Stormwater Best Management Practices
The primary method to control stormwater runoff is the use of best management practices (BMPs). Stormwater BMPs are devices, practices, or methods that are used to manage stormwater runoff by controlling peak runoff rate, improving water quality, and managing runoff volume.
Important considerations when selecting BMPs include but are not limited to: 1) site conditions (e.g. slope and soil types); 2) existing and surrounding land uses; 3) priority stormwater management goals (e.g. water quality regulations); and, 4) additional site development or redevelopment goals (e.g. recreational opportunities).
See our Sustainable Development page for more information on selecting stormwater BMPs to fit the natural environment and systems.
Types of BMPs
Pennsylvania’s Stormwater Best Management Practice Manual divides common stormwater best management practices (BMPs) into two categories: structural or non-structural. Structural BMPs are engineered systems that “reduce and mitigate impacts of development” while non-structural BMPs are “broader planning and design approaches…that prevent stormwater generation” (PA Stormwater BMP Manual). More information on each BMP is available below.
The most effective way to manage stormwater begins with the prevention of problems. Non-structural BMPs include design approaches and practices that are used for their ability to prevent the occurrence of stormwater runoff. Utilizing non-structural BMPs during site development is much more efficient and cost-effective than attempting to correct problems after development has occurred. Read below to learn about specific types of non-structural BMPs.
A riparian corridor includes a body of water (stream, river, pond or lake), its lower and upper banks, and the vegetation that stabilizes the area of land adjacent to the body of water. This area of land adjacent to the body of water can also be referred to as a “riparian buffer”. This corridor or buffer is important because natural trees and vegetation can filter out air and water pollution, roots from tree and other vegetation can hold the soil in place providing protection from significant erosion and sedimentation, provide cover and shade, provide food and habitat for fish and wildlife, and can provide flood water retention.
Preservation and restoration of riparian corridor/buffers has been identified as one of the most important ways to protect and improve water quality by government and state agencies.
Protect Sensitive and Special Value Features
Special Value Features are those that provide exceptional value stormwater benefits. Examples include riparian areas, wetlands, hydric soils, and floodplains. Sensitive Features are those that are exceptionally vulnerable to stormwater damage. Examples include steep slopes and neighboring properties. Damage to both special value and sensitive features can exacerbate stormwater volume, rate, and quality problems. When developing a site, special attention should be paid to these areas.
Protect / Utilize Natural Flow Pathways in Overall Stormwater Planning and Design
Sites usually have areas where stormwater is being stored and/or conveyed prior to development. These features should be identified and preserved during planning and construction in order to minimize the impacts of stormwater. The preservation of such features can reduce the need for structural BMPs.
Cluster Uses at Each Site and Build on Smallest Area Possible
Through clustering uses at each site and building on the smallest area possible, additional runoff that is generated through the development process is minimized. Additional benefits of this design approach include the preservation of open space, the minimization of impervious area, and many others. Practical examples of this non-structural BMP include reducing lot size and building vertically.
Use Smart Growth Practices
Smart Growth practices are typically used at the community, municipal, or multi-municipal level. This planning technique guides growth towards parcels that are most desirable for this use. The PA Stormwater BMP Manual describes this particular BMP as “Super Clustering.” Smart Growth employs similar methods on a macro scale as clustering does on a micro (site) scale. Tools used in Smart Growth include urban growth boundaries, agricultural zoning, transfer of development rights, donation of conservation easement by owners, and many more.
Minimize Total Disturbed Area–Grading
This design approach works with the existing site topography instead of against it. By reducing the need for site grading, soil disturbance, and removal of vegetation, this planning and development approach aims to prevent the generation of stormwater. Additional benefits of Minimizing Total Disturbed Areas & Grading include reduction of areas that need to be landscaped and maintained.
Minimize Soil Compaction
Minimizing soil compaction and maintaining topsoil quality during construction provides numerous stormwater benefits. Stormwater benefits of this practice include: minimizing runoff and erosion, maximizing water retention capacity, filtering of stormwater, and reducing resources needed to maintain landscaping.
