Sep 1, 2018 - barrier i sland/barrier beach shores (Bal si 11 i e, 1985; Bodge and Kriebel , ..... BOB. H. 7/21 -7/26. 6 5. 1002. 3. CLAUDETTE. H. 8109-8/17. 75. 980. 4 . .... Bodge, K. R., and Kri ebel , D.L. , 1985, Storm surge and wave damage a1 ong ... manual, Volume 1: Superintendent of Documents, U.S. Government.
I
*+p 4%
a
EFFECT OF HURR/CRNE El EN4 ON FL OR/DR 'S MARS#-DOM/NR TED COAST;.
PRSCO, UEUNRNDO, A N D C / 7 R U S C O U N 7 / E S
EFFECT OF HURRICANE EI;ENA ON FIDRIDA'S MARSH-DOMINATED COAST: PASCO, 7, AND CITRUS COUNTIES
Albert C. Hine
Mark W. Evans David L. Mearns Daniel F. Belknap* Department of Marine Science University of South Florida St. Petersburg, F'L 33701 *Department of Geological Sciences 110 Boardman Hall University of Maine Orono, ME 04469
Project No. IR-85-14 Grant No. NA85AA-D-SO59
Technical Papers are duplicated i n limited quantities for specialized audiences requiring rapid access to information. They are published with limited editing and without formal review by the Florida Sea Grant College Program. Content is the sole responsibility of the author. This paper was developed by the Florida Sea Grant College Program with support frcan NOAA Office of Sea Grant, U.S. Department of Ccmnerce, grant number NA85AA-D-SG059. It was published by the Sea Grant Wension Program which functions as a ccmponent of the Florida Cooperative Extension Service, John T. Woeste, Dean, in conducting Cooperative Ektension work in Agriculture, H c ~ n eEconanics, and marine Sciences, State of Florida, U-S. Department of Colmnerce, and Boards of County Ccnsnissioners, amperating. Printed and distributed in furtherance of the Acts of Congress of May 8 and June 14, 1914. The Florida Sea Grant College is an Equal mloyment-Affirmative Action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, or national origin.
TECHNICAL PAPER NO. 49 March 1987 Price $3.00
EFFECTS OF HURRICANE ELENA ON FLORIDA'S MARSH-DOMINATED, OPEN-MARINE COASTLINE: PASCO, HERNANDO, AND GITRUS COUNTRY COAST ABSTRACT
During late August and early September, 1985, Hurricane Elena passed erratically t h r o u g h the Gulf of Mexico, threatening landfall across the west-central Florida coast. This class 3 (maximum winds were 110 knots) hurricane's unusual p a t h caused i t t o remain approximately stationary about 100 km off the west-central coast of Florida for 36 hours. Eventually, Elena passed off t o the west-northwest making 1 andfall along the Mississippi coast. Hurricane Elena caused the largest evacuation in . U.S. history of people from coastal lowlands. This storm also caused widespread property damage and i s one of the most expensive storms on record. Hurricane Elena occurred just as a detailed geologic reconnaissance of a three country sector of Florida's open-marine, marsh-dominated coast was completed. Hurricane Elena provided an excel 1ent opportunity t o examine the effect of high energy events on this type of coast. The Pasco, Hernando, and Citrus County coast i s distinctly different from the sandy barrier island coast t o the south which sustained heavier damage from Elena. The marsh coast has a very low regional gradient, low wave energy, low sediment input, and i s largely controlled by underlying antecedent, karstified rock topography. Hurricane Elena had very l i t t l e impact upon the natural and human structures along the marsh coast. There are several reasons for this: (1) the storm never came closer t h a n 81 km t o the west central Florida Gulf coast: ( 2 ) the dominant winds in the study area were never sustained above hurricane force (74 kts); (3) the dominant winds were alongshore/even slightly offshore; (4) the storm surge peaked a t only 2m above MSL; ( 5 ) the marsh grasses absorbed wave energy and retarded erosion; ( 6 ) much of. the coast has rock exposed or nearly exposed; and ( 7 ) there are relatively few people and few buildings/seawalls near the Gul f compared t o the sandy coast1 i nes
.
