MARINE HABITAT TREND ANALYSIS SARASOTA COUNTY

FINAL REPORT

prepared f o r SARASOTA COUNTY

N a t u r a l Resources Department P o s t O f f i c e Box 8

S a r a s o t a , EL 34230

by MANGROVE SYSTEMS, INC. P o s t O f f i c e Box 291097

Tampa, FL 33687

September 1988

INTRODUCTION

I n o r d e r t o document h i s t o r i c a l c o n d i t i o n s and e v a l u a t e t r e n d s of mar ine and

e s t u a r i n e h a b i t a t s i n S a r a s o t a County, a Marine H a b i t a t Trend A n a l y s i s h a s

been accomplished comparing t h e p e r i o d s 1948, 1972 and 1987. The p r o j e c t

r e p r e s e n t s t h e f i r s t a t t e m p t t o a n a l y z e t r e n d s i n a r e a l e x t e n t of mar ine

h a b i t a t s u s i n g S a r a s o t a County as t h e s t u d y area.

P r e v i o u s s t u d i e s v a r i e d g r e a t l y i n s e l e c t i o n of s t u d y a r e a boundar ies , o r

t a r g e t e d on ly s p e c i f i c h a b i t a t s , s u c h a s s e a g r a s s beds . P r e v i o u s t r e n d

a n a l y s e s i n w e s t c e n t r a l F l o r i d a have focused on t h e l a r g e r e s t u a r i n e sys tems

of Tampa Bay and C h a r l o t t e Harbor. S i n c e p r o d u c t i o n of t h e s e a n a l y s e s ,

i n f o r m a t i o n concern ing t h e S a r a s o t a Bay complex h a s been c o n s i d e r e d a c r u c i a l

m i s s i n g l i n k and w i l l p rov ide c o n t i n u o u s coverage a l o n g t h e sou thwes t c o a s t of

F l o r i d a .

T h i s p r o j e c t documents h i s t o r i c a l c o n d i t i o n s and e v a l u a t e s t r e n d s i n mar ine

h a b i t a t s t o p rov ide an a c c u r a t e f o u n d a t i o n f o r s u b s t a n t i v e management

d e c i s i o n s a f f e c t i n g t h e c o a s t a l mar ine r e s o u r c e s i n S a r a s o t a County.

METHODOLOGY

The h a b i t a t t r e n d a n a l y s i s i n v o l v e s t h e mapping of mangrove f o r e s t s ,

s a l t m a r s h e s , s e a g r a s s meadows, o y s t e r b a r s , bay waters, and d r i f t a l g a l

communities of t h e mar ine and e s t u a r i n e a r e a s of S a r a s o t a County. The mapping

w a s accompl ished u s i n g USGS 7.5 ' quadrang le maps ( F i g u r e 1) a s a b a s i s of

c o m p i l a t i o n of p h o t o i n t e r p r e t i v e work p r o d u c t s f o r t h r e e time p e r i o d s : 1948,

1972 and 1987. These t i m e p e r i o d s were chosen based on a v a i l a b i l i t y and

q u a l i t y of v e r t i c a l a e r i a l photography.

SARASOTA COUNTY

MEXICO

USGS QUADRANGLE

1 Bradenton Beach

2 Bradenton

3 Sarasota

4 B i r d Keys

5 Laure l

6 Venice

7 Englewood NW

8 Englewood

9 Ftyakka R iver

F igu re 1.

2

The maps produced i n t h i s p r o j e c t d e p i c t e i g h t n u m e r i c a l l y d e s i g n a t e d mapping

u n i t s o r h a b i t a t t y p e s d e f i n e d i n T a b l e 1. I n a d d i t i o n t o t h e s e , t h r e e

a lphanumeric d e s i g n a t i o n s were added t o t h e i n i t i a l scope t o d e f i n e t h e

p r e s e n c e of l a r g e d r i f t a l g a l communities ( lA , sparse/medium; 2A, dense ; 3A,

pa tchy) p r e s e n t i n L i t t l e S a r a s o t a Bay and Lemon Bay.

