A Summary of Stormwater Best Management Practices (BMPs)
Learn more about the different techniques used to manage stormwater.
Stormwater Best Management Practices (BMPs) are practices that manage stormwater runoff to improve water quality and reduce stormwater volume and velocity. Examples of BMPs include detention ponds, gravel wetlands, infiltration trenches, and bioretention practices. Scroll down or click on the navigation bar above to read more about the different Stormwater BMPs on this page, and see the summary chart for a comparison between them.
Summary Comparison Chart
Stormwater Best Management Practices (BMPs) are selected for a site based on the site conditions, desired co-benefits, and implementation and maintenance feasibility. This chart compares the considerations including soil requirements, cost and maintenance requirements, and water quality and stormwater volume benefits. See below to learn more about each type of stormwater BMP.
Bioretention
Bioretention or rain gardens capture and treat stormwater runoff from impervious surfaces by passing it through a vegetated filter bed, with a filter mixture of sand, soil, and organic matter. Filtered stormwater is either returned to a conveyance system or infiltrated into the native soil. Bioretention provides water quality treatment and aesthetic value, and can be applied to parking lot islands, linear roadway or median filters, terrace slope practices, residential cul-de-sacs, and ultra-urban planter boxes.
Rain gardens are a great example of bioretention. They are a garden of native shrubs, perennials, and flowers planted in a small depression, which is generally formed on a natural slope. It is designed to temporarily hold and soak in rain water runoff that flows from roofs, driveways, patios or lawns. Rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground.
Buffers
Protective vegetated areas (variable width) along stream banks that stabilize stream banks, filter sediment, slow stormwater runoff velocity, and shade streams to keep waters cool in the summer months.
Check Dam
A small dam, often constructed in a swale, that decreases the velocity of stormwater and encourages the settling and deposition of sediment. They are often constructed from wood, stone, or earth.
Dry Well
A subsurface storage facility that temporarily stores and infiltrates stormwater runoff. Concentrated flow from a stormwater pipe or gutter is directed into the dry well, which then allows the water to infiltrate into the subsurface soil as groundwater, which returns to the stream as baseflow. Infiltration reduces the amount of surface storage required. Mapped soils of Hydrologic Group A or B (sandy, well-drained soils) are an indicator of infiltration potential.
Gravel Wetland
A water treatment practice that utilizes a saturated bed of gravel and wetland plants to filter incoming water and remove pollutants through a combination of physical filtration, adsorption, biological uptake, and microbial transformation (Center for Watershed Protection, 2007).
Infiltration Trench
A trench, typically filled with gravel. Stormwater is directed into the trench which allows the water to infiltrate into the subsurface soil as groundwater, which returns to the stream as baseflow. Infiltration reduces the amount of surface storage required. Mapped soils of Hydrologic Group A or B (sandy, well-drained soils) are an indicator of infiltration potential.
(Photo credit: Lake Wise Program)
Curb Bumpouts
Vegetated extensions of the curb that protrude into the street, often at an intersection. An inlet or curb cut collects water from the street and directs it into the bumpout where it can be stored or treated by the plants and soil medium. In addition, curb bumpouts can slow traffic and narrow crossing width, improving pedestrian safety.
Sand Filter
Surface sand filters or underground sand filters are dry pond systems that capture and temporarily store stormwater runoff. Runoff then passes through a filter bed of sand or augmented media.
Stabilization
Vegetated or structural practices that prevent erosion from occurring.
Swale
An open vegetated channel used to convey runoff and to provide pre-treatment by filtering out pollutants and sediments.
Underground Storage
Constructed chambers installed underground. Often a series of concrete or plastic pipes, vaults or chambers. Stormwater is directed into the chambers and stored during weather events, reducing peak water flow. Eventually the water is released through an outlet pipe; or if the soils are suitable, allowed to infiltrate into the subsurface soil as groundwater.
Permeable Pavement
A hardscape surface that allows water to flow through it or through gaps between pavers. The water flows into an underlying reservoir course that captures and temporarily stores rainfall before infiltrating into the underlying soil or conveying it elsewhere. These practices are typically most applicable to areas of low traffic, such as residential driveways, parking spaces, alleys, sidewalks, bike paths, courtyards, and residential streets.
Tree Boxes
Tree boxes, or stormwater planters, are planting boxes for a tree or shrubs filled with a formulated soil media to filter stormwater. Above ground it may look similar to a typical tree planting.
