Date of Award

8-2025

Document Type

Thesis

Degree Name

Master of Science in Geology

Department

Geological Sciences

First Reader/Committee Chair

Cato, Kerry

Abstract

Four years after the occurrence of the 2020 El Dorado Fire, Yucaipa Ridge and the surrounding communities of Oak Glen and Forest Falls still experience the devastation caused by debris flows. Wildfires can instigate a series of events leading to hydrophobic soils, loss of vegetation, and increased sediment availability which amplify post-fire debris flow risks. This study tested the hypothesis that post-wildfire geomorphic changes can be accurately quantified and predicted using high-resolution LiDAR-derived digital elevation models. To investigate this hypothesis, multi-temporal LiDAR datasets were analyzed to quantify geomorphic changes, including erosion and deposition, within two severely burned basins in the area. The comparison of pre- and post-event topographic data enabled the quantification of sediment dynamics. These quantified changes, examined in conjunction with available event data and hazard models, allow workers to better understand factors influencing debris flow likelihood and volume. Outcomes include an improved understanding of post-fire debris flow dynamics and sediment volumes, alongside enhanced capabilities for generating debris flow runout forecasts. Ultimately, this research contributes to the scientific understanding of post-wildfire geomorphological changes by demonstrating an integrated approach for detailed watershed characterization and improved debris flow volume estimation, crucial for enhancing hazard assessment in fire-prone landscapes.

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