OPTIMAL RESPONSES TO SHORELINE CHANGES: AN INTEGRATED ECONOMIC AND GEOLOGICAL MODEL WITH APPLICATION TO CURVED COASTS

The placement of sandy fill on an eroding beach, also known as beach nourishment, is a soft-structure response to property loss often undertaken by coastal property owners. Here, we examine optimal beach nourishment along a curved shoreline with a model that couples geomorphic shoreline evolution with human responses to that evolution. The model includes the exogenous effects of shoreline recession due to sea-level rise and the endogenous shoreline changes due to gradients in alongshore sediment transport. Human responses (nourishments) to shoreline changes that are not constant along the coast will change the shoreline curvature, thereby influencing local rates of shoreline change. We examine the net benefits of two alternative strategies to undertake soft structural responses to erosion: (i) the decisions of property owners to respond independently and (ii) the decisions of property owners to coordinate their individual responses. Under plausible parameterization, we find that a strategy to coordinate can dominate a strategy to act independently, and the benefits of coordination increase with greater shoreline curvature. This integration of economic and geological models demonstrates how feedbacks between human activities and natural processes can affect the evolution of the shoreline.