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Dams and Development E-Paper Contents

p. -1 of 74 BACK | NEXT Home Page of Dams and Development Foreword I. Why an e-paper on dams and development? II. Assessing options III. Participatory processes IV. Social impacts V. Environmental impacts VI. Benefit distribution VII. Dam safety and sustainability VIII. Existing projects IX. Improving governance X. What other organizations say XI. ADB, Dams, and Development XII. References Contact Us

Sediment flushing - evacuation of sediments from reservoirs

An introduction to removal of accumulated sediments in a reservoir by sediment flushing is provided in Thematic Review V.5 Operations, Monitoring and Decommissioning of Dams prepared for the WCD:

'Sediment flushing is a technique in which the flow velocities in a reservoir are increased to such an extent that deposited sediments are remobilized and transported through bottom outlets. .. However the technique is only effective under certain favourable conditions and is not universally applicable'.

A review of worldwide experience with sediment flushing is summarized in a contributing paper to the WCD thematic review Flushing of Sediment from Reservoirs by White W.R.

'There is a distinction between sediment flushing and sediment sluicing. Sediment flushing is concerned with the removal of sediments which have settled in the reservoir at a previous time whereas sediment sluicing is concerned with passing sediments straight through the reservoir during times of flood. The distinction is sometimes difficult to make but, generally, sediment flushing is used to remove sediments up to and including sands and gravels whereas sediment sluicing removes only the finer fractions'.

The paper goes on to outline the design implications necessary for effective flushing programs. More detailed coverage is provided in a book by the same author, Evacuation of sediments from reservoirs.

'This technique can be applied to existing dams, with adaptation of the engineering works, and to new dams. The book gives practical guidance on the necessary hydrological, hydraulic, sedimentological and topographical features for successful flushing'.

Book Contents:

• Review of sedimentation in reservoirs
• Research into factors which influence flushing
• World-wide experience of sediment flushing
• Geographical areas suited to flushing

A computer simulation model to predict the extent and location of sediment within a reservoir used in some of the associated studies is RESSASS - Reservoir Survey Analysis and Sedimentation Simulation.

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