Maryland Department of the Environment

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Watershed Studies

MDE believes that comprehensive watershed ​analyses are necessary to understand the causes of flooding events, both inside and outside of the Federal Emergency Management Agency’s (FEMA) mapped 100-year floodplains. Coordination and data sharing regarding flooding events, stormwater infrastruct​ure, and stormwater and flood management programs are necessary to allow MDE to be successful in predicting flood risk. Watershed studies for high flood risk watersheds are being persued to identify sources of flooding and develop mitigation plans. As climate change continues to impact Maryland’s rainfall patterns, flooding in the state is becoming more frequent and severe. This watershed studies initiative will produce watershed assessments using watershed scale HEC-RAS 2D models, starting with those watersheds that have the highest risk for flooding. ​​


Scoping a Comprehensive Flood Management Watershed Study


The Watershed Modeling Units map below is a tool for local and County governments to help scope a watershed study. The HUC-12 delineation, level of modeling detail (low, medium, and high), and estimated cost using the Maryland Environmental Service (MES) open ended contract are identified on the map below.  ​
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Activity outline for MDE Watershed Studies

Connections to Other MDE and State Initiatives

Comprehensive Flood Management Grant Program (CFMGP)

Maryland first performed watershed studies in the 1980s as part of the State's CFMGP initiative. This MDE program provided grants to local jurisdictions for comprehensive flood management studies, plans, and mitigation projects. Although some flood management plans were developed, and some are still in use, Maryland’s plan to develop flood mitigation plans in the 1980s was not fully implemented as originally envisioned.

Advancing Stormwater Resilience in Maryland (A-StoRM)

In response to growing local concerns regarding precipitation-based flooding, Maryland’s General Assembly enacted Chapter 641 of the 2021 Laws of Maryland, previously introduced as Senate Bill 227. This legislation made addressing precipitation-based flooding a priority for MDE. Known as A-StoRM, it required MDE to do three things: report on the most recent precipitation data available, investigate flood events since 2000, and update Maryland’s stormwater quantity management standards for flood control.

More information about MDE’s A-StoRM efforts is available online. MDE has met or is in the process of meeting all three mandates. While developing strategies to meet A-StoRM requirements, MDE identified that comprehensive watershed studies complement its approach by providing a tool for applying appropriate stormwater quantity management in the watersheds most at risk for flooding.

Maryland Department of the Environment
1800 Washington Blvd
Baltimore, MD 21230