Lolo National Forest
U.S. Forest Service
Missoula, MT 59804
MEYERS POST-FIRE BAER ASSESSMENT REPORT SUMMARY
FS-2500-8 Burned-Area Report: Watershed Analysis, Condition, and Response
The Meyers Fire, ignited by lightning on July 14, 2017, merged with the Whetstone Fire that also started from a lightning strike on July 13. The fire is located on the Bitterroot National Forest (NF) and Beaverhead-Deerlodge NF, approximately 25 miles southwest of Philipsburg, Montana. The fire burned 64,362 acres on Forest Service System (NFS) land (47,831 acres on the Beaverhead-Deerlodge NF and 16,531 acres on the Bitterroot NF), and 130 acres on private land. The dominant vegetation types within the burned area are mixed-conifer stands of primarily lodgepole pine and Douglas-fir with a beargrass, pinegrass and whortleberry/huckleberry understory. Subalpine areas with white bark pine, alpine larch and high elevation grasslands were also affected.
The Meyers Fire 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 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 Supervisors for the Bitterroot NF and Beaverhead-Deerlodge NF for review and funding.
The following is a summary of the BAER team’s burned area assessment report for the Meyers Fire:
- 2 sub-watersheds on the Bitterroot NF were analyzed and modeled to compare pre-fire conditions to post-fire predicted response: East Fork Bitterroot River-Clifford Creek, and Moose Creek.
- 9 sub-watersheds on the Beaverhead-Deerlodge NF were analyzed and modeled to compare pre-fire conditions to post-fire predicted response: Carpp Creek, Copper Creek, Fishtrap Creek, Howell Creek, Lower Middle Fork Rock Creek, Middle Middle Fork Rock Creek, Middle Ross Fork, Pintler Creek, and Upper Middle Fork Rock Creek.
Within the fire perimeter:
- There are 95 miles of perennial stream, and 94 miles of intermittent streams
- There are 36.3 miles of NF system roads, and 75 miles of NF trails.
- There are 1,994 acres with high hazard ratings for soil erosion, 37,531 acres with moderate hazard ratings for soil erosion, and 12,174 acres with low hazard ratings for soil erosion. Elevated soil erosion hazard is only applicable for the first few years following the Meyers Fire - until revegetation occurs to stabilize the slopes.
- There are approximately 1,336 acres of water repellent (hydrophobic) soils scattered around the fire area. Hydrophobic soil conditions are common within moderate and high burn severity areas and rare in the low burn severity areas.
- There are about 10,272 (17%) unburned acres, 12,174 (20%) acres of low soil burn severity, 37,531 (61%) acres of moderate soil burn severity and 1,994 (3%) 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 Meyers Fire were identified by the BAER team for the following on-forest values-at-risk:
Human Life and Safety: There are high risks to the safety of forest recreating visitors traveling and Forest Service employees working within the burned area. Potential threats exist along roads, trails, and trailheads from falling hazard trees and rockfall.
Property: There is a high risk to the road and trail infrastructure from post-fire increased surface flows.
Natural Resources: A high risk is anticipated to native plant communities due to the threat from the spread of noxious weeds. The wildfires created conditions conducive to noxious weed spread and establishment by reducing competition, and exposing bare mineral soil.
There is a moderate to high risk to Bull Trout, Cutthroat Trout, and Western Toads habitat due to sediment delivery from road and trails within the Middle Fork Rock Creek, Copper Fork Creek, East Fork Bitterroot River, and other downstream water bodies during precipitation events
Cultural/Heritage Resources: No risk is anticipated to known cultural and heritage resources within the Meyers burn perimeter, due to the increased threat sedimentation from upslope burned areas.
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 water run-off flows and soil erosion/sediment yield, 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 area.
- Storm-proof and stabilize NFS transportation roads and stream 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 stream crossings and road treatments are functioning as intended.
- Storm-proof and stabilize NFS trails with improved water drainage structures and features to prevent damage resulting from post-fire watershed conditions.
- Continue to communicate risks to the public, community groups, and cooperating agencies.
- Continue to work and coordinate with interagency cooperators, partners, and affected parties and stakeholders.
- Assist cooperators, including local, county, state, and federal agencies with the interpretation of BAER assessment findings to identify potential post-fire impacts to communities and private land owners, domestic and agricultural water supplies, and public utilities (such as power lines, state roads, county roads, and other infrastructure).
- Trap floatable debris and suspended sediment above culverts determined to have marginal capacity to pass post-fire flood flows to provide refuge for fish and improve channel stability in road crossing vicinity.
- Conduct early detection surveys and rapid response eradication with herbicide aerial application on 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.
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.