Public Works and Environmental Services

CONTACT INFORMATION: Our offices are open 8 a.m. – 4:30 p.m., Mon - Fri
703-324-5500 TTY 711
12000 Government Center Parkway
Suite 449, Fairfax, Va 22035
Joni Calmbacher
Director, Stormwater Planning

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Flood Protection Newsletter

This newsletter includes important flood protection related information including flood safety, floodproofing, permit requirement, drainage service requests, special flood hazard areas, emergency alert systems, natural floodplain functions, and flood insurance.

Your property is In or Near a Floodplain.

What is a Floodplain?

A floodplain is a generally flat or low-lying area of land adjacent to a river, stream, lake, or ocean that periodically floods. 

For regulatory purposes, in Fairfax County, floodplain means those land areas in and adjacent to streams and watercourses subject to continuous or periodic inundation from flood events with a 1 percent chance of occurrence in any given year (i.e., the 100-year flood frequency event) and having a drainage area greater than 70 acres. The floodplains that have drainage area greater than 70 acres but less than 360 acres are defined as “Minor Floodplains,” and that have a drainage area equal to or greater than 360 acres are as “Major Floodplains.”

The Federal Emergency Management Agency (FEMA) defines floodplain i.e., Special Flood Hazardous Areas (SFHAs) as land areas that are at high risk for flooding. These areas are indicated on Flood Insurance Rate Maps (FIRMs) and on Digital Flood Insurance Rate Maps (DFIRMs).

Anywhere it can rain, it can flood! Even outside of floodplains!

  • Flooding can occur during any storm event
  • Fairfax County is taking steps to mitigate flooding
  • You should take steps to protect yourself and property. 

Fairfax County participates in the National Flood Insurance Program (NFIP) Community Rating System (CRS) sponsored by FEMA since 1993. Participation in the CRS is a service for county residents and provides an opportunity for property owners to purchase flood insurance for their buildings and contents at discounted rates.

For information on floodplain locations, visit:

Know your flood risk and stay informed

FEMA initiated an update of the county’s 2010 FIRM and associated Flood Insurance Study (FIS) in 2016, and on April 30, 2021, provided the county with a preliminary FIRM and FIS with updated information. The County notified all residents affected by the proposed changes to the FIRM in October/November 2021 and held a series of virtual meetings in January and February 2022 to publicize the changes and receive comments on the proposed changes. FEMA initiated the appeal period for the preliminary FIRM and FIS on April 22, 2022. An appeal letter was submitted to FEMA on July 21, 2022. FEMA issued a revised preliminary FIRM on August 30, 2024. The second appeal period concluded on August 28, 2025. The County re-appealed the revised Preliminary FIRM panels 51059C0168F and 51059C0281F regarding Tripps Run (upstream of Lake Barcroft). In May 2026, the County met with FEMA consultants to discuss appeal of the revised Preliminary FIRM panels for part of the Tripps Run. FEMA is expected to send a resolution letter by Fall 2026, followed by a 30-day comment period. Afterward, FEMA will issue a Letter of Final Determination (LFD), and the County will have six months to adopt the study. Fairfax County is in FEMA Region 3. The current status of FIRM projects within Region 3 can be viewed at Region 3 FIRM Project Status and Age.

Flooding may occur at any time, with little or no warning. There are three main sources of local flood hazards: rivers and streams during heavy storms; inadequate overland relief during heavy storms; and tidal surcharges in the lower Potomac River caused by hurricanes, tropical storms and earthquakes. Please note that the County has identified flood areas beyond those labeled on the DFIRM. Always refer to the Fairfax County Flood Risk Awareness tool.

Areas of flood hazards are identified on the 2010 DFIRMs. In general, SFHAs are labeled as Zone A, Zone AE, or Zone AH.

Zone A is the area subject to inundation by the one-percent-annual-chance flood (also known as the base flood) event generally determined by using approximate methodologies.

