Post-Fire Burned Area Emergency Response (BAER) Assessment - Fork Complex
Incident: Fork Complex Wildfire
Fork Complex Post-Fire BAER Assessment Report Summary
Release Date: Sep 28, 2015
Contact(s): BAER Information: (415) 881-1871
FS-2500-8 Burned-Area Report:
Watershed Analysis, Condition, and Response
A Forest Service Burned-Area Report, which included the BAER assessment team’s analysis of the burned areas within the Fork Complex and recommended emergency treatments, was recently submitted to the Pacific Southwest Region (Region 5) Regional Forester by the Forest Supervisor for the Shasta-Trinity National Forest:
5 watersheds were analyzed and modeled to compare pre-fire conditions to post-fire predicted response.
- There are 145 miles of ephemeral streams, 73 miles of intermittent streams, and 64 miles of perennial streams within the burned areas.
- There are 125 miles of roads and 21 miles of trails within the burned areas.
- There are 459 acres of high soil burn severity (1%), 22,600 acres of moderate soil burn severity (62%), and 13,438 acres of low/unburned soil burn severity (37%).
- The BAER soil burn severity map identifies areas and classes of impaired soil function and is the key element in determining if threats exist.It is a map of fire-caused changes in soil characteristics that affect the soil hydrologic function.The identified soil burn severity levels in the burned areas of a wildfire become a baseline for resource specialists to monitor changes in soil hydrologic function and vegetative productivity as the burned watersheds recover.
- Soil burn severity patterns varied for the Fork Complex wildfires due to different topographies and fire behavior.
- High and moderate soil burn severity classes have evidence of severe soil heating in a patchy distribution.Soil seedbank and water infiltration characteristics are impacted in the areas that have burned repeatedly for the high and moderate soil burn severity areas. So natural recovery of these areas is slower where little or no vegetative ground cover remains along with high water run-off and soil erosion.
- The low to very low soil burn severity areas still have good surface structure, contain intact fine roots and organic matter, and should recover in the short-term once revegetation begins and the soil surface regains its cover.
- Water repellency is common and varying from slight and surficial in all soil burn classes on about 13,500 acres and water run-off is expected to greatly exacerbate.
- There are 7,927 acres of a very high hazard rating for soil erosion, 15,163 acres of a high hazard rating for soil erosion, 11,060 acres of a moderate rating for soil erosion, and 1,164 acres of a low hazard rating for soil erosion.
As a result of the removal of vegetation by the wildfires, excessive sediment and available material of rocks and woody material in channels within and downstream of the burned areas have the potential of high water run-off as a result of moderate to high rainstorms. Debris-flow probabilities are high in some watershed basins. Soils are exposed and have become weakened, and rocks on slopes have lost their supporting vegetation. The risk of flooding and soil erosion events will increase as a result of the fire, creating hazardous conditions within and downstream of many of the burned areas.
Identified Values-at-Risk, Threats, and Emergency Conditions
Threats to the values-at-risk were identified to exist that result from the potential for increased water flows, loss of water control, increased sediment delivery, increased debris flows, and the establishment of invasive weeds.
Based on the BAER assessment team’s observations and burned area post-fire conditions, an emergency exists regarding human health and safety, road and trail infrastructure, and spread of noxious weeds. Risks and threats were identified for 1) roads located downstream from high and moderate soil burned areas; 2) fish habitat for the Coho salmon critical habitat in Philllpot, Tule, and Browns creeks; 3) the potential for the spread of noxious weeks by the use of heavy equipment for fire suppression line construction; 4) exposed archeological sites are at risk to vandalism and erosion; 5) severely burned soils lost needle and leaf litter and duff, and have deep soil charring that compromise their structure and fertility; and 6) the potential of burned hillslopes above wilderness trails to compromise and impact trail treads especially at mid-slope switchbacks.
Particular areas of concern are Little Barker Creek, Upper Wilson Creek, Upper Rattlesnake Creek, and Midas Gulch which were entirely burned at moderate to high soil burn severities. These areas have soils that have strong natural water repellency due to their porous fine gravel nature. All vegetation, including an existing conifer stand was 100% killed along with in-channel vegetation with undersized culverts that could plug and cause these roads in these areas to fail.
Risks to human life, roads, trails, and natural resources are high. Emergency post-fire conditions for these identified values-at-risk were assessed by the BAER team:
Human Life and Safety – As a result of the severely burned watersheds, risks to life and safety for Forest visitors and Forest Service personnel entering certain areas of the burn are likely to pose a moderate risk due to burned hazard trees along roadways and flooding impacts from undersized culverts and poor drainage.
Property: Roads – Roads are at risk from rolling rock, plugged culverts, debris slides and debris flows. Stream channels and mountainside ephemeral channels will be flushed of the sediment that in some places is loose and deep, in other places shallow.
As a result of the expected increase in watershed response, significant damage will occur on come roads within the burned areas due to undersized culverts and poor drainage. There is a likelihood that post-fire conditions will increase water run-off and the movement of sediment into drainage features such as, culvert inlets, over road-side drains, roadway dips and run-outs, this occurrence could cause drainage function to fail and uncontrolled water to diver, resulting in a high risk of damage to the invested road improvements, loss of road function, and the denial of access. Highway 3 below Kingsbury Ridge could be an area of concern due to limited culvert sizes and the potential for flooding.
