Siltation

About: Siltation is a research topic. Over the lifetime, 1420 publications have been published within this topic receiving 20983 citations.

Shape optimization of egg-shaped sewer pipes based on the nondominated sorting genetic algorithm (NSGA-II)

Abstract: Overflow pollution is an undesired issue that commonly occurs in combined sewers under wet weather conditions. There is a lack of existing studies on the structural optimization of sewers to prevent siltation, and no previous study on egg-shaped sewers with this purpose has confirmed satisfactory anti-sedimentation performance. To achieve reduced sedimentation and lower energy loss under low- and high-flow conditions, respectively, the nondominated sorting genetic algorithm (NSGA-II) was adopted in this study based on a constant full filling discharge capacity equal to that of a 300 mm (diameter) circular sewer. The results showed that egg-shaped sewers with bottom and top arc radii of 58.3 and 116.6 mm, respectively, and a height of 408.1 mm performed significantly better than circular sewers (d = 300 mm). Notably, at a low flow ratio below 0.2, the shear stress of the optimized egg-shaped sewer was 5.2%-20.6% higher than that of the circular sewer. At a flow ratio of 0.2-0.6, both the egg-shaped and circular sewers were capable of maintaining a balanced amount of sediment between deposition and erosion. As the flow ratio increased to 0.6-1, both types of sewers completely scoured sediments: in this situation, the shear stress of the egg-shaped sewer was 5.5%-10.1% lower than that of the circular sewer, thus exhibiting reduced energy loss. This study indicates that egg-shaped sewers have an attractive future in replacing circular sewers for sedimentation prevention and cost control.

Sediment Deposition in Nigeria Reservoirs: Impacts and Control Measures

Abstract: This work examines the issue of sediment deposition in reservoirs. As death is an inevitable end for humans, so is siltation an inevitable end for reservoirs. Sediment content of river inflows into reservoirs depletes the available storage capacity thereby reducing the benefits such as domestic and industrial water supplies, hydro power generation, irrigation, navigation, fish and wild life, sanitation and recreation, flood control, ground water recharge, etc. Sediment distribution pattern of the reservoir was examined. Factors affecting siltation in reservoirs were also captured. Impacts of reservoirs on the environment and our health were discussed. Different methods of controlling silting in reservoirs were examined. It was recommended that there should be periodic monitoring of sedimentation in our reservoirs to prolong the life of the reservoirs and sustain their benefits. Keywords: sediment deposition, storage capacity, reservoir life.

Depositional Environment of a Tropical Estuarine Beach near Sharavati River Mouth, Central West Coast of India

Abstract: Beach sediments of Pavinkurve and Kasarkod, located adjacent to the Sharavati River mouth at Honnavar, Central West Coast of India are medium to fine grained (1.21 - 2.30Φ) and moderate to well sorted (0.17-0.55). The convergence of long-shore circulation and interaction of river and wave processes are the main influence for the distribution of sediments along these beaches. The sediment transport land-ward during fair weather season (pre-monsoon) is mainly due to westerly wave approach. The re-suspension of sediments owing to agitation of sea during westerly wave approach, their land-ward movement during high tide, and the obstruction caused by the submerged bar formation during falling tide leading to their deposition are the main causes for siltation in the river mouth.

Four terrestrialization characteristics of Baiyangdian Lake, China

Abstract: Terrestrialization is the process by which a water body changes from a wetland to a terrestrial ecosystem. Many factors contribute to the process, including climate change and macrophyte expansion. Among such factors, water level and eutrophication result in quantitative and qualitative changes on macrophyte communities, while expansion of macrophytes can accelerate the rate of terrestrialization by bioaccumulation. The siltation of sand also greatly contributes to terrestrialization. Here, the water quality, water level, siltation of sand, and vegetation of Baiyangdian Lake were analyzed to assess the terrestrialization characteristics of this lake and understand its terrestrialization process.

To What Extent Can a Sediment Yield Model Be Trusted? A Case Study from the Passaúna Catchment, Brazil

Abstract: Soil degradation and reservoir siltation are two of the major actual environmental, scientific, and engineering challenges. With the actual trend of world population increase, further pressure is expected on both water and soil systems around the world. Soil degradation and reservoir siltation are, however, strongly interlinked with the erosion processes that take place in the hydrological catchments, as both are consequences of these processes. Due to the spatial scale and duration of erosion events, the installation and operation of monitoring systems are rather cost- and time-consuming. Modeling is a feasible alternative for assessing the soil loss adequately. In this study, the possibility of adopting reservoir sediment stock as a validation measure for a monthly time-step sediment input model was investigated. For the assessment of sediment stock in the reservoir, the commercial free-fall penetrometer GraviProbe (GP) was used, while the calculation of sediment yield was calculated by combining a revised universal soil loss equation (RUSLE)-based model with a sediment delivery ratio model based on the connectivity approach. For the RUSLE factors, a combination of remote sensing, literature review, and conventional sampling was used. For calculation of the C Factor, satellite imagery from the Sentinel-2 platform was used. The C Factor was derived from an empirical approach by combining the normalized difference vegetation index (NDVI), the degree of soil sealing, and land-use/land-cover data. The key research objective of this study was to examine to what extent a reservoir can be used to validate a long-term erosion model, and to find out the limiting factors in this regard. Another focus was to assess the potential improvements in erosion modeling from the use of Sentinel-2 data. The use of such data showed good potential to improve the overall spatial and temporal performance of the model and also dictated further opportunities for using such types of model as reliable decision support systems for sustainable catchment management and reservoir protection measures.