Project Summary
Post-wildfire mudslides occur on hillslopes covered with water-repellent (hydrophobic) ash and/or cohesionless soil layers. During post-wildfire rainfall, water flows downhill over the hydrophobic soil and causes excessive sediment erosion. Hydrophobic surfaces enhance acceleration of water overflow due to two main reasons: prevented infiltration into soil and significantly reduced drag due to low surface wettability. Although measures for erosion prevention are used by Caltrans, such as downed trees for sediment trapping or stream regulation and aerial distribution of mulches or polymers, these take considerable time and effort to apply especially on steep slopes. Environmentally friendly, fast to implement, and temporary measures with minimal impact on vegetation redevelopment are needed. The proposed research aims to assess maintenance strategies for sandy hydrophobic steep slopes using bio-stabilization via selective areal application of biopolymers using drones. The proposed research is based on promising preliminary results from small-scale slope experiments conducted at UCSD. This applied research project will involve rain-induced erosion tests on steep hydrophobic slopes treated with different biopolymers using drones in a net-protected area available at UCSD. If successful, this project will provide Caltrans with rapid response strategies for slope remediation projects to prevent erosion and minimize damage to transportation networks after a wildfire.