The observed effects were: (1) some coastal erosion i n the southern part of the study area (Bayonet Point, Pasco County); ( 2 ) development of small overwash fans penetrating seaward marshes; (3) flattening down of. marsh grasses; ( 4 ) redistribution of small, nearshore sand bodies; ( 5 ) extensive Juncus wracks in high marsh areas; and (6) breakage of dead mangroves - m d by earl ier freezes). The response of open-marine, marsh coasts t o a direct s t r i ke by a major hurricane i s s t i l l unknown. Storms like Hurricane Elena have a recurring frequency of 10 years. In the future, the combined effect of a greater sea-level rise with a class 5 hurricane could have much more ,devastating effects.
TABLE OF CONTENTS
Page
ABSTRACT
.............................
i
. . . . . . . . . . . . . . . . . . . . . . . . ii LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . . . . i i i LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . .... INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 BACKGROUND GEOLOGIC INFORMATION . . . . . . . . . . . . . . . . . . 1 PAST HURRICANE ACTIVITY . . . . . . . . . . . . . . . . . . . . . . 3 HISTORICAL SHORELINE RESPONSES . . . . . . . . . . . . . . . . . . 9 PHYSICAL CHARACTERISTICS OF HURRICANE ELENA . . . . . . . . . . . 9 Storm Formation and Storm Track . . . . . . . . . . . . . . . 9 Wind Circulation. Water Levels. Waves . . . . . . . . . . . . 13 COMPARISON OF HURRICANE ELENA TO HURRICANE KATE . . . . . . . . . 19 EFFECTS OF HURRICANE ELENA . . . . . . . . . . . . . . . . . . . . 19 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 REFERENCES CITED . . . . . . . . . . . . . . . . . . . . . . . . . 33 TABLE OF CONTENTS
'
111
'
iii
LIST OF ILLUSTRATIONS Page Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure
. ... .
1 2 3 4 5 6 7 8 9 10
.. .
.. Figure 11 . Figure 1 2. Figure 13A. Figure 138 . Figure 14A. Figure 14B. Figure 15. Figure 1 6. Figure 17. Figure 1 8. Figure 19. Figure 20 . Figure 21 . Figure 22 .
............ . . . . .. .. .. .. .. .. .. .. .. .. ....... . . . . . . . . . .. .. .. . . . . . . . . . . . .. .. .. ..
Location map o f study a r e a Calculated storm s u r g e curves Hurricane t r a c k l i n e s Tracks of Hurricanes Agnes and Alma F l u c t u a t i o n s i n water l e v e l l s p r i n g d i s c h a r g e Tracks o f 1985 h u r r i c a n e s D e t a i l e d t r a c k of Elena/wind/pressure d a t a Space image of Elena Wind d i s t r i b u t i o n map Water l e v e l s a s s o c i a t e d with Elena i n studyarea Peak storm-tide e l e v a t i o n along c o a s t Wave h e i g h t l p e r i o d f o r Elena a t Clearwater Detailed t r a c k of Kate/wind/pressure d a t a Water l e v e l s a s s o c i a t e d with Kate i n study a r e a Wave h e i g h t l p e r i o d f o r Kate a t Clearwater Wave height/period f o r Kate a t S t e i n h a t c h e e Aerial photo o f small cuts i n marsh/washover Aerial photo of new sand s p i t Aerial photo of Juncus wrack Aerial photo of Juncus wrack Aerial photo of m a r s h i s l a n d Aerial photo of marsh i s l a n d a r e a Aerial photo of o y s t e r reef Comparison of beach p r o f i l e s
.............. . . . . . . . . . . . .. .. .. .. .. .. .... .... . . . .. .. .. .. .. ... ... ... ... ... ... ... ... ... ... ........... .. .. .. ... ... ... ... ... ... ... ...
2 4 6 7 8 10 11 14 15 17 18 20 21 22 23 24 27 27 28 28 29 30 30 31
LIST OF TABLES
. . .