S e a g r a s s e s were mapped i n t h r e e c a t e g o r i e s of a p p a r e n t d e n s i t y ( 1 , s p a r s e /

medium; 2 , dense ; 3 , pa tchy) based on s i g n a t u r e i n t e n s i t y on t h e imagery and

subsequen t f i e l d v e r i f i c a t i o n o f t h e c u r r e n t t i m e p e r i o d s e r i e s . A c a t e g o r y

e n t i t l e d "Other H a b i t a t s " (mapping u n i t 8) was i n c l u d e d t o f a c i l i t a t e

d i g i t i z a t i o n and t o i d e n t i f y non- ta rge t a r e a s ( i . e . , n o t h a b i t a t s 1 th rough

7 ) .

B lack and w h i t e v e r t i c a l aerial photography d a t e d February 1948 of scale

1:20,000 ( lH=1 ,666 .67 ' ; o b t a i n e d from t h e U.S. Department of A g r i c u l t u r e ,

A g r i c u l t u r a l S t a b i l i z a t i o n and Conserva t ion S e r v i c e ) provided t h e b a s i s of t h e

h i s t o r i c a l p h o t o i n t e r p r e t i v e component of t h e t r e n d a n a l y s i s . Photo-

i n t e r p r e t i v e d e l i n e a t i o n s were p repared on t r a n s p a r e n t mylar o v e r l a y s of e a c h

9"x9" p r i n t compr i s ing t h e image base . These o v e r l a y s were s u b s e q u e n t l y

compiled on mylar b a s e s produced from USGS 7.5 ' q u a d r a n g l e s a t a s c a l e of

1:24,000 (1"=24,000') .

The 1972 map s e r i e s is based on 1972 b l a c k and w h i t e v e r t i c a l a e r i a l b l a c k

d i a z o p r o d u c t s o f photography flown by Mark Hurd A e r i a l Surveys , I n c . ( s c a l e

1 :24 ,000) . P r o d u c t i o n of t h e 1987 map series was s i m i l a r l y accomplished u s i n g

n a t u r a l c o l o r v e r t i c a l a e r i a l photography d a t e d December 1984, e n l a r g e d t o

Table 1. Habi ta t des ignat ions , d e f i n i t i o n s and a r e a , Sarasota County Coastal Marine Habitat Trend Analysis conducted by Mangrove Systems, Inc.

HABITAT SARASOTA CO. FDOT 1987 AREA NO. DESCRIPTION - APOXSEE FLUCCS USEWS - ac - ha

1 Seagrass, sparse I V A . Brackish bays 9111 E2AB2 835 337 t o medium Seagrass beds

2 Seagrass, dense I V A . Brackish bays 9112 E2AB2 2,654 1,075 Seagrass beds

3 Seagrass, patchy I V A . Brackish bays 9113 E2AB2 554 224 Seagrass beds

Seagrass, t o t a l I V A . Brackish bays 91 1 E2AB2 4,043 1,636 (not mapped; t o t a l Seagrass beds of 1, 2 and 3)

1 A Macroalgae, sparse t o medium

2A Macroalgae, dense - - E2AB1 293 119

3A Macroalgae, patchy - - E2AB1 111 45

4 Mangrove swamp IIIA. Estuar ine edges 612 E2SS3 84 3 341 Mangrove swamps E2F03

5 Tida l marshes, I I I B . Es tuar ine edges 642 E2EM5 45 17 sa l twa te r T ida l marshes

6 Oyster beds (bars ) IVB. Brackish bays 654 E2RF2 132 54 Oyster beds

7 Bay waters IVC. Brackish bays 541 ElOW 13,802 5,585 Bay waters (510)

8 Other h a b i t a t s (not mapped)

1:24,000 ( l W = 2 , 0 0 0 ' ; o b t a i n e d from AeroColor, I n c . ) . T h i s photography

p rov ided t h e b a s i s of f i e l d v e r i f i c a t i o n of p r e s e n t (1987-88) c o n d i t i o n s .

The a r e a l e x t e n t of mar ine h a b i t a t s were c a l c u l a t e d by d i g i t a l i n c o r p o r a t i o n

i n t o t h e Marine Resource Geograph ica l I n f o r m a t i o n System [MRGIS] a t t h e

F l o r i d a Department of N a t u r a l Resources Bureau of Marine Research i n S t .

P e t e r s b u r g . The d i g i t a l d a t a b a s e s produced were d i v i d e d i n t o s i x a r e a s (SC 1

t h r o u g h SC 6) t o f a c i l i t a t e i d e n t i f i c a t i o n of t r e n d s w i t h more r e s o l u t i o n t h a n

p o s s i b l e a t t h e o v e r a l l county l e v e l . T a b l e 2 d e f i n e s t h e p h y s i c a l b o u n d a r i e s

of t h e s e s u b a r e a s which are d e p i c t e d on t h e accompanying map series.

