Pre-fire assessment of post-fire debris-flow hazards in the Santa Fe Municipal Watershed
Wildfire greatly heightens debris‑flow risk in the Santa Fe Watershed. Modelling shows >90% likelihood in most fire–rain scenarios. Fuel‑treated sub‑basins had lower burn severity, debris‑flow likelihood, and sediment volume, though benefits declined with harsher conditions. Treatments and mitigation can reduce future impacts.
Subject Tags
- Climate impacts
- Fire management
- Watersheds
Abstract
Background: Wildfires are increasing in size and severity due to climate change combined with overstocked forests. Fire increases the likelihood of debris flows, posing significant threats to life, property, and water supplies.
Aims: We conducted a debris-flow hazard assessment of the Santa Fe Municipal Watershed (SFMW) to answer two questions: (1) where are debris flows most likely to occur; and (2) how much debris might they produce? We also document the influence of fuel treatments on fire severity and debris flows.
Methods: We modelled post-fire debris-flow likelihood and volume in 103 sub-basins for 2-year, 5-year, and Probable Maximum Precipitation rainfalls following modelled low-, moderate-, and high-severity wildfires.
Key Results: Post-fire debris-flow likelihoods were >90% in all but the lowest fire and rain scenarios. Sub-basins with fuel treatments had the lowest burn severities, debris-flow likelihoods, and sediment volumes, but treatment effects decreased with increased fire severity and rain intensity.
Conclusions: Post-fire debris flows with varying debris volumes are likely to occur following wildfire in the SFMW, but fuel treatments can reduce likelihood and volume.
Implications: Future post-fire debris flows will continue to threaten water supplies, but fuel reduction treatments and debris-flow mitigation provide opportunities to minimise effects.
Citation
Lopez, M., Margolis, E., Tillery, A., Bassett, S. and Hook, A., 2024. Pre-fire assessment of post-fire debris-flow hazards in the Santa Fe Municipal Watershed. International Journal of Wildland Fire, 33(9), p.WF23065. https://doi.org/10.1071/WF23065
TNC Authors
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Steve Bassett
Director of Conservation Programs, New Mexico
The Nature Conservancy
Email: sbassett@tnc.org