A framework for in‐stream jams formed by snow avalanche‐delivered large wood

Abstract In‐stream large wood moderates flow dynamics, enhances sediment and nutrient storage, and supports biodiversity through habitat creation. While the significance of large wood in stream systems has been well documented, wood behavior in avalanche‐prone landscapes remains poorly understood. Here, we generate a conceptual framework for large wood jam complexes observed in avalanche‐prone landscapes that incorporates valley morphology, snowpack regime, and wood characteristics. We examined six avalanche‐prone drainage basins in Colorado, USA, with visible snow avalanche and large wood interactions. We identified jams using high‐resolution aerial imagery and measured jam structure, orientation, and hydrologic and sediment impacts. We determined that snow avalanche debris jam complexes fall into two primary categories: blanket jams and transport jams. Blanket jams are large, valley‐floor spanning structures that experience minimal post‐avalanche transport. They extend for 62.5 m along the channel and increase channel widths by 4.9x. Transport jams experience a higher degree of post‐avalanche transport, yet they maintain a structural link to the debris field on the floodplain. Transport jam complexes span 30 m in length and widen channels by 3.4x. We further explored geomorphic controls and found that transport jams are associated with steeper (38° vs 31°) and rougher hillslopes, which are prone to more frequent—and potentially lower magnitude—snow avalanches. Log lengths are longer in blanket jam complexes, with a mean of 11.7 and 7.7 m for blanket and transport jams. We propose that jam complex style is a function of avalanche frequency and magnitude, which is controlled by the climate and valley morphology. Our framework is the first to systematically address large wood in avalanche‐prone landscapes and provides a foundation for regional comparison of LW dynamics in high alpine settings. This framework can also serve as a basis to understand the impacts of changing snowpack and shifting forest ecozones on large wood accumulations and valley bottoms.