Hydraulic model studies for estimating scour cone development during pressure flushing of reservoirs: Fid-Bau Portal

Hydraulic model studies for estimating scour cone development during pressure flushing of reservoirs

Kamble, S. A. / Kunjeer, P. S. / B, Sureshkumar / Isaac, Neena

Sediment removal from reservoirs is the major challenge faced by developers of hydropower projects in the Himalayan region. Sediment removal can be achieved by drawdown flushing or sluicing. In drawdown flushing, the water level in the reservoir is lowered sufficiently to establish riverine flow conditions. A flushing channel will be developed and retrogressive erosion will take place. However in the case of sluicing, the water level is kept sufficiently high to maintain pressure flow conditions. During sluicing, the incoming sediment is passed through the sluices and since water level is not lowered, previously deposited sediment will not be removed. Only a scour cone will be developed in the vicinity of the low level sluice outlet. In the case of run-of-the-river hydropower projects, it is important to estimate the parameters of the scour cone such as length, width and depth. The projects are generally operated at MDDL during monsoon season, when sediment concentration is high. Power intakes are generally located very near to the dam and in the scour cone area. Hydraulic model studies carried out to investigate the development of scour cone under pressure flushing of a reservoir is presented in this paper. The experiments were carried out in a laboratory flume. A single spillway bay was reproduced in the model. Experiments were conducted by varying the sluicing discharge and water depth. The various parameters of the scour cone were measured. Dimensional analysis was carried out to establish the relationship of scour cone parameters and hydraulic parameters. The available relationships in the literature also were verified.