Predicting Wave-Induced Sediment Resuspension at the Perimeter of Lakes Using a Steady-State Spectral Wave Model

A steady-state spectral wave model, STWAVE, is evaluated as a tool for predicting wave-induced sediment resuspension in lake littoral zones. Steady-state wave height and bed-shear stress estimates are tested against 2years of high-frequency wave height and turbidity data from six littoral measurement stations in Lake Tahoe. Average wave and sediment resuspension response to a broad range of wind conditions are well captured by the model. Despite steady-state assumptions, the model reproduces patterns in wave height and sediment resuspension under time-varying wind conditions at sites with different wave exposure. Model results are insensitive to the measurement location of wind data input among six offshore meteorological buoys. Uniform and variable wind field assumptions yield similar resuspension predictions. Results representing the steady-state response to spatially uniform wind speed-direction combinations enable output from a single set of model runs to serve as a reasonable static reference for hindcasting and predicting wave resuspension patterns. This obviates the need for repeated model runs, making STWAVE output an efficient tool for exploring long-term spatio-temporal patterns in nearshore wave forcing. Application of this tool is limited by wave height overprediction for short fetches and presumably by the validity of uniform wind field assumptions over very long fetches. Applied successfully at Lake Tahoe, we find that the north and east shores, exposed to the prevailing southwesterly winds, see resuspension conditions upward of 3,000hr/year, while the south and west shores typically see less than 500. Location-specific resuspension hours can vary by upward of 200hr/year due to shifting interannual wind patterns. Plain Language Summary A tool that describes lake-wide wave conditions as a function of combinations of wind speeds and directions is tested using 2years of wave height and water clarity data from six nearshore locations at Lake Tahoe. The data confirm the modeling tool's ability to predict wave-driven resuspension of lake bed sediments. An example application details seasonal and interannual variability in wind wave influence at the perimeter of Lake Tahoe. Due to the prevailing southwesterly winds, exposed sections of the north and east shores of the lake can see in excess of 3,000hr of sediment resuspension-inducing wave conditions per year, while the south and west shores are comparatively calm. In representative year 2016, wave forcing was more prevalent in the fall and winter seasons.