Researcher(s)
- Maya Morefield, Marine Science, University of Delaware
Faculty Mentor(s)
- Arthur Trembanis, College of Earth, Ocean, and Environment, University of Delaware
Abstract
Seafloor bedforms can appear as a range of features, from small ripples to large sand waves, and form when currents and tides interact with sediment. Understanding sediment transport processes is essential in unique coastal environments, such as inlets, in order to improve hydrodynamic and morphological modeling of the coast. This research aims to characterize bedforms within Roosevelt Inlet in Lewes, Delaware by mapping and analyzing inlet bedforms and sediment composition. Two surveys of Roosevelt Inlet and adjacent Broadkill River and Canary Creek were conducted using a Norbit Multibeam Echosounder for bathymetric mapping of the inlet and identifying areas of pronounced bedforms. Ten sediment samples were taken across the survey area for grain size analysis using photos, visual analysis, and a Camsizer Particle Size Analyzer. Bathymetric profiles were used to measure wavelength, amplitude, slope, and orientation of notable bedforms, while acoustic backscatter and grain size analysis were conducted to determine seafloor hardness, energy level of the inlet, and sediment transportation and deposition. Bedforms with the largest wavelengths appear in the inlet heading towards the Delaware Bay, and the smallest wavelengths appear in Canary Creek. Steeper slopes were measured on the seaward sides of the bedforms, indicating they are ebb tide dominated. Backscatter and grain size analyses show a range of seabed hardness and grain sizes from silt to pebbles, with softer, fine-grained sediment in the boat basin and the center of the inlet; harder, coarse-grained sediment in Broadkill River and Canary Creek; and harder, fine-grained sediment towards the bay. Future work will include deploying a rotary sonar and current profiler, and mapping bedforms during a full tidal cycle to assess temporal changes in the bedforms. This knowledge will contribute to predictive models for sediment transport and inform strategies for maritime navigation and coastal resilience and management.