The Community Base Map identifies political boundaries and features within Douglas County that are pertinent to the county’s wildfire situation. These include fire protection districts, incorporated and unincorporated areas, public land ownership, fire station locations, and transportation.
The Community Hazard Ranking Map is a visual description of population areas within Douglas County and their associated wildfire hazard potential. Rankings were based on the hazard map in addition to local knowledge from core team members. Rankings identify the “potential” hazard a community may have based on resistance to control, values at risk, and ignition risk.
The rankings do not take into account specific factors including defensible space, access, and construction materials which could affect the hazard rank at a finer scale. The broad-based communities identified in the Community Hazard Ranking Map may include multiple local communities such as home owner’s associations and/or platted subdivisions. The Hazard Ranking Map is intended to raise awareness of the landscape-scale wildfire hazard potential within and around local communities and assist them in developing finer-scale community wildfire protection plans.
Douglas County-owned parcels were assessed to identify hazards, adjacent values, and potential ignition risk. Individual parcels that were assigned treatment recommendations are identified in this map. The following defines the recommendation categories used:
Recommended for treatment: Vegetation treatment on the parcel would be beneficial in reducing wildfire hazards or serve as an educational demonstration site for public viewing of wildfire mitigation treatments.
Conditionally recommended for treatment: Parcel size or quantity of hazardous fuels on parcel is minor enough where treatment on parcel alone would not provide benefit for reducing wildfire hazard. The benefit of treatment requires participation of neighboring ownership(s).
Management Plan: Parcel is part of a larger property managed for multiple resource values and objectives. Refer to the property management plan for wildfire mitigation hazard reduction recommendations on these parcels. If no management plan exists for the property, one should be put in place that addresses wildfire hazard reduction.
Structure: A structure exists on the parcel. Ensure the structure has adequate defensible space.
Every wildfire requires an ignition source that can be naturally occurring or human-caused. Although a potential ignition source can reside anywhere, areas where ignition sources regularly exist or are more common have a higher potential for wildfire occurrence. The Douglas County CWPP Core Team has determined that high lightning density regions and areas adjacent to railroads, campgrounds, major roads, and hiking trails have the highest potential ignition risk. Some ignition sources tend to spark more fires than others. Because of this, a relative weighting was given to each major potential ignition source. High lightning density regions and areas adjacent to railroads and campgrounds were given the highest weight, areas adjacent to major roads were given the second highest weight, and areas adjacent to hiking trails were given the third-highest weight. Areas where no apparent major ignition source existed were given the lowest weight.
The Douglas County CWPP Core Team has identified strategic areas within Douglas County where landscape-scale fuel treatments could be beneficial in suppressing or preventing large fires as well as augmenting already completed fuel treatments. Communities are encouraged to identify smaller-scale fuel treatments within and surrounding their area of interest during localized CWPP planning efforts.
The difficulty of controlling a wildfire depends on fire behavior, tactical flexibility during suppression operations, and approximate response time of the nearest suppression resources. The Resistance to Control Map combines all of these elements to predict the relative difference of difficulty in controlling a wildfire during high fire danger weather conditions. Flame length was used as the fire behavior metric as it indicates suppression difficulty and is affected both by heat per unit area and rate of spread (for more see the Flame Length Map). Response time was determined by using the ArcGIS Network Analyst. Inputs for determining response time included travel distance from the nearest fire station, travel speed, and slope.
The steepness of the ground highly influences how fast wildfire spreads and how intensely it burns. With all other conditions being equal, the steeper the slope the faster and hotter a fire burns. Slope is also an important factor in determining the feasibility of hazardous fuel reduction treatments. Slopes over 40% are typically untreatable due to the operational limitations of machinery.
A key purpose of community wildfire protection plans is to identify and work toward protecting values at risk to wildfire. The Douglas County CWPP core team identified several values potentially at risk of wildfire within the county. These include populated areas within the wildland-urban interface/intermix, critical infrastructure, municipal watersheds, and protected publicly-held lands.
The Hazard Map is a composite overlay of the Resistance to Control, Values, and Ignition Risk Map. The map is influenced most highly by the Resistance to Control outputs, while Values were given the next highest weight and Ignition Risk was given the least amount of weight. Areas where these three inputs are the highest and overlap are considered the highest hazard areas. The input data for the hazard map should be used at a landscape scale to determine hazardous areas at a strategic planning level. Due to the coarseness of the input data is inappropriate to use the Hazard Map at a parcel level. For parcel-level data, onsite assessments should be conducted.
Hard copies of draft wildfire hazard assessment maps are available at the 6 Douglas County Libraries including Castle Pines, Highlands Ranch, Lone Tree, Parker, Phillip S. Miller (Castle Rock), and Roxborough.