ABSTRACT: Modeling Waves and Circulation in Lake Pontchartrain
SIGNELL, RICHARD P. and JEFFREY H. LIST
The U.S. Geological Survey is conducting a study of storm-driven sediment resuspension and transport in Lake Pontchartrain, LA. One hypothesis is that bottom sediments are resuspended by wind-generated storm waves and transported horizontally by the lake currents that occur during these storm events.
To examine this hypothesis, sediment resuspension is being studied with the wave prediction model HISWA (HIndcasting Shallow-water WAves), which simulates local generation of waves by wind and shallow-water effects (refraction, shoaling, bottom friction, and breaking). Data obtained from three sites in the lake indicate that the model simulates wave amplitude and period remarkably well. The regional "climate" of wave-induced currents at the lake bottom, based on long-term wind measurements and the model, suggests more frequent and intense sediment resuspension in the western part of the lake due to the easterly component of most storm winds.
The circulation of the lake is being studied with a three-dimensional hydrodynamic model. The model results show that remote forcing due to changes in water levels in Mississippi Sound dominate the circulation near the passes in the eastern end of the lake, while local wind forcing dominates water movement in the western end. During typical storms with winds from the northeast or the southeast, currents along the south coast near New Orleans generally transport material westward, while material in the central region moves against the wind. When periods of sustained winds are followed by a drop in coastal sea level, a large amount of suspended sediment can be flushed from the lake.
AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana