Surficial patterns of debris flow deposition on alluvial fans in Death Valley, CA using airborne laser swath mapping data

Debris flows are a common event in mountainous environments. They often possess the greatest potential for destruction of property and loss of lives in these regions. Delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones. Current research indicates debris flow fans have two distinct depositional zones. However, the two zones were derived from studies containing detailed analyses of only a few fans. High resolution airborne laser swath mapping (ALSM) data is used to calculate profile curvature and surface gradient on 19 debris flow fans on the eastern side of Death Valley. The relationship between these parameters is assessed to 1) identify if debris flow fans are accurately represented by two depositional zones, and 2) to assess how these terrain parameters relate to one another at the individual fan scale. The results show at least three zones of deposition exist within the sampled fans. These zones do not hold consistent when individual fan morphometry is analyzed in conjunction with localized fan surface gradients. Fans with consistently shallower gradients exhibit numerous depositional zones with more subtle changes in profile curvature. Steeper gradient fans exhibit significantly fewer zones with more pronounced local changes in profile curvature. The surface complexity of debris flow fans is evident from these analyses and must be accounted for in any type of hazard studies related to these features.