Alice Creek Post-Fire BAER Assessment Report Summary
Incident: Northern Region-2017 Post-Fire BAER Burned Area Emergency Response
ALICE CREEK POST-FIRE BAER ASSESSMENT REPORT SUMMARY
FS-2500-8 Burned-Area Report: Watershed Analysis, Condition, and Response
The Alice Creek Fire was discovered on July 22, 2017, in the Alice Creek Drainage on the Helena-Lewis and Clark National Forest (NF), approximately 15 miles northeast of the town of Lincoln. The fire start was likely a holdover lightning strike from a large thunderstorm event that passed across the forest on July 14. The fire burned a total of 33,537 acres, with 20,106 acres on National Forest System (NFS) land.
The Alice Creek Fire burned in dense conifer forest and grass, with a large amount of dead and downed beetle killed timber, making suppression efforts difficult. Within the fire area, tree species such as Douglas-fir, lodgepole pine, ponderosa pine, and sub-alpine spruce occur along with grassland and sagebrush vegetative communities.
This burned area was surveyed and assessed by a BAER team comprised of Forest Service scientists and specialists. The BAER team evaluated the burned watersheds to determine post-fire conditions, and identify values-at-risk such as threats to human life and safety, property, and critical natural and cultural resources. In addition to these critical values, other threats were also assessed, such as the risk for increased post-fire flooding, sediment flows, rock slides, hazard trees and noxious weed spread.
The BAER assessment team’s analysis of the burned area within the Alice Creek Fire and recommended emergency treatments are documented in a Forest Service (FS) Burned-Area 2500-8 Report. This report was submitted to the Northern Region (Region 1) Regional Forester by the Forest Supervisor for the Helena-Lewis and Clark NF for review and funding.
The following is a summary of the BAER team’s burned area assessment report for the Alice Creek Fire:
- 8 sub-watersheds were analyzed and modeled to compare pre-fire conditions to post-fire predicted response: Big Skunk Creek, Falls Creek, Green Creek, Lower Alice Creek, Lower Landers Fork, Middle Fork Dearborn, Middle Landers Fork, and Upper Alice Creek.
- There are 39 miles of perennial stream, and 68 miles of intermittent/ephemeral streams.
- There are 8 miles of NF roads, 49 miles of other roads, and 20 miles of NF trails.
- There are 1,469 acres with severe hazard ratings for soil erosion, 4,701 acres with moderate ratings for soil erosion, and 7,873 acres with slight hazard ratings for soil erosion.
- There are 3,765 acres of water repellent (hydrophobic) soils. Hydrophobic soil conditions are common within moderate and high burn severity areas and rare in the low burn severity areas.
- There are about 10,940 (33%) unburned acres, 6,331 (19%) acres of low soil burn severity, 12,623 (38%) acres of moderate soil burn severity and 3,643 (11%) acres of high soil burn severity.
Soil burn severity is the fundamental indicator used to evaluate post-fire conditions. The soil burn severity categories reflect changes in soil properties from pre- to post-fire and are a key element used to identify post-fire threats. The distribution of unburned, low, moderate, and high soil burn severity levels become a baseline for resource specialists to monitor changes in soil-hydrologic function and vegetative response as the burned watersheds recover.
High and moderate soil burn severity categories have evidence of severe soil heating and the consumption of organic material; the soil seedbank and water infiltration characteristics are reduced. Natural recovery is slower where little or no vegetative ground cover remains, with increased surface water runoff resulting in increased soil erosion. Areas of moderate soil burn severity have viable roots and some soil cover, but may still be vulnerable to erosion on steep slopes. The low to very low soil burn severity areas still have good surface soil structure, intact fine roots and organic matter, and should recover more quickly once revegetation begins and soil cover is re-established.
Identified Values-at-Risk, Threats, and Emergency Conditions
Summer thunderstorms have the greatest likelihood of generating large runoff and soil erosion events. If large summer thunderstorms occur, the primary values-at-risk within the burned area are human life and safety, transportation infrastructure (roads and trails), soil productivity, water quality, fish habitat, and native vegetation communities. The primary threats caused by the fire include 1) increased runoff, which is expected to intensify the first 2-3 years following the fire until the burned watersheds recover, and 2) accelerated hillslope erosion as a result of increased runoff and decreased infiltration rates. High intensity, short duration rainfall may result in valley bottom flooding and localized debris flows. Additional threats originating from the destabilized hillslopes throughout the burned area include falling trees and rolling rocks.
