Understand how stormwater management plans reduce rainwater runoff

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Stormwater management plans work to implement ways to reduce runoff from rainwater that can cause flooding by overwhelming local stormwater systems

Benefits of stormwater management 

Stormwater management plans work to implement ways to reduce runoff from rainwater that can cause flooding by overwhelming local stormwater systems. Additional benefits of managing rainwater runoff besides reduced flooding include the reduction of pollutants in water systems and groundwater replenishment. To find your local stormwater management plan you can search your town, city, or county’s government website. 

Stormwater management plans work to recognize structural improvements that are needed for the actual stormwater system as well as nonstructural management practices. Nonstructural management practices refer to changes that can be made to local legislation to improve stormwater quality and stormwater quantity. Stormwater ordinances limit the number of surface runoff volumes that are allowed in communities, especially in regard to new construction sites. Stormwater regulations work to ensure that as an area develops and loses its permeable surfaces to impervious concrete, rules are in place to require the creation of green or gray infrastructure to decrease the amount of runoff from these impervious areas. Gray infrastructure practices include the addition of stormwater drainage pipes, stormwater vaults, and pumps whereas green infrastructure practices include bioswales, rain gardens, and detention ponds.

stormwater_management_.pngDepiction of rainwater runoff entering a drain and stormwater system

Separate sewer and stormwater systems 

Structural improvements include how a municipality intends to update and upgrade the local stormwater system. Many cities and towns have moved to having separate systems for sewer water and stormwater rather than having both of these in a combined, single-pipe system. Separating these two systems allows for reduced flooding because the flows of the two systems are no longer combined so stormwater can be conveyed and discharged into a receiving body of water. If your community is moving away from a combined sewer system (CSS), towards a separate sewer system and stormwater system, this would be laid out in your local stormwater management plan. 

Additional benefits

Stormwater management plans also can identify project areas; areas where there are drainage issues, consistent flooding, or stormwater infrastructure that is in need of repair. The plan may be to repair or replace existing stormwater drainage pipes, clear debris that may be clogging ditches and other drainage infrastructure in your area such as stormwater outfalls or channels, or create new adaptation infrastructure to capture stormwater such as stormwater vaults, retention ponds, rain gardens, or bioswale. Your local plan will identify the areas that are most in need, decide what the most effective way to manage stormwater in this area is, and estimate the cost and length of time of each proposed project. 

Flood risk reduction

Information on Flood Factor® comes from the First Street Foundation Flood Model. Stormwater management plans often contain multiple of the 40 different types of flood risk reduction projects, known as adaptation, that this model considers when calculating and validating flood projections. 

The Adaptation Team continues to collect information on the flood infrastructure that exists across the country to make sure the Flood Model includes as many adaptation projects as possible. If your local stormwater management utility has made recent improvements to their infrastructure, or if the existing system can successfully manage stormwater in areas we show flooding, or if you know of any projects that are not shown today, please help the team by submitting this flood protection project user input form. The adaptation database contains 23,000 features today. We know there are more projects to include and value your input!

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