Modeling long term alternatives for sustainable sediment management using operational sediment transport rules

2014 ◽  
pp. 241-248
Keyword(s):  
Sediment Transport ◽  
Sediment Management

scholarly journals Current and Future Study Topics on Reservoir Sediment Management by Bypass Tunnels

2018 ◽  
Vol 13 (4) ◽  
pp. 668-676 ◽  
Author(s):  
Sohei Kobayashi ◽  
◽  
Takahiro Koshiba ◽  
Tetsuya Sumi
Keyword(s):  
Sediment Transport ◽  
Future Study ◽  
International Workshop ◽  
Sediment Management ◽  
Sediment Supply ◽  
Reservoir Sediment ◽  
Efficient Operation ◽  
Abrasion Rate ◽  
Runoff Model

Herein, we summarized the current and future study topics of sediment management using bypass tunnels based on the discussions at the Second International Workshop on Sediment Bypass Tunnels (SBTs) at Kyoto in May 2017. Although reservoir sediment management using bypass tunnels has appeared since the beginning of the 20th century in Kobe, the number of SBTs worldwide is still limited. To promote the installation of SBTs as an effective sediment management measure, it is essential to appropriately evaluate their long-term advantages economically and for the restoration of the aquatic ecosystem. An abrasion model has been developed to predict the abrasion rate of tunnels from the volume of sediment transport. Further, methods to monitor sediment transport in tunnels have advanced. With a significant amount of sediment supply by SBTs, the ecosystems in the downstream reaches of dams can be restored within a few years. A precise rainfall and runoff model for predicting the inflow hydrograph and sediment is essential for the efficient operation of dam gates and SBT (e.g., diverting minimum amount of water for sediment transport). Further studies are needed to clarify the suitable grain size for transportation through SBTs in terms of both the mitigation of tunnel abrasion and promotion of the restoration of downstream ecosystems.

scholarly journals SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT

2020 ◽  
pp. 31
Author(s):  
Yan Ding ◽  
Sung-Chan Kim ◽  
Richard B. Styles ◽  
Rusty L. Permenter
Keyword(s):  
Sediment Transport ◽  
Shoreline Change ◽  
Breaking Wave ◽  
Beach Profile ◽  
Shoreline Evolution ◽  
Longshore Sediment Transport ◽  
Wave Energy Flux ◽  
Semi Empirical ◽  
Evolution Modeling

Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.

Sedimentary facies on the rises and slopes of passive continental margins

1980 ◽  
Vol 294 (1409) ◽  
pp. 169-176 ◽  
Keyword(s):  
Sediment Transport ◽  
Debris Flows ◽  
Thermohaline Circulation ◽  
Dominant Role ◽  
Sedimentary Facies ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Passive Margins ◽  
New Evidence

JOIDES drilling results provide new evidence concerning facies patterns on evolving passive margins that strengthens and extends hypotheses constructed from studies of morphology, seismic reflexion data and shallow samples on modern margins, and from field geologic studies of uplifted ancient margins. On the slopes and rise, gravity-controlled mechanisms - turbidity currents, debris flows, slides and the like - play the dominant role in sediment transport over the long term, but when clastic supplies are reduced, as for example during rapid transgressions, then oceanic sedimentation and the effects of thermohaline circulation become important. Sedimentary facies models used as the basis of unravelling tectonic complexities of some deformed margins, for example in the Mesozoic Tethys, may be too simplistic in the light of available data from modern continental margins.

3D hydro-morphodynamic models as support tools for obtaining sustainable sediment management strategies of reservoirs

2020 ◽  
Author(s):  
Kilian Mouris ◽  
Leon Saam ◽  
Felix Beckers ◽  
Silke Wieprecht ◽  
Stefan Haun
Keyword(s):  
Sediment Transport ◽  
Water Level ◽  
Management Strategies ◽  
Sediment Management ◽  
Transport Processes ◽  
Water Levels ◽  
Hydraulic Structures ◽  
Suspended Sediment Transport ◽  
Reservoir Sedimentation ◽  
Bottom Outlets