Tab le 2. Boundar ies of s u b a r e a s SC 1 t h r o u g h SC 6 d e p i c t e d on t h e accompanying map series.

SC 1 Mana tee /Saraso ta County l i n e s o u t h t o R i n g l i n g Causeway

SC 2 R i n g l i n g Causeway s o u t h t o S t i c k n e y P o i n t Br idge

SC 3 S t i c k n e y P o i n t B r i d g e s o u t h t o Blackburn P o i n t Road

SC 4 Blackburn P o i n t Road s o u t h t o Albee Road a t Nokomis Beach ( s o u t h end of Blackburn Bay)

SC 5 Albee Road s o u t h t o Manasota Br idge

SC 6 Manasota Br idge s o u t h t o S a r a s o t a / C h a r l o t t e County l i n e ; a l s o i n c l u d e s G o t t f r i e d Creek n o r t h of county l i n e .

RESULTS

The d a t a r e p o r t e d i n T a b l e s 3 th rough 5 r e p r e s e n t s t h e a n a l y s i s of 1948, 1972

and 1987 map s e r i e s . Tab le 6 shows t h e change i n p e r c e n t compos i t ion and

a c r e a g e o f c o a s t a l h a b i t a t s between 1948 and 1987; Tab le 7 summarizes t h e

changes o c c u r r i n g among a l l t h r e e t ime p e r i o d s .

C o a s t a l mar ine h a b i t a t s covered 20,331 a c r e s i n 1948, and were reduced by 2%

(416 acres) i n 1972. Between 1972 and 1987, t o t a l a c r e a g e was f u r t h e r reduced

t o 19,269 acres, f o r a n o v e r a l l r e d u c t i o n of 5.2% o r 1 ,062 a c r e s . The

d i f f e r e n c e s between 1948 and 1987 r e p r e s e n t a 13% i n c r e a s e i n open water a r e a ,

a 21% d e c r e a s e i n o y s t e r b a r a r e a , and d e c r e a s e s of v e g e t a t e d h a b i t a t s a s

f o l l o w s :

S e a g r a s s Mangroves T i d a l Marsh

DISCUSSION

The changes observed are a t t r i b u t a b l e t o d r e d g i n g and f i l l i n g of s h a l l o w wate r

h a b i t a t s t o s u p p o r t u r b a n i z a t i o n , a s w e l l as t o wa te r q u a l i t y d e g r a d a t i o n

r e s u l t i n g from a g r i c u l t u r a l and m u n i c i p a l s o u r c e s . T h i s l o s s of we t l and

h a b i t a t is c o n s i s t e n t w i t h r e d u c t i o n s q u a n t i f i e d f o r o t h e r a r e a s of F l o r i d a .

H a r l e n (1979) r e p o r t e d s e a g r a s s l o s s of -43% f o r n o r t h e r n Biscayne Bay; a -29%

l o s s of s e a g r a s s i n C h a r l o t t e Harbor h a s been r e p o r t e d by H a r r i s -- e t a l .

(1983). Lewis st. (1985) r e p o r t e d -81% l o s s of s e a g r a s s e s i n Tampa Bay,

and Mangrove Systems, I n c . (1984) r e p o r t e d -75% d e c l i n e of s e a g r a s s e s i n

C l e a r w a t e r Harbor .

w a m . 3 . 3 0 U d m 3 d d

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N m

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m m m z 3 a, ffl * m . lo 5 r c m 0 !+ ffl

a, !+ a * c Y m h L r c r a, rc on aa, a, m Y M M a m +J

P rd m~ a a o m c 2 z!

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Table 4. Percent composition of coas t a l marine h a b i t a t s i n Sarasota County, 1972.

