Jorsted Creek Landslide
In late February of 1999, heavy rains triggered the Jorsted Creek Landslide, moving debris across Highway 101. During the reconnaissance flight over Mason County, we flew over the Jorsted Creek landslide. As expected, there was no discernable movement on the deep-seated Jorsted Creek landslide. Since the rain event was intense, but short lived, the water would be expected to primarily flow on the surface and in the shallow subsurface. This type of an event is a perfect combination for shallow landslides, especially in areas that have shallow soil on bedrock, or any medium that water cannot readily absorb into. Typically, deep-seated landslides require an extended wet period lasting more than a year, so the water can gradually accumulate in the subsurface.
Location of event
Map 1: Location map of Jorsted Creek Landslide. The location is approximate for the landslide complex, which includes areas that failed during 1999. Click on map to view larger image.
Figure 1: The left side of the landslide primarily failed during the storms of 1999. During our flight, no discernable movement was noticed. Click on photo to view larger image. (photo by Kelsay Davis)