How snow modulates hydrogeomorphic change and recovery after fire

Colorado State University, Fort Collins CO

Investigators

Abstract

In the aftermath of wildfires, flooding, erosion, and debris flows can damage buildings, infrastructure, and waterways. This research will examine the role that snow plays in both short-term hazards and longer-term landscape recovery from fire. Focusing on the 2020 Cameron Peak and East Troublesome burn scars in northern Colorado, the project addresses how and why post-fire hazards and vegetation recovery vary between snow zones of the Rocky Mountains. Initial observations at these fires indicate that burned areas with limited snow have greater flooding, erosion, and debris flow activity during the first few years after fire compared to locations with deep winter snowpack. In contrast, vegetation recovery has proceeded more rapidly in low snow than in high snow areas. The research will explore reasons for these differences between snow zones, with the aim to identify what types of settings are most vulnerable to post-fire hazards. Findings will inform flash flood forecasts and help land managers prioritize actions such as erosion mitigation and channel stabilization. The project incorporates public outreach through a citizen science stream monitoring program and presentations to stakeholders, and it includes a 5th grade river field day, education resources for K-12 teachers, and undergraduate and graduate student training. The research will involve two main components: (1) evaluating causes of post-fire hazards during the first 1-3 years post-fire, and (2) examining snow changes and their effects on vegetation recovery over a decade or more post-fire. The hazard analysis will examine three possible causes for greater post-fire hazards in lower snow zones: (1) higher rainfall intensity; (2) greater overland flow generation, and (3) greater hillslope-stream connectivity. Rainfall analyses will use rain gauges and gridded rainfall products; overland flow analyses will use stream stage measurements and rill network mapping from drone imagery, and hillslope-stream connectivity metrics will be computed from LiDAR and drone topographic data. The snow and vegetation analysis will incorporate both a field and a remote sensing component. Field measurements will compare snowpack in burned and unburned areas, with a focus on how tree char depth affects snow albedo. Vegetation plot surveys and drone imagery will document vegetation recovery rates. Remote sensing analyses will extend the findings beyond the study fires to the full Southern Rockies eco-region, evaluating fire effects on snow-free dates and post-fire vegetation recovery rates. The combination of local field observations and regional scale analysis will enable connecting site-specific findings to their implications for larger watersheds. This award is co-funded by the Hydrologic Sciences and Gemorphology & Land-use Dynamics programs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.