A Case Study of Digital Elevation Model-Based Slope Stability Assessment on Managed Forestland in the Oregon Coast Range

An aerial photo-based inventory of landslides on recently harvested and reforested land after a significant landslide-producing storm in February 1996, was compared with a digital elevation model-based assessment of slope stability (shallow landsliding stability model [SHALSTAB]) for Confederated Tribes of Siletz Indians (CTSI) and surrounding forestland. The SHALSTAB predictions of landslide locations did not correlate well with the locations of observed landslides. Eighty-nine percent of the landslides on the more stable landform in the southern portion of the CTSI ownership occurred on land that SHALSTAB indicated to be at a low risk of landsliding. Seventy-two percent of the landslides on the less stable landform to the north occurred on land that SHALSTAB indicated to be at a low risk of landsliding. Conversely, only 11 and 28%, respectively, of the observed landslides occurred on lands predicted to be “chronically unstable” or at “high risk” by SHALSTAB. This level of correct prediction of landsliding was judged to be unacceptable for SHALSTAB to be used for slope stability assessment as a part of forest management planning. West. J. Appl. For. 21(4):195–202.