Veldhuisen, C., 2018. Temporal trends and potential contributing factors to shallow landslide rates in the timberlands of the Skagit River basin, Washington. Skagit River System Cooperative, La Conner, WA. pp. 19.

To better understand decadal watershed and fishery impacts of shallow landsliding, I assessed landslide rates in six sub-areas of the Skagit River basin of northwestern Washington. All inventory areas contain predominantly forestry lands with ongoing timber management. I compiled existing landslide inventories documenting landslides occurring in the 1950s through the early 2000s and collected new information through 2011. Data were compiled by decade to assess temporal patterns. Landslide rates climbed during the 1980s and 1990s, then dropped sharply from 2002 to 2011. I evaluated numerous possible contributing causes of this pattern, including major precipitation events, logging rates, forestry mitigation practices, legacy effects and changes in landslide detection. Because this landscape-scale approach provides limited insight on individual landslide triggers, I evaluated potential causes based on temporal correlation and conceptual arguments. I conclude that declines in logging rates and improved forestry mitigation practices are likely to be major contributing factors. The effectiveness of strengthened forestry regulations is crucial to land management and watershed recovery, and these results suggest a favorable response. However, stronger conclusions will require additional time to see if landslide rates remain low after 2011, especially in areas where logging rates have accelerated. Extended observations may provide greater certainty on the relative strength among other possible driving mechanisms