Advancing process-based restoration in human-impacted systems: A synthesis, conceptual model, and demonstration of potential in the Chesapeake Bay Watershed

Process-based restoration (PBR) techniques offer a low-cost, adaptive alternative to traditional form-based stream restoration by targeting the physical and hydrologic processes that drive degradation. However, their implementation and evaluation remain limited in human-impacted watersheds shaped by stormwater, historical agriculture, and legacy sediment. To address this gap, we conducted a systematic review of 118 peer-reviewed U.S.-based field studies implementing PBR approaches to evaluate reported outcomes across geomorphic, hydrologic, biological, and water quality domains. Hierarchical cluster analysis revealed three major groupings of co-reported outcomes, reflecting a strong focus on either in-stream habitat and channel structure or riparian and floodplain processes, but rarely both within the same study. Despite their high potential for mitigating flashiness and incision, ephemeral and low-order streams were infrequently addressed in the literature. Only 4% of studies evaluated beaver dam analogs (BDAs), a promising tool that mimics natural dam functions to slow flow, retain sediment, and restore floodplain connectivity. To assess their utility, we conducted a focused review of BDA studies, which reported overwhelmingly positive outcomes for key hydrologic and geomorphic metrics. Building from these findings, we introduce a conceptual framework linking restoration strategies to stream order, land use, and process impairment, and use the Chesapeake Bay watershed as a representative case. This framework emphasizes prioritizing headwater and ephemeral streams, demonstrating how high-resolution flow path data can improve site selection and planning for scalable, impairment-based restoration in small headwater systems typically omitted from national stream inventories. • Synthesizes 118 studies on low-cost, process-based restoration (PBR) in streams. • Identifies common outcome clusters and key gaps in PBR monitoring. • Highlights underuse of PBR in stormwater-impacted and ephemeral streams. • Presents conceptual framework linking stream order, land use, and technique. • Reviews beaver dam analog outcomes and potential in flashy, incised stream systems.