Utilizing microcomputer-based models to simulate changes in the nearshore environment

Abstract

This paper demonstrates that changes in the dynamic nearshore environment could be successfully simulated by utilizing a combination of appropriate wave and sediment models. With the use of two microcomputer-based simulation models (WAVE and NSCWIS), nearshore sedimentary fluxes, and eventual beach and nearshore changes have been simulated. The ‘WAVE’ model was modified by the Canada Center for Inland Waters, and the ‘NSCWIS’ model was put forward by the US Army Engineer Waterways Experiment Station, Coastal Engineering Research Center. The ‘WAVE’ model is a parametric-type numerical wave prediction model, and uses as input a standard bathymetric grid and meteorological wind data. When initialized with input wind data the ‘WAVE’ FORTRAN '77 program calculates the wave advection terms at user-specified grid locations. The outputs from the ‘WAVE’ model are used as inputs into the ‘NSCWIS’ model in order to simulate shallow water wave and current conditions, and volumetric sediment transport rate. The ‘NSCWIS’ FORTRAN '77 program provides results on volumetric sediment transport rates. The immersed weight sediment transport rates have been calculated after obtaining estimates of the volumetric sediment transport rate. The model results have been compared with data collected from the Northeast, Northwest and East Beaches of Point Pelee, the southernmost promontory of Canada, on the north shore of Lake Erie. Total sediment flux data were collected each October from 1984–1987 at the East and Northwest Beaches, and from 1982–1989 along the Northeast Beach. To compare the actual total sediment flux data obtained from the study beaches with the simulated immersed transport rate, simulation runs were executed for both models (WAVE and NSCWIS). The simulated net annual immersed sediment flow outputs were then compared to the annual total sediment flux observed in the topographic bathymetric surveys using standard regression methods. Approximately 85.0% of the total sediment flux variations could be accounted for by variations in the estimated net annual immersed sediment flow associated with longshore currents.