Rapid Sedimentation in Low-Energy, Microtidal Estuary: ABSTRACT

Abstract

The St. Lucie River is an elongate, forked estuary formed during the Holocene rise in sea level and located on the southeast coast of Florida. It is 15 km (9 mi) long from its mouth to the end of each fork, and is a maximum of 3 km (2 mi) wide. Mean depth is about 3 m (10 ft). Although seasonal variation does exist, the combination of freshwater runoff and microtidal conditions produces a well-mixed, nearby freshwater estuarine system. Extensive subbottom profiling and vibracoring have provided data for interpretation of the Holocene history of sediment accumulation in the estuary. Well-developed paleochannels and thickness of the surficial mud layer can be delineated by seismic profiling and confirmed by cores. Analysis of the distribution of 137Cs shows that the rate of sediment accumulation in the estuary over the past 3 decades has approached 1 cm/year. Comparison of bathymetry between the late 19th century and the present shows a similar rate of accumulation. Agriculture and residential development has been pronounced in the drainage basin, beginning in the 1920s. It is likely that this activity has produced a great increase in the rate of sediment influx to the estuary. The configuration of the estuary in combination with inefficient tidal flushing has permitted much of this sediment to accumulate. End_of_Article - Last_Page 469------------