MAPPING UNIT SC 1 -- SC 2 -- SC 3 -- SC 4 -- SC 5 -- SC 6 --

Seagrass :

sparse / 1 ac 102 56 . 319 136 24 93 medium % 1.1 1.5 13 .3 7.5 4.3 4.1

dense 2 ac 1696 668 695 348 57 822 % 18.8 17.5 29 .O 19.1 10.2 36.0

patchy 3 ac 23 - 1 2 7 38 % 0.3 0 <0.1 0 . 1 1 .3 1 .7

Tota l ac 1821 724 1015 48 6 88 953 Seagrass % 20.1 19.0 42.3 26.7 15.7 41.7

Macroalgae:

sparse / 1 A ac - - 255 - - - medium % 0 0 10.6 0 0 0

dense 2A ac - - 120 - - - % 0 0 5 .o 0 0 0

patchy 3A ac - - - - - - % 0 0 0 0 0 0

Mangrove 4 ac 239 23 1 177 165 113 107 Z 2.6 6 .1 7.4 9.1 20.2 4.7

T ida l 5 ac - - 11 16 11 6 Marsh % 0 0 0.5 0.9 2.0 0.3

Oyster 6 ac - 9 67 33 1 5 Bar % 0 0.2 2.8 1 . 8 0.2 0.2

Bay 7 ac 6985 2843 753 1120 346 1215 Waters % 77.2 74.7 31.4 61.5 61.9 53.1

TOTAL ac 9045 3807 2398 1820 559 2286 % 45.4 19.1 12.0 9.1 2.8 11.5

TOTAL

Table 5 . P e r c e n t composition of coas t a l marine h a b i t a t s i n Sarasota County, 1987.

MAPPING UNIT - SC 1 -- SC 2 -- SC 3 -- SC 4 -- SC 5 -- SC 6 --

Seagrass :

sparse / 1 ac 257 82 250 134 3 109 medium % 2.9 2.5 10.3 7.8 0.5 4.7

dense 2 ac 873 470 42 2 375 85 429 % 9.7 14.5 17.4 21.7 15.0 18.5

patchy 3 ac 123 98 150 26 - 157 % 1 . 4 3.0 6.1 1.5 0 6.8

To ta l ac 1253 650 82 2 535 88 695 Seagrass % 14.0 20 .O 33.8 31 .O 15.5 30.0

Macroalgae:

dense. 2A ac %

patchy 3A ac - - 6 - - 105 % 0 0 0.3 0 0 4.5

Mangrove 4 ac 138 250 134 113 106 102 % 1.5 7.7 5.5 6.6 18.7 4.4

T ida l 5 ac - - 5 11 21 8 Marsh % 0 0 0.2 0.6 3.7 0.3

Oyster 6 ac 1 14 71 33 1 12 Bar % <0.1 0 .4 3.0 1 .9 0.2 0.5

Bay 7 ac 7586 2330 1100 1033 352 1401 Waters % 84.5 71.9 45.2 59.9 61.9 60.3

TOTAL ac 8978 3244 2431 1725 568 2323 % 46.6 16.8 12.6 8.9 3.0 12.1

TOTAL

T a b l e 6. P e r c e n t c h a n g e i n a r e a o f c o a s t a l m a r i n e h a b i t a t s i n S a r a s o t a County between 1948 a n d 1987.

MAPPING UNIT

S e a g r a s s : SC 1 -- SC 2 -- SC 3 -- SC 4 -- SC 5 -- SC 6 -- TOTAL

s p a r s e l 1 1948 a c 172 202 267 140 6 143 930 medium 1987 257 82 250 134 3 109 835

change +85 -1 20 -17 -6 -3 -34 -95 % +49 -58 -6 -4 -50 -24 -10

d e n s e 2 1948 a c 1513 890 1114 411 180 706 4814

p a t c h y 3 1948 a c 141 15 7 31 3 244 441 1987 123 $8 150 26 - 157 554

change -18 +83 +I43 -5 -3 -87 +I13 % -13 +553 +2042 -16 -100 -36 +26

T o t a l 1948 a c 1826 1107 1388 582 189 1093 6185 S e a g r a s s 1987 1253 650 822 535 88 695 4043

change -573 -457 -566 -47 -101 -398 -2142 % -31 -41 -40 -8 -53 -36 -35

Macroa lgae :

d e n s e 2A 1948 a c - - 1987 - - c h a n g e n o t c a l c u l a t e d

p a t c h y 3A 1948 a c - - 1987 - - change n o t c a l c u l a t e d

Mangrove 4 1948 a c 257 364 1987 138 250

change -119 -114 % -46 -31

T i d a l 5 1948 a c - 15 Marsh 1987 - -

O y s t e r 6 1948 a c - 17 Bar 1987 1 14

change +1 -3 % - -18

Bay 7 1948 a c 6933 2486 W a t e r s 1987 7586 2330

change +653 -156 % +9 +6

T a b l e 7. Summary of changes i n a c r e a g e and p e r c e n t compos i t ion of c o a s t a l mar ine h a b i t a t s i n S a r a s o t a County between 1948 and 1972, and between 1972 and 1987.

