03 Dec 2021
03 Dec 2021
Status: a revised version of this preprint is currently under review for the journal NHESS.

Augmentation and Use of WRF-Hydro to Simulate Overland Flow- and Streamflow-Generated Debris Flow Hazards in Burn Scars

Chuxuan Li1, Alexander L. Handwerger2,3, Jiali Wang4, Wei Yu5,6, Xiang Li7, Noah J. Finnegan8, Yingying Xie9,10, Giuseppe Buscarnera7, and Daniel E. Horton1 Chuxuan Li et al.
  • 1Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, 60208, USA
  • 2Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, 90095, USA
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
  • 4Environmental Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
  • 5Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, CO, 80309, USA
  • 6NOAA/Global Systems Laboratory, 325 Broadway Boulder, Denver, CO, 80305-3328, USA
  • 7Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL, 60208, USA
  • 8University of California Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA, 95064, USA
  • 9Program in Environmental Sciences, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
  • 10Department of Biological Sciences, Purdue University, 915 W State St, West Lafayette, IN 47907, USA

Abstract. In steep wildfire-burned terrains, intense rainfall can produce large volumes of runoff that can trigger highly destructive debris flows. The ability to accurately characterize and forecast debris-flow hazards in burned terrains, however, remains limited. Here, we augment the Weather Research and Forecasting Hydrological modeling system (WRF-Hydro) to simulate both overland and channelized flows and assess postfire debris-flow hazards over a regional domain. We perform hindcast simulations using high-resolution weather radar-derived precipitation and reanalysis data to drive non-burned baseline and burn scar sensitivity experiments. Our simulations focus on January 2021 when an atmospheric river triggered numerous debris flows within a wildfire burn scar in Big Sur – one of which destroyed California’s famous Highway 1. Compared to the baseline, our burn scar simulation yields dramatic increases in total and peak discharge, and shorter lags between rainfall onset and peak discharge. At Rat Creek, where Highway 1 was destroyed, discharge volume increases eight-fold and peak discharge triples relative to the baseline. For all catchments within the burn scar, we find that the median catchment-area normalized discharge volume increases nine-fold after incorporating burn scar characteristics, while the 95th percentile volume increases 13-fold. Catchments with anomalously high hazard levels correspond well with post-event debris flow observations. Our results demonstrate that WRF-Hydro provides a compelling new physics-based tool to investigate and potentially forecast postfire hydrologic hazards at regional scales.

Chuxuan Li et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-345', Paul Santi, 05 Jan 2022
  • RC2: 'Comment on nhess-2021-345', Anonymous Referee #2, 25 Jan 2022

Chuxuan Li et al.

Chuxuan Li et al.


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Short summary
In January 2021 a storm triggered numerous debris flows in a wildfire burn scar in California. We use a hydrologic model to assess debris flow hazards in pre-fire and postfire scenarios. Compared to pre-fire conditions, the postfire simulation yields dramatic increases in total and peak discharge, substantially increasing debris flow hazards. Our work demonstrates the utility of 3-D hydrologic models for investigating and potentially forecasting postfire debris flow hazards at regional scales.