Presenter/s: David (DJ) Bandrowski
Symposium Session: 2020 - 11 Dam removal in the Pacific Northwest
Topics covered: beavers, community involvement, fish passage, floodplain, hydraulics, instream structure (culvert/bridge/dam), riparian, risk and resilience, sediment transport, and stream
ABSTRACT
Four dams on the Klamath River are planned for removal in 2022 to restore volitional fish passage and salmonid habitat across more than 400 miles of river in the upper Klamath basin. During dam removal a substantial portion of the accumulated sediment will be released to the river downstream in a relatively short period of time. The release of reservoir sediment has the potential to impact downstream reaches in a variety of ways across a range of temporal and spatial scales. Sediment erosion, transport, and deposition provide the underlying physical framework for the responses of aquatic and riparian ecosystems to dam removal. Thus, pre-dam removal baseline survey of river bed bathymetry and near shore terrestrial topography are necessary to understand potential responses and impacts to flood hydraulics, geomorphic evolution, and sediment transport dynamics. System-wide topographic surveys will underpin a quantitative understanding of both the short and long term river response to dam removal. This data collection effort will also serve as the foundational dataset to be used in the future to quantify and compare physical change and sediment transport processes over time.
During the summer of 2018 a multi-agency team collected this topographic data across the Klamath basin from the estuary to Iron Gate Dam. Phase I of the project was an Aerial Imagery and LiDAR (topo-bathy) survey flown in June of 2018 by Quantum Spatial Inc. (QSI) with funding support from USGS, NOAA, KRRC, and others. Phase II was a bathymetric boat-based hydrographic multi-beam sonar survey through a collaboration between the Yurok Tribe, Hewlett Foundation and US Army Corps of Engineers – Engineering Research and Development Center (ERDC). Currently the multiagency team is in the process of completing Phase III which is the post-processing of the entire data set into a fully integrated mosaic that will produce a seamless topographic Digital Terrain Model (DTM) of the entire Klamath River. Phase IV will be the development of a 2D-Hydrodynamic Model of the river’s existing flow conditions that will be implemented by the Bureau of Reclamation – Technical Service Center (TSC) – Sedimentation and River Hydraulics (SRH) Group. The final goal of the project is to have a foundational data set that management and the scientific community will utilize to better understand the effects of dam removal, measure geomorphic evolution, and help monitor the biological response of a newly free-flowing Klamath River.