1. River dredging purposes and selection of the dredging position

The dredging of he world's major rivers has no more than two purposes, the first purpose is dredging the rivers, increasing the vertical slope and drainage capacity of river, reducing river siltation rate, to ensure flood safety; the second purpose is dredging and reducing the river, reducing the river bed elevation, to maintain a certain depth, easy navigation.

There are so many factors affecting the reducton of the sedimentation, project location or dredging location is one factor, if the choice is inappropriate, the reduction effect can not be brought ; the right choice can maximize the benefits of sedimentation reduction. Thus, the selection of the dredging location is important. The dredging selection should follow the several principles : 1. the main chanel is relatively stable, not easy to happen the rolling river; 2. dredging the riverbed, submission of the river channel; 3. the role of erosion can be reduced, as large as possible to shape retrogressive erosion, have a beneficial effect on the upper reaches of the river; 4. difficult to deposition, able to maintain long-term benefits of dredging; 5. sediment can be effectively utilized.

2. Choice for Dredgers

Dredgers are main dredging equipment, with the development of dredging career in domestic market. To adjust to various of project construction, the type of dredgers are continually increasing. Reasonable device option is the key to fully use of machinery equipment and yield the greatest returns on investment.

It is very important to choosing the dredgers according to the project site condition. It will increase dredging cost and damage the device even delay the project if we choose the inappropriate item.  There are two basic principles to choose dredgers ,firstly to meet dredging demand technically, secondly to reduce dredging cost with high limit financially .To choose dredging device, we should know the dredging performance for all kinds of dredgers, then choose optimal dredging device according to the situation , demand of project construction combining with technology ,efficiency, and economy.  

3. Main factors for dredger option

1). Type and character of dredged soil

 Soil is the main target for dredging, soil dredging extent is decided by soil type and density. Kinds of dredgers can function well in their working soil but if we don’t operate in proper soil, the dredgers may cannot work efficiently even cannot work

2). Scale of dredging groove and discharging way

Scale of dredging groove is meaning the width, depth and mud thickness of dredging groove. It will increase moving forward amount thereby influence productivity if we use narrow groove. It cannot easy to sail if we choose mud barge and floating pipeline to discharge mud. If we choose groove wider than the max width of dredger ,we can dredging in subsection .But it will increase time for moving and dropping anchors and also to influence efficiency. Otherwise, the dredger can´t work when the water depth of groove is deeper than the dredger max depth .The dredger can´t sail to dredging site when it less than the drafted depth .As for dredger with mud cabin,we should consider the depth of full loaded draft. All of these factors should be taken into account.

 3). The amount of dredging and working time

If the amount of dredging is very small and select and use the dredger with large capacity. It will reduce time availability when dispatch and distribution, very uneconomical. Other conditions, such as flow rate, storms, weather, flight depth, bridge clearance and fuel supply and other factors should be considered appropriate when selecting the dredger.

4). Performance of the dredger

Mentioned earlier about dredger's dredging features and appropriate engineering is the prerequisite common sense when choosing the dredger. But at the same time should also understand hull structure and basic performance of the dredger. Such as minimum, maximum and optimum dredging depth, which is limited by the dredger, the minimum width of dredge work, most effective and maximum thickness of the mud, maximum draft of the dredger and dredger’s capacity all kinds of construction conditions.

4. Construction process