Passive Barriers
Inside the Floodplain

What Is It?

Cost: Dependent on project. See supplier examples below for estimated project costs.
Applications: Protection of low-lying buildings, infrastructure along waterways and coastlines, coastal promenades, and riverfronts or canals.
Service Life: Barriers can last about 50 years. Seals and gaskets may require replacement every 5-10 years, depending on model.

Passive barriers will operate automatically in a flood or storm event, requiring no human intervention or electricity. In its guidance for floodproofing non-residential buildings, FEMA recommends passive intervention whenever possible. A passive barrier can be permanently fixed, such as a floodwall or levee, or a barrier that activates during a flood. Barriers that self-activate are generally used in tandem with permanent floodwalls or other barriers, and deploy to protect entryways or other openings behind the barrier. Typically, self-activating barriers use water pressure or action to deploy. Many retractable barriers, particularly folding or drop-down barriers, can be outfitted with water level sensors for passive use.


  • Passive barriers minimize human intervention in many areas, including deployment, demounting, and storage.
  • Many do not use electricity to activate, allowing for constant flood protection.
  • Passive barriers do not need to be deployed ahead of a flood event. This provides protection against flash floods while allowing site access and egress until flood waters reach the building site.
  • Passive barriers can be permanently installed onsite and are typically customized for the site’s needs.
  • Recessed permanent barriers can be modified to minimize disruption to building aesthetics.
  • Passive barriers have low long-term maintenance costs.


  • Upfront costs, especially for barriers requiring on-site construction, will be significantly higher than temporary barriers and flood shields.
  • Local jurisdictions will likely require a building permit for the construction and placement of the barrier, which will include project review, approval, and inspection by applicable departments.
  • Passive barriers usually need to be combined with other site protection (e.g. flood walls) to maximize effectiveness for larger sites.
  • Onsite construction and excavation are usually needed to install permanent barriers.
  • Passive flood barriers will still fail if floodwaters rise higher than the barrier.
  • Products currently available are designed to protect against flooding, and not for regular fluctuations in coastal water levels caused by tidal and wave action.

Regulatory Impacts and Requirements

A summary of regulatory touchpoints follows below:
Regulatory Impacts

Financing Options, Incentives, And Rebates

Installing passive flood barriers may allow building owners to negotiate for lower flood insurance rates. Additionally, federal funding is available from several sources outlined below.

  • FEMA provides funding for flood and disaster mitigation through three grant programs under the umbrella of Hazard Mitigation Assistance:
    • Pre-Disaster Mitigation: Individual homeowners, businesses, and private nonprofits can apply through their local government to fund projects that will reduce risks to people and structures from future hazards.
    • Flood Mitigation Assistance: Individual homeowners, businesses, and private nonprofits can apply through their local government to fund projects that reduce or eliminate the long-term risk of flood damage to structures insured under the National Flood Insurance Program.
    • Hazard Mitigation Grant Program: After a federally declared disaster, grant money is available to help communities implement hazard mitigation measures. Individual applicants apply through their local government for funding
  • Hazard Mitigation Funding under Section 406 of the Stafford Act: Local, state, tribal, and some non-profit facilities damaged by disasters may use Section 406 funding to restore damaged facilities, as well as undertake preventative measures for future flood mitigation.

Additional Resources


  • Lourdes Hospital, NY: 11 FloodBreak passive floodgates combined with 11-foot floodwall at a cost of approx. $7 million
  • Kensington Gate, NY: Floodbreak passive vehicle gate that has experienced 8 saves since installation in 2008.
  • West Wickham: UK Flood Barriers implemented to alleviate flood in a Thames Water pumping station.
  • Cockermouth, Cumbria: 19 barriers installed to protect 360 homes and 55 businesses.