The following post summarizes the article “First the wildfires, then the flooding? How to assess the risk,” by Leslie Connelly, Aff.M.ASCE in the ASCE American Society of Civil Engineers, Civil Engineering Source online, Technical Note section.
Over recent decades, wildfires are increasingly more frequent and severe, with incidents like Los Angeles highlighting the destructive potential. Beyond the threat to human life and damage to physical property, wildfires also significantly impact water resources in watersheds. The events disrupt hydrological processes by altering interception, infiltration, storage, evapotranspiration, runoff, erosion, snow, and groundwater recharge patterns. Following a wildfire, the reduction in foliage allows more precipitation to reach the ground, leading to flash floods, water shortages, and increased erosion.
A recent publication in the Journal of Hydrologic Engineering has proposed a novel approach for quickly assessing the hydrological impact of wildfires without the need for extensive data. 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 evaluate flood flow scenarios before wildfires occur. This pioneering method does not require data on fire regime factors like burn severity and extent, and it was applied to four wildfire-prone watersheds in Canada.
The study, “A Streamlined Model-Based Strategy for Screening Wildfire Impact Scenarios Related to Peak Flood Flows: Hazard Prevention in Data-Limited Regions,” provides valuable insights for hydrologic practitioners and researchers to conduct post-fire flood analysis. For more information, visit https://doi.org/10.1061/JHYEFF.HEENG-6318. The abstract is provided 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.”
(Source: https://doi.org/10.1061/JHYEFF.HEENG-6318)
© 2025 American Society of Civil Engineers. All rights reserved.
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