Variability in Post-Wildfire Soil Hydraulic Properties Related to Local and Regional Climatological, Geological, and Burn Characteristic Factors.

Rainfall infiltration into soil is a key factor in both landscape development and generation of rainfall-runoff hazards like flash flooding and debris flows in areas that have been recently burned. However, infiltration capacity is variable on spatial and temporal scales that make its prediction challenging, particularly in burned environments. The extent of fire-prone areas in the western United States is growing, highlighting a need for additional study of post-wildfire soil hydrology and associated hazards. Here, we have compiled and re-analyzed in a consistent manner new and existing post-wildfire Mini Disk infiltration datasets from more than two dozen wildfires across the western United States. To test if the observed variability in post-wildfire infiltration behavior can be explained by other landscape and climatological factors, we analyze these datasets in conjunction with burn severity, climatological, and geological data from each site. Our preliminary results show that, in arid to semi-arid landscapes, infiltration rates commonly decrease following moderate to high severity burning, which in turn enhances run-off and contributes to debris flow hazard. However, this pattern does not hold in all burned environments, indicating a more complex set of factors that influence the soils response to burning. Better understanding of these variations in post-wildfire infiltration behavior with other, more easily measured variables will be valuable in post-wildfire hazard modeling and prediction under the current regime of rapidly changing wildfire behavior.