From the rim to the river: The geomorphology of debris flows in the Green River canyons of Dinosaur National Monument, Colorado and Utah.

摘要

Debris flows in the Green River canyons of the eastern Uinta Mountains initiate via the firehose effect, where overland flow generated on dominantly bedrock slopes cascades down steep cliffs where it saturates and impacts colluvium stored in bedrock hollows and on resistant ledges, causing failure. Climatic and geologic characteristics of the study area cause bedrock and precipitation to have a greater influence than recent wildfires on the hillslope processes that lead to initiation. Monitoring of two recently aggraded debris fans shows that Green River floods with magnitudes as low as 75% of the pre-dam 2-year flood cause significant reworking, whereas floods with magnitudes less than 40% of the pre-dam 2-year flood do little reworking. These results have implications for both the catchment conditions that lead to debris flow initiation in the canyons of the Colorado Plateau, as well as the management of large dams on the Green and Colorado Rivers.