Paper No. 4
Presentation Time: 8:45 AM


RILEY, Karin L., Numerical Terradynamic Simulation Group, University of Montana, Missoula, MT 59812 and HYDE, Kevin D., WY Center for Environmental Hydrology and Geophysics, University of Wyoming, 1000 E. University Ave, Laramie, WY 82071,

As human infrastructure and the wildland-urban interface in the United States grow, debris-laden flow hazard following wildfires is becoming a greater concern. The volume of a debris flow is used as a common proxy for hazard. Relatively few records of debris-laden flow volumes exist in the published literature, however; we combined these records with unpublished work and our own field data to create a catalog of debris-laden flow events. We compared the frequency-magnitude distributions of post-fire and non-fire-related debris-laden flows, and found that post-fire debris-laden flows tend to be smaller. We then investigated the role of fire severity and basin topography in determining debris-laden flow volume. While fire severity has been shown to be a strong driver of debris-laden flow probability, fire severity was not related to debris-laden flow volume. Topographic factors, however, explained more than 50% of the variability in volume. Precipitation and time since last debris-laden flow are also expected to be strong drivers of volume, but data were not available for testing their role. The increasing probability of debris-laden-flow generation with increasing fire severity is likely due to a number of changes in the post-fire environment, including removal of overstory vegetation and litter and duff, which may lead to increased runoff. Future work can combine fire severity as a proxy for probability with basin topography as a proxy for volume in order to derive risk to highly valued resources such as municipal water supplies following wildfire.