Property: Trails – Segments of trail systems are at risk. As a direct consequence of the wildfires, there is a risk of damage to trails caused by the loss of water control. Increased flow rates can be expected due to the loss of vegetation. The increased water flow rate will result in trail tread eroding and obscure trail definition, causing users to wander off the established trail, especially in trails with switchbacks. Repeated off-trail travel eventually re-defines a new trail that most likely will be non-conducive to natural water flow and subject to further erosion. Trails that follow and repeatedly cross stream channels are subject scouring and washout where the stream channels increase flow rate which is directed towards unstable stream embankments. Trail segments which are supported by these burn weakened stream banks are in jeopardy of being washed out.
Natural Resources: Water Quality and Fisheries – An emergency threat exists to the water quality of streams due to increased sediment and soil erosion. Increased post-fire flood flows may overwhelm existing Forest Service road crossing structures, causing washouts, and stream diversion down roads. This can result in damage to roads and increased sediment delivery to downstream channels. Coho salmon and winter run steelhead are federally listed threatened fish species and both species are known to occur in the Hayfork Creek. There is a high potential for sediment delivery to stream and river systems due to steep burned hillslopes that lack cover, so aquatic habitat and water quality effects from sediment will be significant.
Natural Resources: Soil Productivity – Soil productivity could be compromised in the areas that have burned moderately high-to-high in the Little Barker sub-watershed, upper Browns Creek, upper Rattlesnake Creek, and Wilson Creek due to the lack of vegetation cover, deep soil charring, and steep hillslopes that could erode productive topsoil.
Natural Resources: Ecosystem Health and Vegetation Recovery – No federally listed threatened or endangered plant species or their critical habitats are known to occur within the burned areas of the Fork Complex. However, an emergency threat exists with post-fire invasive weed introduction and spread. There are known noxious weed occurrences within the burned areas of the Fork Complex. These occurrences are mostly restricted to roadsides, campgrounds and other developed recreation sites, but some are found within openings that have been disturbed. Observations in other areas have shown that the patterns seen in the known populations can be extended in a general sense throughout the fire perimeters. The value-at-risk is the ecosystem health and integrity of the native plant communities with the burned areas. The threat is the potential loss of that ecosystem health and integrity due to new invasive plant introductions and spread from existing infestations which could inhibit the return of the native plant communities and crowd out recovering native vegetation resulting in non-functioning or poorly functioning ecosystems.
Cultural/Heritage Resources – Field assessments and analysis indicates that cultural resources within the Fork Complex burned areas are not at risk from post-fire erosion, storm run-off, debris flows, or increased visibility. Therefore, no emergency condition exists for cultural resources.
Natural Resources: Wildlife – Within the fire perimeters, there is suitable Northern spotted owl habitat adjacent to the high severity burned areas of the Fork Complex.
Emergency Stabilization Treatments
The BAER assessment team’s emergency stabilization objectives for the burned areas are to mitigate and reduce the potential for increased soil erosion/sediment yield and water runoff over steep slopes to lessen the overall threats to allow safe passage of water to protect infrastructures, watersheds, cultural sites, and fish habitat from accelerated sheet and rill erosion, and to protect watersheds from the spread of noxious weeds:
- Reduce the potential for impaired vegetative recovery and the introduction and spread of invasive weds by conducting detection surveys, rapid response eradication efforts where feasible, and seed (native species) and mulch 50 feet of dozer lines where they meet travelable roads.
- Stabilize the transportation roads system and water drainage structures to prevent damage resulting from soil erosion and storm water run-off, public safety hazards, and improve the safety of national forest personnel by clearing and improvement of catch basins and ditches along roads; maintenance and up-grading of drainage structures; and construction of rolling dips in critical locations along roads.
- Storm-proof roads and trails and close portions of roads and trails to the public as warranted until properly stabilized.
- Re-evaluate the need for temporary closures of roads and trails within and adjacent to the burned areas.
- Install burned area warning signs along roads and trails to alert the public to potential dangers of falling trees, rolling rocks, and potential increased water flows during storm events within the burned areas.
- Continue to work and coordinate with interagency cooperators, partners, and affected parties and stakeholders.
- Conduct storm patrols to monitor roads and drainage structures at risk, maintain and/or repairs any damage to road surfaces, remove sediment and debris from drainage and treatment structures within the burned areas.
- Mitigate hazard trees at BAER treatment locations to provide for national forest personnel safety.
SPECIAL NOTE: Everyone near and downstream from the Fork Complex fire areas should remain alert and stay updated on weather conditions that may result in heavy rains over the burn scar. Flash flooding may occur quickly during heavy rain events. Current weather and emergency notifications can be found at the National Weather Service, Eureka Office (http://www.wrh.noaa.gov/eka/) website.
Shasta-Trinity NF Post-Fire BAER Assessment information is available athttp://inciweb.nwcg.gov/incident/4601/.