SURFACE WATER FLOW FROM A SOUTH FLORIDA WETLAND AREA 



J. van de Kreeke 



Division of Ocean Engineering 

 Rosenstiel School of Marine and Atmospheric Science 

 University of Miami, Miami, Florida 



and 



Ernest Daddio 



Evans-Hamilton, Inc., Bethesda, Maryland 



INTRODUCTION 



The study site is a wetland 

 region of approximately 5,300 acres 

 near Marco Island in southwest Flor- 

 ida (Figure 1). Vegetation ranges 

 from impounded mangrove wetlands on 

 the south, to freshwater marsh, to 

 pine, palmetto, and farm areas on the 

 north. Elevations grade from about 

 0.6 m above mean sea level along the 

 southern boundary to 1.5 m above sea 

 level on the north. 



The drainage area, established 

 from aerial photographs and field 

 inspection, is defined by a drainage 

 divide on the north, north-south 

 roads on the east and west, and on 

 the south by east-west roads, a golf 

 course, an airport, and a man-made 

 lake. The basin has been divided 

 into two separate hydrologic units 

 of approximately equal area by con- 

 struction of the Belle Mead Grade. 

 The region to the north is composed 

 of roughly equal proportions of farm- 

 land and pine and palmetto forest 

 receiving little or no tidal in- 

 fluence. To the south is an area of 

 about 400 acres of pine and palmetto 

 forest, 700 acres of freshwater 

 marsh and 1,000 acres of mostly white 

 and red mangroves. On an additional 

 400 acres along the southern peri- 



meter 



course 



1977). 



is a man-made lake, golf 

 and airport (Tabb et al. 



Surface water is exported 

 westward from the regions both north 

 and south of the Belle Meade Grade 

 via sheet flow until it reaches the 

 State Road 951 Canal which conveys 

 it southward. On the southwest cor- 

 ner of the drainage basin is a road 

 crossing the canal. Water is con- 

 veyed past this obstruction by three 

 0.91-meter diameter, 16.8-meter long 

 culverts. Flow direction through 

 the culverts alternates with the 

 tide except during the rainy season 

 when flow is exclusively out of the 

 region for extensive periods of time. 

 As will be discussed in the next 

 section, the culverts are a conven- 

 ient device for quantifying the flow 

 in and out of the wetland area. 



EXPERIMENTAL METHODS 



Water discharges through the 

 culverts were determined by measur- 

 ing water levels at the north and 

 south ends of the culverts with 

 two Fisher Porter tide gauges. 

 Water levels were recorded on paper 

 tape every 6 minutes for an 18-month 

 period beginning in May 1977. 



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