Wave Resolution Effects on Predicted Shoreline Positions

Abstract

The sensitivity of predicted shoreline positions to input wave conditions is examined using the numerical shoreline evolution model GENESIS. Simulated shoreline change over a 70-month period is compared to measured shoreline change for the same period. Shoreline change simulations were performed using seven different descriptions of the input incident wave conditions. Also examined is the influence of using estimates of wave conditions concurrent with the simulation period versus using representative wave conditions selected from a 20-yr database of hindcast wave conditions. The findings indicate that a more representative shoreline planform shape is predicted when the input wave specification includes alongshore variability due to wave transformation over the nearshore bathymetry. At sites where the nearshore contours are straight and parallel to the shoreline, there is little alongshore variability in the breaking wave conditions and inclusion of nearshore wave information in the input wave specification is less important. Although an improved prediction of shoreline change is obtained when nearshore wave conditions are used, ambiguity surrounds selection of an appropriate bathymetric grid resolution for nearshore wave transformation. Finally, it was found that the inclusion of nearshore wave information in the input wave specification is likely to improve the modeling result more than using offshore wave information concurrent with the period of evolution.