The Dune Engineering Demand Parameter and Applications to Forecasting Dune Impacts

Abstract

Breaching or overtopping of coastal dunes is associated with greater upland damages. Reliable tools are needed to efficiently assess the likelihood of dune erosion during storm events. Existing methods rely on numerical modeling (extensive investment) or insufficiently parameterize the system. To fill this gap, a fragility curve model using a newly developed dune Engineering Demand Parameter (EDP) is introduced. Conceptually, the EDP is similar to the Shield’s parameter in that it represents the ratio of mobilizing terms to stabilizing terms. Physically, the EDP is a measure of storm intensity over the dune’s resilience. To highlight potential applications, the proposed EDP fragility curve models are fit to a spatially and temporally robust dataset and used to predict dune response subjected to varying storm intensities including both extratropical and tropical storm. This approach allows for the probabilistic prediction of dune impacts through an innovative, computationally efficient model. Several different forms of the EDP are tested to determine the best schematization of the dune resilience. The final recommended EDP is the Peak Erosion Intensity (PEI) raised to the fourth power over the product of the dune volume and berm-width squared. Including both storm intensity and resilience terms in the EDP enables comparison of different beach configurations in different storm events fulfilling a need existing vulnerability assessors cannot currently account for directly.