Re-Vegetate and Re-Forest Disturbed Areas
Disturbed areas should be re-vegetated with native plants, grasses, shrubs, and trees. Since these species are adapted to local climate and conditions, they require less fertilizers and pesticides and have better chances of surviving. Stormwater benefits of established native plantings include runoff volume and rate reduction as well as water quality improvements.
Reduce Street Imperviousness and Parking Imperviousness
The benefits of reducing impervious areas for streets and parking through innovative planning are numerous. Benefits include: increased infiltration, decreased stormwater volume, pollutant load reduction, and preservation of natural habitats.
Rooftop disconnection is also known as downspout disconnection. Disconnecting rooftop leaders from the storm sewer system and re-directing towards vegetated areas is an effective way to manage stormwater volume. This BMP can be more effective when the flow is directed towards a structural BMP such as a rain garden.
Disconnection from Storm Sewers
Disconnecting stormwater generated from impervious areas, such as roads and driveways, from storm sewers and directing towards structural BMPs, such as bio-infiltration areas, is effective in many ways. Managing the flow near the source instead of sending downstream via traditional piping allows for increased infiltration and evapotranspiration, increased filtration, and decreased runoff volume.
Streetsweeping is a form of source control that is key to ensuring the function of stormwater facilities and keeps local waterways free of debris and other pollutants. In order for streetsweeping to be effective, the equipment used should have a vacuum filter.
For resources related to non-structural BMPs, visit our Stormwater Resources page.
Infiltration Basins and Infiltration Trenches
Infiltration devices drain or infiltrate water directly into the ground, providing opportunity for groundwater recharge. Infiltration facilities are below ground; the length of time that water is allowed to be on the surface is determined by municipal codes.
Dry wells collect and infiltrate roof runoff at gutter downspouts, roof valleys, and other places where large amounts of concentrated water flow off of a roof. The water is conveyed typically through an underground pipe into an excavated pit (the dry well). They help reduce erosion on your property and can reduce ponding and sitting water.
A rain barrel is a device to collect rainwater from downspouts. Rain barrels can be purchased or can be made at home. They come in all sizes and shapes. Some benefits of rain barrels include: reduction of stormwater runoff, promotion of local watershed awareness, education of neighbors about stormwater issues, lowered water bill by reducing metered water usage, and water reuse for landscaping, washing, etc.
A rain garden is a landscaped area planted with wildflowers and other native vegetation that is used to soak up rainwater from the roof, driveway, and lawn. The water slowly seeps into the ground instead of heading for the nearest storm drain. A rain garden allows for significantly more water to soak into the ground than a conventional lawn.
Porous asphalt, porous concrete, and porous pavers are all types of pervious pavements. These are typically used with infiltration beds below the pervious surfaces, which allow for the temporary stormwater storage and infiltration into the ground. These technologies are used for stormwater peak rate control.
Subsurface Infiltration Bed
Temporary storage and infiltration can be attained when including subsurface infiltration beds underneath vegetated surfaces. Subsurface infiltration beds are typically filled with stones (for void space) and wrapped in geotextile fabric. Subsurface infiltration beds work well in large and generally flat spaces that are located downhill from impervious areas.
Vegetated swales, also known as bioswales, are broad channels that are densely planted with vegetation. Designed to attenuate and sometimes infiltrate flow, vegetated swales provide peak rate control and also allow for pollutants to settle out, therefore improving water quality. In sloped areas, check dams are needed to enhance the stormwater management functions of vegetated swales.
Vegetated Filter Strip
Vegetated Filter Strips, also called buffer strips, are areas in between sources of nonpoint source pollutants and the receiving body of water. They can include native or indigenous vegetation such as grasses, shrubs, and trees. Turf grasses are also used sometimes but their functionality in stormwater management is limited. The primary stormwater function of vegetated filter strips is water quality improvement, however, some volume reduction and ground water recharge can occur depending on site conditions such as soil and slope.
A constructed stormwater filter is a structure or excavated area that is filled with material that filters stormwater. These devices can be designed to filter floatables, sediments, metals, hydrocarbons, and other pollutants. There are many variations on the constructed filter, including vegetated and non-vegetated, infiltration, contained, subsurface, and linear perimeter filters.
