The Olympic Experimental State Forest (OESF), a commercial forest lying between the Pacific coast and the Olympic Mountains, is a region of steep slopes and high annual rainfall (2500-6000 mm/year) and is therefore highly susceptible to landslides. As this area is critical habitat for numerous organisms, including salmon, there is a need to investigate potential management plans to promote the economic viability of timber extraction while protecting the natural habitat, particularly in riparian areas. As clear-cutting reduces the root contribution, and as projected climate change may result in storms with higher intensity precipitation, this area may become more susceptible to landslide activity. This may result in potentially severe consequences to riparian habitat due to increased sediment loads. The primary objective of this study is to provide high resolution (10 m) landslide susceptibility maps over the study area to inform land management decisions in an altered climate. The Distributed Hydrology Soil Vegetation Model (DHSVM), a physically-based hydrology model with a mass wasting module, was used to explore the sensitivity of landslide risk to timber extraction over areas with varying terrain features and soil characteristics. To investigate the impacts of climate change on landslide susceptibility we applied downscaled output from two General Circulation Models (GCMs) with two greenhouse gas (GHG) emission scenarios, A1B and B1, for the year 2045. Areas with high landslide risk increased on average 7.1% and 10.7% for the B1 and A1B GHG emissions scenarios, respectively. The maps produced in this study will enable forest managers to plan for climate change by indentifying areas that are less prone to landslide activity in an altered climate
