Winter floods, erosion feared in wake of Rough fire

The Rough fire east of Fresno is 95 percent contained and should be fully out by winter, but its effects will be felt for years to come.

The most pressing concern for foresters now is winter rains running off the scorched earth – severely burned soil erodes more easily – and sending debris crashing onto roads and into campgrounds, historic sites or, in a worst case, people and property.

For the past month, foresters have been hiking the hillsides to map the worst burned areas and making emergency measure recommendations to help protect people and property.

“Water gets hungry” when it flows off a burned hillside, said Linn Gassaway, a Hume Lake Ranger District archaeologist. “It just eats up soil and gets hungrier and starts taking it down the slope.”

About two-thirds of the Rough fire area experienced no, low or very low soil damage in the blaze. But in other areas, the high heat damaged fine roots in the soil, creating conditions for flooding and erosion.

Hume Lake, Pinehurst, Dunlap, Sequoia Lake and other areas where people live are out of the danger zone, according to initial assessments.

But elsewhere in the 151,623-acre fire zone, there are plenty of roads, campgrounds, trails and historic sites at risk of damage.

First look

After a big forest fire, the Forest Service sends in a team to analyze watershed conditions for erosion, flooding and instability.

The first task of the Burn Area Emergency Response team is to decide if increased water runoff or erosion from winter storms could put lives at risk, said team leader Fletcher Linton, a 20-year Forest Service veteran.

“A flood caused by a storm is the bowling ball,” Linton said. “The values at risk – a human life – is the bowling pin. Because of the fire, the bowling ball gets bigger.”

The burn team – foresters, geologists, map experts, soil scientists, hydrologists, road engineers, ecologists, archaeologists, botanists and others – will present their report to Sequoia National Forest officials on Tuesday.

The report predicts 11.4 percent more runoff than normal from the Rough fire area if rains statistically likely in a two-year period occur.

Highway 180 past Grant Grove will remain closed until the fire is completely out and the area is considered safe, Forest Service officials said. After that, the highway will be open to the road leading to Hume Lake.

Burn team recommendations are likely to include putting mulch on unstable soils around historic and archaeological sites, as well as “stormproofing” measures, such as adding better drainage so water moves across trails and roads instead of washing them out.

“There are resources we don’t want to lose,” Linton said. “We don’t want roads to wash out or trails deteriorating. It’s expensive to fix.”

The Rough fire was large and expensive to fight – $120 million had been spent as of Tuesday – but fire managers prevented major post-fire problems for populated areas, officials said.

They “drew a box” around populated areas and kept the Rough fire out, Linton said.

“Luckily, the watershed above Hume Lake did not burn” so no increased runoff is expected this winter that would threaten life or property from flooding, he said.

Meanwhile, Pinehurst residents still fear fire due to the drought and dead trees, but their worry about floods and erosion is low, said resident Mahalia LoMele.

“They kept the fire away from Pinehurst and Dunlap,” she said. “It’s not a problem.”

This story was originally published October 10, 2015 at 6:30 AM with the headline "Winter floods, erosion feared in wake of Rough fire."