Table 1 . Hurricanes passing w i t h i n 120 n a u t i c a l miles of CrystalRiver Tab1 e 2 Preliminary b e s t track-Hurricane E l ena Table 3 Wind d a t a from Withlacoochee F o r e s t Center Table 4 Summary o f North A t l a n t i c t r o p i c a l cyclone s t a t i s t i c s . 1985
.
Page
. . . . . . . . . . .. .. .. .. .. .. .. .. .. 125 . . . . . . . 16 . . . . . . . . . . . . . . . . . 25
INTRODUCTION The purpose of this document is to assimilate the basic, physical characteristics of Hurricane Elena, which threatened the west-central coast of Florida in late August/early September of 1985, and to report on the effects that this storm had on the open-marine, marsh-dominated coastline of the Pasco, Hernando, and Citrus Counties. Several reports have already been written concerning Hurricane Elena's effect on the barrier i sland/barrier beach shores (Balsi 1 1 i e, 1985; Bodge and Kriebel , 1985), however, 1 i ttl e has been mentioned concerning this storm's effect on the sand-starved, northern Suncoast. Hurricane Elena appeared in the Gulf of Mexico after the authors had completed a major, detailed reconnaissance of this three county coastal sector (Hine and Be1 knap, 1986). As a resul t, we had a .firm understanding concerning the major depositional processes, geomorphology, and stratigraphy prior to the arrival of Elena. This helped considerably in our assessment of the storm's impact. BACKGROUND GEOLOGIC INFORMATION The northwest Florida coast along the.Gulf of Mexico has been recognized for some time as a unique coastal sector primarily due to its relatively low wave energy and dominance by an open-marine marsh system (Fig. 1 ) Indeed, many coastal' scientists have -viewed this area as the classic zero energy coast (Price, 1954; Tanner, 1960). Perhaps, as a result of this coastl ine' s outwardly monotonic appearance, its unappetizing appeal to physical ly-oriented sedimentologists, and the strong interest in sandy, barrier i sland coastl ines resul-ting from problems associated with human development the coastal geological community has looked elsewhere for questions to address. As a result, an enormous stretch of the Florida shoreline (32%), and.an important type of coast have been ignored and have remained poorly understood including the effects of storms. Indeed, even to this day, the State's Bureau of Beaches and Shores, an agency charged with shoreline research, feels that this biologically-dominated coast is beyond their purview. Only as the result of a handful of studies by marsh biologists has this coastline avoided escape from scientific inquiry
.
The recent geologic research along this coast has shown that the morphologic and stratigraphic complexity has resulted from a unique interaction of a suite of physical, chemical, and biological processes (Hine and Be1 knap, 1986).
'
Within just the southern 65 km, of this 300 km long non-barrier island coastal sector, four major geomorphologic subdivisions have been distinguished: (1) berm ridge shoreline, (2) marsh peninsula shoreline, (3) marsh archipelago shoreline, and (4) shelf embayment shoreline (Fig. 1). These sharply contrasting coastal zones have resulted from the interplay of five major processes/sedimentation control s: ( 1) antecedent topography resulting from chemical dissolution of the exposed bedrock, 2) fresh-water di scharge from spri ngs , 3) 1 ow regional gradi ent/l ow wave
.
energy, (4) l a c k o f sediment i n p u t , no r e l i c t sand supply, and (5) r i s i n g sea 1eve1 The reader i s r e f e r r e d t o H i ne and Be1knap ( 1986) f o r an i n depth a n a l y s i s o f these geomorphic subdivisions. None o f these subdivisions appear t o have i n h e r i t e d o r p r e s e n t l y d i s p l a y e f f e c t s of past hurricanes o r t r o p i c a l storms.
.
