CAREER: Spatial Quantification of Fundamental Mechanisms that Initiate Post-Wildfire Wetting-Induced Shallow Landslides

This Faculty Early Career Development (CAREER) award will explore how dynamic changes in a forest environment that is recovering from a wildfire control the stability of burnt hillslopes against wetting-induced shallow landslides over time. The US wildfire management strategy has changed from “fighting wildfires” to “living with wildfires,” which involves community adaptation to wildfires. Post-wildfire landslides have been identified as a serious cascading risk to community adaptation to wildfires, but the fundamental initiation mechanisms are not yet understood. There is currently no wildfire-specific approach to evaluating the landslide susceptibility of burned hillslopes. This project will be the first step toward developing a wildfire-specific framework for analyzing the stability of hillslopes as a function of time, saturation, and forest use practices for different intensity fires and different landslide mechanisms. The research will be integrated with an education program aiming to place a new generation of engineers in a position to analyze and alleviate the risk of post-wildfire landslides, inform the policy makers, and promote community education about such risks.The primary research objective of this study is to quantify the fundamental mechanisms that change mechanical and hydrologic soil behavior and therefore slope stability in post-wildfire environments. The fundamental mechanisms are hypothesized to be controlled by forest system dynamics (i.e., tree loss, regrowth, ash movement), that synergistically control suction stress. To achieve the primary research objective, the following specific objectives will be achieved: 1) quantify post-wildfire suction stress and forest system dynamics over time, 2) identify the change functions for the components of forest system dynamics in relation to suction stress, and 3) evaluate post-wildfire shallow landslide susceptibility using a probabilistic approach. This will require a multiscale investigation of soil behavior in post-wildfire environments. The research plan involves testing soil behavior from the atomic scale to the hillslope scale and will allow multi-sensor data fusion. Field and laboratory data will be combined with spatial data from LiDAR scans and aerial photographs. The spatial variability in suction stress along the hillslope will be presented as a distribution function and will be an input for a probabilistic slope stability model for evaluating the wetting-induced shallow landslide susceptibility of burned hillslopes. In addition, the dependency of the adsorptive component of suction stress on the soil water retention curve will be investigated through water vapor sorption isotherms. This will improve our understanding of the degree of physicochemical forces on mechanical soil behavior.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.