What Is Stormwater?

Stormwater refers to a heavy quantity of water, such as rain or snow, that falls to the surface of the Earth. When it reaches the surface, stormwater becomes polluted as it picks up, carries, and transports various pollutants (oil, grease, chemicals, sediment, nutrients, pathogens) along streets, drains, open channels, and storm sewer systems.

When it reaches the surface, stormwater becomes polluted as it picks up, carries, and transports various pollutants (oil, grease, chemicals, sediment, nutrients, pathogens) along streets, drains, open channels, and storm sewer systems. Most of the untreated runoff is eventually discharged into nearby water bodies. However, in combined sewer systems, stormwater flows with wastewater and is treated at a water resource recovery facility.

In urban areas, stormwater management is especially important because of decreases in natural land cover and the expansion of impervious surfaces, such as rooftops, sidewalks and roadways. These surfaces exacerbate runoff because they change the permeability of the landscape — preventing rainwater from soaking in or infiltrating the soil. Some of the impacts of stormwater include flooding, sewer overflows, and non-point source pollution.

Stormwater is managed using storm sewers and stormwater controls, including green infrastructure and low-impact development.

Join the discussion about stormwater issues on WEF's LinkedIn Stormwater and Watershed Group. 

Visit the Stormwater Report Website

Opportunities for Involvement

Stormwater Community
WEF staff contact: Lisa Deason
ldeason@wef.org

STORMWATER INITIATIVES

National Municipal Separate Storm Sewer System (MS4) Needs Assessment Survey

The WEF Stormwater Community conducts the MS4 Needs Assessment Survey biennially to understand the challenges, drivers, and resource needs within the MS4 sector by:

• Identifying MS4 program challenges and drivers.
• Determining information and technical resource needs.
• Estimating current funding levels and identifying funding gaps.

The survey results help advocate for closing the funding gap and supporting the inclusion of stormwater as an independent infrastructure sector.

National Municipal Separate Storm Sewer (MS4) Awards for Municipal Stormwater and Green Infrastructure Programs

The National Municipal Stormwater and Green Infrastructure Program for Municipal Separate Storm Sewer Systems (MS4) aims to recognize high-performing communities that meet and exceed regulatory requirements in a technically effective and financially efficient manner. Led by the Water Environment Federation (WEF), the awards were established in 2015 through a cooperative agreement with the U.S. Environmental Protection Agency (EPA).

Submissions undergo a thorough review by an expert committee and are evaluated in two categories: program management and innovation.  The three highest-scoring programs(s) in Phase I and II within each category will be honored at the 2026 National Stormwater Policy Forum in Washington, DC during Water Week.

Please contact Lisa Deason, Stormwater Practice Leader, at ldeason@wef.org 

National Stormwater Policy Forum

The National Stormwater Policy Forum is an annual event co-hosted by the Water Environment Federation (WEF) and the National Municipal Stormwater Alliance (NMSA). This half-day forum is part of Water Week and brings together stormwater professionals, policymakers, and other stakeholders to discuss the latest legislative and regulatory issues affecting the stormwater sector.

The forum provides a platform for participants to engage with national policymakers, learn about current policy issues, and advocate for the needs of the stormwater community. Topics typically covered include updates on stormwater design standards, climate change resilience, and emerging contaminants like PFAS.

The next forum is scheduled for April 7, 2025. It will be a hybrid event, allowing both in-person and virtual attendance.

In-person event will be held from 11:30 AM to 5:00 PM at 660 North Capitol Street NW, Suite 400, Washington, DC 200011.

The virtual event will be held via Zoom from 12:00 PM to 5:00 PM Eastern Time.

Forum participation is free.

Register for in-person participation  |  Register for virtual participation