Landslide hazards in The Dalles, Wasco County, Oregon

Human activity has led to the reactivation of portions of a Pleistocene landslide complex in The Dalles, Oregon. Slope movements are in rocks of the Chenowith formation: agglomerate, conglomerate, tuff breccia, sandstone, and siltstone. Slope movements occur in at least two distinct areas in The Dalles. At one, the shear surface is defined by the contact between the Chenowith formation and the underlying Columbia River Basalt. Data from inclinometer readings at the other area fail to reveal a well-defined shear surface. Slope movements in The Dalles cause tens of thousands of dollars worth of damage annually and may present a threat to human safety. So far there has been little organized response to this hazard