CAREER: Mechanics of Post-Wildfire Debris Flow and Transport

This Faculty Early Career Development (CAREER) award addresses devastating impacts of post-wildfire debris flows on civil infrastructure. Climate change has led to an increase in wildfires, posing multi-hazard threats to communities and natural environments. After wildfires, soil on burned scars becomes water repellent, which causes rainwater runoff to rush down hills and erode soil, carrying heavy boulders and debris.

There is an urgent need to evaluate post-wildfire debris flow and transport to protect communities’ welfare and prosperity, and natural resources in California and the United States. This award aims to develop novel methodologies and models of debris flow impact forces that will lead to better design and retrofit strategies for impacted civil infrastructure.

The project supports the education of underrepresented high-school, undergraduate, and graduate students and motivates them to pursue interdisciplinary and STEM topics. This project connects stakeholders, such as soil scientists at the California Geological Survey (CGS) and Burned Area Emergency Response (BAER), eager to update their one-dimensional risk assessment models with the latest research findings.

While students on this project spend time with CGS engineers and communicate with BAER teams, they have an opportunity to collect field reconnaissance data on post-wildfire mudflows location, local soil properties, weather, and infrastructure damage in quantitative forms, as well as thoughts, recommendations, and concerns from experts. Results from this project will significantly improve the safety of communities below burned scars, as well as the resilience of civil infrastructure against natural hazards.

This project includes an integrated research and education plan that establishes urgently and critically needed procedures for assessing post-wildfire debris flow effects on communities through a fundamental, across-scale micro-to-macro evaluation of post-wildfire debris flow, transport, and impacts on civil infrastructure and buildings using coupled Discrete Element Model and Material Point Method. Novel physics-based rheology of water-air-particle mixes is integrated into general correlations between mudflow downhill velocity and significant changes in mixture composition related to various initial conditions.

Impacts on civil infrastructure will be assessed and categorized to develop systematic approaches to mitigation strategies, structure strengthening, new design codes, and early warning systems. Research outcomes will secure resilient civil structures facing adverse climate change in high-risk wildfire areas.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.