Siltation

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

Sedimentation in small dams. Development of a catchment characterisation and sediment yield prediction procedure

Abstract: The British Government's Department for International Development commissioned HR Wallingford to develop guidelines presenting appropriate methods for predicting, and where possible reducing, siltation rates in small communal dams in semi-arid zones in Eastern and Southern Africa. Small dam designers must be able to use these methods; they typically need to carry out assessments rapidly using limited local data, and may not have software skills or access to computers. The report describes the development of a method for predicting small dam catchment sediment yields. The objective was to develop a simple procedure which would distinguish between dams that will silt up rapidly from dams that will have a sedimentation lifetime well in excess of twenty years.

Challenging established narratives on soil erosion and shifting cultivation in Laos

Abstract: The official environmental discourse in Laos describes a “chain of degradation” stretching from upland shifting cultivation, increased runoff and soil erosion to the siltation of wetlands and reservoirs. This perspective has had wide-ranging impacts on rural development policy which, in the uplands, has long favoured forest conservation over agriculture. Integrating soil erosion and water sediment data with local perceptions of land degradation in an upland village of northern Laos, this study tests the validity of the official environmental discourse. Biophysical measurements made in a small agricultural catchment indicate a significant correlation between the spatial extent of cultivation and soil erosion rates. However, sediment yields recorded at the outlet of the catchment highlight relatively low levels of off-site sediment exportation. Furthermore, farmers' perceptions suggest that local land degradation issues and crop yield declines could be less related to soil erosion than to agricultural land shortage, increased weed competition, and fertility losses resulting from the intensification of shifting cultivation. The study concludes that a better understanding and management of land degradation issues can be achieved by developing more inclusive and scientifically-informed approaches to environmental perceptions and narratives. (Resume d'auteur)

Linking Short- and Long-Term Soil—Erosion Modelling

Abstract: Soil erosion by overland flow is a significant process over large areas of the Earth. It leads to specific forms of landform development over both short and long time scales. In some cases, the landscape can be dramatically modified in a matter of hours, as a result of an extreme storm event. Understanding soil erosion is therefore fundamental in being able to explain the geomorphology of these areas. The soil is also a fundamental resource for human food supplies, and its loss means direct and indirect impacts on sustainability. Off-site effects of erosion can be significant both for pollution, particularly when chemical fertilisers and pesticides have been used, and for siltation of reservoirs and other structures. In extreme cases, persistent erosion can lead to a total loss of productivity, leading to desertification. The understanding of soil erosion therefore also has important practical implications.

The Variation Process of Water and Sediment and Its Effect on the Yellow River Delta over the Six Decades

Abstract: In order to find out the variation process of water and sediment and its effect on the Yellow River Delta,this paper,by means of statistics,analyzed the water and sediment discharge from 1950 to 2007 at Lijin and the reduction of water and sediment in Yellow River Basin caused by human activitiesResults show that the water and sediment discharge into sea decreased from 1950 to 2007 with serious fluctuationThe human activities were the main cause for the reduction of water and sediments into seaFrom 1950 to 2005,the multiyear average reduction of water and sediment by means of water and soil conservation were 202×109 m3 and 341×108 t,respectively,while the multiyear average usage of water and sediment for industry and agriculture were 252 × 1010 m3 and 242 × 108 t,respectivelyFrom 1960 to 2007,the multiyear average sediment silted in the Sanmenxia Reservoir was 145×108 t and that silted in the Xiaolangdi Reservoir was 2398×108 tCompared to the data of Huayuankou,in the lowere reaches,the water and sediment discharge into sea decreased with siltation and increased with erosionThe coastline near the estuary extended and the delta increased when the ratio of total water and sediment into sea was about 00257 t/m3 in different periods

Response of delta sedimentary system to variation of water and sediment in the Yellow River over past six decades

Abstract: In order to find out the variation process of water-sediment and its effect on the Yellow River Delta, the water discharge and sediment load at Lijin from 1950 to 2007 and the decrease of water discharge and sediment load in the Yellow River Basin caused by human disturbances were analyzed by means of statistics. It was shown that the water discharge and sediment load into the sea were decreasing from 1950 to 2007 with serious fluctuation. The human activities were the main cause for decrease of water discharge and sediment load into the sea. From 1950 to 2005, the average annual reduction of water discharge and sediment load by means of water-soil conservation practices were 2.02×109 m3 and 3.41×108 t respectively, and the average annual volume by water abstraction for industry and agriculture were 2.52×1010 m3 and 2.42×108 t respectively. The average sediment trapped by Sanmenxia Reservoir was 1.45×108 t from 1960 to 2007, and the average sediment retention of Xiaolangdi Reservoir was 2.398×108 t from 1997 to 2007. Compared to the data records at Huanyuankou, the water discharge and sediment load into the sea decreased with siltation in the lower reaches and increased with scouring in the lower reaches. The coastline near river mouth extended and the delta area increased when the ratio of accumulative sediment load and accumulative water discharge into the sea (SSCT) is 25.4–26.0 kg/m3 in different time periods. However, the sharp decrease of water discharge and sediment load into the sea in recent years, especially the Yellow River into the sea at Qing 8, the entire Yellow River Delta has turned into erosion from siltation, and the time for a reversal of the state was about 1997.