Flooding Frequently Asked Questions

The County started the Comprehensive Flood Management Planning (CFMP) process in September 2022 after severe rainfall from the remnants of Hurricane Ida in September 2021 caused significant flooding in the Rockville area, leading to the death of a Rockville resident. The County determined it must work proactively to respond to the ever-growing flood risk in the County driven by climate change. The goals of the CFMP process are to:

• Understand the County’s current and future flood risk and vulnerability through flood modeling
• Understand and modify the County’s programs, regulations, communications, and other government activities that address, or contribute to, flood risk and vulnerability
• Ensure racial equity and social justice issues are considered during every facet of this effort

A number of County entities participate actively in the CFMP process:

• Department of Environmental Protection
• Department of Permitting Services
• Office of Emergency Management and Homeland Security
• Department of Transportation
• Montgomery Planning
• Montgomery Parks
• Office of the County Executive

Other entities will participate on an as needed basis as the process proceeds.

The Federal Emergency Management Agency (FEMA) does define floodplains, and the County has used these floodplains to limit unsafe development for decades. However, FEMA floodplain models focus on the flood risk around larger rivers, streams, and other bodies of water, and do not look at flood risk outside of these limited areas. FEMA models also use historical information and don’t project how flood risk may increase in the future due to changing rainfall patterns due to climate change. The flood risk areas identified by the County’s new models will cover land outside of the areas mapped by FEMA and include future risks based on changing climate conditions.

The purpose of sharing non-FEMA flood risk modeling is to more effectively communicate about the risk of flooding outside of the FEMA floodplains. This information can help residents prepare before the next significant rain event.

The best way to stay safe in a flood is to take the five actions below. Each action has a link to more information:

• Know your flood risk.
• Sign up for Alert Montgomery.
• Plan and protect your home or business.
• Review home, renters, and flood insurance.
• Be weather aware.

There are many ways to reduce your flood risk. Check out the pages on the Resident Portal for information about how to plan for severe weather events, steps you can take to help protect your property, and how to find flood insurance.

There are several options available for residents to review their flood risk that you can find on the Prepare Your Home page.

Stormwater management systems are designed to capture pollutants and manage stormwater runoff from smaller rain events. Flood mitigation measures such as large conveyance or detention facilities are designed to deal with much larger volumes of water from much larger storm events.

Information about the watersheds that are being modeled as part of the CFMP process, including a map of the watersheds and the estimated schedule for completion of the modeling, can be found on the Montgomery County’s Flood Model page.

There are a wide variety of factors that influence property values such as location, school districts, home and lot size, and market demand. Because of this, it is difficult to isolate the discrete impact flood risk mapping may have on property values. Research on this topic indicates that the record of flooding events for a property has a much bigger impact on property value than flood risk modeling. The County feels there are more positives than negatives to property owners of sharing non-FEMA flood risk information. Providing this information can help property owners take steps to reduce flood risk for themselves and future owners.

No. FEMA uses its own flood risk assessment process that is unique to FEMA’s National Flood Insurance Program (NFIP).

These studies will not impact requirements to buy flood insurance. However, the County still advises all property owners and renters to evaluate whether purchasing flood insurance makes sense based on individual circumstances.