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Abstract During a storm, as the beach profile is impacted by increased wave forcing and rapidly changing water levels, sand berms may help mitigate erosion of the backshore. However, the mechanics of berm morphodynamics have not been fully described. In this study, 26 trials were conducted in a large wave flume to explore the response of a near‐prototype berm to scaled storm conditions. Sensors were used to quantify hydrodynamics, sheet flow dynamics, and berm evolution. Results indicate that berm overtopping and offshore sediment transport were key processes causing berm erosion. During the morphological evolution of the beach profile, two sand bars were formed offshore that attenuated subsequent wave energy. The landward extent of that energy was confined to the seaward foreshore, inhibiting inundation of the backshore. Net offshore‐directed transport was dominant when infragravity motions increased in the swash zone. Conversely, the influence of incident‐band motions on sediment transport was relatively greater in the inner‐surf zone. Near‐bed flow velocities and sheet flow layer thicknesses were larger in the swash zone than in the inner‐surf zone. This paper also provides a valuable analysis between morphology‐estimated total sediment transport rates and rates derived from in situ measurements. Sheet flow dynamics dominated foreshore cross‐shore sediment processes, constituting the largest portion of the total sediment transport load throughout the berm erosion.
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Radar Estimates of Surfzone Dissipation Drive a Morphological Evolution Model
Abstract The dissipation of wave energy is important to nearshore circulation and beach profile evolution. Here, radar measurements of wave dissipation at the water surface across the surfzone are used to estimate water velocities and sediment transport in the lower water column to drive an energetics model for morphological change. The radar‐driven model accurately simulates both the 25‐m onshore and the 50‐m offshore migration of a sand bar observed on an Atlantic Ocean beach with a single set of calibration coefficients. Similar to previous studies, wave asymmetry dominated during mild wave conditions when the bar migrated shoreward, and undertow dominated during energetic conditions when the bar migrated seaward. Model results were improved by accounting for both wave bottom boundary layer effects near the sand bar (especially during onshore migration) and the vertical extent of sediment suspension in the undertow transport (especially during offshore migration).
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- Award ID(s):
- 2341381
- PAR ID:
- 10668547
- Publisher / Repository:
- Wiley-AGU
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 53
- Issue:
- 2
- ISSN:
- 0094-8276
- Subject(s) / Keyword(s):
- • Radarmderived wave energy dissipation is used in sediment transport calcula- tions for the first time • Onshore and offshore sand bar migration is replicated with one set of calibration coefficients • Including boundary layer effects and the vertical extent of suspended sediment improved results
- Format(s):
- Medium: X
- Associated Dataset(s):
- View Associated Dataset(s) >>
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2025GL119305
