T141 Advances in the Science of Wildfire-Related Earth-Surface Processes I

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
205

INTEGRATING PRECIPITATION ESTIMATES FROM AN ATMOSPHERIC MODEL ENSEMBLE WITH DEBRIS-FLOW MODELS TO ASSESS POST-FIRE DEBRIS-FLOW INUNDATION HAZARDS

Paper number: T141-5
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Intense rainfall on watersheds burned by wildfire can generate debris flows that travel for several kilometers or more. When these fast-moving flows interact with downstream communities and infrastructure, they can have devastating impacts on life and property. Short-duration, high-intensity rainfall is a key driver of post-fire debris flows. Past studies developed models to estimate debris-flow likelihood and volume at the outlets of recently burned watersheds given information about topography, soil erodibility, burn severity, and rainfall intensity averaged over a 15-minute duration (I15). These models are often used following a fire to assess debris-flow hazards associated with design storms, which are characterized by a particular value of I15. While this approach provides valuable information for post-fire hazard planning, it does not account for the impacts of spatially varying rainfall intensities across the burn scar. Here, we utilize existing debris-flow likelihood and volume models in combination with an ensemble of rainfall intensity estimates from a high-resolution atmospheric model to derive probability distributions for debris-flow likelihood and volume at the outlet of a series of watersheds burned by the Thomas Fire near Montecito, California. Based on these distributions of likelihood and volume, we perform a series of debris-flow runout simulations to generate an uncertainty-rated prediction of debris-flow inundation. Specifically, we use Monte Carlo sampling methods together with a recently developed debris flow inundation model, the Progressive Debris-Flow routing and inundation model (ProDF). The 100-member atmospheric model ensemble was configured to provide a 24-hour forecast of peak I15 over the study area during a rainstorm on 9 January 2018 that produced a series of damaging debris flows. This work serves as a proof-of-concept experiment for how real-time weather forecast products could be integrated with land surface models to assess debris-flow impacts in an operational setting.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-383310

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.