Time-dependent Effects of Wildfire Ash and Root Decay on Hydrologic Behavior and Shallow Landslide Susceptibility of Wildfire-Burnt Slopes

由于气候变化，野火的发生率增加，加上高强度风暴，增加了山坡的湿润诱发浅层滑坡的易感性。近年来，美国西部发生的山火后山体滑坡和泥石流造成了数十人死亡和巨大的经济损失。该项目将提供一个特定于野火烧毁斜坡的框架，用于分析山坡随时间的浅层滑坡敏感性。新框架可用于识别关键斜坡，防止威胁人类生命、基础设施或自然资源的灾难性事件。该项目的目标是了解野火烧毁的斜坡的浅层滑坡敏感性为什么以及如何随着时间和饱和度的变化而变化，这是由于根部腐烂和野火灰烬的运输。在山火发生后，将立即在山坡上安装吸力和含水量传感器，以确定水保持行为随时间的演变。现场样品将每月收集一次，并使用x射线计算机断层扫描（XCT）进行扫描，以量化大孔隙体积随时间的变化。细根的腐烂率将通过实验室控制烧伤实验和XCT扫描进行量化。野火灰向土壤的迁移将通过饱和水力导电性试验来确定。采用基于吸力的边坡稳定性分析方法，评价了火灾边坡浅层滑坡敏感性随时间和饱和度的变化规律。在拟议的研究中产生的理解将是形成一个新颖而完整的框架的第一步，该框架专门用于野火后边坡稳定性分析，作为时间和饱和度的函数。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An increased incidence of wildfires combined with high-intensity storms due to climate change has increased the wetting-induced shallow landslide susceptibility of hillslopes. Post-wildfire landslides and debris flows in recent years in the Western US have caused dozens of fatalities and tremendous economic loss. This project will deliver a framework specific to wildfire-burnt slopes for analyzing shallow landslide susceptibility of hillslopes with time. The new framework could be used to identify critical slopes and prevent catastrophic events that threatens human life, infrastructure, or natural resources. The goal of this project is to understand why and how the shallow landslide susceptibility of wildfire-burnt slopes changes with time and saturation due to root decay and transport of wildfire ash. A hillslope will be instrumented with suction and water content sensors immediately after a wildfire to determine the evolution of water retention behavior over time. Field samples will be collected monthly and scanned using X-ray computed tomography (XCT) to quantify macropore volume over time. The decay rate of fine roots will be quantified using laboratory-controlled burn experiments and XCT scans. The migration of wildfire ash into soil will be identified through saturated hydraulic conductivity tests. A suction-based slope stability analysis will be used to evaluate the change in the shallow landslide susceptibility of a wildfire-burnt slope with time and saturation. The understanding generated in the proposed research will be the first step toward forming a novel and complete framework specific to post-wildfire slope stability analysis as a function of time and saturation.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.