New Mexico Geological Society Annual Spring Meeting — Abstracts

High severity wildfires are becoming increasingly common in western forests. Burned areas are prone to increased soil erosion, stream flooding, and water quality impairment. Proactive management strategies are necessary for watershed protection and recovery from forest fire. The > 341,000-acre 2022 Hermits Peak/Calf Canyon (HP/CC) fire severely affected multiple watersheds in northern New Mexico, including major, critical areas like the Upper Pecos, Gallinas, and Tecolote Watersheds, impacting regional water supplies and ecosystem services. Soil burn severity was high across significant portions, creating hydrophobic soils that directly led to major post-fire flooding and debris flows in the region.

This study reproduced methods used by Fairfax, et al. (2024) to examine the influence of beaver occupation on burn severity and post-fire sediment loads in the 2022 HP/CC burn scar. Beaver dams were located via satellite imagery throughout the HP/CC burn scar. Beaver dam capacity results calculated by the Beaver Restoration Assessment Tool (BRAT) were downloaded for the Gallinas, Sapello, and Mora watersheds and segmented into bundles (< 2; 2-5; 5-12; and >12 dams/km). Dam capacity is used as a measure of riparian characteristics that would influence fire severity regardless of beaver occupation. A Difference Normalized Burn Ratio (dNBR) was calculated throughout the HP/CC burn area then used to analyze the burn intensity in valley bottoms near dams compared to valley bottoms without dams but within the same dam capacity range. Additionally, turbidity was measured above and below two active and two inactive beaver dam sites on the Rio Pueblo near Sipapu downstream of the HP/CC burn area in Spring 2026.

Analyses showed that for river reaches with the same dam capacity, those with beavers had a statistically significantly lower dNBR than those without beavers (p < 0.0001). Analyses also showed that many of the beaver-occupied river valleys did not burn at all. At all sites, turbidity values tended to be lower below dams than above them. This study supports beaver reintroduction or beaver dam mimicry as a low-cost, low-technology, and nature-based fire mitigation and post-fire restoration tool.

References:

1. Fairfax, E., Whipple, A., Wheaton, J.M., Osorio, B., Miller, J., Kirksey, K., Perez, N., Gilbert, J.T., and Jordan, C.E., (2024), Impacts of beaver dams on riverscape burn severity during megafires in the Rocky Mountain region, western United States, in Florsheim, J.L., O Dowd, A.P., and Chin, A., eds., Biogeomorphic Responses to Wildfire in Fluvial Ecosystems: Geological Society of America Special Paper 562, p. 131–151, https://doi.org/10.1130/2024.2562(07).