Infiltration Berm & Retentive Grading
Infiltration berms are linear landscape features that are parallel to existing site contours in areas with moderate slopes. They are earthen embankments that divert, retain, slow down, divert, and promote the infiltration of stormwater. Berms are most effective in areas that receive runoff from small impervious areas. Retentive grading creates small depressions that store and infiltrate stormwater.
Vegetated Roofs are roofs that are covered with specialized media and planted with vegetation; this enables the roof to hydrologically perform in a manner similar to vegetated surfaces. The media holds water, which is eventually evapotranspired by the plants. The primary function of the vegetated roof in stormwater management is volume reduction. Additional stormwater benefits include water quality improvements and some peak rate control. Environmental benefits beyond stormwater control include building temperature moderation and wildlife habitat.
Runoff Capture & Reuse
Runoff Capture and Reuse refers to the variety of techniques that are used to capture precipitation, store it for a period of time, and reuse the water. Devices used to capture and store stormwater include rain barrels, cisterns, vertical storage mechanisms, and below ground storage systems. These BMPs are most effective for use in controlling small, frequent storm events. Stormwater management benefits of runoff capture and reuse devices include volume reduction, water quality improvements, peak rate control, and groundwater recharge.
Constructed Wetlands (CWs), also known as stormwater wetlands, are shallow aquatic systems planted with emergent vegetation. They are highly effective at removing pollutants from stormwater; they also mitigate peak flow rates and reduce runoff volume. Beyond stormwater management, CWs provide wildlife habitat and aesthetic value. Detention Basins, a basic BMP that temporarily stores stormwater, are often retrofitted into CWs in order to maximize stormwater management function of the space and obtain the added benefits.
Wet Pond/Retention Basin
Wet Ponds (WPs), also called retention basins, are stormwater basins that include a permanent pool of water, as well as additional capacity for the temporary storage of stormwater. They are very effective at controlling peak stormwater rates and also provide water quality benefits. Beyond stormwater management, WPs can also provide aesthetic and wildlife benefits.
Dry Extended Detention Basin
Dry Extended Detention Basins (DEDBs) are detention basins, which are designed to provide temporary stormwater storage and water quality benefits. The temporary storage of stormwater prevents downstream flooding. Water quality benefits are achieved through sediment settling out of the stormwater while held in the DEDB. DEDBs are often used in conjunction with other BMPs to maximize stormwater management benefits on site. The DEDB is a design enhancement from the Dry Detention Basin, which has been popular since the 1970s. The extended detention of stormwater maximizes water quality benefits.
Water Quality Filters & Hydrodynamic Devices
Water Quality Filters are stormwater inlets that are fitted with devices to filter pollutants from stormwater. Hydrodynamic devices are separate from inlets, but serve the same function of filtering pollutants. Both Water Quality Filters and Hydrodynamic Devices rely on some form of settling and filtration to remove pollutants from runoff. There are numerous variations available commercially.
Riparian Buffer Restoration
Riparian Buffer Restoration (RBR) is the restoration of the area surrounding streams, lakes, ponds, and wetlands. The restoration of these areas provides numerous stormwater management benefits, including water quality improvement, volume reduction, groundwater recharge, and peak rate control. Ecological benefits beyond stormwater management are numerous, including providing wildlife habitat and providing aesthetic value.
Landscape Restoration is the term used for the implementation of sustainable landscape practices outside of the Riparian Buffer and/or other specially protected areas. Landscape Restoration can include forest restoration, meadow restoration, and the conversion of turf to meadow. Native plants should be used and the use of pesticides and herbicides should be eliminated, if possible.
Soil Amendment & Restoration
The Soil Amendment & Restoration BMP refers to the process of improving disturbed soils. By reducing compaction and adding organic materials, stormwater infiltration and pollutant removal capacity can be greatly increased. In addition to the added stormwater capacity of the soil itself, soil amendment and restoration improves conditions for growing vegetation, which further improves stormwater management.
Floodplain Restoration aims to restore a floodplain to conditions present prior to development (pre-1600s). It is a system-based BMP that strives to mimic undisturbed conditions between groundwater, stream base flow, and vegetation. Floodplain Restoration provides substantial water quality and quantity stormwater management benefits.
