The natural South Florida system I: Climate,geology, and hydrology

Developing hypotheses for sustainability requires an understanding of the natural forces that shaped the historical Everglades prior to extensive engineering of the landscape. The historical Everglades marsh covered 10,000 km² in a 100-km-long basin that has an extremely low gradient (slope of only 3 cm · km^-1). The region is characterized by a heterogeneous landscape that has developed over the past five millennia, functioning as an interconnected mosaic of wetland, upland, estuarine, and marine ecosystems. The boundaries of this system were defined as the historic drainage basin from the Kissimmee River system through Lake Okeechobee, the Everglades, Florida Bay, and out through the Florida Keys to the coral reef tract. This geographic area is interconnected through the regional hydrology, with its unifying surface and subsurface freshwater transport system. However, in the final analysis, the interaction of geologic and climatic processes determine the system's hydrology, a major determinant of community and landscape structure and the point of connectivity between natural and human systems. This review examines the role of climate, geology, soils and sediments, topography, and hydrology in shaping and modifying ecological systems through time. However, it is clear from the wetland nature of this system that the predrainage hydrologic features were critical to the sustainability of the Everglades. Important hydrologic features include sufficient water quantity, storage, and sheetflow, and the appropriate hydroperiod and timing of water releases over both annual and interannual variations in precipitation.