Louisville Wildfire Risk Assessment

In response to the 2021 Marshall Fire that severely affected homes and livelihoods of residents in Louisville, the City hired  Lynker Corporation  and  The Ember Alliance  to develop a wildfire hazard and risk assessment for public lands in and around the city. The purpose of this project is to develop a comprehensive, science-based wildfire hazard and risk assessment and to provide mitigation recommendations for the City of Louisville’s public lands to be more resilient against future events. 

This Story Map shares a high-level overview of the results of the wildfire risk and mitigation assessment, including the following content:

• Risk assessment overview
• Wildfire risk results
• Mitigation assessment recommendations
• Wildfire resiliency and adaptation resources

More information about the wildfire behavior model, data inputs, assessment details, and site-specific mitigation recommendations can be found in the comprehensive report, link coming soon.

A risk assessment identifies a community’s resources such as lands, buildings, and other landscape elements to quantify their susceptibility to hazards, like wildfire. Wildfire risk is an estimation of the impact or damage from a fire, calculated as the product of wildfire hazard and vulnerability. 

Risk = Hazard x Vulnerability

Hazard is quantified using a  wildfire behavior model  that estimates annual burn probability and fire intensity (flame length). Vulnerability is quantified by estimating the susceptibility of public lands and other important community assets to fire.

This wildfire risk assessment surveys the wildfire hazard that exists within the City of Louisville, the public lands and structures vulnerable to wildfire, and the relative risk throughout the City.

Louisville owns an interest in approximately 2,600 acres of open space and parks, and facility grounds. This land provides recreational opportunities along neighborhood corridors, supports a variety of plant and animal species, houses critical infrastructure and community amenities, and creates visual and physical buffers between adjacent communities. 

The interactive map below displays the Louisville public lands explored in this risk assessment. Other properties jointly owned by the City are not included in this map.

1. Expand [top right]: Expand the map to fit the page.
2. Move [mouse]: Click and drag the map to move around the study area.
3. Magnification [lower right]: Zoom in/out of the area of interest.
4. Home button [lower right]: Return back to the original map location.
5. Legend button [lower left]: Open the legend to learn about the different layers on the map.

The wildfire risk assessment indicates that the regions of the City of Louisville with the highest wildfire risk are located along the western and northern municipal boundary, from the Howard Berry Water Treatment Plant (WTP) on Marshall Road to the North WTP and North Open Space, including Davidson Mesa and adjacent public and private land. Additional lower wildfire risk exists in the southeast portion of the City, including Coal Creek Regional Trail and private property. These areas are highlighted in yellow in the interactive map below.

Within the City of Louisville, the areas with the highest relative risk were identified to help prioritize resources for mitigation treatments. A list of the 10 areas with the highest wildfire risk are shown to the right.

Explore the City's wildfire risk using the interactive maps below.

There are benefits and tradeoffs to different actions to mitigate wildfire risk, and there are no management strategies that can optimize all values for public land and minimize wildfire risk at the same time. Reducing wildfire risk and restoring native grasslands often requires a variety of approaches including prescribed fire, grazing, and herbicide. Social values, ecological impacts, feasibility, cost, and likelihood of success must be considered when deciding where to conduct different management options. 

When approaching wildfire risk mitigation, fire and fuel managers, natural resource managers, and the public need to answer the following questions—questions that are as much of a social nature as a scientific one:

• What intensity of fire weather conditions are fuel treatments designed to be effective against?
• How much uncertainty is acceptable in terms of predicted effectiveness?
• What tradeoffs are acceptable? For example, wider fuel treatments with less remaining vegetation might be more effective at slowing the spread or reducing the intensity of wildfire, but they might degrade wildlife habitat, reduce privacy for adjacent property owners, and be more costly than narrower, less aggressive treatments.
• What marginal returns are acceptable? For example, is a treatment requiring two times the amount of work to increase potential success by 50% satisfactory? By 10%?

Becoming a  fire adapted community  requires a recognition that wildfires will occur and that collective and strategic action before, during, and after a wildfire can decrease the likelihood of devastating consequences. Often wildfire mitigation is viewed through the lens of fuel treatments, where fuel reduction (mowing of grasses, tree limbing, etc.) can reduce the fire hazard, but these same fuel treatments can alter other values that are a part of the community such as open space lands, trails, and natural habitat. Therefore, wildfire mitigation is a balance between hazard reduction and community values, where fuels treatments are just one part of a comprehensive adaptation strategy to wildfire.

