University of California Institute of Transportation Studies

Wildfires in California have increased due to climate change, poor forests maintenance, and human factors. Post-wildfire mudflows frequently occur during rain events on burn scars due to loss of vegetation, change of surface morphology, and soil surface hydrophobicity. Spreading Xanthan gum biopolymer on slopes after wildfires may mitigate the risk of extensive erosion of hydrophobic soil layers during rain. Experiments test identified rain intensities from 15 mm/hr to 50 mm/hr and seven natural rain events on a separate set of experiments on fine, medium, and coarse sand slopes 10° to 25°. Different approaches to Xanthan gum application are considered. Surficial erosion occurs due to rain and is extreme in untreated slopes in all three sand types. Sprinkling surfaces with pure Xanthan gum leads to erosion as well. However, when xanthan gum is mixed with sand in small quantities and wetted, gel-like connections form between sand particles, which prevents further erosion when allowed to harden. Experiments focused on cured Xanthan gum and sand mix covers yielded a better understanding of coupled conditions necessary for successful erosion mitigation and the advantages and limitations of the proposed approach. Furthermore, practical guidelines for improving burned scars are recommended.