Sediment Sluicing Research Articles

Tracing sediment transport history using mineralogical fingerprinting in a river basin with dams utilizing sediment sluicing

Sediment causes a serious problem in relation to dam function. A cooperative sediment sluicing operation has been under way since 2017 to prevent sediment from accumulating in dams in the Mimi River, Miyazaki, Japan. To achieve a smooth and stable operation, it is very important to determine the sediment source and a sediment transport system to maintain the dam's function. In the current study, the source and transport of sediment from the Mimi River basin have been analyzed with X-ray diffraction (XRD) to reveal the peaks of mineral species. The sediment samples were collected in the Mimi River basin from the Tsukabaru Dam to the sea in an area including 4 dams and 5 tributaries. In addition, the minerals in samples collected in 2014, before the start of the sediment sluicing operation, and from 2018 to 2020, after the start of the operation, were analyzed. An evaluation of the similarity of the sediment at each sampling point based on the X-ray diffraction peaks of mineral species showed that sediment distributed upstream was transported downstream in the year when the sediment sluicing was done. This result indicates that the sediment sluicing operation at dams ensured the continuity of the sediment distribution in the Mimi River basin. In addition, an investigation done in 2020 showed that sediment particles very similar to those of the upstream tributaries were deposited downstream because of extensive flooding caused by a large typhoon. The management of sediment transport has the greatest importance in a river basin where a dam is to be constructed. It is possible to trace the history of the sediment distribution and movement resulting from the operation of sediment sluicing by using sediment mineral analysis.

Preliminary assessment of the impacts of sediment sluicing events on stream insects in the Mimi River, Japan

Dam sedimentation is a crucial issue that interferes with flood control and electric power generation. To address this, sediment dredging, bypass tunnel, flushing, and sluicing have been applied. Despite the potential impacts of these operations on stream environments, few studies have explored the environmental/ecological consequences of such regime shifts in sediment dynamics. Specifically, impacts of sediment sluicing on stream fauna have never been reported. This study assessed primary impacts of sediment sluicing events operated with the two cascade dams (the Saigo and Ouchibaru Dams) on stream insects in the lower Mimi River, Japan. The sediment sluicing, accompanied by a major flooding event in the river, was first operated in September 2017. Stream insect data downstream of the four cascade dams, including the two sluicing dams and a reference river, were collected yearly or biyearly in winter and summer from 2010 to 2018. Following the initiation of retrofitting the Saigo Dam for optimizing sediment sluicing, a downstream reach of the dam experienced marked perturbations in terms of both individual density and species richness. The density and richness dramatically decreased and the community significantly differed in winter 2017 from pre-impact conditions. The density, richness, and community composition subsequently recovered in winter 2018, even after the sediment sluicing impact, suggesting that the anticipated negative ecological impacts of the sluicing are limited. Non-metric multidimensional scaling and permutational multivariate analysis of variance revealed distinct differences in communities between summer and winter samples at non-regulated sites or sites farther downstream of the dam that are characterized by fewer Simuliidae in summer and relatively abundant Heptageniidae. This could serve as a reference for assessments of ecological consequences of sediment sluicing in the region.

Simulation of Sediment Flushing in Paonia Reservoir of Colorado

AbstractA one-dimensional sediment transport model (SRH-1D) was updated to simulate a sediment sluicing and flushing plan for the Paonia Reservoir, located on Muddy Creek in western Colorado. The P...

Environmental Impact Assessment Plan Due to Sediment Sluicing at Dams Along Mimikawa River System

The 2005 typhoon disasters taught us that the Mimikawa River system in Miyazaki Prefecture had various problems with sediments in the river basin (the riverbed in dam reservoirs rise so much that flooding risk increases, sediments captured at dams granulate the downstream river channel and destabilize the bridge piers in the downstream river channel). In one of the approaches to solve these problems simultaneously, since 2017, sediment sluicing at a series of dams has been operated cooperatively. Using this approach, we can expect that the river will recover its continuity of sediment movement, returning its physical environment and animal habitats to their original states. Based on environmental surveys and numerical analyses of the current conditions, we have predicted the environmental impacts due to sediment sluicing at dams and defined the method to assess them. This paper presents: 1) an overview of sediment sluicing at dams in the Mimikawa River system, 2) the analysis of the river environment prior to operating sediment sluicing at dams, 3) the prediction of the impacts of sediment sluicing at dams in the river environment, 4) the environmental impact assessment after operating sediment sluicing at dams.