A holistic approach also requires defensible space on private properties and around community infrastructure, reducing the ignitability of structures, public education, planning and zoning regulations, and enhanced emergency preparedness.

Below are examples of the wildfire mitigation options that can be implemented on different types of public land within the City of Louisville. For more detailed definitions, additional mitigation approaches, and the full list of sources, please refer to the full report.

The following table outlines which mitigation strategies are appropriate on different types of public land—open space, unirrigated parks, irrigated parks, and public works facilities. These recommendations are generalizations—within property types and in different parts of the same property, mitigation approaches can differ in their feasibility, desirability, and potential benefits.

✓✓ = highly recommended approach with greater risk-mitigation benefits. ✓ = recommended approach with moderate risk-mitigation benefits. ✘ = approach not recommended. (✘) = approach not recommended except under specific circumstances. N/A = approach not applicable.

Wildfires are a natural part of Colorado’s varied ecosystems, and there is inherent risk from wildfires where natural vegetation and the built environment meet. Given the right weather conditions and ignition source, any vegetation can burn—fires under extreme weather conditions, like the Marshall Fire, can occur regardless of mitigation measures put in place.

There are many great resources for Coloradans looking to adapt to changing wildfire conditions and improve their resilience. While wildfires are a natural phenomenon, especially in Colorado’s ecosystems, the intensity, timing, and impact of these wildfires are evolving with climate change and landscape modifications. According to the CSFS WUI Risk Assessment ⁶  , “more than half of Colorado residents live in the wildland-urban interface and are at some risk of being affected by wildfire.” Because of this, communities must be ‘wildfire prepared’ year-round. In light of the increasing threat of wildfire in Colorado, Colorado State University (CSU Extension) and the Colorado State Forest Service have developed resources for community members concerned about their wildfire risk. This section introduces the concepts of defensible space for homes and structures, firewise and low flammability landscaping, and strategies for community adaptation to wildfire.

• Live Wildfire Ready
  • The new  CSFS Live Wildfire Ready website  serves as a one-stop-shop to prepare your home for wildfire. Among its resources, the webpage provides a ‘ checklist of practical and low-cost actions ’ that residents can do to decrease the impacts of wildfire on their home.
• Home Ignition Zone Guide
  • This  comprehensive guide  to ‘home hardening’ provides a structural ignitability best practice checklist (page 7) and a thorough home maintenance checklist (page 10). The guide also provides information on wildfire behavior and surface fuels. Additional maintenance tips are provided based on surrounding forest types.
• Wildfire Mitigation
  • The  Wildfire Mitigation webpage  provides links to great resources including private property protection, CWPPs, Fire Adapted Communities, and the FireWise USA program.
• Fire Adapted Communities
  • The  Fire Adapted Communities Learning Network  provides resources that promote community resilience and adaptation to wildfire.
• Defensible Space (Colorado Springs Fire Department)
  • The website provides a shortened summary (9 items) to ‘help protect your family and home’. It includes the  Colorado Springs Fire Department Wildfire Mitigation guide  that provides tips for reducing risk in and around a home.

• Low Flammability Landscape Plants
  • The  Low-Flammability Landscape Plants fact sheet  (2023) introduces the WUI, defensible space and the flammability of plants. It provides an in depth summary into managing defensible space with low flammability plants particularly useful in home defense zones 1 and 2. The table in the document (page 4) provides information about the water needs, sun/shade preference, mature height, elevation, bloom month, and low flammability rating for each recommended plant and grass.
• FireWise Plant Material
  • The  FireWise Plant Materials fact sheet  (2012) provides a list of flowers, ground cover, shrubs, and trees that meet FireWise specifications (page 3). It includes information on each vegetation’s water needs, sun/shade preference, mature height, elevation, and bloom month, as well as general guidelines and tips on landscaping.
• Fire Resistant Landscaping
  • The  fire resistant landscaping webpage  and  fact sheet  (2012) explores how to develop and maintain a home’s defensible space. The document further expands on the types of grasses, ground cover plants, wildflowers, shrubs, and trees that can be used when landscaping for defensible space.
  •  This webpage  recommends vegetation types based on the ignition zones around a home or structure. For example, the non-combustible zone (0-5 feet within a home) should be modified to remove all flammable materials (e.g., mulch, shrubs, pine needles).

