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Christian Torgersen

Research Landscape Ecologist

Forest and Rangeland Ecosystem Science Center

Office Phone: 206-616-1874
Fax: 541-750-1069
ORCID: 0000-0001-8325-2737

University of Washington
College of Forest Resources
Seattle , WA 98195-2100

Supervisor: Martin Fitzpatrick
Abstract Dams have been a fundamental part of the U.S. national agenda over the past two hundred years. Recently, however, dam removal has emerged as a strategy for addressing aging, obsolete infrastructure and more than 1,100 dams have been removed since the 1970s. However, only 130 of these removals had any ecological or geomorphic assessments, and fewer than half of those included before- and after-removal (BAR) studies. In addition, this growing, but limited collection of dam-removal studies is limited to distinct landscape settings. We conducted a meta-analysis to compare the landscape context of existing and removed dams and assessed the biophysical responses to dam removal for 63 BAR studies. The highest...
Categories: Publication; Types: Citation
Water temperature data were collected in summer 2018 and 2019. Temperature data loggers were deployed in tributary confluences and the mainstem of the lower Priest River between Priest Lake Outlet Dam and the confluence with the Pend Oreille River. Data loggers were checked every 2 to 3 weeks throughout the summer. Data for Lagrangian longitudinal thermal profiles were obtained on August 21, 2018 and August 7, 2019.
This dataset includes georeferenced high-resolution, airborne thermal infrared (TIR) imagery, a polyline shapefile of the channel centerline, and a tabular file with longitudinal stream temperature profiles for Hat Creek, California. The two aerial TIR surveys were conducted with a helicopter by NV5 Geospatial (formerly Quantum Spatial, Inc.) and are published as two raster mosaics in GeoTiff format with a resolution of 0.5 m. The TIR mosaics and longitudinal stream temperature profiles contain corrected surface temperatures in degrees C (multiplied by 10 to create an unsigned integer pixel type). The TIR dataset encompasses a 64.6-km reach of Hat Creek that extends from 50 m upstream of the confluence with Lost...
Aging infrastructure coupled with growing interest in river restoration has driven a dramatic increase in the practice of dam removal. With this increase, there has been a proliferation of studies that assess the physical and ecological responses of rivers to these removals. As more dams are considered for removal, scientific information from these dam‐removal studies will increasingly be called upon to inform decisions about whether, and how best, to bring down dams. This raises a critical question: what is the current state of dam‐removal science in the United States? To explore the status, trends, and characteristics of dam‐removal research in the U.S., we searched the scientific literature and extracted basic...
Categories: Publication; Types: Citation
This data release combines seven airborne thermal infrared (TIR) remote sensing data sets of stream temperature collected along the mainstem of the Middle Fork John Day River (MFJD) in Oregon from 1994 to 2003. Years 1994, 1995, 1996, 1998, and 2002 have single datasets. Year 2003 has two data sets. Most of the TIR data covered the upstream half of the MFJD mainstem between river km 50 and 110, while the 2002 profile covers the lower half starting at the confluence of the MFJD with the North Fork John Day River through river kilometer 64. All TIR data sets were collected by helicopter in an upstream direction in August with the intent of capturing data at or near the maximum summer daily stream temperature. Ground-truthing...
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