Zone AE is the area subject to inundation by the one-percent-annual-chance flood event determined by detailed methodologies. Base Flood Elevations (BFEs) are shown on the FIRMs.

Zone AH is the area subject to inundation by the one-percent-annual-chance of shallow flooding, usually in the form of a pond, with an average depth ranging from 1 to 3 feet. BFEs derived from detailed analyses are shown at selected intervals within these zones.

More information about Zones A and AE may be seen at Flood Zones | FEMA.gov.

Fairfax Alerts Logo

New users may register their wireless devices and land lines with voice mail (home or business) at: Alerts & Emails | Topics.
Please update your information at the link above.

The Fairfax Alerts system is specific to Fairfax County. Everyone who lives or works in the county is welcome to sign up for Fairfax Alerts to receive information about public safety, traffic, weather, police, emergency preparedness drills and exercises, flooding, Metro Safe Track, county news, Fairfax Connector, public meetings and events and other information from Fairfax County. The Fairfax Alerts system provides timely emergency information during a crisis and provides daily updates. Messages are delivered to registered devices that may include email accounts, text pagers, cell and satellite phones and other wireless devices.

Residents may:

  • Choose weather, traffic and public safety notices.
  • Use the “do not disturb” feature.
  • Customize alerts relevant to home, school, day care and work.
  • Choose up to ten delivery methods.
  • Manage alerts by downloading the iPhone or Android app

Short messages are sent during critical situations to cell phones in a geo-targeted area. There is no need to sign up or download an app.

  • Imminent threats to safety or life, sent by state and local officials.
  • Extreme weather: tornados, flash floods, hurricanes or wind warnings issued by the
    National Weather Service.
  • Amber alerts: serious child abduction cases issued by the National Center for
    Missing and Exploited Children and the state police.
  • Presidential alerts during a national emergency.

Report Flooding Issues, Solve Drainage Problems, FMAP, and CAP Information

To report storm drainage system flooding, issues with a stormwater management pond or for a determination of who maintains a stormdrain, call the Maintenance and Stormwater Management Division at 703-877-2800, TTY 711, or use the form at Contact Maintenance and Stormwater Management | Public Works and Environmental Services.

For more information, visit Storm Drainage System | Public Works and Environmental Services.

Staff of the Northern Virginia Soil and Water Conservation District (NVSWCD) and of the Stormwater Management Program provide information and advice on private drainage and erosion problems. A free guidebook, “Solving Drainage and Erosion Problems: A Guide for Homeowners,” may be downloaded from Solving Drainage and Erosion Problems: A Guide for Homeowners | Northern Virginia Soil and Water Conservation District.

Since July 1, 2024, NVSWCD has been administering a new grant called the Flood Mitigation Assistance Program (FMAP). This grant program provides up to $5,000 per applicant on a cost-share basis (50% County, 50% applicant) for proactive measures to prevent flooding. Funding will be available to residential and multi-family properties, places of worship, and homeowner associations. In 2025, the program’s first full year, 53 applications were approved and $178,277 was disbursed in reimbursement monies, averaging $3,364 per application.

For more information, call NVSWCD at 703-324-1460, TTY 711, or visit Flood Mitigation Assistance Program (FMAP) | Northern Virginia Soil and Water Conservation District or email conservationdistrict@fairfaxcounty.gov.

Conservation Assistance Programs are urban cost-share programs that help property owners address stormwater concerns on their own property with environmentally friendly practices. They provide financial and technical assistance for installing projects to address erosion, poor vegetation, and/or excess stormwater runoff. The purpose of the program is to help improve water quality in our region by addressing these concerns. By reducing the amount of water runoff from our land, we reduce the pollutants going into our streams and Chesapeake Bay. CAP funding is available for installing specific practices.

For more information, call NVSWCD at 703-324-1460, TTY 711, or visit Conservation Assistance Programs | Northern Virginia Soil and Water Conservation District or email conservationdistrict@fairfaxcounty.gov.

