Eldorado Fire at Walker Ranch

On September 15, 2000, the Eldorado Fire was started by human causes. Because of high fuel loading, the fire grew to 1,062 acres and was almost exclusively on the Walker Ranch property. Most of the fire occurred within the Tom Davis Gulch watershed which is about 2,400 acres in size. The following represents a summary of acres burned, rehabilitation costs, fire rehabilitation,  wildfire impacts,  weed management, volunteer opportunities, and trail information. Additional information is available on fire maps compiled of the area.

Fire Summary

Of the 1,062 acres that were burned in the Eldorado Fire, 450 acres were moderately or severely burned. 

275 acres were severely burned. 

• 50% to 100% of the canopy was burned

• Needles are gone

• Ground cover was partially consumed

• Weak areas of hydrophobic or water resistant soils may be present

175 acres were moderately burned.

• Up to 50% of the canopy was burned

• Needles are gone from many trees, but not all

• Ground cover was partially consumed

• There may be weak areas of hydrophobic soils may be present.

Rehabilitation Costs

South Boulder Creek is one of the main drinking water delivery routes to Denver, Louisville, Lafayette, Superior and Eldorado Springs. Approximately 200,000 to 250,000 people could be negatively impacted by sediment deposited into South Boulder Creek. Because of this threat, the Natural Resources Conservation Service will be paying for 75% of the rehabilitation costs through the Emergency Watershed Protection Program. Boulder County Parks and Open Space and other local agencies will be responsible for the remaining 25%.

Boulder County Parks and Open Space is using a variety of fire rehabilitation techniques to restore the Walker Ranch burned area.

Expected Wildfire Impacts

Wildfires affect watersheds primarily by increasing soil erosion and surface runoff. Erosion increases because of the reduction of surface cover. Forest soils are protected by a combination of live overstory (trees) and understory vegetation (grasses and shrubs) and litter (leaves, pine needles, dead grasses). When a fire removes the vegetative cover, the soil surface is susceptible to both wind and water erosion.

Burning vegetation melts resins and waxes which then coat soil particles, causing them to become hydrophobic or water repellent. Hydrophobic soils have a decreased water infiltration rate and an increased water runoff rate, creating extreme soil erosion potentials.

Fire effects can be expected to persist for 2 to 10 years until vegetation reaches pre-burn extent and density.

The greatest off-site concern is increased sediment load and dissolved material which could be delivered to South Boulder Creek during thunderstorms. This can cause water treatment problems for municipal water providers who divert water below the burned area. If sediment loads are extremely heavy, sediment can clog diversions and cause problems for both municipal and irrigation users. High sediment loads also impact fish habitat.

The highest suspended loads will likely occur during the first significant runoff after the fire, when a large portion of the easily transportable ash, char and fine sediment will be moved.

Weed Management

Diffuse knapweed invades open canopy sites where soils are exposed to sunlight. The severely burned areas were closed canopy sites where diffuse knapweed had not been able to invade prior to the burn. As a result of the fire, several hundred acres of previously uninfested, closed canopy forests are now prime areas for invasion by diffuse knapweed and other non-native species. 

Research has demonstrated how fire in diffuse knapweed occupied sites actually increases knapweed seedling germination. Three weeks after the fire, diffuse knapweed seedlings had already emerged in the moderately burned areas. Additional observations noted that first year rosettes that were present prior to the fire had survived.

To effectively minimize the spread of diffuse knapweed to the severely burned areas, intensive treatments involving localized herbicide on first-year rosettes and hand pulling the unburned, seed-bearing plants from the previous growing season will be required. This work will be extremely labor intensive and will require twice the resources that would normally be dedicated to the management of Walker Ranch had the fire not occurred.

Volunteer Opportunities

Volunteers are needed to assist with weed pulls at Walker Ranch. If you are interested, please contact the weeds manager at 303-678-6110.

Trail Information

Visitor use is restricted to the trail at all times because of hazards that persist off trail. Trees killed in the fire will rot and eventually fall. Many potentially hazardous trees have been felled along the sides of the trail system. Logs and slash remain in some areas until crews can properly dispose of them.

 

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