After homes and a section of U.S. 30 were inundated near of the northwestern Oregon town of Clatskanie last week, rain got the blame, at first.

Turns out, though, that Oregon State University’s College of Forestry now seems partly to blame because the two landslides that caused the flooding stemmed in good part from university foresters’ clear-cutting of trees in 2004 on a 2,440-acre tract of land that it manages. That was the beginning of a chain of events that resulted in a cascade of what The Oregonian calculated as “thousands of truckloads’ worth of mud and debris.” Much of it ended up in the small town of Woodson, half a mile north of the slide site.

Fortunately no one was injured, although many properties were seriously damaged.

As university forestry officials study the landslides, they are finding that the event chain dates back at least 15 years. Among the “multiple mechanisms” that led to the landslides, a university geologist told The Oregonian, were the collapse of areas of rain-soaked ground, the clogging by silt of a small dam, and accelerated erosion caused by a bursting dam. —Peter Monaghan