Siltation

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

Numerical Modeling of the Tidal Current Movement of the Baima Port, China

Abstract: The Sanduao Bay is the bay with many of islands where the coastline is very winding with complex hydrodynamics and sediment transportation. Using a 2-D wave-current coupling hydrodynamic model of the Mike21 software package, the hydrodynamics condition on the Pingang Operation Area of Baima Port in the Sanduao Bay is simulatated. The results show that the current field in the berth is smooth that is beneficial to maintenance of water depth and reduction of siltation in berth. And the velocity in reclamation and dredging area is reduced less than 0.05m/s. the reclamation near the coastline and dredging in the berth make the velocity varied and the varying range is between 0.3m/s and 0.4m/s.

Micro watershed to basin scale impacts of widespread adoption of watershed management interventions in Blue Nile Basin

Abstract: High population pressure, inappropriate agricultural policies, improper land-use planning, over-dependency on agriculture as source of livelihood and extreme dependence on natural resources are inducing deforestation, overgrazing, expansion of agriculture to marginal lands and steep slopes, declining agricultural productivity and resource-use conflicts in many parts of Blue Nile. Increased land degradation from poor agricultural practices and erosion results in increased siltation and the reduced water quality in the river basin. The rainfall, runoff and sediment are highly variable both in time and space. Poor water and land management upstream severely affect runoff characteristics and the quality of water reaching downstream. The result is a downward spiral of poverty and food insecurity for millions of people both within the upper catchment and downstream across international borders. Quantification of the erosion, sedimentation processes and evaluation of impacts of interventions are difficult tasks. This paper schematizes the Blue Nile Basin (BNB) at various spatial levels as micro watershed, watershed, sub-basin to basin. It is revealed that sediment in the river systems are temporally varying phenomenon and strongly related to the early onset of rainfall. The hydrographs of the systems shows that the peak of sediment reaches first followed by peak of rainfall and then runoff. Furthermore, the sediment cumulative curve shows that most of the sediment volume passes in the river in the first three months of the rainy season. The paper also considers a particular watershed to model runoff, sediment and impact of watershed intervention. The result shows that runoff can be reasonably simulated with calibration of R2=0.87 and validation of result of 0.82, and comparable sediment modelling results. The study also demonstrates, by undertaking spatial analysis using topographic, soil and land use parameters it is possible to identify the high sediment risk sub-watersheds. Impact of typical watershed intervention using various widths of vegetative filter and application on high erosion risk watersheds shows reduction of sediment yield from 52% to 74%.

Quaternary erosion agents, Holocene landscapes and soils of the Tamar Estuary Basin, Tasmania

Abstract: Ongoing siltation in the upper Tamar Estuary is problematic for reasons of amenity, navigation, human health and Launceston city’s flooding hazard. Regional authorities commissioned catchment to estuary sediment flux computer-based modeling in 2008 to identify sediment sources or erosion hotspots. It had been over 20 years since sediment inputs were quantified and sedimentation processes in the Estuary identified. The present research critically considered the modeling results in the context of the attribution of sediment provenance to land use and the validity of application of the Revised Universal Soil Loss Equation (RUSLE) using the KLS component of the equation from digital soil mapping. Two major research themes developed: 1. The role of land use in sediment flux to the Tamar Estuary compared to “natural” rates of change was placed in context by researching landscape change through recent earth history to Pleistocene human migration and contemporary history. 2. Soils from a pilot study area were sampled and characterised to assess the feasibility of using soil types from existing soil mapping as an alternate basis to land use in modeling and to improve field data quality and resolution for sediment flux modeling as well as contribute data to the Soils and Landscape Grid of Australia (SLGA). The literature was reviewed for qualitative pre-historical analyses and presentation, while landscape spatial data analyses were undertaken using a project geographic information system (GIS), using both digitised historical maps and digital datasets. The pilot study area selected for soil characterisation and detailed examination of modeled erosion hazard was the upper South Esk catchment in the north-east highlands of the Tamar basin, over 1,000 km\(^2\) in area. Modeling suggested the area had some of the highest exports of sediment in the basin, which is known for its apparently highly erodible granite-based soils. Pre-historical and historical phases of landscape instability and erosion events were identified and documented, placing historical human settlement and land use in long term context. It was found that the arid glacial climates and Aboriginal land management practices of the Pleistocene provided an abundance of sediment available for aeolian transport across the Tamar catchments from Tasmania’s centre and west, a sediment source to the Tamar and its Esk rivers catchments by “natural” or background processes now ceased. Since then, erosion rates reduced and stabilised and a virtual dynamic equilibrium regime of sedimentation and scour in the estuary was established, albeit within the more gradual evolution of a drowned river valley infilling with sediment. Nevertheless, while according to the literature the total suspended sediment (TSS) values of the Esk rivers are very low compared to world rivers, the dominantly fine (<63 μm) sediment flux has increased post-colonisation. From the literature research and GIS, the resolution or detail of historical data was sufficient to indicate four periods of historic landscape instability, the last still extant. These periods of instability, in which landscapes have been more vulnerable to erosion and siltation of the Tamar Estuary likely increased, can be attributed to a combination of specific climatic (“natural”) and anthropogenic (land use) factors. While the development of sustainable agricultural systems has been prioritised, research suggests that the reinstatement of a dynamic equilibrium that minimises estuarine siltation is uncertain in the context of anthropogenic climate change and landscape transformation. Contemporary geological mapping was found on the basis of soil geochemistry to be reliable for use, within specified limitations, in sediment provenance modeling or sediment source attribution. The project GIS, compiled from geological spatial data, land systems and contemporary land use and vegetation, enabled the classification of soils by four geological parent materials using strategic sampling stratification. The cartography produced includes land use and soil type overlays on erosion hazard values. Elemental properties of top- and sub-soil samples from 54 sites were analysed using inductively coupled plasma mass spectrometry (ICP-MS) following mixed acid (HNO3-HF-HCl) digestion. Subsequent to elimination of redundant elemental properties out of 35 analysed, the four soil types were differentiated by discriminant (function) analysis (DA or DFA) using a “fingerprint” of 13 elements. A satisfactory proportion (87%) of the samples were robustly classified, including discrimination of the alluvium derived from three other soil types, one of which comprised 50% of the total pilot area. The sampling and analytical methodologies developed represent a minimalist yet robust approach, optimised for a sole researcher and/or limited facilities, suitable for application in sediment flux modeling or direct suspended sediment fingerprinting techniques in physiographically complex catchments such as the Tamar basin. The soil work undertaken and methodologies developed have value in confirming soil characteristics in the study catchment and in application in ground truthing where and as required. It is intended by the Department of Primary Industry, Parks, Water and Environment (DPIPWE) to combine the project soil results with the new LIDAR (light detection and ranging) products when they become available, to enable more useful second generation soil mapping products e.g. for erosion hazard assessment at the subcatchment scale.

