Assessing morphodynamics north of Indian River Inlet from offshore dispersal of Massey's Ditch dredged sand
Date
2021
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Publisher
University of Delaware
Abstract
Indian River Inlet was protected by two jetties in 1940. It is located in southern Delaware connecting the Atlantic Ocean to the Rehoboth Bay and the Indian River Bay. Since the creation of the inlet, the downdrift beach has experienced severe erosion due to the interference of the inlet with the natural littoral processes. In an attempt to mitigate the erosion, beach nourishment methods have been used. ☐ Beach nourishment is the process whereby sediment from a borrow area or pit (usually offshore) is placed in the nearshore to increase protective capacity of the beach. The Delaware Department of Natural Resources and Environmental Control (DNREC) has a 50-year plan (Garriga and Dalrymple, 2002) for nourishing the major Delaware beaches with a typical 3 to 5 year nourishment interval. In the past, beach nourishment methods, including a fixed sand bypassing system, have been used but were unable to counteract the severe erosion. There is the potential for an alternative, potentially more cost-effective method for nourishment. ☐ The project takes an alternative approach by placing dredged sand (from Massey’s Ditch) adjacent to the berm as opposed to the standard construction template. A solar-powered buoy system that measures real time wave data was used to validate the model. The nourishment project provides a unique opportunity to measure before, during and after the dredging process to create a full temporal/spatial morphological analysis of a standard nearshore nourishment. A cross-shore time-averaged model was applied to test the parameters of different nourishment placements on the beach profile. Using the United States Army Corp of Engineers Surface-Water Modeling System (SMS), simulations and numerical modeling are conducted to forecast how the actual and various other sediment placements evolved over time. After the dredging process the beach is surveyed over twenty set profile lines. The volumetric change in morphology was analyzed using the survey data showing that all the sand was removed from the dispersal zone after 5 months. Alternative templates, including a thin layer template, bar template and berm template were compared with the original template through SMS runs which showed that no template was particularly better than any of the other templates, but the sandbar template had the most change in elevation over a 10-day period.
Description
Keywords
Coastal, Morphodynamics