Level spreaders are a structural BMP that are designed to reduce the erosive energy of stormwater. Examples of Level Spreaders include earthen berms, level perforated pipes, or concrete curbs. Level spreaders are often used in conjunction with other BMPs such as Filter Strips. Filter Strips function significantly better when stormwater is distributed across the BMP.
Special Detention Areas
The implementation of Special Detention Areas entails using spaces that are not typically utilized for stormwater management, such as parking lots, to temporarily detain stormwater. A flow control structure is typically used to allow runoff to a pond. This BMP is specifically used to control peak rate volume and is more effective when combined with other BMPs that address water quality and volume reduction.
For more information on Structural Stormwater BMPs, visit our Stormwater Resources page.
By Land Use
Nonpoint source water pollutants enter streams and other aquatic environments through precipitation that runs off the land. Pollutants originate from a variety of different land uses such as residential, agricultural, commercial, urban, brownfields, and highways/roads. Explore BMPs for each land use below.
Water pollutants that may originate from residential properties include sediment, pathogens, nutrients, toxins such as pesticides, yard waste, and trash. Homeowners can help control stormwater runoff and improve water quality by utilizing best management practices (BMPs) on their property. Common stormwater runoff and infiltration practices for the homeowner can consist of structural, non-structural, and behavioral changes. Examples of structural BMPs include rain gardens, infiltration trenches, permeable pavement, walkways, patios, and rain barrels/cisterns. Non-structural BMPs for residents include downspout disconnection, riparian stream buffers with native vegetation, and minimizing disturbed area. Behavioral changes can include scooping animal waste, containing garbage, bagging or composting grass clippings, reducing de-icer, washing cars on lawns or in car washes, and proper car maintenance. See figure 1 for common sources and BMPs to address each pollutant.
|Pollutant||Common Source||BMP Examples|
|Sediment||Home construction/renovation, streambank erosion, eroding ditches, bare spots in lawn||Proper permitting for home grading and construction, restore stream buffers, cover bare spots in lawn|
|Pathogens||Animal waste, leaking septic systems, garbage||Proper installation and maintenance of sanitary sewer lines, establish stream buffers, scoop the poop, contain garbage to cans|
|Nutrients||Animal waste, fertilizers, soap from washing cars, grass clippings, septic systems||Scoop animal waste, reduce use of fertilizers, wash car on lawn or in car wash, plant native species, create rain gardens, establish stream buffers|
|Chemicals||Misapplication of pesticides/herbicides, improper disposal of chemicals, home car repairs, de-icer||Proper car maintenance, proper disposal of hazardous waste, reduce use of de-icer|
|Trash||Uncontained garbage||Contain garbage to cans, pick up trash on lawns/streets|
Figure 1. Common residential stormwater pollutants, their source, and how to manage.
Find more resources on our Stormwater Resources page.
Stormwater management on agricultural land focuses on both protecting water quality and reducing runoff volumes and rates. Potential water quality pollutants from agriculture include sediment, nutrients, bacteria, and pesticides. Runoff quantity management aims to protect stream and groundwater quality, stability of streams, cropland, and infrastructure and encourages groundwater recharge.
Stormwater management on agricultural lands can be broken into two major categories: 1) Erosion and Sediment Control and 2) Manure and Nutrient Management. Specific best management practices (BMPs) to consider under erosion and sediment include but are not limited to: Crop Field Soil Erosion and Sediment Control, Streamside Pasture Management, Management of Farm Lanes, Walkways and Forest Lanes, Maintenance of Existing BMPs, and more. Factors to consider that are associated with manure and nutrient management include Manure Storage, Heavy Use Areas Protection, Record Keeping, Surface and Roof Water Control, Well Head and Groundwater Protection, Maintenance of Existing BMPs and more.
Learn more about stormwater management on agricultural lands, best management practices, regulations, and more on our Stormwater Resources page.
