Filters: Tags: dam removal (X)49 results (185ms)
Large-scale dam removal on the Elwha River, Washington, USA: River channel and floodplain geomorphic change
A substantial increase in fluvial sediment supply relative to transport capacity causes complex, large-magnitude changes in river and floodplain morphology downstream. Although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution, few opportunities exist to quantify those processes over field scales. We investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years. As 10.5 million t (7.1 million m3) of sediment was released from two former...
Effects of removal of a small dam on downstream macroinvertebrate and algal assemblages in a Pennsylvania stream
Dam removal is often proposed as way to restore ecological integrity to rivers and streams, but ecological responses to dam removals are poorly understood, especially for downstream benthic communities. We examined the responses of benthic macroinvertebrate and algal assemblages in downstream reaches to the removal of a small, run-of-river dam on Manatawny Creek, Pennsylvania. Benthic macroinvertebrates, algae, and habitat characteristics were monitored upstream and downstream of the dam for 4 mo before removal, 3 mo after partial removal (i.e., when the impoundment was largely eliminated but sediment remained trapped behind the remaining structure), and 12 mo after complete dam removal. Macroinvertebrate density,...
Morphological responses and sediment processes following a typhoon‐induced dam failure, Dahan River, Taiwan
The rates and styles of channel adjustments following an abrupt and voluminous sediment pulse are investigated in the context of site and valley characteristics and time-varying sediment transport regimes. Approximately 10.5 x 106m3 of stored gravel and sand was exposed when Barlin Dam failed during Typhoon WeiPa in 2007. The dam was located on the Dahan River, Taiwan, a system characterized by steep river gradients, typhoon- and monsoon-driven hydrology, high, episodic sediment supply, and highly variable hydraulic conditions. Topography, bulk sediment samples, aerial photos, and simulated hydraulic conditions are analyzed to investigate temporal and spatial patterns in morphology and likely sediment transport...
Characterization of seafloor photographs near the mouth of the Elwha River during the first two years of dam removal (2011-2013)
We characterized seafloor sediment conditions near the mouth of the Elwha River from underwater photographs taken every four hours from September 2011 to December 2013. A digital camera was affixed to a tripod that was deployed in approximately 10 meters of water (Tripod location from September 2011 to April 2013: 48.15333, -123.55931; tripod location from April 2013 to December 2013: 48.15407, -123.55444). Each photograph was qualitatively characterized as one of six categories: (1) base, or no sediment; (2) low sediment; (3) medium sediment; (4) high sediment; (5) turbid; or (6) kelp. For base conditions, no sediment was present on the seafloor. Low sediment conditions were characterized by a light dusting of...
Suspended sediment, dissolved organic carbon, and dissolved nitrogen export during the dam removal process
Total suspended solids (TSS), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) loads were calculated for all stages of the dam removal process (dewatering, breaching, and removal) at various points upstream, within, and downstream of Lowell Mill Impoundment on the Little River, North Carolina. The impoundment dewatering exported loads of TSS, DOC, and TDN which were all 1–2 orders of magnitude less than loads associated with historic floods. Conversely, floods exiting the former impoundment following dam removal produced TSS, DOC, and TDN loads comparable to, but slightly greater (1.2–1.75 times) than historic floods. Exported loads were greatest following the complete removal of the dam, most...
Although dam removal has been increasingly used as an option in dam management, and as a river restoration tool, few studies provide detailed quantitative assessment of the geomorphological response of rivers to dam removal. In this study, we document the response of the Pine River, Michigan, to the gradual removal of Stronach Dam. In 1996, prior to the initiation of removal, 31 permanent cross-sectional transects were established in the 10-km study area. These transects were surveyed annually during the course of the removal (1996–2003) and for the three years following removal (2004–2006). Dam removal resulted in progressive headcutting of sediments in the former impoundment, extending upstream 3.89 km of the...
Long-term implications of dam removal for macroinvertebrate communities in Michigan and Wisconsin Rivers, United States
The removal of the numerous ageing dams in the United States has become an important stream restoration technique. The extent to which the ecological damage done to streams by dams is reversed upon removal is unknown, especially on decadal time scales. The objectives of this study were to determine if macroinvertebrate assemblages within rivers recover following the removal of a dam and to estimate the time needed for recovery. A space‐for‐time substitution approach was used on eight rivers in various stages of recovery following a dam removal, ranging from <1 to 40 years post‐removal. Within each river, macroinvertebrates were sampled in a zone unaffected by the dam removal (reference zone) and two zones impacted...
Migration of a coarse fluvial sediment pulse detected by hysteresis in bedload generated seismic waves
Seismic signals near rivers are partially composed of the elastic waves generated by bedload particles impacting the river bed. In this study, we explore the relationship between this seismic signal and river bedload transport by analyzing high-frequency broadband seismic data from multiple stations along the Chijiawan River in northern Taiwan following the removal of a 13 m check dam. This dam removal provides a natural experiment in which rapid and predictable changes in the river's profile occur, which in turn enables independent constraints on spatial and temporal variation in bedload sediment transport. We compare floods of similar magnitudes with and without bedload transport, and find that the amplitude of...
Environmental DNA (eDNA) is an Effective Tool to Track Recolonizing Migratory Fish Following Large-Scale Dam Removal, field data
We collected environmental DNA (eDNA) data from the Elwha River, home to the world’s largest dam removal project, to track the spatial and temporal patterns of species responses following dam removal. In total, we collected data for 11 different fish taxa, sampled at 25 sites ranging across 56 river kilometers in a wilderness river for 4 years following dam removal. We show that eDNA can effectively be used to determine whether fish have recolonized past former dams, and in some cases determine the spatial extent of that recolonization.
