Liu et al. (2025) Temporal persistence of postfire flood hazards under present and future climate conditions in southern Arizona, USA

Identification

• Journal: Natural hazards and earth system sciences
• Year: 2025
• Date: 2025-10-24
• Authors: Tao Liu, Luke A. McGuire, Ann Youberg, Charles J. Abolt, A. L. Atchley
• DOI: 10.5194/nhess-25-4135-2025

Research Groups

• Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
• Department of Geosciences, University of Arizona, Tucson, AZ, USA
• Arizona Geological Survey, University of Arizona, Tucson, AZ, USA

Short Summary

This study investigates the temporal evolution of post-fire hydrologic parameters and quantifies changes in flash flood peak discharges under future climate conditions in a 49.4 km² watershed in southern Arizona. It finds that while soil hydraulic properties recover over three post-fire years, climate change-driven rainfall intensification will significantly increase the magnitude and persistence of post-fire flood hazards, potentially doubling the likelihood of 100-year floods by mid-century under medium emissions scenarios.

Objective

• To use rainfall and runoff observations to constrain temporal changes in effective hydrologic parameters following fire for watershed-scale flash flood simulations.
• To use the calibrated model to quantify changes in post-fire flash flood peak discharges between the present day and the middle–late 21st century due to rainfall intensification under future climate conditions.

Study Configuration

• Spatial Scale: Upper Cañada del Oro (CDO) watershed, southern Arizona, USA, with an area of 49.4 km².
• Temporal Scale: Observed post-fire recovery over 3 years (2020–2023) following the 2020 Bighorn Fire. Future climate projections for mid-21st century (2045–2074) and late-21st century (2075–2100) under SSP2-4.5 (medium emissions) and SSP5-8.5 (high emissions) scenarios, compared to a historical reference period (1950–2014).

Methodology and Data

• Models used:
  • Hydrologic model: KINEROS2 (K2)
  • Climate models: Coupled Model Intercomparison Project Phase 6 (CMIP6) via Localized Constructed Analogs version 2 (LOCA2) for temperature projections.
  • Rainfall frequency estimates: NOAA Atlas 14.
• Data sources:
  • Rainfall: Six Automated Local Evaluation in Real Time (ALERT) tipping-bucket rain gauges and four additional tipping-bucket rain gauges installed by the authors.
  • Runoff: Pressure transducer at the outlet of the CDO watershed.
  • Soil moisture: Daily volumetric soil moisture (0–0.05 m depth) from Climate Forecast System Reanalysis (CFSR).
  • Remote sensing: Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) from MODIS Terra satellite imagery (500 m resolution).
  • Topography: 1 m lidar-derived digital elevation model (DEM).
  • Soil burn severity: Burned Area Emergency Response (BAER) team mapping using differenced normalized burn ratio (dNBR) and field observations.

Main Results

• Soil saturated hydraulic conductivity (Ksp) increased from approximately 3.06 × 10⁻⁶ m s⁻¹ in the first post-fire year to 8.06 × 10⁻⁶ m s⁻¹ in year 2 and 1.67 × 10⁻⁵ m s⁻¹ in year 3. The average rate of change was 6.67 × 10⁻⁶ m s⁻¹ per year.
• Net capillary drive (Gp) increased from 0.019 m in the first post-fire year to 0.030 m in the third.
• Hydraulic roughness (nc) remained relatively constant, fluctuating between 0.085 and 0.105 s m⁻¹/³.
• Under the SSP2-4.5 scenario, the likelihood of a 100-year flood (180 m³ s⁻¹) is projected to double by the mid-21st century.
• Under the SSP5-8.5 scenario, the maximum expected discharge associated with a post-fire flood (909 m³ s⁻¹) could be triggered by a 10-year rainstorm covering approximately 90% of the watershed by the late 21st century.
• Rainfall intensification will lead to greater persistence of elevated flood hazards following fire by the late 21st century under both SSP2-4.5 and SSP5-8.5 scenarios.
• Peak flows under future warming scenarios are projected to be 2.1–3.6 times greater than reference levels for a specific annual recurrence interval (ARI) in the first post-fire year.
• A rainstorm with a peak intensity of 3.33 × 10⁻⁶ m s⁻¹ over 2640 s in the first post-fire year produced a peak discharge of 35 m³ s⁻¹. In contrast, a rainstorm with a peak intensity of 8.61 × 10⁻⁶ m s⁻¹ over 4260 s in the third post-fire year produced no measurable flow.

Contributions

• Provided better constraints on the temporal changes in watershed-scale effective hydrologic parameters (soil saturated hydraulic conductivity, net capillary drive, and hydraulic roughness) following fire using observed rainfall-runoff data and a hydrologic model.
• Quantified the combined effects of post-fire hydrologic recovery and climate-change-driven rainfall intensification on future flash flood peak discharges.
• Offered valuable guidance for parameterizing post-fire hydrologic models and assessing post-fire hydrologic hazards in infiltration-excess-dominated settings, particularly in the southwestern USA.
• Demonstrated the increased persistence of post-fire flood hazards under future climate scenarios due to rainfall intensification.

Funding

• U.S. Geological Survey (grant/cooperative agreement no. G23AC00447-00 and grant no. G25AP00142)
• Pima County Regional Flood Control District (grant agreement no. RFCD-2020-003)
• Laboratory Directed Research and Development program of Los Alamos National Laboratory (project no. 20240448ER)

Citation

@article{Liu2025Temporal,
  author = {Liu, Tao and McGuire, Luke A. and Youberg, Ann and Abolt, Charles J. and Atchley, A. L.},
  title = {Temporal persistence of postfire flood hazards under present and future climate conditions in southern Arizona, USA},
  journal = {Natural hazards and earth system sciences},
  year = {2025},
  doi = {10.5194/nhess-25-4135-2025},
  url = {https://doi.org/10.5194/nhess-25-4135-2025}
}

Generated by BiblioAssistant using gemini-2.5-flash (Google API)