River floods under wetter antecedent conditions deliver coarser sediment to the coast

Amy E. East; Alexander G. Snyder; Andrew W. Stevens; Jonathan A. Warrick; David J. Topping; Matthew A. Thomas; Andrew C. Ritchie

doi:10.1029/2025gl115232

USGS · 70265714

River floods under wetter antecedent conditions deliver coarser sediment to the coast

Amy E. East·Alexander G. Snyder·Andrew W. Stevens·Jonathan A. Warrick·David J. Topping·Matthew A. Thomas·Andrew C. Ritchie

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Abstract

Increasing hydrologic volatility—more extreme rain, and larger variations between wet and dry years—has become apparent in some regions, but few data exist to determine how intensifying hydrologic extremes affect sedimentary systems. Using uniquely high-resolution records of fluvial suspended sediment and coastal morphology, we quantify sedimentary responses from a steep, 357-km 2 watershed in California under extreme wet and dry hydrologic conditions. In years with multiple 2- to 10-year floods, fluvial sediment coarsened significantly as the wet season progressed, with late-season floods delivering dominantly sand-sized material to the coast. Greater and coarser sediment supply under wetter antecedent conditions affected nearshore geomorphic evolution for 4–5 years. The watershed and coastal changes we documented point to an increasing role of sediment-related hazards (flooding and hillslope erosion) and resources (nearshore accretion) as wet seasons intensify.

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Geophysical Research Letters Article

Source-reported bounding extent: 36.95309077205526° to 37.28890656527331° latitude; -122.2795738662301° to -121.9584157989861° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

Amy E. East, Alexander G. Snyder, Andrew W. Stevens, Jonathan A. Warrick, David J. Topping, Matthew A. Thomas, Andrew C. Ritchie. 2025-04-13. River floods under wetter antecedent conditions deliver coarser sediment to the coast. https://doi.org/10.1029/2025gl115232

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