Test: Sediment Transport & Design of Irrigation Channel - 1 - Civil Engineering (CE) MCQ

For stability

A lot of mathematical calculations are required in designing irrigation channels by the use of Kennedy’s method . To save mathematical calculations, graphical solution of Kennedy’s and Kutter’s equation, was evolved by Garret.

The wetted perimeter P of a channel is given by, 

P = 4.75√Q

Lacey said that even a channel showing no silting no scouring may actually not be in regime. He differentiated between three regime conditions.
(i) True regime
(ii) Initial regime and
(iii) Final regime
According-to him, a channel which is under ‘initial’ regime is not a channel in regime, as there is no silting or scouring and hence regime theory is not applicable to such channels. His theory is therefore applicable only to; those channels, which are either in true regime or in final regime.

Solution:

Hydraulic depth (D) is defined as the ratio of the cross-sectional area of flow (A) to the top water surface width (T). This parameter is commonly used in open channel flow to describe the average depth of water.

Mathematically, it is given by:

Where:

• A is the area of the flow section.
• T is the top water surface width.

Therefore, the correct answer is Option B: Area of flow section and top water surface width.

If after providing sufficient section for bank embankment, the saturated gradient cuts the downstream end of the bank the saturation line is covered by atleast 0.5 metre with the help of counter berms at the outer side of the canal banks.

Lacey states that silt is kept in suspension due to force of vertical eddies. According to him, the eddies are generated from bed and sides, both normal to surface of generation. Hence vertical component of eddies generated from sides will also support the silt.