The Rim Fire has severely burned soil in about 12 percent of the Turlock Irrigation District watershed, reducing or eliminating its ability to absorb water, according to research from a specialized team.
The U.S. Forest Service Burned Area Emergency Response Team is tasked with mitigating the fire's impacts, doing things like clearing culverts, securing infrastructure, and ensuring roads don't wash out. The team is currently conducting burned area field surveys as part of that work.
“They look at how hot the fire got and how much it affected the soil,” explained Jason Carkeet, TID Utility Analyst.
Those surveys indicate that 44 percent of the 254,926 acres within the Rim Fire perimeter are either moderately or severely burned. Those soils are now at least partially hydrophobic – unable to absorb water – and susceptible to erosion.
As the Rim Fire has now burned roughly 25 percent of the TID watershed, about 12 percent of the watershed's soil has been severely burned. That's better than expected, the BAER team says.
“BAER specialists concluded that the amount of high severity burn is fairly low given time of year and comparison to other fires,” the BAER team sad in a press release.
The BAER scientists are now in the process of modeling post-fire water run-off and erosion risk levels. BAER is also working with the U.S. Department of Geological Survey to model debris flow potential. TID is being kept informed of all BAER research.
Though reports are still being prepared, it is likely that TID's Don Pedro Reservoir will receive more of the rain that falls in the watershed this year, with the soil unable to absorb the water. But that water could come quickly in flood-like conditions, and will likely be full of soot and other debris.
Dealing with the conditions will likely mean increased costs to the district. TID is currently drafting preliminary estimates of that cost, in hopes of obtaining funding as part of the emergency cleanup.
“We're pursuing avenues of federal reimbursement,” Carkeet said.