Showing papers on "Siltation published in 2001"

Conservation Tillage — A New Strategy in Flood Control

Abstract: It may seem at first that there is no connection between tillage methods on arable land and flood disasters in a watershed. But flood disasters are frequently the consequence of extensive amounts of water originating from surface runoff from soils due to a lack of infiltration caused by soil sealing or crusting. The last has to be seen in context with soil erosion on arable land, which results from inhibited water infiltration through soil siltation. Soil sealing is caused by raindrops hitting the soil surface with a force great enough to destroy soil aggregates. Dispersed surface clods and aggregates form a thin sealing soil layer, which inhibits water infiltration in a very efficient way [1]. On sloped arable land, inhibited infiltration by soil sealing causes surface water runoff, which causes on- and off-site damages through soil erosion.

Flood control and shrinkage in the Haihe River Mouth

Abstract: Because of overusing water resources in the upper and middle reaches of the Haihe Basin, less and less water flows to the river mouth The Haihe River flow is cut off in most time of the seasons, sediment deposited in the river mouth channel is rarely scoured away, and many of the river mouth channels have been shrinking quickly The discharge capacity of the channel is consequently reduced greatly, which results in more and more serious flood hazard Many tide gates have been built for storing fresh water and preventing the salty and turbid water The channel downstream of the gate is silting up and people have to dredge the channel every year before the flood season This paper studies the laws of the siltation and strategies controlling channel shrinkage The strategies are digger dredging, trailer dredging, scouring with pumping water or storing tidal water, building double guiding dikes and building a new gate Comparison of various strategies is performed, suggesting the most effective strategy controlling estuarine channel shrinkage

An Exploration on the Natural Morphology and the Siltation and Erosion Development of the Jiaozhou Bay in Recent 130 Years

Abstract: Based on the bathymetric charts for the Jiaozhou Bay in different periods, the quasi quantitative analyses of the Jiaozhou Bay siltation and erosion situations were made by using digitizer and geo software to determine the siltation and erosion areas in the bay and to give the historic development trends. It is shown from the analysis results that the Jiaozhou Bay before the 1980s was basically in a siltation and shrink situation with the Cangkou channel, the central bay area and the inlets along the coastline being siltation areas and the bay mouth and outer bay being erosion areas; but the Jiaozhou Bay from the late 1980s to the early 1990s was in an erosion situation with radial erosion areas from the bay mouth to the inner bay and small siltation patches between the erosion areas.

Soil Erosion as a Community Issue: Public Perceptions of Off-Site Impacts

Abstract: Research on perceptions of soil erosion and conservation has involved primarily farmers. With off-site impacts being problems of the larger community, however, other sectors of the community also must be included. The literature on community action suggests that in relation to community problems or issues there is no one single public interest to which all will agree. This article examines the differences in perceptions of three community sectors - farmers, agribusiness proprietors, community leaders - of the problems and solutions to reservoir siltation. The three sectors are compared on their perceptions of importance of the lake to the community, the need to solve the siltation problem, who has responsibility for solving the problem, degree of support for different funding alternatives, and effectiveness of possible solutions. Differences found among the three groups support the hypothesis of a lack of a common public interest across different community sectors and provide suggestions for policy and ac...

Hydrographic and Sediment Analyses of Xinghua Bay

Abstract: By means of tidal flow mathematical model,wave mathematical model,analyses of sediment sources,sediment transport trend,sediment siltation and changes of underwater topography,studies and analyses of hydrographic and sediment characteristics of Xinghua Bay are made.

Species of phosphorus in core sediments from the Changjiang Estuary and its environmental significance

Abstract: Species of phosphorus and the property of their distribution with depth are discussed by comparing Shidongkou to Chaoyang core sediments in this paper. Phosphorus in the core sediments from Changjiang Estuary mainly consists of DP, Al P, Fe P, Ca P and OP, predominating OP and Ca P. It is founded there is obvious coupling between Al P and TOC in core sediments near sewage discharge outlet, which indicates human activities have an obvious effect on the existing species of phosphorus in sediments. In addition, this finding shows that the distribution of phosphorus species is markedly subjected to sedimentation rate in vertical core sediments from slightly and highly siltation in the coastal areas.

Storm rapid sedimentation of Maotou deep trough in the Sanmen Bay of Zhejiang

Abstract: The Sanmen Bay is frequently influenced by the typhoon, sediment exchange between beach and channel is stronger when storms hit this bay. Tidal currents are forceful with strong bottom current due to the topographic effect and predominant ebb occurs in the Maotou Channel. These features of tidal currents are a dynamic foundation to form deeper trough and to keep stability. The seabed is in the equilibrium of erosion and siltation with slight siltation in last 100 a. However, when the storms hit the bay, siltation occurs obviously in the trough and erosion in the broad tidal flat. The sediments which are eroded from tidal flat provide resources for rapid deposit in the Maotou Channel. An average depth of profile across deeper trough reduced about 142 cm measured on August 26, 1994, a week after No.9417 typhoon passed the bay. The data show that siltation strengthens from the slope to the bottom. Then the setting sediment by the storm can be resuspended and removed with the tidal current during normal weather. The depth in the trough is restored with slight erosion measured in January 1995, comparing the depth measured in June 1994. But some years, sedimentation occurred in the Maotou Trough. Three and 4 continued strong tropical storms hit the bay in 1989, 1990 respectively, they resulted in storm sediment to retain the trough. It is considered that deposited strata have stored in information of storm sediments in the deeper trough. Some "black mud" layers which contain higher water content, high organic content, low solidity and no bedding in the undisturbed core are recognized as a rapid deposit retained in the Maotou deeper trough by all previous storms.