<p>Reservoir sedimentation reduces not only the available storage volume of reservoirs, but may also create other serious problems, such as an increase of bed levels or accumulations of nutrients and contaminants, which affect the environment. An increase in bed levels at the head of the reservoir can reduce flood safety and increase the risk for the surrounding areas. Deposited sediments close to the dam may block hydraulic structures, such as the bottom outlets, or, in case they enter the intake, lead to possible abrasion of plant components (e.g. wear of turbines and pipes).</p><p>Prior to reservoir construction, a pre-evaluation of the sediment yield from the catchment is usually performed by using soil erosion and sediment delivery models. However, the trapping efficiency is often only obtained by empirical approaches, such as Brune’s or Churchill’s curve, which are based on the capacity of the reservoir and the mean annual inflow. This is still common practice, although 3D hydro-morphodynamic models became powerful tools to numerically study sediment transport and reservoir sedimentation prior to the construction of reservoirs as well as during its operation.</p><p>Within this study, a fully 3D hydro-morphodynamic numerical model, based on the Reynolds-averaged Navier-Stokes equations, is applied to a case study to simulate, on the one hand suspended sediment transport within a hydropower reservoir and on the other hand a reservoir flushing operation as potential management scenario, with the goal to remobilize already deposited sediments and to release these sediments from the reservoir. The modeled reservoir has a total storage capacity of around 14 million m³, whereby the water level can fluctuate due to pumped-storage operation by 40.5 m (difference between the maximum operation level and the operational outlet). At the head is the natural inflow of two creeks into the reservoir and a lateral transition tunnel is located on the orographic right side, which collects several headwater streams from adjacent catchments.</p><p>Simulations are performed for different operation modes of the reservoir. The results clearly show that through active reservoir management (variation of water levels as well as using the momentum of the discharge from the transition tunnel) the sediment motion in the reservoir can be affected to a certain extent. It is for instance possible to almost completely avoid reservoir sedimentation in front of the dam and the hydraulic structures (water intake and bottom outlets) during sediment-laden flows when simultaneously high discharges are provided from the laterally located transition tunnel. The conducted simulation results of reservoir flushing also show that the success of the flushing operation is strongly dependent on the water level. As expected, flushing with full drawdown of the water level is the most efficient method to release sediments.</p><p>Through the detailed results of the 3D hydro-morphodynamic model, it is feasible to receive a deeper knowledge of the ongoing sediment transport processes within the studied reservoir. The gained knowledge can further be used to derive sustainable and efficient management strategies for the sediment management of the reservoir.</p>

Morphology and Pipeline Design Through a Dynamic Landfall Area: The Black Sea Pipeline Case

2002 ◽  
Author(s):  
Z. Chen ◽  
Marco Venturi ◽  
R. Bijker
Keyword(s):  
Sediment Transport ◽  
Environmental Impact ◽  
Black Sea ◽  
Morphological Changes ◽  
The Black Sea ◽  
Burial Depth ◽  
Short Term ◽  
Pipeline Route ◽  
Long Term Variations

The Blue Stream pipeline project is a gas transportation system for the delivery of processed gas from a gas station in the southern Russia across the Black Sea to Ankara, Turkey. The Turkish landfall of the offshore pipeline in the Black Sea is located near Samsun, see Figure 1 for the pipeline route. One of the main aspects of the design of pipeline through a morphologically dynamic area such as landfall is the required burial depth (Chen et al, 1998, 2001 and Bijker et al 1995). The burial depth is the result of an optimisation between: • safety of the pipeline (which often requires a large burial depth), and • environmental impact and trenching costs (a small burial depth means less dredging and less environmental impact). This paper presents a method of predicting the future extremely low seabed level in a morphologically dynamic landfall area, which is required to determine the burial depth of the pipeline. Both short term and long term coast evolution were assessed to quantify the expected lowest seabed level along the pipeline route in the landfall area during the pipeline lifetime of 50 years. The results were used to determine the required pipeline burial depth. The long term morphological changes originate from long term variations in the morphological system (e.g. river input), gradient in the longshore sediment transport and long term variations in the hydrodynamic conditions. The short-term morphological changes originate from beach profile variations due to cross-shore sediment transport as a result of seasonal and yearly variations in the wave and current conditions. Numerical modelling was applied to compute the longshore and cross-shore sediment transport rates and the resulting coastline evolution and cross-shore profile evolution. The longshore transport model was validated using the available data on the coastline changes in the past 20 years, which was derived from the satellite images. The 50-year lowest seabed level has been determined as the sum of the coastline retreat and the cross-shore evolution in the next 50 years.

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