BOX 2-1 ORIGIN OF THE RIDGE AND SLOUGH LANDSCAPE

The White Paper recognizes that the conditions responsible for the development of the ridge and slough landscape may be different from those responsible for its maintenance. This committee concurs. For example, ridge and slough landforms may have been initiated by preferential formation of peat in bedrock depressions as peat deposits were first forming in the Everglades 5000 years ago. As these deposits mounded above the surrounding bedrock, they would have diverted flow. Peat may have preferentially accreted downstream of the mounds, thereby causing the mounds to elongate. Over time the system of elongated mounds and intervening depressions then may have evolved into the present system. Under this model, once the ridge and slough pattern became established, the bedrock would not be a factor in maintaining the pattern. (This does not appear to be the case with tree islands that have bedrock at the head.)

The absence of ridge and slough landforms in the sawgrass prairie south of Lake Okeechobee is consistent with this hypothesis. When wetlands first formed in this area about 5000 years ago, overflow from the lake was likely diverted around them by the bedrock Loxahatchee Channel (a broad topographic low area in the bedrock draining to the east and southeast). As a result, the initial deposits consisted of calcitic mud, which blanketed the bedrock surface south of the lake and which undoubtedly reduced surface heterogeneity. (Modern calcitic muds are associated with periphyton, and form in place of peat if the period of inundation is relatively short. Without Lake Okeechobee as a source of water, the hydroperiod in the region would have been relatively short compared to the hydroperiod in the Loxahatchee region.) After the Loxahatchee Channel filled with peat and Lake Okeechobee began flooding the sawgrass prairie region, there may have been no irregularities to trigger the formation of peat mounds and initiate the formation of ridges and sloughs.



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