SEDHYD-2023, Sedimentation and Hydrologic Modeling Conference

Full Program »

View File
PDF
0.7MB

Remote Sensing of Geomorphic Change In Mulched and Unmulched Watersheds Burned In The 2020 East Troublesome Fire, Colorado

Remote sensing of geomorphic change in mulched and unmulched watersheds burned in the 2020 East Troublesome Fire, Colorado

John T. Murray, Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO, jmurr21@colostate.edu

Peter A. Nelson, Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO, peter.nelson@colostate.edu

Abstract

Wildfires often lead to elevated levels of surface runoff and transport of surface sediment and debris, potentially resulting in areas of erosion and deposition, posing threats to downstream structures, and degrading water quality in downstream channels and riparian zones. To mitigate these risks to human safety, infrastructure, and water supply, management agencies may apply post-fire treatments aimed at reducing runoff and erosion. Mulching – application of material such as straw or wood directly on the burned surface – is a commonly used post-fire treatment and has been shown at the hillslope scale to reduce erosion from rainfall impacts and surface runoff. However, the effects of mulching at the watershed scale are generally unknown. This gap in knowledge provides a valuable opportunity for our research to have a profound impact on the implementation of mulching in the future.

We have been monitoring paired mulched/unmulched watersheds burned in the 2020 East Troublesome Fire, the second-largest wildfire in Colorado’s recorded history. Our objectives are to determine how mulch applications affect the distribution and magnitude of erosion and deposition across the watershed, and to relate these findings to geomorphic and fire characteristics to inform future post-fire mulching operations. Spatial patterns of erosion and deposition are quantified by differencing high-resolution digital elevation models (DEM), including one pre-fire airborne LiDAR dataset collected in 2020 and several post-fire DEMs generated from drone-based imagery using structure-from-motion (SfM) processing.

We began collecting high resolution (~3 cm/pixel) aerial imagery in mid-July 2022 of 6 watersheds draining into Willow Creek, and portions of the Willow Creek channel and riparian zone. During summer 2022, the study area experienced many hillslope failures and debris flows resulting in repeated closures of highway 125 that runs adjacent to Willow Creek. Alignment and differencing of drone-based imagery has been performed using a co-registration workflow during SfM processing, enabling detection of topographic changes on the order of a few centimeters. We will soon begin data analysis focusing on quantifying the sediment transport within the watersheds and from the watershed outlets to Willow Creek. Repeat drone flights will be conducted through early fall to allow for further analysis of the sediment transport occurring in these watersheds and Willow Creek itself. Ultimately these findings will be related to precipitation intensity, slope, burn severity, and mulching application. These results should provide guidance for prioritization of future post-fire mulching operations.

John Murray
Colorado State University
United States

Peter Nelson
Colorado State University
United States

 



Powered by OpenConf®
Copyright©2002-2021 Zakon Group LLC