The bed of an alluvial channel along the flow will always be
The minimum size of sediment that may remain stable in an alluvial channel, carrying discharge intensity q, with hydraulic radius R and bottom slope S, is
The Garret’s diagrams are based on
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 most important shape parameter in sediment analysis is
The wetted perimeter P of a stable channel is proportional to where, Q is the discharge
The wetted perimeter P of a channel is given by,
P = 4.75√Q
Lacey’s regime theory is not applicable to a channel in
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.
Hydraulic depth is the ratio of
For a most economical trapezoidal channel section
Counter berms are provided in an irrigation canal
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 assumed that the silt is kept in suspension because of normal components of eddies generated from
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.