Hillslope Sediment Yield and Delivery to Whiskeytown Reservoir in Response to the 2018 Carr Fire, Northern California
Abstract
Post-fire hillslope sediment yields are commonly substantially greater than pre-fire yields, but the degree to which they increase can vary substantially. Published estimates range from a doubling of sediment yield after wildfire to an increase of more than three orders of magnitude, as a function of post-fire precipitation, slope, soil type, and the extent of vegetation loss. Effects of wildfire on sediment yield have important implications for hazards (debris-flow risk), ecosystem disturbance and recovery, and downstream water resources (storage capacity in reservoirs, as well as water quality). We present initial estimates of hillslope sediment export after the Carr Fire, a federally declared wildfire disaster that burned 93 hectares in northern California in July and August, 2018. High ambient temperatures and high wind speeds contributed to extreme fire behavior that burned forested and chaparral-covered hillslopes at high intensity. We estimate sediment yields from a portion of the Carr Fire burn area using a combination of bathymetric sonar surveys in Whiskeytown Lake, a federally owned reservoir entirely surrounded by the Carr Fire perimeter, and Structure-from-Motion aerial photogrammetry of the reservoir shoreline and the lowermost portions of streambeds draining into the reservoir. Reservoir bathymetry and hillslope/streambed topography were mapped in December 2018 (after the fire but before the winter storm season) and May-June 2019, after storm runoff had eroded hillslope material during a winter with above-average precipitation. We use the resulting measurements of geomorphic change, together with aerial photographic evidence, to estimate post-fire sediment yield, delivery mechanisms, and effects on reservoir capacity and water resources in Whiskeytown reservoir.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H23S2181D
- Keywords:
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- 1813 Eco-hydrology;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1860 Streamflow;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY