Email:
jbountry@usbr.gov
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Abstract Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals--particularly large dams--and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal...
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Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m 3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011-September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial...
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Two large dams were removed from the Elwha River in Washington, starting in 2011 and ending in 2014. The Elwha and the Glines Canyon dams were located approximately 7 km and 20 km upstream, respectively, from the Elwha River's mouth on the Strait of Juan de Fuca. The dams trapped over 20 million cubic meters of sediment. Dam removal changed the river's sediment budget and water flow, which affected the river's morphology. This data release presents digital elevation models (DEMs), orthomosaic images, dam height measurements, sediment measurements and river streamgage data that were collected by the U.S. Geological Survey (USGS) and U.S. Bureau of Reclamation (USBR) to support studies on morphodynamic and sediment...
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Dam decommissioning is rapidly emerging as an important river restoration strategy in the U.S., with several major removals recently completed or in progress. But few studies have evaluated the far-reaching consequences of these significant environmental perturbations, especially those resulting from removals of large (>10-15 m tall) structures during the last decade. In particular, interactions between physical and ecological aspects of dam removal are poorly known. From recent work, however, observations are now available from several diverse settings nationwide to allow synthesis of key physical and ecological processes associated with dam removals, including fish and benthic community response, reservoir erosion,...
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Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether these concerns are warranted at a particular site. We used a dam-removal science database supplemented with other information sources to explore seven frequently raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are the following: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream...
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