Feasibility Study of Land-making Project at Wenzhou Shoal

Abstract: By means of analyses of natural conditions, satellite remote sensing analyses of suspended sediment and numerical simulations of wave field, tidal flow field, salinity field , suspended sediment field, and the erosion and siltation of the bottom topography, the hydrologic and sedimental environment and evolution of the Whenzhou Shoal are analyzed, the influences of the land making project on the flood discharge of the Oujiang River, on the aquatic product breeding industry of the Yueqing Bay and on the harbors and navigation channels in the Oujiang Estuary are analyzed and proved The analysis and study results show that the land making project of the Wenzhou Shoal is feasible

Discussion on Treatment Countermeasure in Bedrock Area on Loess Plateau

Abstract: The bedrock area in loess plateau is a core source of coarse sand.It is also one of the sources of sand storm and dust in China.If you want to eliminate the damage of coarse sand siltation on the channel of lower Yellow River,to curb the extension of sand storm and dust, to realize good cycle of local ecology and economy, the concentrated treatment will play a critical role.This paper is based on the result of plant“flexible dam”experiment in soft\|rock area.It presents an operational treatment model in the area so as to accelerate ecological environment recovery progress.

Prediction Of Suspended Fine-sediment Concentration And Siltation AtKapar Coastal Region In Malaysia

Abstract: Field studies of fine-sediment transport were carried out at Kapar coastal region, on the west coast of Malaysia Peninsula, during 1999 and 2000, in particular, near the Kapar power station construction where serious siltation was found. The work was aimed at the development of predictive models of suspended sediment concentration (SSC) and sedimentation rate in the vicinity of the Kapar power station construction. This paper reports the model development and its prediction of siltation in this particular region. A new approach is proposed to predicting sediment deposition rate (siltation) from a time derivative of the suspended sediment concentration, i.e. the erosion (dC/dt>O) or deposition (dC/dt

A Study on the Side Slope and Surplus Water Depth Concerning Siltation in Tianjin Port Main Channel Expansion Project

Abstract: It introduces that in Tianjin Port Main Channel Expansion Project, owing to the study and adjustment of the side slope and surplus water depth concerning siltation, the investment was greatly saved and the social＆ economic benefits were improved.

Solving the Off-site Impacts of Soil Erosion by an Integrated Environmental Watershed Management?

Abstract: In central Belgium, soil erosion by water has many detrimental off-site impacts including muddy floods,silting of riverbeds and sediment deposition within small flood retention ponds. These problems cause highfinancial costs, which are increasing very fast. A controlling strategy is highly needed and given thegeographical nature of soil erosion by water and its impacts, this should be spatially oriented. Integration ofseveral incentives in an environmental management can reduce the off-site impacts of soil erosion to aminimum. If 10% of the most erodible parcels are put under fallow, the erosion risk in central Belgium could bereduced by 20-25%. By constructing small ponds in agricultural areas, much of the eroded and non-pollutedsediment can be trapped, hence diminishing sediment delivery to rivers up to 50% or more. At the same time,muddy floods in downstream villages can be reduced by diminishing the presence of sediments in runoff.

Dredged Soils Solidification Treatment Technique

Abstract: In combination with the Ten－Year－Plan of “40,000 ha of land recl amation and 73,800 ha of siltation promotion”of Shanghai City and to meet to t he requirements of the dredged soils treatment of the Yangtze Estuary Deepwater Channel, it discusses the solidification treatment technique and relevant mechan ical properties of dredged soils

Transport of Fine-Grained Sediments in the Dutch Coastal Zone

Abstract: This paper discusses the effects of a change in discharge regime of the River Rhine on the cohesive sediment transport in the Dutch coastal zone and towards the Wadden Sea. Two 3D numerical models are used to quantify these effects in a comparative study. It is shown that a different discharge regime may influence the sediment concentration in the Wadden Sea. INTRODUCTION Large amounts of fine-grained, cohesive sediments are transported in the Dutch coastal waters, estimated at 10 to 60x106 ton/year. This transport is confined to a nearshore coastal zone of 10 to 20 km width, the so-called coastal river, as a result of a balance between Coriolis effects and a cross-shore gravitational circulation, induced by the outflow of the River Rhine. A proper estimate of the total flux of fine-grained sediments, their pathways for transport and fate is important, as 9 these sediments cause large siltation, hence require costly maintenance operations, in the harbour basins and navigational channels in the coastal zone (e.g. the Port of Rotterdam); and 9 these sediments have a key contribution to the ecological functioning of the Wadden Sea in the northern part of The Netherlands, Germany and Denmark. The present paper describes a three-dimensional numerical model to calculate the transport and fate of these sediments, with emphasis to the effects on the Wadden Sea. The numerical model (hereafter SNS-model) covers the entire southern part of the North Sea, including the Strait of Dover, the Wadden Sea and the German Bight, on a 1) WLIdelft hydraulics, PO Box 177, 2600 MH Delft, The Netherlands, tel: 31-15-2858839, fax: 31-15-2858582, email: Thijs.vanKessel@wldelft.nl, 2) Expert Centre for Project Mainport development Rotterdam 3) also Delft University of Technology, Faculty of Civil Engineering and Geosciences.