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Jim Post-Fire BAER Assessment Overview

The BAER assessment team characterizes the burned watersheds in terms of a typical post-fire watershed response for:

•       Geologic response,

•       Hydrological response, and

•       Soil hillslope response to develop a comprehensive post-fire watershed response.

Factors the team considers:

•       Steep slopes, channels filled with ash and sediment, and high burn severity – all result in sediment being easily mobilized, and

•       The lack of precipitation interception where the vegetation canopy is consumed.

BAER specialists recently completed their field data evaluation to produce a Soil Burn Severity (SBS) map for the approximately Jim Fire.

The map and the data delineate Unburned/Very Low, Low, and Moderate SBS categories. 

The BAER team field assessed the Jim Fire burn area and determined that no acres were identified as having High SBS conditions.

Across the Jim Fire burned area, approximately 60% of the fire is either Unburned/Very Low and/or Low SBS, while 40% sustained a Moderate SBS.

The photo above left shows soil that still contain roots that are considered intact—so a moderate soil burn.

The photo above right shows a landscape image of the Jim Fire area.

The BAER assessment team used ERMiT (erosion risk management tool) to describe its sediment delivery prediction analyses and displayed their peak flow modeling results in the image above.

The USGS (US Geological Survey) combined basin hazards by basin and stream segment probability which was converted to “BAER Values” for 24 mmh 15-min storm intensity:

•       IT IS A SCREENING TOOL ONLY!

•       Team used the data to identify Critical Values in “high risk area” for field work

•       Word of Caution - The USGS post-fire debris flow hazards map displayed on their website shows a default design storm with at 24 mm/hr.

•       USGS shows the 24 mm/hr data for three reasons:

•       1) post-fire debris flows are most often triggered by high-intensity, short duration bursts of rain,

•       2) a 24 mm/hr rain burst is likely to happen in most areas of the western U.S. (i.e., a 1-5 year recurrence interval), and

•       3) this value is known to trigger debris flows at USGS monitoring sites in burn areas.

Per Forest Service BAER Program policy, the above image shows the categories of list of critical values at potential risk as identified and determined by the BAER assessment team for the Jim Fire burned area.

The BAER team identified Critical Values that fall into the four BAER categories and evaluated the threats posed by the post-fire watershed responses that were just described by the team hydrologists, soil scientists, and geologist.

Some Critical Values have more than one BAER value associated with them (for example, a Forest Service (USFS) road has a USFS property/investment value and may have a human life-safety component that is threatened by one or more post-fire response events).

There are no threatened nor endangered species identified within the Jim Fire burn area.

For Non-USFS values, the BAER team did evaluate them and worked with Agency partners and cooperators to share the team’s data, information, and findings.

Forest Service Road 3S04 is a main road that traverses 1.9 miles through the upper part of Jim Fire area.

There is less than one mile (.8 miles) of road in the moderate soil burn severity.

The BAER assessment team expects a higher post-fire response in the eastern portion of the burn area, which is near, or at the ridgetop that may help to mitigate a post-fire response.

These two Forest Service roads, 6s14 Holy Jim and 6s13 Trabuco, are outside the fire footprint but the BAER team expects post-fire impacts and high risk to certain sections of these roads.

The BAER assessment specialists identified the Holy Jim Trail as safety and property critical values at potential risk from damaging storm events.

The Holy Jim Trial has 1.6 miles within the fire footprint with 1 mile with moderate soil severity burn where the loss of the trail or sections of the trail is likely after storm events.

There is a high risk in certain sections of the trail.

After the Holy Fire, the Holy Jim Trail was buried, and access was limited in the Trabuco Canyon and is likely to happen again to a lesser extent for the Jim Fire.

The BAER team’s bigger concerns are where the trails are in, or below Moderate soil burn severity areas.

There is also team concern where trails cross drainages with increased flow rates can be anticipated due to loss of vegetation and soil cover with a high potential to cause trail tread erosion and degradation.

Fact: Dozer fire containment lines are vectors for weeds.

Native or naturalized plant communities are considered critical BAER values.

The BAER assessment team specialists determined that there is a high and very high risk to those areas from the threat of invasive weeds.

The fire can also provide a suitable seed bed for invasive weeds.

The Fig plant that is in riparian areas can easily spread into recently burned areas.

Winter storms will come next season—but upcoming summer monsoon rains are also hazards to recent burn scars!

The key to mitigating the biggest threats is preparing for and communicating hazards of post-fire effects to appropriate responders and the public. 

Th Forest Service is actively participating in cooperator/partner preparedness such as NOAA National Weather Service, USDA Natural Resources Conservation Service (NRCS), USDI Geological Survey (USGS), and Orange and Riverside Counties to coordinate and accomplish critical tasks before damaging storms.