2023 Post-Fire Restoration Plans for the Cameron Peak Burn Area

The Cameron Peak Fire burn area (Photo credit: Cory Dick)

Large-scale wildfires can profoundly impact watershed processes and function, and impacts can be observed for many years post-fire, often for a decade or more. Impacts generally include more rapid runoff and larger runoff volumes. This increase in runoff volume and velocity substantially increase sediment yield that can lead to water quality degradation (USDA, 2016). Because these effects are more pronounced in the first few years of watershed recovery, post-fire mitigation and restoration efforts are essential to protect water quality and river health.

Post-fire impacts in the watershed generally include:

• Hillslope Erosion - The removal of protective vegetation due to forest fires results in the destabilization of soils and soil structures (USDA, 2016). Destabilized soils are more vulnerable to increase runoff volumes caused by reduced evapotranspiration, raindrop interception, and infiltration. This increased vulnerability and runoff volume combine to create massive riling on burnt hillslopes which mobilizes sand, silt, and ash into adjacent river systems to be transported downstream.

• Debris Flows – hillslope erosion can also trigger debris flows. Hillslope erosion of disturbed creates a positive feedback loop that can build immensely powerful and destructive debris flows. During a rainfall event, overland sheet flow and sediment increases the density of the runoff, which consolidates into river channels, creating in-channel erosion and debris flows.

• Stream Degradation – Increases in flows can cause headcuts in river channels to form, which can cause pulses of sediment that are transported downstream and can impact riparian habitat and infrastructure. Increased flows can also cause downcutting of the river channels which can degrade and destroy valuable riparian and wetland habitat.

• Roads – Increased peak flows can overwhelm road drainage infrastructure. The roads can channelize increased peak flows and may become new stream channels, and can contribute to excess sedimentation issues.

• Water Infrastructure - Increased sediment inputs can result in additional intake shutoffs, increased treatment costs, and degraded water quality for communities across northern Colorado, as seen during 2021. During 2021, all water providers were unable to treat water from post-fire watersheds for prolonged periods due to degraded water quality.

Large headcut, Sheep Creek (Ayers)

Black Hollow Debris Flow, July 2021 (Ayers)

What can be done to help mitigate some of these impacts and restore priority areas?

Recognizing the significant impact that the Cameron Peak Fire has on the Poudre Watershed, the Coalition for the Poudre River Watershed (CPRW) has worked closely with partners to identify and treat priority areas (see map below) for mitigation and restoration.

CPRW is working with partners, including City of Greeley, City of Fort Collins, US Forest Service, Colorado Water Conservation Board (CWCB), Colorado Department of Health and Environment (CDPHE), and state, local and private entities to develop a strategy of layered post-fire mitigation and restoration treatments within priority areas. This strategy includes an aerial mulch program conducted in 2021 and 2022, additional mitigation and restoration on key perennial and ephemeral stream locations, and reforestation of critical areas unlikely to regenerate on their own.

Some of the techniques we use for stream and gully mitigation and restoration include:

• Log Structures – Using burnt, large material found onsite, crews place and interlock large logs in the channel to increase roughness, reduce flow velocities, and enhance sediment deposition. These features reduce flow velocities by acting as speed bumps for downstream areas. Log structures return flow to the overbank and floodplain areas, reducing stream incision and rehabilitating the floodplain.

• Post-assisted log structures - On-site woody material of various sizes is pinned together with posts driven into the streambed to initiate and simulate natural wood accumulation that is typically seen in similar river systems. The installations provide opportunity for sediment storage behind the structures while promoting floodplain connectivity, additional wood recruitment, and riparian health.

• Rock Stabilization – Rock is typically harvested on-site and placed to stabilize headcuts and help slow channel incision. This improves water quality by stabilizing actively eroding channels and limiting upstream incision.

• Riparian Revegetation and Stabilization - Recovery of riparian areas is critical to improving water quality. Establishing woody riparian vegetation such as cottonwoods, willows, and other native plants increases the capacity for sediment storage and nutrient uptake, provides additional stability, and enhances habitat in riparian and aquatic ecosystems. Native willow and cottonwood stakes are harvested from nearby areas and installed in sites (either staked or bundled as wattles) with shallow water tables that would support successful establishment.

• Road and Crossing Improvements - Hardened river crossings on roads provide resistance to erosion during flood events while providing stabilization for the stream system. Crossings typically omit use of culverts which adds resiliency to the system and opportunities for upstream sediment storage. Treatments typically allow for flows to overtop the crossing without causing total failure to the embankment. The in-channel portion of the treatment includes native alluvial surface layer to maintain consistent channel roughness and limit habitat disruption.  Willow stakes are installed in the rundown on the downstream side for additional bank stability. These types of crossings can improve access and reduce long-term maintenance.

Log structure installed at Sheep Creek (Ayers Associates)

Rock stabilization at Sheep Creek (Ayers Associates)

Post-Assisted Log Structure installed at Elkhorn Creek (Ayers Associates)

Road and crossing improvement at Sheep Creek (Ayers Associates)

These projects are generally constructed with local contractors, youth corps, or volunteers using hand tools. Some of the larger installations, particularly for road and crossing improvements, require heavy machinery with contractors. CPRW and partners have raised funds to support these projects from a variety of partners, including CWCB, CDPHE, USFS, and local contributions.

2023 Project Locations

Over the past two years, CPRW and partners have led projects on over 9,000 acres of priority land in the Cameron Peak burn area, including federal, state, local and private lands. Projects will continue in 2023 and 2024, and CPRW will continue to monitor a portion of completed projects through 2025 to better understand the effectiveness of various treatments. Our 2023 projects will focus on priority locations on federal lands. These projects are currently under review for required permits and clearances and have not yet been finalized. Once permitting is complete, 2023 projects are expected to begin in summer 2023 and continue through the fall. As those projects progress we will post updates to our blog, social media and email newsletter. Stay tuned for more info!

If you have a fire-impacted location of concern, please reach out to CPRW to discuss further, and see if viable treatments are an option for mitigation and restoration.

Sources Cited:

United States Department of Agriculture. 2016. Hydrologic Analyses of Post-Wildfire Conditions. Hydrology Technical Note No. 4.