Planning and Analysis of Sedimentation Countermeasures in Hydropower Dams Considering Properties of Reservoir Sedimentation

Sedimentation in hydropower reservoirs is one of the most important problems facing power generation. Many of the reservoirs our company’s dams, built in the postwar reconstruction period, have been storing up sedimentation for decades. The percentage of sedimentation is now considerable, about 9%, because of a combination of a high degree of sediment production and the river flow regime. We have been trying to excavate the sedimentation from the reservoirs to avoid aggradations of upstream riverbeds and to eliminate obstacles to intake and outlet functions. Considering sediment properties, we have carried out representative five different ways of managing reservoir sediment. At the Sakuma dam, which is comparatively large, provisional transporting inside the reservoir is the main countermeasure, but radical management will be required in the near future. At the Futatsuno dam and Taki dam, which are medium-sized, the current volume of sedimentation excavation is not sufficient to maintain the size of the reservoir, due to flow sedimentation. Sediment routing methods, such as bypassing, will therefore be urgently planned. At the Setoishi and Yambara dams, the testing of sediment sluicing or hydro-suction sediment removal systems has already started. Regarding sedimentation sluicing, we have studied the feasibility of sediment bypass tunnels and gated outlets in the dam reservoir that is unsuitable for sluicing with the existing spillway. We found that gated outlet will be effective. Although there are no quick remedies that can reduce reservoir sedimentation dramatically, there are some methods that may be suitable, considering the size, life and basin of each reservoir. Not only the technical feasibility, but also the economic advantages and ecological acceptability should be considered. To sustain reservoirs and hydropower, sedimentation should be managed effectively and adaptively, based on the specific conditions of each reservoir.

Measurement and control of high suspended sediment concentration during the Kurobe River sediment flushing with submersible type SMDP

In the Kurobe River, coordinated sediment flushing and sediment sluicing of Dashidaira and Unazuki dams have been executed since 2001. From the view point of the comprehensive sediment management in the sediment routing system, monitoring of quantity and quality of sediment transport during these events in rivers and reservoirs is very important. This paper shows the results of continuous measurement of high suspended sediment concentration during sediment flushing and sluicing operation of Unazuki dam in 2015 and 2016. These data have been obtained by submergible type of Suspended Sediment Concentration Measuring System with Differential Pressure Transmitter (hereinafter we call ‘submergible type SMDP’), which is designed to be placed underwater. Measured data have good correlation with manual sampling and effectively utilized to control gate operation by real-time basis during the most critical timing producing extreme high concentration just before free flow starts for sediment flushing.

Transboundary sediment transfer from source to sink using a mineralogical analysis. Case study: Roseires Reservoir, Blue Nile, Sudan

ABSTRACTSediment accumulation hampers optimal water resources management of reservoirs. In the Roseires Reservoir across the Blue Nile River, in Sudan, about 30% of the storage capacity has been lost by sedimentation before dam heightening (2012), despite regular sediment sluicing and flushing. At the same time, increasing soil erosion in the upper river basin in Ethiopia is significantly reducing land productivity.

水位低下による土砂スルーシング時の超音波を用いた SS 濃度と粒度分布の連続計測

In recent years, ultrasonic attenuation spectroscopy has been frequently used for the measurement of suspended sediment concentration and particle size distribution. Sediments are derived from the rock masses at the upper basin and transported downstream owing to floods, and then deposited in the reservoir. The reservoir sediments affect the entire river system because the sediment transport is blocked by dams. For this reason, sediment sluicing has been performed in several rivers. In such cases, it is important to monitor the suspended sediment concentration and particle size distribution. Therefore, we have measured the suspended sediment concentration and particle size distribution using an ultrasonic spectrometer during sediment sluicing by drawdown operation. The applicability of our measurement technology using ultrasonic attenuation spectroscopy for monitoring of suspended sediment concentration and particle size distribution was verified.

PERBANDINGAN EFEKTIFITAS HASIL PENGGELONTORAN SEDIMEN DI WADUK CARA FLUSHING DAN SLUICING

This study compares the effectiveness of the flushing of sediment in the reservoir by means of flushing andSluicing way, based on Physical Hydraulic Test (Model Test) in the laboratory. Flushing is removingaccumulated deposited sediment. While slucing is releasing of sediment through the reservoir beforesettled or keep sediment remain in suspension and its occur during flood period. Sediments FlushEffectiveness represented by the percentage of released sediment by sediment deposited or the amount ofsediment entering the reservoir during the flushing period.The model based on the prototipe from DetailDesign of Structural Countermeasures for Sedimentation on Wonogiri Reservoir by Nippon Koei 2009.Running model duration is one hour, used free flow and submergence condition, with discharge variationQ=100, 200 and 400 m3/s. Sluicing experiments conducted with some 60 liters of sediment sprinkle evenlywide flow, and Flushing implemented by 2,00 m thickness of deposited sediment that spreaded over thereservoir bottom before running. From this research showed that Sluicing way more efficient than theflushing way, where the number of efficiency of sediment Sluicing way bigger than the efficiency offlusing way, in the running an hour in the laboratory test

CHARACTERISTICS OF FINE SEDIMENT DISCHARGE DURING SEDIMENT FLUSHING OF UNAZUKI DAM

In the Kurobe River, coordinated sediment flushing and sediment sluicing of Dashidaira and Unazuki dams have been executed since 2001. From the view point of the comprehensive sediment management in the sediment routing system, monitoring of quantity and quality of sediment transport during these events in rivers and reservoirs is very important.This paper shows the results of field data obtained during sediment flushing and sluicing operation of Unazuki dam in June-July, 2005. Suspended sediment concentration measured by the manual sampling and SMDP ( Suspended Sediment Concentration Measuring System with Differential Pressure Transmitter), turbidity measured by a high rage turbidimeter and grain size distribution are discussed. Cleary, based on the progress of sedimentation of Unazuki reservoir, sediment discharge characteristics of Unazuki dam have been changed year by year.