This article, published by Crosscut, quotes a study done by Discovery Institute’s Cascadia Center for Regional Development:
The problems associated with landslides were serious enough to command a section of a recent study by Seattle’s Cascadia Center for Regional Development on rail service in the Seattle-Vancouver corridor. The study placed much of the blame on land use. “The slides are inextricably related to the pattern of land use, at least in this primary problem area. Clearing of timber and construction of homes on the bluffs overlooking the shoreline that the tracks follow has [sic] destabilized soils, leaving the slopes prone to movement,” the researchers reported.
The rest of the article can be found here.