Public Works and Environmental Services Alert:
Fairfax County has miles of beautiful shoreline and wetlands along the tidal Potomac River. However, living close to the river means that some neighborhoods are at risk of flooding, even on sunny days! Factors like heavy rain, unusual tides, tropical systems, nor’easters, and even strong winds can lead to flooding in communities at low elevations.
Flooding in areas adjacent to coastal waters can be caused by several reasons. The primary causes are high-tide flooding during extreme high tides (also known as king tides), and storm surge resulting from tropical systems and nor'easters, as strong winds drive water onshore. For additional information on the factors contributing to coastal flooding, please see the Understanding Stormwater Inundation tool provided by the National Oceanic and Atmospheric Administration (NOAA). For more information on storm surges and the factors that affect the magnitude of a storm surge, please see NOAA’s Storm Surge Overview page.
The County operates and maintains two flood control measures in the Belle Haven area: the New Alexandria Tide Gate and the New Alexandria Pump Station (See Video: County Tidal Control Facilities). The tide gate and pump station protect the upstream communities from storm surges up to about a 25-year event. County staff perform proactive pre-storm inspections of the pump station and tide gate to confirm they are operational and that the channels and facilities are free of blockages. In the event of a flooding threat, the County has an emergency plan in place to mitigate the impacts of flooding where possible.
While protection to a 25-year event means homes in the community have a four percent chance of flooding every year, it also means that over the course of 30-year mortgage, the likelihood of flooding is quite high – greater than 70 percent (see NWS Flood Return Period Calculator). This risk is further increased when considering sea level rise.
In addition to coastal flooding, the New Alexandria community is also at risk of flooding when large storm events occur at or near high tide. The area protected by the tide gate is most susceptible to these events. During coincident high tide and rainfall events where there is sufficient advance warning, the County employs mobile pumps to reduce water levels upstream of the tide gate, but these pumps cannot protect against very large rainfall events.
We encourage all residents in this area to subscribe to Fairfax Alerts, including Riverwatch, a Fairfax Alerts group designed to send local information. (See Video: Be Prepared and Stay Informed)
(See Video: Flood Risk and Hurricane Isabel)
Click images to view full screen.
See the US Army Corps of Engineers study report for potential sea level change.
(See Video: Flood Risk and Hurricane Isabel)
Belle View, New Alexandria, and River Towers have a history of significant structural flooding. In 2003, Hurricane Isabel resulted in the flooding of 160 homes and 60 condominiums in the area.
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Following the aftermath of Hurricane Isabel in 2003, the County has worked with community residents to inform them of their flood risk and assess, evaluate, and recommend potential flood mitigation measures to reduce flood risk.
In 2022, The United States Army Corps of Engineers (USACE) approached Fairfax County regarding a potential federally funded flood mitigation project to protect the Belle View, New Alexandria, and River Towers communities. The USACE proposed project included a 6.5-ft floodwall on the east side of Boulevard View to protect the community. The proposed project was not supported by the community as proposed and they requested that the wall be installed on the other side of the George Washington Memorial Parkway (GWMP), on the U.S. National Park Services (NPS) property. USACE coordination with NPS led to elimination of floodwall/levee measures along the GWMP due to concerns about detraction from the character or viewshed of the road and its historical integrity. The opposition to the proposal floodwall eliminated the only USACE proposed structural solution. (See Video: US Army Corps of Engineers Flood Mitigation Study)
The County continues to develop and implement flood risk awareness outreach programs to improve the resilience of community residents.