Build responsibly and keep flow paths open

Construction in a floodplain is not allowed under most circumstances.

  • Before building, filling or excavating in a floodplain, or near any natural or man-made watercourse, call Land Development Services (LDS) at 703-324-1720, TTY 711, to determine if the proposed activity is allowed and what types of permits are required.
  • Any construction or land disturbance within or adjacent to a natural or man-made watercourse may require a wetland permit from the U.S. Army Corps of Engineers and the Commonwealth of Virginia.
  • An addition to an existing building that is located in a floodplain may be allowed if the building was constructed prior to August 14, 1978, and the cost of the addition is less than 50 percent of the market value of the existing building, not including the land.
  • New dwellings and additions constructed adjacent to a floodplain must be elevated 18 inches above the 100-year flood level and set back 15 feet from the edge of the floodplain.
  • Existing buildings in floodplains that have been damaged by flood, fire or other casualty loss may be reconstructed.
  • A dwelling damaged to the extent that the cost of repairs equals or exceeds 50 percent of the market value of the building before it was damaged must meet the same requirements as a new building.
  • For new construction or substantial improvement in SFHAs, the NFIP requires a completed Elevation Certificate (EC) to document that the lowest floor is elevated at or above the Base Flood Elevation (BFE). A new EC is required upon completion of construction to officially document the “as-built” elevation. This document is essential for verifying compliance with the County’s floodplain management ordinances. The EC must be filled out by a licensed land surveyor, engineer, or architect, and submitted to LDS.

For more information call LDS at 703-324-1720, TTY 711, or visit Land Development Services | Land Development Services.

Land use and development in Fairfax County is governed by the Comprehensive Plan, the Public Facilities Manual, the County Code and the Virginia Uniform Statewide Building Code. LDS reviews all subdivision, site and grading plans and building permit applications to determine if the land is located in a floodplain.

The goal of floodplain management regulations is to prevent loss of life and property damage, promote flood safety, preserve wildlife habitats and maintain the natural integrity of streams, protect water quality and increase groundwater recharge.

The county participates in the NFIP. NFIP rules state that if the cost of reconstruction, rehabilitation, additions or other improvements to a building equals or exceeds 50 percent of its market value, then the building must meet the same construction requirements as a new building.

If a residence in a floodplain is damaged to the extent that the cost of repairs equals or exceeds 50 percent of the market value of the building (exclusive of the land) before it was damaged, the building must be constructed 18 inches above the base flood elevation.

To update FEMA maps and changes to FEMA floodplain or flood elevations, the Conditional Letters of Map Revision (CLOMR) and Letters of Map Revision (LOMR) may be required. More information is available at Letters of Map Revision and Conditional Letters of Map Revision | FEMA.gov. It is important to note that an approved Letter of Map Amendment (LOMA) does not revise the FEMA or county floodplains.

FEMA recommends several ways to protect a building from flood and wind damage:

  • Keep flow paths open.
  • Re-grade the lot to drain water away from the building.
  • Waterproof walls and install watertight enclosures over entrance ways. This is not recommended for houses with basements or if flood waters may exceed two feet.
  • Raise the house above flood levels. Flood waters may pass under the house, causing less damage.
  • Protect buildings from high winds during tropical storms and hurricanes by installing storm shutters and reinforced garage doors.

Any alteration to a building or land, including re-grading, filling or modifying a sewer line, requires a permit. For information regarding building and site regulations, call LDS at 703-324-1720, TTY 711.

Some houses, including those that are not in a floodplain, may have sewers that back up into the basement occasionally during heavy rain. A plug for the basement floor drain, shower drain, or standpipes for these drains, may reduce or eliminate backups. Plugs are available at many hardware and plumbing supply stores. A plumber should be consulted when installing a plug, overhead sewer or back-flow valves. More information about flood proofing is available at Flood Information | Public Works and Environmental Services.

