A new report released Thursday focuses on areas of the Gorge that are highly susceptible to landslides — which also happen to overlap with some of the areas hit by this year’s wildfires.

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Geologists for the state of Oregon are warning of the risk of major landslides in parts of the Columbia River Gorge that were hit by wildfires this year.

A new report released Thursday focuses on areas of the Gorge that are highly susceptible to landslides — which also happen to overlap with some of the areas hit by this year’s wildfires.

“When an area like this has a wildfire, it actually increases the susceptibility,” said Bill Burns, an engineering geologist with the Oregon Department of Geology and Mineral Industries. He is one of Oregon’s top experts on landslides and the author of the new report.

Typically, landslides happen when soil becomes unstable after heavy rain or rapid snowmelt. Earthquakes may also play a part.

When logging or fire strips the topography of trees, shrubs and grasses, water can infiltrate the ground and make it more prone to sliding.

Forest fires can also scorch the soil and cause more runoff.

The Gorge has seen big slides in the recent past.

“In 1996 and ’97 we had several large storms that caused landslides in the Columbia River Gorge,” Burns said. “And these landslides came down the Gorge walls, engulfed the communities and Interstate I-84.”

Burns said his study helped create new maps of where landslides have occurred in the past.

He said these past slides greatly determine where landslides will occur in the future.

For his study, Burns compiled information from historic records down to the county level, along with old photos. He also looked at landslides through LIDAR images — high definition aerial data that can reveal the contours of past landslides.

So far, in the area that he studied in eastern Multnomah County, Burns has found evidence of 286 landslides — recent, historic and prehistoric. Some have been catastrophic, with mud traveling a mile. By contrast, the 2014 Oso landslide in Washington had a runout of about three-quarters of a mile.