Simulating cross-shore material exchange at decadal scale. Theory and model component validation

A model is developed to simulate the cross-shore (CS) exchange of sand and the resulting profile response at decadal scale to be used in regional coastal evolution models. The CS model consists of modules for calculating dune erosion and overwash, wind-blown sand transport, and bar-berm material exchange. The sand transport equations included in these modules are formulated based on relevant physics in combination with empirical observations and then validated towards laboratory and field data. In order to couple the transport equations to the evolution of key morphological features describing the profile a set of sand volume conservation equations are employed and solved together with the transport equations. The features that are modeled include dune height (from dune foot to crest), the locations of the landward dune foot, seaward dune foot, berm crest, and shoreline as well as the longshore bar volume. The CS model is employed and tested at three different field sites in a companion paper (Palalane et al., 2016), whereas in the present paper the properties of the model are demonstrated by simulating the evolution of the dune, berm, and shoreline in connection with accretion and erosion of sand in a groin compartment. This case derives from a study at Westhampton Beach that focused on shortening the length of a number of groins in order to release accumulated sand in the groin field to eroding downdrift beaches.