Hydrologic Retention and Sediment Redistribution Following Beaver Dam Analog (BDA) Installation in a Flashy, Ephemeral, Stormwater‐Impacted Stream

In many watersheds, urbanization and agriculture have altered stream hydrology and morphology, increasing flow variability, and sediment transport imbalances. Beaver dam analogs (BDAs) offer a process‐based alternative to conventional gray or hard‐engineered stormwater infrastructure to slow flow, promote sediment deposition, and enhance channel‐floodplain connectivity, but their hydrologic and geomorphic performance in stormwater‐driven, mixed land use watersheds is not well understood. This study describes the geomorphic and hydrologic responses 1 year after installing eight BDAs in an ephemeral, stormwater‐driven stream within a mixed‐land use watershed (68% agricultural, 28% developed, 4% forested) in Selinsgrove, Pennsylvania. Water‐level loggers showed significantly longer retention time in upstream BDA pools than downstream pools ( p < 0.01), suggesting that BDAs moderate flow during storm events along the downstream gradient. Cross‐sectional surveys showed net sediment deposition in upstream BDAs 1–5 and net erosion at BDAs 6–8, with the most upstream BDAs accumulating up to 10–20 cm of vertical sediment. Substrate analyses revealed a shift from coarse to finer materials, with median grain size declining from 27 to 14 mm ( p < 0.0001) and fine earth content (<2 mm) increasing by 6.7% post‐installation ( p < 0.05), consistent with reduced stream energy and enhanced deposition upstream of BDAs. Together, these results document how BDAs alter hydrologic retention and sediment transport in a flashy, human‐impacted stream, suggesting that process‐based restoration responses commonly reported in perennial systems can also emerge under episodic, storm‐driven flow conditions.