Study on Stability of Eden Navigational Channel in Hooghly River Estuary

Abstract: Hooghly estuary is a complex dynamic estuary facing dredging maintenance and navigation-related problems due to the high rate of sediment load brought by the Hooghly River. The present study is to investigate the hydrodynamics and morphodynamics of the Hooghly estuary, with specific reference to stability of Eden navigational fairway and permanent operation of the channel as a possible main navigational route to HDC in the place of Auckland channel from the Bay of Bengal. Impact of stoppage of dredging at Auckland bar on the other channels (Eden and the Rangafalla channel that connect to Kolkata Dock System, KDS) is investigated. Simulations involving different scenarios like Auckland channel dredged and non-dredged conditions are considered to investigate the stability of the Eden channel and also to address the aspects relating to the maintenance of other channels. In the study, for the Auckland open condition, the predicted siltation levels are of about 8–12 cm over Auckland and about 4–8 cm over Eden bar, over 15 days of simulation. For Auckland closed condition and for Auckland with two tracks, the results indicate a marginal reduction in siltation over the entire Eden area, and it is also observed that the siltation in Jellingham and Haldi River confluence is significantly reduced. For the monsoon conditions in all the above scenarios, the results, as per the siltation patterns and as per the siltation levels on the edges of the channels, indicate that there will be a marginal increase in siltation, by about 20% when higher silt load is considered. The study suggests that Eden channel could continuously be used with little dredging in the longer term of more than 5 years with monitoring and realignment of the channel to cater for movement of sandbars. Further, non-dredging of Auckland channel may not have any bearing on the operation of Eden, Jellingham and Rangafalla channels.

Study on High-Resolution Suspended Sediment Distribution under the Influence of Coastal Zone Engineering in the Yangtze River Mouth, China

Abstract: In this study, we analyzed the influence of coastal zone engineering on suspended sediment concentration (SSC) in the Yangtze River mouth based on HY-1C and Chinese GaoFen (GF) satellite data. The results show that: (1) SSC in the Yangtze River mouth is mainly in the range of 200–1300 mg/L, which changes due to natural factors as well as coastal zone engineering; (2) The sand blocking engineering effectively protects the channel from siltation, and SSC in the central line of the channel is 100–300 mg/L lower than that near the dikes in the north and south; (3) Qingcaosha Reservoir plays a stabilizing role in the hydrodynamic force, promoting the deposition of suspended matter, so that the water in the reservoir is clear. SSC inside the Qingcaosha Reservoir, located in the center of the estuary, is 100–500 mg/L lower than the high SSC water outside the reservoir; (4) The bridges interact with the current, facilitating the transport of local sediment, resulting in the increase in SSC downstream of these bridges, and obvious vortexes appear with the length up to nearly 2400 m; and (5) Corresponding protection and development suggestions were put forward as follows. A linear array of wind power plants can be built near and parallel to dikes and leading jetties; to increase the depth of the southeast end of the reservoir; and the location of the bridge should be selected in the place of river where siltation is easy. This study aimed to study the SSC distribution under the complex impact of coastal zone engineering with satellite and to provide possible improvement suggestions.