Welcome to the Jupiter Inlet District
Jupiter Inlet & the Loxahatchee River
Natural Resources
Geology of the Lower Loxahatchee River
The Loxahatchee River flows in a "barrier-impounded, drowned river valley." That is, the present valley is the upper reaches of a larger, longer valley formed when sea level was much lower-most recently in the Pleistocene glaciation (Ice Ages) that ended about 10,000 years ago. The river can flow freely to the ocean, and tidal currents can efficiently flush the river's lower reaches, only when Jupiter Inlet is open through the coastal barrier islands. Studies of sediments in the river by University of Florida scientists, in partnership with the Jupiter Inlet District, reveal a complex history over thousands of years, affected by sea level change, many natural closings and openings of the inlet, and, recently, the actions of man.
Digital photographs and X-radiographs of sediment core sample reveal eons of geological history. |
Technicians collect sediment core samples from the river. |
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Over geologic time, sediment deposition has kept the riverbed elevation nearly in equilibrium with sea level. However, in the 1930s, the Northwest Fork (the main river channel) was dammed. In the 1950s, channelization of the Southwest Fork and a new sluice-gated control structure began to affect the natural stream flow. When the inlet is closed, the limited tidal flushing creates a stratified, stagnant water body with low dissolved oxygen concentrations. Jupiter Inlet has been stabilized and open continuously since 1947.
These changes, along with significant alteration in use of the nearby lands due to increasing population, modify the river's sediment load and freshwater contribution to the Central Embayment, affecting ongoing sediment deposition. Distinguishing manmade sedimentary changes from natural variation is a challenge. Except in dredged channels, sediment sequences from the past century are hard to distinguish from those formed in the last several thousand years. Further studies, with greater emphasis on fossils in the sediments, will provide additional insights.
Adapted from manuscript by Jaeger, John M., Ashish Mehta, Richard Faas, and Michael Grella, Anthropogenic Impacts on Sedimentary Sources and Processes in a Small Urbanized Subtropical Estuary, Florida, 2005.