Ag BMP Spotlight: Riparian Buffers
Riparian buffers are non-structural BMPs that are extremely beneficial tools for stormwater management. Agricultural land is often an ideal setting to preserve or restore riparian buffers. Their many stormwater benefits include:
- Filter pollutants
- Reduce peak rate
- Reduce runoff volume
- Stabilize banks
- Moderate in-stream temperature
- Facilitate groundwater recharge
These land management practices have numerous benefits beyond stormwater management, including but not limited to the following:
- Provide habitat for aquatic and terrestrial wildlife
- Moderate temperature
- Improve aesthetics
- Improve air quality
The Clean Water Act (CWA) requires best management practices on construction sites, due to the high possibility of pollutant runoff during precipitation events. Sediment is the primary water pollutant in the United States; therefore it is the main pollutant being controlled on construction sites. Construction sites are required to obtain an NPDES permit, as well as a Chapter 102 permit for land disturbance. Stormwater Pollutant Prevention Plans (SWPPPs) are required on construction sites. These plans detail the BMPs that are to be used to prevent sediment from traveling off the site.
The list below provides a few common best management practices (BMPs) that can be used on construction sites. This is not a complete list. Please refer to your permit or contact your local conservation district for more information.
- Silt fence
- Sediment Basin
- Inlet protection
- Clean sediment out of stormdrains regularly
- Stabilize sediment by covering soil – vegetation, phased development, mulch, sod, rock riprap, mats, and blankets
- Sediment trap
- Concrete washout area
- Vehicle maintenance
- Building maintenance – dispose of debris properly
- Construction exit
Explore more on our Stormwater Resources page.
Non-point source pollution, localized flooding, and degraded waterways are just some of the stormwater management challenges in urban areas. Impervious surfaces often account for a majority of the land associated with commercial areas due to large parking areas, rooftops, and sidewalks. The densely-developed nature of many urban areas can be problematic when looking for ways to retrofit locations to incorporate green stormwater infrastructure. Fortunately, due to the significant need across the nation to effectively manage stormwater in urban areas, an extensive body of literature has been developed on the subject. When developing, redeveloping, or retrofitting an area, the incorporation of structural and non-structural stormwater best management practices can greatly reduce and mitigate the impacts of stormwater. Act 167 Stormwater Management Plans detail development and re-development requirements – for more information, visit our Planning Documents page.
Visit our Stormwater Resources page to learn more about the challenges of and solutions to urban stormwater management.
Stormwater management on brownfields must be done very carefully due to contaminants in the soil. Best management practices (BMPs) that promote infiltration should not be utilized on brownfield areas. Infiltration into potentially contaminated soil may introduce additional pollutants to groundwater and streams. BMPs that are appropriate for use in brownfield redevelopment include those that temporarily detain, treat, and release the stormwater without coming into contact with contaminated soil. Specific BMPs that may be suitable for use on brownfield areas include but are not limited to: vegetated roofs, stormwater capture and reuse (such as rain barrels or cisterns) and stormwater planters.
Learn more about stormwater management in brownfield areas on our Stormwater Management page.
Mitigating the impacts of runoff from highways and roads is a concern for highway managers (such as PennDOT and the PA Turnpike Commission) and for municipalities; particularly those tasked with stormwater management and NPDES Phase II responsibilities. Highways and roads face specific challenges in managing stormwater, including:
- The need to manage stormwater while maintaining safe road conditions
- Limited available space and the need to locate BMPs within the right-of-way, if possible.
- Drainage area imperviousness greater than 50 percent, and sometimes 100%.
- Areas of extensive disturbance and compaction of soils (cut and fill).
- The potential for spills of hazardous materials.
- The use of deicing chemicals and salts as well as anti-skid materials, and the need to dispose of removed snow.
- Higher concentration of pollutants as compared to many other land uses.
(Taken from PA Stormwater Best Management Practices Manual)
Although there are many challenges associated with stormwater management and transportation infrastructure, there are also many opportunities. Communities across the nation are incorporating innovative stormwater management practices into their design and re-design of transportation networks. Many cities are creating “Green Streets” and “Green Alleys” to manage stormwater runoff while also reaping the additional environmental and social benefits of green infrastructure. Visit the Stormwater Management page to learn more about stormwater management and transportation infrastructure.
Learn more about routine and non routine stormwater maintenance.