Protect the life you’ve built, get INSURED

A newly written policy on a compliant building in the County will receive the CRS discount when the policy is issued. If a newly written policy qualifies to receive a statutory discount (e.g., newly mapped, preFIRM), then those discounts will be applied to the policy in addition to a CRS discount. The CRS discount is applied to the total of the building, contents, and premium after any mitigation discounts (e.g., flood vents) and before any statutory discounts, annual increase cap, and fees, surcharges, and assessments.

FEMA’s new flood rating methodology, Risk Rating 2.0, has fully implemented since April 1, 2023. More information may be seen at NFIP’s Pricing Approach | FEMA.gov.

In Risk Rating 2.0, because the flood zone is no longer a rating variable, the discount that had applied to just SFHA policies now applies to all policies. Also, even though ECs are not required for policies in Risk Rating 2.0, they are required to ensure compliance with community floodplain management building requirements, which can affect eligibility for CRS discounts as an EC shows the location of a building, its Lowest Floor Elevation (LFE), its building characteristics, and flood zone. ECs can also be used to support requests for a LOMA or Letter of Map Revision based on fill (LOMR-F). ECs can be prepared by any Virginia licensed land surveyor and may cost $800 to $2000. Call the Stormwater Planning Division at 703-324-5500, TTY 711, or Land Development Services at 703-324-1720, TTY 711, for information about the ECs the County may have on file.

ECs are available for a limited number of properties in the County. Please visit Elevation Certificates | Public Works and Environmental Services to determine if an EC for your property is available. Available ECs will be provided to property owners on request.

Flood insurance is mandatory for properties located in a SFHA that are financed with federally backed mortgages. This includes all loans from banking institutions with deposits guaranteed by the Federal Deposit Insurance Corporation.

Flooding is the most common natural disaster in Virginia. Repairs are expensive. One inch of water in a home or office may cause significant damage. Most homeowners’ insurance policies do not cover losses from flooding.

Property owners and residents are encouraged to contact their insurance agent to determine the extent of their policy coverage.

Flooding may occur at any time of the year. After applying for flood insurance, typically there is a 30-day waiting period before coverage begins.

Renters may buy flood insurance for personal belongings or business inventory. Coverage may include cleanup expenses and repair or replacement of such items as furnaces, water heaters, washers, dryers, air conditioners and freezers.

Flood insurance benefits do not have to be repaid. Flood related claims may be covered even if a disaster was not declared. Flood insurance may cover homes and businesses and protect the property owner’s financial security.

Visit Floodsmart | The National Flood Insurance Program or call 1-888-379-9531. Call your insurance agent. 

Risk Rating 2.0 determines flood insurance premiums based on

  • Flood frequency
  • Multiple flood types (river overflow, storm surge, coastal erosion and heavy rainfall)
  • Distance to a water source along with property characteristics such as elevation and the cost to rebuild 

Those who rent, or lease property may purchase a ‘contents only’ policy.

Be prepared, make a plan, build a kit

Online at Community Emergency Response Guide | Emergency Management.

The Fairfax County CERG is a guide that provides residents with the tools needed to be better prepared. The guide includes:

  • a family emergency plan
  • a business or organization emergency plan
  • a neighborhood preparedness plan
  • an emergency supply kit check list
CERG

Important documents and contact information

  • Battery operated radio
  • Batteries, flashlight, solar chargers for cell phones
  • First aid kit, medications
  • Emergency blankets
  • Change of clothes
  • Tools and duct tape
  • Whistle and light sticks
  • Trash bags and sanitation supplies
  • Waterproof container
  • Food and water
  • Cash
  • Can opener
  • Local maps

For more information, please visit Make an Emergency Kit | Emergency.

