Dynamic Behavior of Suspended Sediment Concentrations in a Shallow Lake Perturbed by Episodic Wind Events

Field experiments were conducted in Lake Balaton, a large (surface area, 600 $km^2$) but shallow (mean depth, 3.2 m) lake in Hungary, to quantify the resuspension and deposition of bottom sediment due to episodic storm events. Meaurements were made of windspeed and direction, surface waves, mean water velocity, and suspended sediments concentration. During significant wind events, the computed bottom stress due to surface waves dominated that due to the mean current, and therefore surface waves were assumed to be the major cause of sediment resuspension. A simple model for the depth-averaged suspended sediment concentration based on surface wave height was calibrated with about 10 h of data collected during one storm event and verified against 15 d of data collected at the same site. The success of the suspended sediment model, which assumes that the bottom sediment was noncohesive, is surprising since the bottom material was composed predominantly of sediment in the clay and fine-silt size ranges. This fit may indicate the presence of a thin surface layer of loosely bound sediment that is continuously involved in resuspension. The suspended sediment model could easily be integrated into a water quality model (e.g. to predict light attenuation), provided that lateral transport is negligible, or it could be used to provide the bottom boundary condition for a more general suspended sediment transport model in which advective transport is included.