August 15, 2022 - A Forest Service Burned Area Emergency Response (BAER) team has been established by the Sierra National Forest (NF) to begin a joint burned area assessment of the Oak Fire that recently burned on Forest Service and Bureau of Land Management (BLM) federal lands, and private lands. The Oak BAER team leader is Kendal Young, Forest Service Natural Resources Staff Officer, and Co-Team Leader is Marcos Rios, Forest Service Engineer. Personnel from California State Office of Emergency Services (CALOES) and Natural Resources Conservation Service (NRCS) are evaluating burned private and county lands and infrastructure.  CALOES and NRCS and the Forest Service BAER Team will be sharing information and data as they complete their assessments and subsequent reports. Forest Service BAER team assessments typically take approximately two weeks to complete.

In addition to working and coordinating with Sierra NF staff, NRCS and CALOES, the team is coordinating with the National Weather Service (NWS), US Geological Survey (USGFS), and other federal, state, and local agencies as they assess potential post-fire impacts to the burned watersheds.

BAER surveys are rapid assessments that evaluate the burned area to identify watersheds having increased potential for post-fire flooding, sediment flows and rockslides, and assist land managers prepare the burned area for the upcoming monsoon rains. The team focus is on potential emergency impacts to life, and safety on federal land but model hydrologic response throughout the burned area and share the team’s findings with the responsible downstream agencies.

BAER teams may consist of scientists and specialists including hydrologists, geologists, soil scientists, road engineers, botanists, biologists, archeologists, and geographic information specialists. BAER teams collect field data during their burned area surveys to analyze through GIS and computer models and present their findings along with recommended BAER emergency stabilization treatments in a BAER assessment report.

BAER teams utilize satellite imagery and specialist data to analyze and produce a runoff map that shows the levels of hydrological potential flows during rain events.  This is the first step in assessing potential watershed impacts from wildfires to any federal values that may be at-risk from potential increased flooding, sedimentation, debris flows, and rockslides.  BAER teams produce a report that describes potential threats associated with the burned area’s post-fire conditions sometimes including recommended emergency stabilization measures and actions.  BAER emergency response efforts are focused on the protection of human life, safety, and property, as well as critical cultural and natural resource values such as the water quality of streams and wetlands on federal lands.

BAER reports are shared with interagency cooperators who work with downstream private home and landowners to prepare for potential post-fire flooding and debris flow impacts.  Homes or businesses that could be impacted by flooding from federal land that resulted from wildfires may be eligible for flood insurance coverage from the National Flood Insurance Program (NFIP).  Information about NFIP is available through FEMA at www.fema.gov/national-flood-insurance-program, or www.floodsmart.gov/wildfires. Other flood preparedness information is available at www.ready.gov/floods at www.floodsmart.gov/.

BAER SAFETY MESSAGE: Everyone near and downstream from the burned areas should remain alert and stay updated on weather conditions that may result in heavy rains and increased water runoff. Flash flooding may occur quickly during heavy rain events – be prepared to act. Current weather and emergency notifications can be found at the National Weather Service websites:  www.weather.gov/sto/ and www.weather.gov/hnx/.

Post-Fire Effects Understanding Soil Burn Severity

BAER Burned Area Emergency Response Information Brief

We tend to think of wildfire burn severity in terms of the visual impacts to above-ground vegetation, but the post-fire landscape response (erosion, flooding, and mass movement) is generally more strongly correlated to soil burn severity. When characterizing soil burn severity, looking at the vegetation is a good starting place to understand the conditions on the ground. Armed with that information, the BAER team’s watershed specialists (soil scientists, hydrologists, and geologists) ground-truth different vegetation burn intensities to tease out patterns of how fire affected and changed the properties of the soil.  Pre-fire ground cover, forest type, fire behavior, slope, aspect, and other factors all influence soil burn severity.  After field observations are collected, specialists adjust the vegetation severity map to create the soil burn severity (SBS) map.  The SBS is broken into four different classes: unburned (green), low severity (blue), moderate severity (yellow), and high severity (red).

So, what do these different classifications mean?

LOW severity areas generally have intact and recognizable litter layers (organic material on the forest floor, such as pine needles and twigs).  These litter layers may be charred, but are not consumed.  Underlying topsoil is intact and near-surface fine roots are unburned.  These soils have enough cover to protect them from erosion during rain events because their natural porosity and structure allow rain to soak into the soil instead of running off, while fine roots provide stability.  In low severity areas, burns may have been patchy—islands of green vegetation and intact canopies may be present. 

MODERATE severity areas generally have more—up to 80% of their pre-fire surface litter layers consumed by fire.  Black or gray ash may be present on the soil surface. Fine roots near the surface may be scorched and killed.  Topsoil layers are generally intact with minimal impacts to the soil’s ability to absorb moisture. Soils with moderate severity are more susceptible to erosion in post-fire rain events because they have lost protective surface cover and may have less surface stability because of root mortality.

HIGH severity areas generally have had all their pre-fire surface litter layers consumed by fire. White or gray ash may be present on the soil surface. Fine roots are often fully burned/consumed within several inches of the soil surface, and even large tree roots may have burned deep into the soil.  Soil may be powdery or grainy and loose, unable to bind together and retain water. These soils are very susceptible to erosion and often have high surface run-off during rainstorms.

So, what does the BAER team do with the SBS map?

The BAER team uses the SBS map to make predictions about how the landscape will respond after fires. Soil scientists consider where soil productivity will be degraded due to erosion losses and where sediment may move into stream channels. Hydrologists use the SBS to predict watershed response—surface runoff from high SBS areas in rainstorms can produce more “flashy” behavior in stream systems.  Geologists use the SBS to inform predictions for debris flow or other mass movement potential based on reduced soil stability in steep drainages.

BAER teams focus on emergency responses to stabilize burned areas that may impact federal lands critical infrastructure or other values located within or immediately downstream of moderate and high soil burn severity areas.