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 infrastructure, 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.

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, some of which 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 enrolled Chapter 641 of the 2021 Laws of Maryland (previously introduced as Senate Bill 227) that made addressing precipitation-based flooding a priority for MDE. This legislation became known as A-StoRM and required three things: MDE to report on the most recent precipitation data available, MDE to investigate flood events since 2000, and MDE to update Maryland’s stormwater quantity management standards for flood control. More information on MDE’s A-StoRM efforts can be found here: https://sb-227-maryland.hub.arcgis.com/. MDE has met or is in the process of meeting all three of these mandates, however, while developing strategies for meeting A-StoRM requirements, it became apparent that comprehensive watershed studies complimented MDE’s approach to meeting the A-StoRM requirements by providing a tool for applying appropriate stormwater quantity management in the watersheds most at risk for flooding.