• Firewise Landscape Design Webinar
  • A  webinar  about how to learn from previous impacts from wildfire to harden a home against future wildfires. The webinar is led by a senior landscape designer (start time = 1:09:16) and goes through the design process with the lens of maintaining a defensible space and Firewise landscaping principles. This is part of the larger Post-Fire Recovery of the Home Landscape webinar hosted by CSU Extension.
• Wildfire Recovery
  • This is the  Wildfire Recovery home page  for the ‘most up-to-date information, resources and contact information related to wildfire recovery and resilience planning from the Colorado Resiliency Office. The webpage categorizes resources for use by local government, businesses, or individuals. The website also hosts additional wildfire resources and documents, a few of which have been summarized below: 1.  Colorado Disaster Recovery (lessons learned)  2.  Colorado Post-Fire Recovery Playbook  3.  Local Government Guide to Recovery  4.  Colorado Post-Wildfire Guide 

References

1. Agee, J. K., Bahro, B., Finney, M. A., Omi, P. N., Sapsis, D. B., Skinner, C. N., Wagtendonk, J. W., & Weathersponn, C. P. (2000). The use of shaded fuelbreaks in landscape fire management. Forest Ecology and Management, 127, 55–66. 
2. Babrauskas, V. (2018). Firebrands and embers. In S. Manzello (Ed.), Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires. Springer.  https://doi.org/10.1007/978-3-319-51727-8_3-1 
3. Decker, K., Rondeau, R., Culver, L. D., Malone, D., Gilligan, L., & Marshall, S. (2020). Guide to ecological systems of Colorado. Colorado State University, Colorado Natural Heritage Program, Fort Collins, CO. https://cnhp.colostate.edu/download/documents/2020/EcologicalSystemsofColorado2020.pdf
4. Gropp, C. (2019). Embers cause up to 90% of home & business ignitions during wildfire events (News Release 12 March 2019). Insurance Institute for Business & Home Safety.  https://ibhs.org/ibhs-news-releases/embers-cause-up-to-90-of-home-business-ignitions-during-wildfire-events/ 
5. Holstrom, M., Orient, S., Gordon, J., Johnson, R., Rodeffer, S., Money, L., Rickert, I., Pietruszka, B., & Duarte, P. (2023). Marshall Fire Facilitated Learning Analysis. Colorado Division of Fire Prevention & Control.  https://storymaps.arcgis.com/stories/83af63bd549b4b8ea7d42661531de512 
6. IIBHS. (2019). California Wildfires of 2017 and 2018. Insurance Institute for Business & Home Safety.  https://ibhs.org/wildfire/ibhs-post-event-investigation-california-wildfires-of-2017-2018/ 
7. Maranghides, A., Link, E. D., Hawks, S., McDougald, J., Quarles, S. L., Gorham, D. J., & Nazare, S. (2022). WUI structure/parcel/community fire hazard mitigation methodology (NIST Technical Note 2205). Department of Commerce, National Institute of Standards and Technology.  https://nvlpubs.nist.gov/nistpubs/TechnicalNotes/NIST.TN.2205.pdf 
8. Miller, D. (2006). Using rangeland “greenstrips” to create natural fire breaks. Rangelands, 22–25. 
9. Palit, R., & DeKeyser, E. S. (2022). Impacts and drivers of smooth brome (Bromus inermis Leyss.) invasion in native ecosystems. Plants, 11, 1340. 
10. Reinhardt, E. D., Keane, R. E., Calkin, D. E., & Cohen, J. D. (2008). Objectives and considerations for wildland fuel treatments in forested ecosystems of the interior western United States. Forest Ecology and Management, 256, 1997–2006. 
11. Webb, A. D., Falk, D. A., & Finch, D. M. (2019). Fire ecology and management in lowland riparian ecosystems of the southwestern United States and northern Mexico (General Technical Report 401). U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.
12. Weise, C. L., Brussee, B. E., Coates, P. S., Shinneman, D. J., Crist, M. R., Aldridge, C. L., Heinrich, J. A., & Ricca, M. A. (2023). A retrospective assessment of fuel break effectiveness for containing rangeland wildfires in the sagebrush biome. Journal of Environmental Management, 341, 117903.