| dc.description.abstract | As many coastal areas suffer from chronic erosion, innovative solutions beyond traditional local nourishment must be explored. One such solution is mega-nourishment (MN) where a large sediment volume is deposited in a single location and redistributed via natural processes thereby feeding adjacent beaches. However, only one MN, the Dutch Sand Motor, has been built to date, and potential MN coastline interactions with engineered features such as groins are unknown. To investigate this, one-line numerical modeling approaches of MN evolution are presented using the Coastline Evolution Model (CEM) and GenCade. CEM is modified to allow for a much more detailed parameterization and higher resolution operation to address MNs specifically. Both models are parameterized for the Sand Motor to explore the feasibility of the MN approach. The models are then used to identify the implications of combining a MN with a groin field (GF). This is accomplished by re-writing CEM in MATLAB and adding highly robust groin-simulating algorithms.
Both models are able to reproduce the morphological patterns observed at the Sand Motor. GenCade produces mean measured-modeled differences on the order of 50 m showing relatively accurate absolute shoreline positions. CEM captures the 400-meter-feature tip migration due to its wave shadowing algorithm. CEM groin algorithms are validated using measured shorelines from Galveston Island. The idealized MN-GF interaction scenarios are modeled using similar baseline conditions. Results also show that a MN placed adjacent to a GF results in sediment feeding of beaches on both sides of the MN and on the far side of the GF on multidecadal time scales. MN feeding rates are highly dependent on the offshore wave climate, with climates rich in high angle waves slowing MN diffusion and feeding rates. Model results also indicate that shoreline advance can be maximized in areas of erosional hot spots near a GF by building a MN on top of a groin field or directly downdrift of it. The advances made to CEM allow its use in future MN research, which should include the examination of different MN/GF parameters as well as temporal variability in forcings. | |
