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Flood Barriers

Learn how flood barriers can help protect your property from flooding.

If your property is prone to flooding, you may want to consider purchasing a temporary flood barrier that can be installed prior to a storm and removed once floodwaters recede. Most flood barriers, except sandbags, can be stored and reused. When choosing a flood barrier, consider the size of the opening or area that needs protection, the worst-case scenario floodwater height and pressure, your ability to deploy the barrier, storage space, and budget. Property owners should consider how water will be redirected by the barrier to prevent nearby properties from being adversely affected. Refer to the Boston Public Works’ Deployable Flood Barrier Guidance for additional information.

Lower-Cost Options

Several relatively small, low-cost barriers are available for protecting doors, basement windows, and other smaller openings. 

Sandbags

Sandbags are an inexpensive, but labor-intensive way to protect against slow-moving water up to 15” deep. They are not effective for storm surge with fast-moving water and they cannot be reused. To properly use sandbags, 

  • Fill the sandbag halfway and tie the bag at the top, giving the sand room to spread out when you lay it down.
  • Cover the lower part of the door or a basement window with a plastic sheet and adhere it with waterproof tape to prevent it from sliding down.
  • Stack the sandbags over the plastic sheet, stepping on the first layer to remove any gaps between the sandbags and the ground and the door. Stagger additional layers of sandbags like bricks, and stack them higher than the expected floodwater depth. For an average-sized door, approximately 10 sandbags are needed.

Sandbags Proper Use

Water-activated bags or tubes:

Water-activated bags or tubes expand on contact with water to create a stackable flood barrier and are a modern alternative to traditional sandbags. These types of barriers should be pre-activated with water, stacked, and positioned prior to a storm. Some products do not work in salt water.

Water-Activates Bags Flood Barrier

Water-filled tubes

Water-filled tubes are PVC tubes or bladders that can be filled with water to create a flexible flood barrier that can be adjusted to fit any shape. These types of barriers must be filled in place, as they are heavy once filled. Barriers are available in a variety of heights and lengths, and many products can be connected together to protect bigger areas.

Water Filled Tube Flood Barrier

Air-filled inflatable barriers for doors and windows

Air-filled, inflatable barriers for doors and windows are lightweight, reusable barriers that fit doorways and windows and inflate in minutes using a standard air pump.

Air-Filled Flood Barrier

Expandable gates

Expandable gates are metal or plastic barriers that can be assembled in minutes in windows or doors without adhesives or permanent fixtures. Most panels can be connected to cover wider openings.

Expandable Gate Flood Barrier

Higher-Cost Options

You may want to consider a larger flood barrier system if your property is located in a high-risk area prone to flooding deeper than one foot of water. Installation should be handled by a professional. Engage a building engineer to create plans for your proposed barrier. Permits are required if your barrier alters existing infrastructure or egress paths or is placed on the public right of way. Visit the city’s Deployables Day page for additional guidance. Owners and/or managers of large flood barriers are required to register their barriers with the City of Boston Office of Emergency Management (OEM). For more information, visit OEM’s Deployable Flood Barrier Procedures page or email oem@boston.gov.

If you have questions about permitting requirements for flood barriers, visit Inspectional Services Permitting in the Flood Hazard District page or email ISDFlood@boston.gov. Before installing the permanent fixtures for any of these flood barrier systems, please contact the Boston Conservation Commission at cc@boston.gov to learn about additional permitting steps you may need to complete. If the flood barrier will impact the right of way, please contact the Public Improvement Commission at pic@boston.gov.

Consult with licensed and qualified professionals and get at least three quotes to compare prices. All information, including cost estimates and useful life expectations, is provided for informational purposes only and may vary based on property conditions, labor rates, materials, and other factors.

Stop-log barriers

Stop-log barriers are a customizable, modular system of aluminum/steel plates that slide into posts to create a watertight seal. The plates are stackable to customize the height of the barrier. A series of posts can be installed to customize the width of the barrier and provide coverage for larger areas. These types of barriers require an even, flat surface. Post bases are permanently installed while the posts and plates can be assembled and disassembled before and after a flood event.

  • Cost: Available as smaller units of 3-4’ which are about $400 and 6-10’ for around $900. For larger, custom units, contact a manufacturer for pricing.
  • Useful life: 20 - 50 years with Advanced Fiber Reinforced Polymer (FRP) options up to 100 years.

Stop-Log Flood Barrier

Modular, interlocking panels

Modular, interlocking panels are typically plastic or metal panels that link together to create a flood protection wall. Some are filled with water while others are L-shaped and are held in place by the weight of the floodwater. Modular barriers are available in several heights and widths and are a good option for protecting larger areas because they can be linked together.

  • Cost: $50-$100 per square foot depending on material and height.
  • Useful life: 10 - 50 years, depending on the material, environmental exposure, and maintenance. Plastic panels have a shorter lifespan than metal.

Modular Interlocking Flood Barrier

Sliding or swinging doors

Sliding or swinging doors are permanently installed to cover an opening such as a storefront, door, or loading dock. These types of barriers are typically made of steel or aluminum and deploy quickly.

  • Cost: $1,500 - $15,000
  • Useful life: 25-50+ years with minimal maintenance

Sliding Door Flood Barrier

Passive barriers

Passive barriers are permanent structures that automatically activate based on flood levels. Some passive barriers are installed flat and flip upward with flood waters while others are installed vertically underground and float upward to seal an opening. These types of barriers have higher installation costs but require minimal maintenance, and eliminate labor and costs associated with deploying manual barriers.

  • Cost: $10,000 per square meter
  • Useful life: 50-100 years

Passive Flood Barrier

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