Emergency post-fire conditions for the Alice Creek Fire were identified by the BAER team for the following on-forest values-at-risk:
Human Life and Safety: There are potential impacts to the safety of Forest visitors traveling and employees working along roads and trails within the burned area. Generally, increased risk occurs within or directly down-slope from high and moderate soil burn severity areas. Potential threats and risks for the general public to be impacted are from rolling rocks, flash flooding, flooding, debris flows, falling hazard trees, and loss of ingress/egress access.
Property: There are potential impacts and threats to Forest Service (FS) Alice Creek 293 Road, trails, and associated infrastructure. There is high potential for failure to road drainage due to increased post-fire flows and thus potential for erosion of trail surface tread and sediment delivery to streams. Soil deposition on trail surfaces from adjacent hillslopes may also occur. The potential threats are from increased water, sediment flows, soil erosion, loss of capacity, and overtopping and breaching during flood events.
Natural Resources: There are potential threats and risks to native plant vegetation recovery from increased spread of noxious weeds, water quality, Bull Trout habitat, Lynx habitat, and reduced soil productivity and hydrologic function from the loss of ground cover, increased sediment flows and accelerated erosion.
Cultural/Heritage Resources: Very high risks potentially exist to cultural resources due to the threat of increased post-fire run-off, deposition, and erosion from upslope burned areas due to loss of pre-fire ground cover.
Emergency Stabilization Treatments
The BAER assessment team’s emergency stabilization objectives for the burned areas are to protect, mitigate and reduce the potential for identified post-fire threats, including increased soil erosion/sediment yield and water run-off on steep slopes, for:
- Human life, safety, and property within and downstream of the burned area;
- Forest Service infrastructure and investments such as roads and trails;
- Critical natural and cultural resources; and
- Native and naturalized plant communities from new noxious weed infestations.
The following post-fire emergency stabilization measures and treatments have been approved:
- Install burned area warning signs to caution forest visitors traveling and recreating within the burned areas.
- Continue to communicate risks to the public, community groups, and cooperating agencies.
- Provide for worker safety during implementation of road and trail drainage improvements by removing hazard trees along the roads and trails where treatment crews are operating for extended periods of time.
- Storm-proof and stabilize Forest Service (FS) System transportation roads and crossings with improved water drainage structures and features to prevent damage resulting from post-fire watershed conditions such as soil erosion, storm water run-off, and public safety hazards to improve the safety of forest visitors and employees. Conduct storm patrol monitoring to ensure road treatments are functioning as intended.
- Storm-proof and stabilize FS trails with improved water drainage structures and features to prevent damage resulting from post-fire watershed conditions. Conduct post-storm inspection of problem areas and implement emergency repairs if needed.
- Conduct early detection surveys and rapid response eradication with herbicide of noxious weeds along areas disturbed by fire suppression activities, equipment concentration points, high and moderate soil burn severity areas near these fire suppression disturbed areas, and other high priority areas, to reduce the potential for impaired native vegetative recovery and the introduction and spread of invasive weeds.
- Conduct lop and scatter of local woody debris to reduce the risk of erosion to cultural resources within the burned area.
- Continue to work and coordinate with interagency cooperators, partners, and affected parties and stakeholders.
- Assist cooperators, including local, state, and federal agencies with the interpretation of BAER assessment findings to identify potential post-fire impacts to communities and private land owners, domestic water supplies, and public utilities (such as power and telephone lines, state roads, county roads, and other infrastructure).
SPECIAL NOTE: Everyone near and downstream from the burned areas should remain alert and stay updated on weather conditions that may result in heavy rains over the burn scars. Flash flooding may occur quickly during heavy rain events. BAER actions are intended to reduce, but cannot eliminate risks. Current weather and emergency notifications can be found at the National Weather Service (www.weather.gov/mso/) website.