Evaluating watershed response and increases in sediment loading to Willow Creek and Willow Creek Reservoir due to East Troublesome fire

Project ID: 22097
Principal Investigator: Kent Collins
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2022, 2023 and 2024
Keywords: None

Research Question

• What will be the response of the Willow Creek watershed in terms of sediment delivery to the channel and reservoir to large-scale wildfire?
• How effective will sediment abatement measures already in place be at reducing sediment loads to the creek and reservoir?
• What will be the increase in sediment loading to the reservoir? How long will it take sediment from the upper portions of watershed to reach the reservoir?

Increase in sediment loading will be largely dependent on hydrology. Large magnitude runoff events (even of short duration) could rapidly increase sediment loads, resulting in faster delivery of sediment to the creek and reservoir. If the hydrograph is primarily driven by snowmelt, sediment delivery will be attenuated. Multiple consecutive years of Repeat hydrographic surveys (including UAS and bathymetric surveys) following spring runoff would provide information necessary to track sediment deposition volumes and distribution as well as increase the likelihood of capturing an above-normal hydrological event.

Wide floodplains and overbank areas provide a large amount of potential sediment storage which could further delay delivery of sediment to the reservoir. Sediment mobilized from hillslopes in the upper watershed may reach Willow Creek, but may not reach the reservoir over the course of this three-year study.

Proposed data collection and analysis will provide answers to these questions and help determine the effectiveness of sediment abatement measures. Results will inform the formulation of future sediment management plans, fire response protocols, and repeat survey interval required to adequately identify watershed responses and potential dam safety hazards.

Need and Benefit

Proposed research meets the need by determining watershed and reservoir response to large-scale fires and measure changes in sediment loads to Willow Creek and Willow Creek Reservoir potentially impacting water delivery operations. Study data will be used to evaluate the effectiveness of sediment abatement measures in the watershed and reservoir, identify immediate dam safety hazards, and inform numerical models aimed at predicting watershed and water quality response to wildfires.

Contributing Partners

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Research Products

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Last Updated: 6/22/20