The frequency and severity of wildfires has grown over the last several decades, and with disasters such as the Palisades and Eaton fires in Los Angeles, their destructive power is at the forefront of people’s minds. Outside the obvious impacts to vegetation, soil, wildlife, and property, wildfires also affect water resources within watersheds. Hydrological processes are disrupted including changes in interception, infiltration, storage, evapotranspiration, runoff, erosion, snow, and groundwater recharge. After a fire, more precipitation reaches the ground owing to reduced foliage. These hydrological changes can result in flash floods, water scarcity, and erosion. A strategy offering a rapid wildfire hydrological impact assessment that doesn’t require extensive data is proposed in a new paper in the Journal of Hydrologic Engineering.
Authors Jonathan Romero-Cuellar, James R. Craig, Bryan A. Tolson, Parisa Aberi, Simon G. M. Lin, Mahkameh Taheri, and Rezgar Arabzadeh developed a screening method to assess impact scenarios on flood flows before wildfires occur. This first-of-its-kind method doesn’t require information related to fire regime factors, such as burn severity and burn extent, and was applied to four Canadian watersheds prone to wildfires. The findings outlined in their paper, “A Streamlined Model-Based Strategy for Screening Wildfire Impact Scenarios Related to Peak Flood Flows: Hazard Prevention in Data-Limited Regions” will help hydrologic practitioners and researchers to implement postfire flood analysis. Learn more at https://doi.org/10.1061/JHYEFF.HEENG-6318. The abstract is below.
Abstract
The recent surge in the frequency, severity, and extent of wildfires, along with the increased risk of wildfire-induced flooding, highlights the need to quantify the potential impacts of wildfires on peak flood flows. However, supporting wildfire impact assessments with imprecise models can be challenging due to the detailed information typically required about the severity and extent of wildfires, degree of dynamic forest recovery, and a lack of postburn flow data. Moreover, making reasonable assumptions about wildfire impacts becomes difficult. To address this challenge, we propose a novel methodology for screening wildfire impact scenarios on peak flood flows in regions with limited data before a wildfire has occurred. This methodology includes prefire process-based hydrological modeling, sequentially screening short wildfire impacts, and flood frequency analysis. As a proof of concept, the current strategy has been applied to four fire-prone watersheds in Canada. Unburned and worst-burn scenarios were generated and compared to quantify changes in peak flood flows and flood frequency curves. The results indicated that annual peak flows and flood frequency curves experienced an increase in the short-term worst-burn scenario across all four watersheds. The proposed screening methodology estimates the upper limits of postfire peak flood flows, offering insights into which watersheds may be disproportionately impacted by a wildfire regime. This model’s outputs can be seamlessly integrated into a risk management framework to inform wildfire management decisions aimed at hazard prevention and risk reduction.
See how this methodology can work for you in the ASCE Library: https://doi.org/10.1061/JHYEFF.HEENG-6318.
