16-15 Inlet Bedform Dynamics: Morphodynamics and Sediment Variation in Roosevelt Inlet, Delaware

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

Presenting Author:

Authors:

Abstract:

Roosevelt Inlet, located near the University of Delaware’s Campus in Lewes, Delaware, is a dynamic environment where human activity, tidal influences, and sediment transport intersect. Monitoring bedform dynamics in this environment is beneficial in supporting coastal resilience and inlet management strategies. Bedform morphology and sediment variation within Roosevelt Inlet were investigated by repeated mapping and analysis of inlet bedforms and sediment composition. From June to September 2025, four surveys of Roosevelt Inlet and the adjacent Broadkill River and Canary Creek were conducted using a Norbit Multibeam Echosounder (400 kHz) for bathymetric mapping and identifying areas of pronounced bedforms. Ten sediment samples were taken across the survey area using a Ponar grab sampler. Grain size analyses of the sediment samples were conducted through visual analysis, wet and dry sieving, and utilizing a Camsizer Particle Size Analyzer. Bathymetric profiles were created to measure and compare bedform wavelength, height, slope, and orientation across the four surveys. Acoustic backscatter and grain size analyses were conducted to determine seafloor hardness, energy level of the inlet, and sediment transport and deposition. Ripple heights of approximately 0.05 to 1.5 m and wavelengths of approximately 2.00 to 35.00 m were observed. Bathymetric profiles revealed a net seaward migration of bedforms, with the most notable bedforms observed to have migration distances ranging from 9.00 to 25.00 m over the four-month survey period, indicating an overall ebb-dominant regime. However, localized areas, such as the mouth of Broadkill River, exhibited flood-dominant characteristics. Therefore, further investigation of tidal data and storm events is needed to characterize sediment transport trends. Acoustic backscatter and sediment sample analyses demonstrated a spatial gradient in seabed hardness and sediment texture. Fine-grained muddy sediments accumulated in the sheltered, shoreside boat basin, while coarse-grained sand and gravel dominated the inlet throat, Broadkill River, and Canary Creek, revealing the considerable variability of the inlet floor. These findings, along with future investigations, will contribute to predictive models of sediment transport, inform strategies for maritime navigation, and improve coastal resilience and management.

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