Aerial mulching on the King Fire

heli-mulching King Fire
A helicopter lifting a sling load of straw mulch. USFS photo.

Two months after 12 firefighters were entrapped and eventually led to safety by a pilot in a helicopter, helicopters again played an important role in the King Fire in northern California.

In late November the U.S. Forest Service (USFS) and the Sacramento Municipal Utility District (SMUD) began a joint project to drop straw mulch from helicopters over approximately 1,200 acres of Eldorado National Forest land that burned with moderate to high intensity during the recent King Fire. The purpose of the project is to protect critical infrastructure from potentially severe post-fire erosion that may occur with winter storms. The infrastructure at risk includes Eleven Pines Road, which serves as the primary route from Highway 50 to the northern end of the Eldorado National Forest, and the Brush Creek and Slab Creek reservoirs, which are integral to SMUD’s hydroelectric facilities in the Sierra Nevada Mountains.

heli-mulching King Fire
A completed straw mulch unit. USFS photo.

“This is a great example of the outstanding collaboration we’ve had during all phases of the King Fire,” said Eldorado Forest Supervisor Laurence Crabtree. A contract was awarded to Bradco Environmental, a company based in Crestline, CA, to complete the work. Large bales of certified weed free straw, a by-product of rice grown in California, were loaded into horizontal grinders which chopped the straw into four to eight inch pieces of mulch prior to aerial application. Two medium sized helicopters were used to drop the mulch onto slopes ranging from 15% to 60% grade, treating approximately 80 acres per day with each helicopter.

All of the treatment areas were identified by Forest Service soil scientists and hydrologists as sites needing immediate attention before heavy winter rains and snow arrived. This emergency erosion prevention project is designed to reduce the amount of sediment eroding off hillsides due to the loss of vegetative cover associated with the fire. Excessive sediment can block culverts and impact water quality in streams and reservoirs which could lead to flooding, road closures, decreased water storage capacity and loss of hydroelectric generation. This joint helimulching project is expected to prevent several thousand tons of sediment from eroding.

On December 4, 2014, due to the predicted weather for the following couple of weeks, all mulching operations were halted until the King Fire receives a significant warming and drying period or until after spring snow melt. This could be several months. Storm patrols and engineering work will continue throughout the winter.

heli-mulching King Fire
Burned Area Emergency Response crew inspects a straw mulched unit. USFS photo.

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Rim Fire: soil severity and vegetation severity

A U.S. Forest Service wildland fire ecologist that the Associated Press quoted as describing the area burned in the 250,000-acre Rim Fire in and near Yosemite National Park as “nuked” stirred up some controversy with his quoted remarks. It is difficult to use a subjective one-word description to sum up the varied fire effects on a huge fire that burned for weeks under an assortment of weather, vegetation, and topography conditions.

Most of the early assessments of burn severity on a large fire are derived from multiple sensors on satellites that are orbiting hundreds of miles above the earth. Using data from individual sensors, or combining information from multiple sensors, scientists can compare recent data with historical records to produce maps highlighting their area of interest. Two of the most common burn severity maps you will see are vegetation and soil severity.

The Burned Area Emergency Response (BAER) team assigned to the Rim Fire has publicized their version, soil burn severity maps which specifically focus on severity to soils and watersheds. The primary objective of the BAER team is to identify imminent post-wildfire threats to human life, safety, property, and critical natural or cultural resources and to take immediate actions to implement emergency stabilization measures before the first major storms. Their map of September 13 shows approximately 56% of the fire is either unburned or received a low-severity burn, 37% sustained a burn of a moderate severity, and approximately 7% burned at high severity.

The September 17, 2013 Rapid Assessment of Vegetation Condition after Wildfire (RAVG) map produced by the USFS’ Remote Sensing Applications Center (RSAC) analyzed vegetation severity produced by a change detection process using two Landsat Thematic Mapper images captured before and after the fire. They came up with very different numbers: 35% unchanged or low-severity, 27% moderate severity, and 38% high severity.

The maps from the two organizations are below. Larger versions can be seen HERE and HERE. Also included in the gallery are photos showing two areas burned in the fire, and a photo taken two hours after the fire started.