The Chetco-Bar Burn Area

The Chetco-Bar fire was sparked by lightning and first reported on Wednesday, July 12th, 2017, at around two o'clock in the afternoon. It would go on to burn for at least four months, cover nearly 200,000 acres of mostly wilderness, and destroy several homes. It caused a substantial reduction of air quality in the nearby town of Brookings and forced the evacuation of five-thousand people. The fire was in rugged and inaccessible terrain, which severely hampered fire-fighting efforts. Propelled by hot, dry winds, the fire became the largest in the State of Oregon, and the top priority fire in the nation.

Wild fires can have several effects on the geology of an area. Burned soils can behave in a hydrophobic manner after a fire, causing increased runoff. Lack of vegetation means that ground water can make its way to stream systems faster, leading for more flash flood events. Without the soil cohesion that plant roots provide, erosion is increased. As a result of all of this, the risk for landslides and debris flows increases substantially following a large forest fire. For that reason, we decided to add the Chetco-Bar fire burn area to the landslide mapping that I was already doing for the BLM at DOGAMI.

Burned Area
The Chetco-bar fire burned so hot that nearly all the vegetation was destroyed right down to the soil. Here is a burned area with some light grass regrowth. This is nearly exactly one year after the fire. Near Brookings, Oregon, Summer 2018.

The mapping was done according to the same method as the main landslide mapping project I was working on at DOGAMI. However, the terrain, which is primarily accreted melange, made identification and delineation of landslides very problematic. Eventually, I mapped more than 1000 landslides within this area, many of them covering huge areas.

The view from on top of Bosley Butte, where we stopped for lunch. Near Brookings, Oregon, Summer 2018

Following the mapping, I performed ground-truthing, along with geologists from DOGAMI and BLM, to verify the locations of slides that I mapped. Once again, the challenging geology made the process difficult. This project, more than any other, really challenged my abilities as a geomorphologist. It required careful and considered study of the terrain and, while it may have been one of the more frustrating projects I've ever worked on, it left me with valuable insight and experience that I didn't have before.