Open Water 12,220 60.1 13,262 66.6 13,802 71.6 S e a g r a s s 6 , 1 8 5 A 30.4 5 ,087 25.5 4 ,043 21 .O Mangroves 1 ,546 7 .6 1 ,032 5 .2 8 4 3 4.4 T i d a l Marsh 271 1.3 44 0.2 45 0.2 O y s t e r B a r s 109 0 .6 115 0.6 132 0 .7

Reduc t ion i n a r e a s i n c e 1948

Area l cover and h i s t o r i c a l l o s s of s e a g r a s s e s i n v a r i o u s a r e a s of t h e S a r a s o t a

Bay complex are r e p o r t e d i n T a b l e 8, as modi f i ed from Lewis and S a u e r s ( i n

p r e p a r a t i o n ) . The major d i f f e r e n c e s i n t h e d a t a a r e p r i m a r i l y t h e r e s u l t of

e a c h s t u d y c o n c e n t r a t i n g on s e a g r a s s c o v e r i n d i f f e r e n t p a r t s o f t h e bay. F o r

example, Evans and Brungard t (1978) i n c l u d e d on ly South S a r a s o t a Bay and

R o b e r t ' s Bay, w h i l e t h e NUS C o r p o r a t i o n s t u d y (1986) i n c l u d e d on ly North

S a r a s o t a Bay. S a u e r s (1981) s t u d i e d o n l y a p o r t i o n of South S a r a s o t a Bay;

McNulty -- e t a l . (1972) i n c l u d e d bo th S a r a s o t a Bay and L i t t l e S a r a s o t a Bay, b u t

d i d n o t i n c l u d e any h i s t o r i c a l d a t a .

T i d a l marsh and mangrove f o r e s t d e c l i n e s of -44% have been documented i n Tampa

Bay by Lewis (1977) , by -82% i n n o r t h e r n Biscayne Bay (Har len 1979) , and -46%

i n C l e a r w a t e r Harbor (Mangrove Systems, I n c . 1984). H a r r i s e t a l . (1983) -- r e p o r t e d a 51% d e c r e a s e i n areal cover of s a l t m a r s h e s i n C h a r l o t t e Harbor and

a 10% i n c r e a s e i n mangrove f o r e s t area. T h i s i n c r e a s e was a t t r i b u t e d to :

enac tment of F e d e r a l , S t a t e and l o c a l p r o t e c t i v e r e g u l a t i o n s p r i o r t o l a r g e

s c a l e development i n t h e a r e a ; c o l o n i z a t i o n of t i d a l f l a t s (which e x h i b i t e d a

r e d u c t i o n i n a c r e a g e ) by mangroves; and o t h e r f a c t o r s such as marsh s u c c e s s i o n

and c o l o n i z a t i o n of a r t i f i c i a l h a b i t a t s s u c h a s s p o i l i s l a n d s .

Tab le 8. S e a g r a s s areal cover d a t a r e p o r t e d f o r v a r i o u s a r e a s of S a r a s o t a Bay (modi f i ed f rom Lewis and S a u e r s , i n p r e p a r a t i o n ) .

HISTORICAL CURRENT PERCENT year a c - h a - year - - h a CHANGE REFERENCE ac

1970 7 , 6 1 0 3,080 - - - - McNulty -- e t a l . 1972

1948 1 , 9 2 5 783 1974 1 , 4 6 0 591 -25 Evans and Brungard t 1978

1948 262 106 1979 121 49 -57 S a u e r s 1981

1 9 5 7 5 ,902 2,389 1982 4 , 4 9 3 1,818 -24 NUS Corp. 1986

1957 10,000 4,047 1986 7 ,565 3 ,062 -25 Lewis and S a u e r s ( i n p r e p a r a t i o n )

MANAGEMENT RECOMMENDATIONS

Resource management recommendations s h o u l d f o c u s on p r e s e r v a t i o n of t h e

remain ing c o a s t a l h a b i t a t s , and maintenance and improvement of wa te r q u a l i t y

which w i l l promote p r o l i f e r a t i o n of s e a g r a s s e s and d i s c o u r a g e a l g a l blooms.

