A new flooding assessment and map have identified watersheds in the West End as some of Alexandria’s most vulnerable flood zones.
Areas considered most at-risk of flooding include the Potomac waterfront, Four Mile Run and Hooffs Run — as well as new additions like Holmes Run, Cameron Run and Backlick Run, according to a map shared by Flood Resilience Plan (FRP) project leaders at a meeting Monday night.
The new map is “identifying gaps” in the city’s current flood preparedness plans, Susan Beck, a senior water project manager at Jacobs Engineering Group, said during the meeting.
“[The assessment] confirmed that, you know, the city is taking action in areas that are vulnerable and flooding,” Beck said. “But, it also identified new areas the city or we hadn’t necessarily done modeling or understood what potential future impacts of flooding could be.”
The assessment and map were based on a combination of three flooding models across the city and used to project storm conditions in 2025 and 2075.
- Urban overland drainage model — Simulates impacts of rainfall and runoff on land surfaces
- Riverine model — Simulates water flow in streams and rivers during storm events
- Coastal model — Simulates activity along the waterfront during storm events
“The city had already done some modeling in some of the very known, very highly problematic flood areas,” Beck said. “This model looked to expand on that, particularly going into other areas of the city that hadn’t been studied before.”
The Holmes Run, Cameron Run and Backlick Run areas will require “further study,” according to the presentation.
“We’re going to look closer at those areas and determine the path forward and what more we can learn for the future of the city,” Beck added.
The map was shared Monday as the FRP team remains in a data gathering phase to craft its flood mitigation strategy. This next implementation phase is expected to begin in the new year, according to the presentation.
Also Monday night, project leaders shared some preliminary results of their ongoing survey, which had collected 140 responses at the time of the meeting.
- 93% of respondents said they had experienced flooding in Alexandria, either at home or around the city
- 52% of respondents said they experienced flooding “often or very often”
- 59% of respondents are “very concerned” about future impacts of flooding
Alexandria residents have until Nov. 30 to participate in the online survey.
Project leaders anticipate hosting another community meeting in the new year, which has yet to be scheduled.