Vegetation habitat units derived from 2014 aerial imagery and field data for the Elwha River estuary, Washington
Estuary vegetation cover delineated from 28 August 2014 0.15-meter-resolution NPS Elwha PlaneCam aerial imagery at a scale of 1:1500.
This database is the result of an extensive literature search aimed at identifying documents relevant to the emerging field of dam removal science. In total the database contains 214 citations that contain empirical monitoring information associated with 181 different dam removals across the United States and abroad. Data includes publications through 2016 and supplemented with the U.S. Army Corps of Engineers National Inventory of Dams database, U.S. Geological Survey National Water Information System and aerial photos to estimate locations when coordinates were not provided. Publications were located using the Web of Science, Google Scholar, and Clearinghouse for Dam Removal Information.
The ability to predict the effects of dam removal in highly sediment-filled systems is increasingly important as the number of such dam removal cases continues to grow. The cost and potential impacts of dam removal are site-specific and can vary substantially depending on local conditions. Of specific concern in sediment-impacted removals is the volume and rate of reservoir deposit erosion. The complexity and potential accuracy of modeling methods used to forecast the effects of such dam removals vary substantially. Current methods range from predictions based on simple analysis of pre-dam channel geometry to sophisticated data-intensive, three-dimensional numerical models. In the work presented here, we utilize...
Note: This item is being used in a data pipeline that supports the Dam Removal Information Portal. We recommend users directly access the American River's Dam Removal Database from Figshare: https://doi.org/10.6084/m9.figshare.5234068. In the last century, the U.S. led the world in dam building for many purposes, including hydropower, irrigation, flood control and water storage. While dams can benefit society, they also cause considerable harm to rivers. Dams have depleted fisheries, degraded river ecosystems, and altered recreational opportunities on nearly all of our nation’s rivers. Today, many dams that were once at the epicenter of a community’s livelihood are now old, unsafe or no longer serving their intended...
This portion of the data release presents riparian plant species richness (number of unique taxa) data from plots sampled in the Elwha River estuary, Washington, in 2007 and 2014. In August 2007, we established 21 vegetation plots within the study area in a stratified random fashion, with three to five plots in five of the vegetation cover types denoted in the habitat classification maps: mixed riparian forest, willow-alder forest, riparian shrub, emergent marsh/marsh-shrub transition, and dunegrass. Each plot was 100 square meters, usually 10 m x 10 m, but in areas where the vegetation patch was narrow, plots were either 4 m x 25 m or 5 m x 20 m. We visually estimated percent cover by species of all vascular plants...
Vegetation habitat units derived from 2009 aerial imagery and field data for the Elwha River estuary, Washington
Estuary vegetation cover delineated from 11 September 2009 1-meter-resolution NAIP aerial imagery at a scale of 1:1500.
Vegetation habitat units derived from 2013 aerial imagery and field data for the Elwha River estuary, Washington
Estuary vegetation cover delineated from 26 August 2013 0.15-meter-resolution NPS Elwha PlaneCam aerial imagery at a scale of 1:1500.
Geomorphic habitat units derived from 2013 aerial imagery and elevation data for the Elwha River estuary, Washington
Estuary geomorphic units delineated at a scale of 1:1500 using a combination of (a) 26 August 2013 0.15 meter resolution NPS Elwha PlaneCam aerial imagery; and (b) elevation-colored and hillshaded digital elevation models from USGS backpack/jetski topobathy surveys (16 September 2013) for areas < MHHW and aerial lidar surveys (17 October 2012) supplemented with NPS Elwha PlaneCam SfM photogrammetry data (19 September 2013) for elevations > MHHW.
Geomorphic habitat units derived from 2014 aerial imagery and elevation data for the Elwha River estuary, Washington
Estuary geomorphic units delineated at a scale of 1:1500 using a combination of (a) 28 August 2014 0.15 meter resolution NPS Elwha PlaneCam aerial imagery; and (b) elevation-colored and hillshaded digital elevation models from USGS backpack/jetski topobathy surveys (5-8 September 2014) for areas < MHHW and aerial lidar surveys (7 November 2014) supplemented with NPS Elwha PlaneCam SfM photogrammetry data (30 September 2014) for elevations > MHHW.
Geomorphic habitat units derived from 2009 aerial imagery and elevation data for the Elwha River estuary, Washington
Estuary geomorphic units delineated at a scale of 1:1500 using a combination of (a) 11 September 2009 1 meter resolution NAIP aerial imagery; and (b) elevation-colored and hillshaded digital elevation models from USGS backpack/jetski topobathy surveys (17 September 2009) for areas < MHHW and aerial lidar surveys (4-6 April 2009) for elevations > MHHW.
Riparian vegetation abundance (percent cover) in the Elwha River estuary, Washington, in 2007 and 2014
This portion of the data release presents riparian plant species abundance (percent cover) data from plots sampled in the Elwha River estuary, Washington, in 2007 and 2014. In August 2007, we established 21 vegetation plots within the study area in a stratified random fashion, with three to five plots in five of the vegetation cover types denoted in the habitat classification maps: mixed riparian forest, willow-alder forest, riparian shrub, emergent marsh/marsh-shrub transition, and dunegrass. Each plot was 100 square meter, usually 10 m x 10 m, but in areas where the vegetation patch was narrow, plots were either 4 m x 25 m or 5 m x 20 m. We visually estimated percent cover by species of all vascular plants within...