A model of sediment resuspension and transport dynamics in southern Lake Michigan

A quasi-three-dimensional suspended sediment transport model was developed and generalized to include combined wave-current effects to study bottom se diment resuspension and transport in southern Lake Michigan. The results fr om a three-dimensional circulation model and a wind wave model were used as input to the sediment transport model. Two effects of nonlinear wave-curre nt interactions were considered in the sediment transport model: the change s in turbulence intensity due to waves and the enhancement of induced botto m shear stresses. Empirical formulations of sediment entrainment and resusp ension processes were established and parameterized by laboratory data and field studies in the lake. In this preliminary application of the model to Lake Michigan, only a single grain size is used to characterize the sedimen tary material, and the bottom of the lake is treated as an unlimited sedime nt source. The model results were compared with measured suspended sediment concentrations at two stations and several municipal water intake turbidit y measurements in southern Lake Michigan during November-December 1994. The model was able to reproduce the general patterns of high-turbidity events in the lake. A model simulation for the entire 1994-1995 two-year period ga ve a reasonable description of sediment erosion/deposition in the lake, and the modeled settling mass fluxes were consistent with sediment trap data. The mechanisms of sediment resuspension and transport in southern Lake Mich igan are discussed. To improve the model, sediment classifications, spatial bottom sediment distribution, sediment source function, and tributary sedi ment discharge should be considered.