Predicting Shoreline Change at Decadal Scale in the Pacific Northwest, USA

Abstract

This paper presents the approach taken to model and predict decadal scale shoreline change in the Columbia River littoral cell along the coast of southwest Washington and northwest Oregon. This work is a principal component of the Southwest Washington Coastal Erosion Study, a research program directed by the Washington Department of Ecology and the US Geological Survey. A primary goal of the study is understanding and predicting coastal change at a management scale of tens of kilometers and decades. Historical morphological changes are viewed in context with coastal change over several centuries prior to human influence as well as with recent data collected by beach monitoring that quantifies morphologic response to forcing conditions. These multi-scale data sets are being used to inform process-based modeling that simulates historical changes and predicts the evolution of the coast several decades into the future. The initial shoreline change predictions mostly depend on extrapolation of historical sediment budgets. The example predictions of shoreline change to 2020 presented in this paper suggest the sensitivity of the present shoreline configuration to potential reductions in sediment supply. The results emphasize the significance of the sediment budget estimates used to predict the shoreline position in future decades.