Effects of distributed and centralized stormwater best management practices and land cover on urban stream hydrology at the catchment scale

Abstract

Key Findings:• Predominant catchment treatments includedo Centralized (gray infrastructure) BMPsWith little tree canopy cover (~15% UTC)With greater tree canopy cover (~57% UTC)o Distributed (GSI) BMPs (~21% UTC)o Non-urbanized, forested landscape (~85% tree canopy cover)• Resultso Compared with centralized treatments, GSI provided Slightly less stormwater runoff (6.5%) Significantly greater base flow (36%) and total water runoff (20%)o GSI BMPs provided better hydrologic control for storms <27mmo Centralized BMPs enabled better hydrologic control for storms >27mmo Watersheds with greater tree cover (57% and 85%) had about 33% lower runoff volumes for stormflow, baseflow, and total flow• Conclusionso GSI BMPs compared with centralized BMPs Had increased baseflow Reduced maximum volume discharge (during smaller rain events) Reduced stream response (during smaller rain events) More closely resembles hydrologic response of forested catchmento Increased tree canopy cover Reduced total stormwater runoff volume Decreased stream response during rain eventso Important considerations for urban stream hydrology Land cover is an effective stormwater BMP• Reduced impervious cover• Increased tree canopy cover Implement distributed (GSI) BMPs with land cover considerationo Implications of GSI BMPs (engineered and natural) Less intense discharge Reduced erosion and particulate transport Improved stream hydrology Increased nutrient retention and removal