| Session IV: Wetlands |
Abstract #: 97406 |
SOIL-BASED ESTIMATION OF PRE-DRAINAGE (CA. 1850) EVERGLADES LANDSCAPES AND THEIR HYDROLOGY
Christopher McVoy
Environmental Defense Fund/South Florida Water Management District Hydrologic Systems Modeling Div., SFWMD West Palm Beach, FL 33416
ABSTRACT
Intensive synoptic studies from the 1940s provide the best available picture of the Everglades as a whole. Accurately portraying the system as it was then, these studies also reflect any alterations caused by thirty years of canal drainage.
In the present research we developed a picture of the landscapes -- the soils, hydrology, topography and vegetation -- present prior to drainage. Development of this picture included two aspects: characterization of the landscapes and determination of their spatial extents. Soil was assumed to be the most stable aspect of each landscape. A comprehensive soil map of the Everglades published in 1948 therefore formed the basis for estimating spatial extents.
Hindcasting of the 1948 soil map and characterization of each pre-drainage landscape was based on synthesis of numerous sources: a 1915 soil survey; published studies of soil change after drainage; federal and state township surveys; historical observations of water levels and vegetation; and reports from expeditions, etc.
Results of the synthesis suggested that a large portion of the Everglades had been altered substantially by the 1940s. The ridge and slough landscape -- containing the deepest water -- originally extended continuously from the present Loxahatchee Wildlife Refuge to Shark River Slough. The sawgrass plains of the northern Everglades occupied less area than when mapped in the 1940s. Areas along the edge of the Everglades mapped as wet prairie on sandy soils were likely originally sawgrass on peat soil. Average annual variation in water depth throughout the Everglades was likely about two feet. Water depths in the sloughs of the ridge and slough landscape, on average, varied between 12 inches in May to 30 inches in October; a hydroperiod of 365 days. The sawgrass plains ranged between six inches below ground in May to 18 inches above in October.
Comparison of this study with results from the South Florida Natural System Model are presented graphically in an associated poster.
