FAQ: Voluntary Property Acquisition to Reduce Flood Risk

Voluntary property acquisition to reduce flood risk is one tool option contained in the FY 2023-2032 Capital Improvement Plan, approved by the Arlington County Board in July 2022. 

Learn more about stormwater management and a Flood Resilient Arlington.

Why is the County investing so much in flood mitigation?

In recent years, Arlington and the surrounding region has experienced more frequent, high-intensity storms which have caused significant flooding in areas throughout Arlington.  

To respond to climate change and increasingly intense storms, Arlington has shifted the stormwater management program to help address this challenge with “Flood Resilient Arlington.” In November 2020, Arlington County voters approved a stormwater bond referendum to help fund watershed-scale projects and local capacity improvements and expansions to mitigate high risk flood areas, as part of a path toward a Flood Resilient Arlington. 

What is Flood Resilient Arlington?

In response to recent flooding challenges, Arlington has shifted the stormwater program to have more of a resilience focus. This includes:  

  • Conducting detailed analysis of the areas experiencing flooding and with the Risk Assessment and Management Plan (RAMP) we are updating the design standards for development, rainfall curves, and creating risk assessments for many areas of the County.  
  • Increased investment in the stormwater system.  
  • Expanding the type and location of capacity projects moving beyond pipe upgrades to detention vaults, pumping stations, land acquisition for flood mitigation etc.  
  • Increased outreach to property owners to take steps to floodproof their properties.    
  • Increased requirements for development projects to require more quantity controls. 

How does voluntary property acquisition work?

Voluntary property acquisition is a long-term approach that will help provide overall watershed improvements to critical watershed areas. The County plans to work with homeowners on a voluntary basis to acquire subject properties by negotiated purchase and sale agreements.

Why purchase properties? Can the County make improvements to the stormwater system instead?

The County is looking at multiple solutions to help alleviate flood risk. Through Flood Resilient Arlington, we are: 

  • Exploring new locations for stormwater facilities on public land 
  • Pursuing a blended engineering approach to provide for flood mitigation to include increased system capacity, property acquisition, and new types of facilities (i.e., stormwater detention vaults) 
  • Working with homeowners on voluntary property acquisition for flood mitigation 
  • Increasing floodproofing outreach to property owners 
  • Solutions to reduce flood risk may include a combination of several strategies as it is dependent on locations. 
  • In many locations, the County doesn’t have the property rights or access to increase pipe sizes or add additional stormwater pipes.  
  • Major civil drainage construction is typically only installed at the time subdivisions are built, before structures, roadways, and other utilities are installed and put into active use. 

What will properties purchased by the County be used for?

Properties acquired through voluntary acquisitions will be used for the following purposes: 

  • Re-establishing overland relief flow paths for water during large storm events for flood mitigation. 
  • Provide access to existing stormwater infrastructure to conduct necessary maintenance or upgrades 
  • Location of future stormwater infrastructure 
  • Construction of stormwater detention facilities  
  • Potential for co-locating water quality and stormwater capacity projects

How do I know if the County is interested in purchasing my property?

The County’s real estate team will begin contacting homeowners this Fall about potential property acquisitions by letter. Properties will be considered based on the degree that they can be used by the County for the purposes noted above and the flood risk present in specific areas of the watershed based on historic development patterns, topography, etc.

Why are some homes impacted by flooding more than others?

  • Some properties are at a higher risk of flooding due to their location and elevation in former stream valleys. 
  • During Arlington’s early development, the stormwater management regulations and standards for storm systems were less rigorous than today. 
  • Streams were buried in storm sewers and homes and businesses were built over the streams and within the former floodplains in some parts of Arlington.  
  • Easements were often not established for the storm sewers, making it difficult to access the infrastructure to maintain or upgrade the system.  
  • Given the low topography in these former stream valleys, these areas remain at higher risk of flooding despite the presence of the underground storm sewer. 

How do I know if I’m in a flood zone?

  • All properties have some level of vulnerability and as a property owner, you should be aware of your flood risk. Knowing your flood risk is the first step to flood prevention. To learn more, visit Risk Factor (previously known as Flood Factor) and search for your property at www.riskfactor.com.  
  • Formal delineated, mapped floodplains are established by a formal process with FEMA; Arlington has such zones along Four Mile Run, but currently not within developed neighborhoods in some of the inland watersheds.


What areas in the County are being prioritized?

Five critical watersheds are being prioritized for improvements because of repetitive flooding in those areas. 

