Enhancement and Development of Numerical Models for Simulating Coastal Sediment Transport and Morphology Evolution
2007
Hanson, Hans
Background Sediment exchange between the subaerial and sub-aqueous portion of the beach occurs primarily across-shore, driven by wave motion in the swash zone. Water level is a leading factor in this process because it defines the starting point of the swash zone and to what elevation the uprushing waves may reach. Over longer time periods, wind-blown sand may also be an important factor for the cross-shore sediment exchange on the subaerial portion of the beach. This exchange takes place between the dune and the broad, flat berm often present on the seaward side of the dune. Since Cascade simulates coastal evolution over decades to centuries, it is important to include wind-blown sand in models of cross-shore sediment exchange. Depending on the morphology of the subaerial beach, different types of response to transport by incident waves and wind-blown sand are expected, implying supply or depletion of sediment from the sub-aqueous beach with associated advance or recession of the shoreline, respectively. Erosion of dunes or soft cliffs supplies the beach with sediment, whereas transport by wind moves sediment from the berm to the dune. Also, during severe storms, the dunes might overwash, causing transport of sediment onshore over the dune crest and deposition on the landward side of the dune crest (Donnelly et al. 2006). Thus, a physics-based approach to model the sediment exchange between the subaerial and sub-aqueous portion of the beach requires description of dunes subject to erosion by wave impact and overwash, as well as to build-up by wind-blown sand.
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