LONG-TERM BIOPHYSICAL MONITORING OF A DAM REMOVAL IN AN UPLAND CATCHMENT

2019 ◽  
Author(s):  
Francis J. Magilligan ◽  
◽  
Keith Nislow
Keyword(s):  
Dam Removal

scholarly journals Time Series Changes in Fish Assemblages and Habitat Structures Caused by Partial Check Dam Removal

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3357
Author(s):  
Shigeya Nagayama ◽  
Nobuo Ishiyama ◽  
Taro Seno ◽  
Hideyuki Kawai ◽  
Yoichi Kawaguchi ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Habitat Preferences ◽  
Dam Removal ◽  
Temporal Changes ◽  
Check Dam ◽  
Side Channels ◽  
Unit Scale ◽  
Bed Materials ◽  
Channel Unit

Despite a steep increase in dam removal projects, there are few studies on the biophysical responses to dam removal. In this study, we evaluated the short-term (1.5 years) and long-term (5.5 years) effects of partial check dam removal on fish assemblages and their habitats. First, the habitat preferences of fish were examined at a channel unit scale: pools, rapids, and side channels satisfied the seasonal habitat requirements of the fish assemblages. Partial check dam removal increased the abundance of these habitats and diversified the habitat structures owing to the sediment release from the dam; in contrast, the bedrock distinctly decreased 1.5 years after dam removal. However, 5.5 years after dam removal, the bedrock proportion increased, and the habitat structures were simplified again owing to the re-transportation of sediments. Similar temporal changes were also determined through a reach-scale analysis with a change in the bed materials. Anadromous Oncorhynchus masou began to spawn and recolonize in the upstream section of the dam after the dam removal, causing similar assemblage compositions between the downstream and upstream sections. The abundance of Salvelinus malma and Noemacheilus barbatulus toni in the upstream reaches decreased over time after the dam removal. The temporal changes in the biophysical responses suggest that long-term monitoring is indispensable for the reliable evaluation of dam removal effects.

LONG-TERM TAXON-SPECIFIC RESPONSES OF MACROINVERTEBRATES TO DAM REMOVAL IN A MID-SIZED SWEDISH STREAM

2012 ◽  
Vol 29 (9) ◽  
pp. 1082-1089 ◽  
Author(s):  
B. M. Renöfält ◽  
A. G. C. Lejon ◽  
M. Jonsson ◽  
C. Nilsson
Keyword(s):  
Dam Removal

Long term change observation of river terrain due to dam removal in Central Taiwan

2020 ◽  
Author(s):  
Tingray Liu ◽  
Chunhung Wu
Keyword(s):  
Cross Sections ◽  
Return Period ◽  
Dam Removal ◽  
The Third ◽  
Time Period ◽  
Accumulated Rainfall ◽  
Time Periods ◽  
Central Taiwan ◽  
First Time

<p>This research focuses on the long-term geomorphologic change in the upstream of the silt dams in the Lan-daw rivers watershed in central Taiwan, adopts the long-term rainfall records in the Lan-daw rivers watershed to calculate the 1-day, 2-days, 3-days accumulated rainfall with different return period, and analyzes the relationship between the geomorphologic change and the accumulated rainfall. This research builds the Digital Surface Models based on the photos shot by UAV at 9 different times. The river in upstream of the Lan-daw rivers watershed is sinuous. The research classifies 3 time periods from 2010 to August, 2019, including the first time period from 2010 to June, 2017, the second time period from June, 2017 to Nov. 2018, and the third time period from Nov. 2018 to Aug. 2019. The target in the first time period is to observe the geomorphologic change after the first dam removal, that in the second time period to observe the geomorphologic change in the 2 years after dam removal, and that in the third time period to observe the geomorphologic change after the second dam removal.</p><p>The longitudinal slopes in the first, second, and third time periods are -30.3%, 14.8%, and 5.98%, and the knickpoint in the longitudinal profile in the first and second time periods occur in the upstream 20 m of the silt dam and that in the third time periods occurs in the upstream 45 m of the silt dam. The research classifies the cross-sections profiles into 3 groups, including the first group from C1 to C7 cross sections, the second group from C8 to C14 cross sections, and the third group from C15 to C22 cross sections. The geomorphologic change in the first group near the silt dam is the most obvious in the three groups. The geomorphologic change in the three groups in the first time period are -6.43 m to -8.13 m (scouring), those in the second time period are 0.23 m to 0.34 m (deposition), and those in the third time period are 0.46 m (deposition) to -1.78 m (scouring). Based on the analysis of the long-term rainfall record in the Lan-daw river watershed, the return period of the heaviest rainfall from 2015 to Aug. 2019 is less than 20-year return period. This means that the geomorphologic change in upstream of silt dam in the Lan-Daw river watershed is easy induced in the short time after dam removal.</p>

scholarly journals Simulation and control of morphological changes due to dam removal in the Sandy River, Oregon, USA

2015 ◽  
Vol 367 ◽  
pp. 207-214
Author(s):  
Y. Ding ◽  
M. S. Altinakar
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Morphological Changes ◽  
Dam Removal ◽  
Roughness Coefficient ◽  
Model Parameters ◽  
Evolution Simulation ◽  
Bed Roughness ◽  
Bed Changes

Abstract. A one-dimensional channel evolution simulation model (CCHE1D) is applied to assess morphological changes in a reach of the Sandy River, Oregon, USA, due to the Marmot Dam removal in 2007. Sediment transport model parameters (e.g. sediment transport capacity, bed roughness coefficient) were calibrated using observed bed changes after the dam removal. The validated model is then applied to assess long-term morphological changes in response to a 10-year hydrograph selected from historical storm water records. The long-term assessment of sedimentation gives a reasonable prediction of morphological changes, expanding erosion in reservoir and growing deposition immediately downstream of the dam site. This prediction result can be used for managing and planning river sedimentation after dam removal. A simulation-based optimization model is also applied to determine the optimal sediment release rates during dam-removal that will minimize the morphological changes in the downstream reaches.

Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders?

2019 ◽  
Vol 42 ◽  
Author(s):  
John P. A. Ioannidis
Keyword(s):  
Mental Health ◽  
Mental Disease ◽  
Brain Disorders ◽  
Social Stressors ◽  
Labor Education ◽  
Mental Diseases ◽  
Long Term Follow Up ◽  
Political Decisions

AbstractNeurobiology-based interventions for mental diseases and searches for useful biomarkers of treatment response have largely failed. Clinical trials should assess interventions related to environmental and social stressors, with long-term follow-up; social rather than biological endpoints; personalized outcomes; and suitable cluster, adaptive, and n-of-1 designs. Labor, education, financial, and other social/political decisions should be evaluated for their impacts on mental disease.

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