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Sustainable Flood Wall Guards Resident Property Against Post-Wildfire Flash Floods

State of Colorado

Colorado

Wildfires that tore through Colorado in 2020 put homes at risk for devastating flash floods and led the state to assess how best to protect resident property. The state deployed several flood barriers, including 2500 feet of a sustainable flood wall to protect homes and structures throughout the affected areas.

Topics Covered

Wildfire

Cost

Not available

Funding

Federal grants

Project Status

Operational since 2021

Problem Addressed

Deadly flash floods and debris flows stemming from large wildfires put Colorado homes and residents at risk.  

In the summer of 2020, Colorado experienced a number of devastating wildfires brought on by high winds and dry weather. In addition to the Pine Gulch Fire and East Troublesome fires, The Cameron Peak Fire became the largest wildfire ever experienced in the state of Colorado and burned over 208,000 acres of land, including 224 homes.

All three fires primarily burned rural, mountainous land, leaving watershed areas, homes, structures, and lives at risk of flash floods and debris flows (mud and rock slides) due to severe loss of vegetation and soil erosion. In 2021, land burned by the Cameron Peak Fire caused heavy flooding, which resulted in four Coloradans losing their lives before any mitigation solutions could be deployed. It became very clear that Colorado’s National Resources Conservation Service (NRCS) needed a plan under the Emergency Watershed Protection Program (EWP) to protect houses and residents at risk, but it was unclear what solution would be most appropriate.

Post-wildfire flood mitigation projects typically erect flood barriers to direct water away from homes or buildings. Some of the most commonly used flood barriers are earthen berms, concrete blocks, and super sack sandbags, but each has shortcomings. Building earthen berms require bringing in heavy machinery that can be a major disturbance and isn’t always feasible in certain areas. Beyond that, berms have a wide footprint that makes building them between homes difficult, and they’re costly on the backend for homeowners. While structures built of earth-filled containers and sandbags are also often used, they can have a wide footprint and deteriorate after providing only a few years of protection.

Residents wanted to see flood barriers that were sustainable and more innovative than the typical solutions being offered. The state brought in several engineering firms, including SGM, HDR Engineering, and Ayers Engineering as consultants to explore new flood barriers that would satisfy residents while still acting as effective flood protection. The requirements for the ideal flood barrier were that it be reusable, semi-permanent with a small footprint, low-impact so that its installation wouldn’t be disruptive to the property owner, and most importantly, effective in protecting homes from damaging flash floods and debris flows.

Solutions Used

Colorado deployed a semi-permanent flood wall in areas where it was the most sustainable option for preventing damage from flooding. 

Engineers from the consultant firms, including Scot Knutson from SGM, were tasked with finding barriers that met the flood protection needs of residents in post-fire areas throughout the state. 

Based on the topography of the affected areas, and after consulting with local landowners, the choice was made in many instances to raise the floodplain using Muscle Wall because it is reusable and could be installed with very little impact on the environment. In instances where Muscle Wall was used, workers could carry the sustainable low-density polyethylene components onto properties where cars or heavy machinery could not reach.  Property owners could maintain the natural beauty of their land while still building protection against flash floods and debris flows. Installation through contractors was quick, with one hundred feet able to be deployed in a half-day and 576 linear feet able to be transported in one truckload. Conversely, the same length of a barrier made of sandbags would take over one day to install and likely require multiple truckloads.

Installation of the Muscle Wall was quick, and the resulting barriers were filled with water to make them more resilient against the forces generated by debris flows. Because the flood barrier is semi-permanent and made out of durable polyethylene, residents can reuse it for years and can easily remove it when no longer needed.

Not long after installing Muscle Wall on a property in the area ravaged by the Pine Gulch Fire, an August 2021 rain event caused a creek to grow from what was usually a few feet wide and a couple of inches deep to 40 feet wide and 10 feet deep at the deepest point. The fast-moving, highly destructive flow also carried tree trunks and other debris from the fire that could have damaged the home on the property if a barrier hadn’t already been in place.

Outcomes

1

The Colorado NRCS deployed 2500 feet of the new low-impact flood barrier onto many rural properties to protect homes and structures from post-fire debris flows

2

The new barrier was able to provide instant protection against post-fire floods without significant disruption to residents or damage to the environment

3

Residents in affected areas can reuse the flood barrier for years and can easily remove it when no longer needed

4

Landowners were involved in the selection process and selected the flood mitigation option that least disrupted the views and use of their properties

5

The state of Colorado now has another sustainable flood barrier to deploy to other post-fire sites across the state

Who Should Consider

States looking to improve how they address and protect residents from post-fire impacts.

Government Project Team

  • Chris Bornholdt, Emergency Operations Commander Garfield County Sheriff’s Office
  • Benjamin Mispagel, Area Engineer, National Resources Conservation Service
  • John Andrews, State Conservation Engineer

Last Updated

Jul 26th, 2022

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