Stormwater management BMPs are control measures taken to mitigate changes to both quantity and quality of urban runoff caused through changes to land use. Generally BMPs focus on water quality problems caused by increased impervious surfaces from land development. BMPs are designed to reduce stormwater volume, peak flows, and/or nonpoint source pollution through evapotranspiration, infiltration, detention, and filtration or biological and chemical actions. BMPs also can improve receiving-water quality by extending the duration of outflows in comparison to inflow duration (known as  hydrograph extension), which dilutes the stormwater discharged into a larger volume of upstream flow.Although structural BMPs can be effective for reducing stormwater loads to receiving waters, studies indicate that they cannot improve in-stream water quality where receiving-water quality is poor. 
Stormwater BMPs can be classified as "structural" (i.e., devices installed or constructed on a site such as silt fences, rock filter dams, fiber rolls (also called erosion control logs or excelsior wattles), sediment traps and numerous other proprietary products) or "non-structural" (procedures, such as modified landscaping practices, soil disturbing activity scheduling, or street sweeping). There are a variety of BMPs available; selection typically depends on site characteristics and pollutant removal objectives. EPA has published a series of stormwater BMP fact sheets for use by local governments, builders and property owners.
Stormwater management BMPs can be also categorized into four basic types:
# Storage practices: ponds; recovery; green infrastructure design. 
# Vegetative practices: buffers; channels; green roofs; wetlands; functional art; stormwater wetland park design; wetland park engineering & design. 
# Filtration/Infiltration practices: filtering; infiltration; rain gardens; porous pavement; civic infrastructure and design; functional stormwater design.
# Water sensitive development: better site design (revisions of local land development rules); open space site design; low impact development.