PAST HURRICANE ACTIVITY Ho and Tracey (1975) have presented a d e s c r i p t i v e summary o f 13 hurricanes t h a t have caused widespread damage along t h e F l o r i d a Gulf coast from Cape San Blas t o S t . Petersburg Beach from 1837 t o 1972. From these data and observations, they have c a l c u l a t e d storm surge (storm t i d e ) frequency curves from t h e 500 year, 100 year, 50 year, and 10 year r e c u r r i n g hurricane (Fig. 2). I n a d d i t i o n , Table 1 i s a l i s t i n g of t r o p i c a l storms o r hurricanes t h a t have passed w i t h i n 216 km (120 nm) of C r y s t a l River. Figure 3 i l l u s t r a t e s t h e t r a c k s o f some o f these storms. The storm surge i s a r a p i d r i s e i n normal water l e v e l due t o reduced atmospheric pressure and t o wind s t r e s s p i l i n g water up a g a i n s t an open coast1 i n e (U.S. Army Coastal Engineering Research Center, 1973). An extreme example i s t h a t o f Hurricane Camil l e , a c l a s s 5 hurricane, which s t r u c k t h e n o r t h e r n coast o f t h e G u l f o f Mexico i n 1969. The maximum e l e v a t i o n o f t h e storm surge was 7.6 m (25 f t ) above mean low water and t h a t a surge, g r e a t e r than 3 m (9.8 f t ) extended over approximately 88 km (55 m i ) o f c o a s t l i n e . Even more important, t h i s g r e a t storm surge reached i t s peak i n l e s s than 5 h o u r s - s t a r t i n g from a p o i n t about 75 cm (2.4 ft) below mean low water, thus r i s i n g a t o t a l o f 8.35 m (27.4 f t ) . The h i s t o r i c a l hurricane data f o r ' our study area does n o t i n d i c a t e t h a t a s t o r m surge o f s i m i l a r magnitude as Hurricane Camil l e has occurred (Fig. 4). However, t h e 1842 hurricane was shown t o have a storm surge of approximately 5.5 m (18 f t ) a t Cedar Key a p o i n t j u s t t o t h e n o r t h of our f i e l d area. T h i s 1842 storm has a p r e d i c t e d r e c u r r i n g frequency o f 200 years. Figure 4 shows t h e t r a c k s o f two more r e c e n t l y o c c u r r i n g hurricanes (Alma, 1966; Agnes, 1972) causing storm surges a t Cedar Key. Each had a storm surge o f approximately 3 m (9.8 f t ) and both have a r e c u r r i n g frequency o f 26 years. Both passed offshore. Had they tracked d i r e c t l y over Cedar Key, t h e storm surges would have undoubtedly been higher. Hurricane E l ena' s h i g h e s t measured surge along t h i s coast was 2 m (Fig. 10) which, when p l o t t e d on t h e graph i n Figure 4, would i n d i c a t e t h a t a storm s i m i l a r t o Elena would r e c u r about every 10 years. ,
-
I t i s i n t e r e s t i n g t o note (Fig. 5 ) how hurricane storm surges affect t h e freshwater discharge a t C r y s t a l R i v e r springs. Note t h a t t h e water l e v e l curve and t h e s p r i n g discharge curve a r e n e g a t i v e l y c o r r e l a t e d t h a t i s , minimum s p r i n g discharge occurs d u r i n g maximum e l e v a t i o n o f t h e storm surge. Maximum s p r i n g discharge occurs e i t h e r before o r a f t e r t h e storm surge d u r i n g low water conditions.
-
t-to
YCO P, I
X C d.W
rt-'m
- k I
-r)
In I 5 - ' 9 , 4 *
*1(go,P,2 9 ID77 3 e n m
P,
TI - h m m
T mI IPn ,wI D1 .* N
-
a C
TIDE HEIGHT (ft. m.s.1.)
C
I -a
m
rD 0 x 0 7 n u UP, 0 0 -'
zg2.g 7 -
0 0 -
-"g_'*: o n
In
E In 0 0 O C U P,
5 3
w o ,
(9
(0
w
m n
Inln
ctt-t
=I - 0
"23
--hmm O
HORSESHOE BEACH CEDAR KEY
O I n O-bC 0 7 k I c P
X9 -re
m *J at - t mmIt-t 5rD W J I n
