Shasta-Trinity National Forest
U.S. Forest Service
3644 Avtech Parkway
Redding, CA 96002
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.
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:
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/.