The re-opening of Midnight P a s s may r e a l i z e some l o s s of s e a g r a s s e s due t o

i n c r e a s e d c u r r e n t v e l o c i t i e s , b u t d a i l y t i d a l i n t r o d u c t i o n of mar ine w a t e r s

would be expec ted t o reduce problems a s s o c i a t e d w i t h n u t r i e n t l o a d i n g . S a u e r s

and S e r v i s s (1985) a l s o r e p o r t e d a p o t e n t i a l f o r i n c r e a s e s exposure of L i t t l e

S a r a s o t a Bay t o r e d t i d e e v e n t s t h a t c o u l d r e s u l t from open ing t h e p a s s .

Another p o t e n t i a l a r e a of i n t r o d u c i n g Gulf waters may e x i s t i n t h e Alexander

I s l a n d a r e a on Manasota Key where t h e seaward e x t e n t of Manasota Key Road

(S.R. 789) h a s exper ienced s e v e r e and c h r o n i c e r o s i o n . A b r i d g e and non-

n a v i g a b l e i n l e t a t t h i s l o c a t i o n would p robab ly improve wa te r q u a l i t y

c o n d i t i o n s .

Convers ions of upland s p o i l a r e a s t o w e t l a n d o r improved upland h a b i t a t ( e . g . ,

c o a s t a l hammocks) r e p r e s e n t t h e s i n g l e l a r g e s t p o t e n t i a l f o r r e - c r e a t i o n of

l o s t we t l and a c r e a g e . S p o i l areas a l o n g t h e Gulf Coas t I n t r a c o a s t a l Waterway

c o u l d b e excava ted t o i n t e r t i d a l e l e v a t i o n s and p l a n t e d w i t h marsh and

mangrove s p e c i e s , a s well as s e a g r a s s e s . C r i t i c a l a r e a s f o r t a r g e t i n g t h e s e

a c t i v i t i e s would be t h e s p o i l areas n e a r Midnight P a s s , B i r d Keys, Red Lake,

and South Venice wes t of Shamrock D r i v e , Longboat Key n o r t h e a s t of New P a s s

B r i d g e , and Alexander I s l a n d . E f f o r t s a t Midnight P a s s c o u l d be c o o r d i n a t e d

w i t h work t o r eopen t h e p a s s , and c o o r d i n a t i o n of any p u b l i c s e c t o r road

p r o j e c t i n t h e a r e a of Alexander I s l a n d .

Development of a model dredged material d i s p o s a l a r e a management program

s h o u l d beg in w i t h i d e n t i f i c a t i o n of County-owned p a r c e l s and a f e a s i b i l i t y

s t u d y i n c l u d i n g c o n c e p t u a l d e s i g n s c e n a r i o s f o r each p a r c e l . S e v e r a l small

s c a l e p r o j e c t s cou ld t h e n be des igned and implemented a s d e m o n s t r a t i o n

p r o j e c t s t o g e n e r a t e p u b l i c s u p p o r t and fund ing .

Other recommendations would i n c l u d e a n a l y s i s and m i t i g a t i v e r e t r o f i t t i n g and

improvement of i n f r a s t r u c t u r a l s u p p o r t f a c i l i t i e s , p a r t i c u l a r l y i n

m u n i c i p a l i t i e s ' i n a d e q u a t e c o n t r o l of s to rmwate r r u n o f f and was tewate r

d i s c h a r g e t o t h e Bay. These measures would b e n e f i t w a t e r q u a l i t y , which h a s

c h r o n i c a l l y s u f f e r e d d e g r a d a t i o n f rom a g r i c u l t u r a l and urban r u n o f f due t o

h i s t o r i c d i s t u r b a n c e of p a l u s t r i n e and r i v e r i n e floodway p e r t u r b a t i o n s .

c h a n n e l i z a t i o n of major f l o o d p l a i n s , p a r t i c u l a r l y e v i d e n t i n Cow Pen S lough ,

r e s u l t s i n :

-- t h e l o s s of f l o o d w a t e r a t t e n u a t i o n a b i l i t y of t h e f loodway;

-- t h e l o s s of b i o l o g i c a l a s s i m i l a t i v e a b i l i t y of t h e floodway t o

u t i l i z e n u t r i e n t s and t r a p s e d i m e n t s ; and

-- t h e l o s s o r d e g r a d a t i o n of w i l d l i f e h a b i t a t by a l t e r a t i o n of

hydroper iod and s p e c i e s compos i t ion of t h e f l o o d p l a i n .

These l o s s e s a r e u l t i m a t e l y r e a l i z e d i n d e g r a d a t i o n of water q u a l i t y i n t h e

r e c e i v i n g body. P e r t u r b e d f loodways w i t h i n a g r i c u l t u r a l b a s i n s c o n t r i b u t e t o

n u t r i e n t l o a d i n g f rom u n a s s i m i l a t e d a g r i c h e m i c a l s and an imal was te . Urbanized

floodways s u c h as P h i l l i p p i Creek a d d i t i o n a l l y c o n t r i b u t e o i l s and g r e a s e s , a s

w e l l a s heavy m e t a l s , from highway r u n o f f .

Water q u a l i t y improvements i n t h e c o n t r i b u t i n g areas as well as t h e r e c e i v i n g

b o d i e s c o u l d be r e a l i z e d by r e d i r e c t i n g f l o o d w a t e r s f rom t h e e x i s t i n g channe l

i n t o t h e a d j a c e n t h i s t o r i c f l o o d p l a i n and r e - c r e a t i n g marshes a l o n g t h e

margins of c h a n n e l i z e d f loodways, e s p e c i a l l y i n h i g h l y u r b a n i z e d s i t u a t i o n s .

Where s t r u c t u r e s such as seawalls are p r e s e n t , marshes c o u l d be c r e a t e d

waterward of s u c h s t r u c t u r e s . T h i s s c e n a r i o may be p a r t i c u l a r l y u s e f u l when

c r e a t e d a t t h e o u t f a l l from s to rmwate r p i p e s . E v a l u a t i o n on a case-by-case

s i t u a t i o n is n e c e s s a r y i n o r d e r t o r e a l i z e s u c c e s s . I n some i n s t a n c e s , t h e s e

t r e a t m e n t s are n o t p h y s i c a l l y f e a s i b l e , w h i l e i n o t h e r s , t h e marsh may need t o

be perched above t h e e x i s t i n g c h a n n e l bot tom e l e v a t i o n w i t h i n a r ange of

e l e v a t i o n where t h e marsh p l a n t s can be e x p e c t e d t o s u r v i v e . Energy

d i s s i p a t o r s o r b a f f l e s may be needed t o r e d u c e wa te r v e l o c i t y a t t h e o u t f a l l

p ipe .

Smal l s c a l e improvement of e x i s t i n g h a b i t a t s c o u l d be r e a l i z e d by p o s t i n g

c a u t i o n a r y s i g n s i n s e a g r a s s s h o a l areas where c h r o n i c p r o p e l l e r damage i s a

problem. I n s t r u c t i v e s i g n s d e s c r i b i n g t h e impor tance of s e a g r a s s h a b i t a t

c o u l d be pos ted a t a l l b o a t l a u n c h i n g f a c i l i t i e s and marinas . Examples of

t h i s t y p e of s i g n a g e a r e now p o s t e d a t a l l p u b l i c l a u n c h i n g sites.

A f u r t h e r recommendation would be t h e p lacement of small d i s s i p a t i o n

b reakwate r s on t h e f l o o d t i d e d e l t a a t New P a s s , t o r educe c u r r e n t v e l o c i t i e s

and promote n a t u r a l r e c o l o n i z a t i o n by s e a g r a s s e s on t h e f l a t . The wavebreaks

c o u l d i n c o r p o r a t e mangrove p l a n t i n g as a p o r t i o n of t h e s t r u c t u r e . Obviously ,

t e c h n i q u e s o f t h i s t y p e r e q u i r e a t leas t modular a n a l y s i s p r i o r t o implementa-

t i o n , a s do many of t h e recommendations p r e s e n t e d h e r e .

SUMMARY

The i n t e n t of t h i s document i s t o p r o v i d e a d a t a b a s e from which a

comprehensive County-wide p r e s e r v a t i o n and r e s t o r a t i o n p l a n can be

developed. Cont inued a n a l y s i s of t r e n d s i n c o a s t a l mar ine h a b i t a t s s h o u l d be

a n i m p o r t a n t e l ement of County p o l i c y and w i l l p rov ide c o n t i n u i n g d a t a f o r

c r i t i c a l management d e c i s i o n s .

LITERATURE CImD

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