p o o l s . When s e a i c e r e a c h e s t h e h i g h
marsh i t a p p e a r s t o remain u n t i l i t m e l t s i n p l a c e ,
A . Smith: Do you n o t t h i n k t h e a d d i t i o n a l sheet i c e farmed behind a h a r r a g e w i l l b r e a k p i e c e s o f f i t s edge and c a u s e problems s u c h as f l o o d i n g ,
D. Gordon: It i s a q u e s t i o n of how f a r seaward t h e zone of f a s t i c e w i l l
e x t e n d . C e r t a i t ~ l yt h e r e w i l l be b r e a k i r ~ g o f f o f i t particularly a t t h e
o u t e r edge b u t t h e r e w i l l p r o b a b l y s t i l l be i c e w a l l s forming i n a l l t i d a l
rivers.
A more i m p o r t a n t f a c t i s t h a t a b a r r a g e would probab-1.y lower t h e
s p r i n g h i g h w a t e r l e v e l by a b o u t a m e t e s and even i f t h e r e i s ~o change i n
f a s t i c e coverage i c e w a l l s w i l l o n l y b u i l d t o n maximurn e l e v a t i o n of 1 m
below p r e s e n t e l e v a t i o n s and t h a t a l o n e would h e l p a l l e v i a t e i c e p r o b l e m s .
We t h i n k t h e a d d i t i o n a l East i c e coverage a c r o s s t h e b a s i n s u r f a c e w i l l
block d r i f t i c e from moving i n l a n d . A t p r e s e n t t h i s s t r a n d e d d r i f t i c e
c a u s e s many of t h e f l o o d i n g problems,