Protect yourself from flood hazards “Turn Around - Don’t Drown”

Flooding occurs in virtually every community, including Fairfax County. Flash floods are the most dangerous and may occur within a few minutes of excessive rainfall, a dam failure or a sudden release of water held by an ice jam. Flash floods often have a dangerous flow of water that may carry with it rocks, mud, tree limbs and other debris. Overland flooding occurs when rivers and streams overflow their banks. Occasionally, the capacity of storm drains that are designed to carry stormwater away from streets and yards is exceeded. For more information, visit Flood Information | Public Works and Environmental Services.

The National Weather Service has released an 80-year summary of severe weather fatalities. According to this data, there have been 8,765 flood-related deaths in the United States since 1940. For more information, visit: Weather Related Fatality and Injury Statistics.

Flash flooding is the most dangerous type of flood as it combines the destructive power of the water with incredible speed and unpredictability. Most people who died in floods made one common and fatal mistake: they drove their vehicles including pickup trucks, vans and sport utility vehicles, into flood waters.

According to the U.S. Geological Survey, water that is one foot deep typically exerts 500 pounds of lateral force on a vehicle. Once the vehicle is floating, the floodwater becomes the steering wheel. If the water is moving, the vehicle may be swept away, tipped on its side or flipped over, trapping the occupants inside. A bridge or road that cannot be seen under floodwater may have been undermined or washed out.

Protect the drainage system and natural floodplain function

Please help improve water quality by recycling trash and keeping storm drains clear.

Anything that is thrown from a vehicle, dropped on a parking lot or deposited into a storm drain is carried by rain or melting snow through the storm drainage system to streams, rivers and lakes; not to a wastewater treatment plant. This includes swimming pool water. Please do not drain pool water into a stream, manhole or storm drain. For more information about draining swimming pools, call 703-324-5500, TTY 711.

Litter blocks storm drains, which may cause street and yard flooding, traffic delays and property damage.

Cigarette butts, plastic and glass bottles, food containers, cans, plastic shopping bags and anything else that is not disposed of properly may flow to and pollute the Potomac River and ultimately the Chesapeake Bay.

Trash is unsightly. It degrades residential and commercial property values, harms the fish and other wildlife, and damages wetlands.

It is illegal to deposit anything into a storm drain. Fertilizer, pesticides, motor oil, pet waste, paint and paint-related products are hazardous to the environment and pollute the Potomac River, a source of drinking water for many Fairfax County residents.

The Fairfax County Municipal Code, chapters 124-1-1 through 124-1-13, contains provisions that address illicit discharges to state waters and the county’s storm drainage system.

Call 9-1-1 to report hazardous materials, such as those listed above, that have been discarded into a storm drain or stream. To obtain further information, please visit Polluted Runoff Inspections | Public Works and Environmental Services.

plastic bottles

Flood protection information and K-12 flood education resources

Printed information about flood protection for people, their property and their personal possessions is available at Fairfax County public libraries, in the reference section.

Topics include:

  • Elevating Residential Structures
  • Protecting Floodplain Resources
  • Reducing Damage from Localized Flooding
  • Protecting Building Utilities from Flood Damage
  • Above the Flood: Elevating Your Flood Prone House
  • Protecting Manufactured Homes from Floods and Other Hazards
  • Answers to Questions About the National Flood Insurance Program

Flood Science Center (FSC) is part of the Association of State Floodplain Managers (ASFPM) with a mission to study, understand, and communicate the technical, biological, social, and economic aspects of flood science to support ASFPM. K-12 flood education resources are special library collections of FSC. For more information about FSC, please visit Flood Science Center - Flood Science Center. More information about K-12 Flood Education Resources, visit K-12 Flood Education Resources - Flood Science Center.

The Stormwater Management Program

Stormwater Planning Division | Maintenance and Stormwater Management Division | Urban Forest Management Division

If residents encounter difficulty accessing links in this newsletter, call the Stormwater Planning Division at 703-324-5500, TTY 711, or email SWPDmail@FairfaxCounty.gov

All photos by Fairfax County.

To request this information in an alternate format call 703-324-5500, TTY 711.

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