  • The watersheds are Spout Run, Lubber Run, Crossman Run, Torreyson Run and Westover Branch. 
  • The Spout Run watershed has the engineering study process and potential solutions at a more complete stage currently, so it is anticipated this watershed may be the first one for stormwater investments to be made as part of the CIP.


What can I do to help reduce my risk of flooding?


The County encourages homeowners to evaluate flooding risks on their property and take action where possible. Arlington offers a home floodproofing checklist. Frequently vulnerable areas: below-grade basement steps, window wells and driveways that slope down toward a house. 

Residents should ask their insurance agent about flood insurance and about a sewer backup endorsement to any homeowner’s or renter’s policy. Most commercially available policies do not cover damage within basements and sub-grade structures. Homeowners who have experienced sewer backup should have a plumber determine if they need a backwater valve on their sanitary sewer and/or a sump pump.  

View more tips to reduce flood risk.  

Assist with Projects 

  • Provide easements if requested for projects. 
  • Have patience with construction.

Stay Safe 

Do not allow sleeping in a basement that is prone to flooding particularly during months susceptible to intense thunderstorms; floodwaters can be powerful and sudden during intense storms and create drowning, debris and electrical risks in homes. 

Stay Informed 

  • Sign up for Arlington Alert.  
  • Ask insurance agent about flood insurance and about a sewer backup endorsement to your homeowner’s or renter’s policy. 

Visit our website on flooding to learn more.

How will the properties be handled once they are purchased?

The home and associated structures will be removed from the site.  Each site will be evaluated, but it is likely that some land grading will be done on the sites. Driveways will be removed unless access to infrastructure is needed, but then only a limited access area would be necessary.  Most driveways would be removed.

What will the empty lots look like, and will there be designs to ensure they are neighborhood amenities?

Some land grading will likely occur on each lot after the home is removed and the property will be re-planted to minimize erosion.  When the County determines the response of the landowners and the rate of acquisitions, staff will begin developing more detailed land use plans for the properties. The properties would not be used for any residential activity, but would instead be preserved as open space. 

Will any of those acquired lots have mini underground vaults?

Distributed detention, or using several smaller detention vaults that may be connected in a series, was not found to be an effective strategy for extreme flood events in the Spout Run watershed.  However, there may be a few specific locations where limited detention would improve the function of the storm system near or adjacent to specific infrastructure, or to control floodwaters in a specific location.  The County may use some distributed detention vaults, but the first priority is to create overland relief, and access to the existing storm system.

Under the 'Prevent and Rebuild' strategy, is there more detailed information on the updated design standards and revised development standards? If not, what is the timeline?

The "Prevent and Rebuild" strategy was discussed in this presentation.  Stormwater management requirements for development projects were recently updated and made more stringent.  The goal to incentivize construction (retrofitting/remodeling/new construction) that is not subject to losses due to flooding.  The goal is to minimize safety issues and minimize property losses resulting from flooding.

Strategies under consideration are:

  1. Setbacks from existing infrastructure and easements
  2. Wider easements on proposed and existing infrastructure
  3. Elevation of buildings above anticipated water levels
  4. Restrictions on building anything (sheds) and especially habitable buildings within the inundation zones (impacts MM)
  5. Updated rainfall design curves – at minimum account for the past 20 years and possibly more forward looking per the RAMP
  6. Restrictions on basements and openings
  7. Incentivizing floodproof design such as use of floodproof materials (flooring and drywall and use of flood barriers)
  8. Elevation of building mechanical and electrical systems and major appliances
  9. Requirements for vents in fencing
  10. Restrictions on landscaping which prevents or retards the flow of floodwaters or causes debris flows
  11. Consideration of projected water surface elevations for all new infrastructure (inlets, etc.)
  12. Restrictions on garages with entrances lower than the street
  13. Potential street parking restrictions (limit parking in streets within inundation zones to minimize flood losses to cars and vehicles)

What are the potential implications for stormwater management in Plan Langston Boulevard?

The Plan Langston Boulevard Preliminary Concept Plan incentives stormwater detention beyond what would be required with a by-right development project.

It was noted there are 500 improvements in place already in the Spout Run watershed via new construction to manage onsite water (rainwater trenches, green roofs, etc.). Are any of those are in Waverly Hills and where?

The stormwater facilities in Waverly Hills are highlighted in the circled area on the map below.



With regard to the negotiation on the value of property, DES staff noted that it will be based on market appraisals. Will the appraisal only cover the value of the land or both the (already flooded) house and land?

When the County has appraisals done, it includes both the value of the land and the house.  The current condition of the house is considered in the appraisal.











(Information as of July 2022)