GUIDELINES ABOUT CANAL  DESIGN  WORKS.......

THE VELOCITY OF CANAL WATER MAY BE OBTAINED BY THE MANNING'S  FORMULA ....

V = (1/N)R(2/3)S (1/2)

DISCHARGE OF CANAL IN CUMECS  Q = A.V 

WHERE V = Velocity in m/sec;

A = Area of channel  in sq. m. ;

N = Rugosity constant ;Varied from 0.0225 to 0.030 as per lined to bad surface ;

R = A/P = Area in sq. m. /Wetted Perimeter of canal in meter  ;  

P = 4.75 (Q)1/2

S = Bed slope ;This is fixed as per Ground Conditions  and Balancing Depth ;

The side slope of channel is generally is    2:1

Depth of Water in meter  D = 0.5 ( B )1/2

 Surface of   CANAL  Recommended Velocity of Water
 Clayey  0.5 m/sec
 Silt  0.7 m/sec
Moorum  1.0 m/sec
 Concrete or Rocky  2.0 m/sec

Viewing above points , it is clear that design of a canal is a trial and error process as per the Requirement of discharge , velocity and   slopes of canal ;

Actually Discharge and Velocity of canal are predecided as per the Area  to be served and Bed material of canal . Breadth and Depth are decided as per most suitable or best fitted conditions. Free Board is kept Minimum to  50 CMS.

BERM...    A BERM IS a narrow strip of land  between cutting edge and Filling edge of a canal. It is provided for safety of canal banks.

Banks ......Banks are provided for the protective cover over Hydraulic gardient line . Bank width should be kept minimum as 1.0 meter. It should give at least 0.5 m cover over the hydraulic gradient line.The other important formulae are....

P = 2.5 (Q)0.51

R = 0.43 (Q)0.51

A = 1.15 (Q)0.873

S =( 3.293) /10000.Q0.1450

FOR Alluvial soil V = 30 R2/3S1/2

OR  = 16 R2/3S1/3

FOR Concrete Lining V = 45 R2/3S1/2

MEAN DEPTH OF WATER, Dm = 0.551 Q0.3374

FOR  2:1 Side Slope  R = A/P =(BD+2D.D)/B+2D(.5)0.5

THE BEST  WAY OF DESIGN( V = 0.75m/sec for soil &V=2.0m/sec for concrete lining)

First get the Discharge of the canal Q = 1 Cumec ( Suppose )

D = 0.551 Q0.3374D = 0.551 meter ;

D = 0.5 B1/2

B = 1.21 m

 

A =  BD + 2.D.D (For side slope 2:1)  = 1.27 sq.m.

 

V = Q/A = 1/1.27 = 0.78 meter /sec = 2.58 ft / sec.

The above Example is the Best Procedure to Design a canal.

Bed Slope S = 3.293/10000.Q0.1450

 = 3.293/10000 = 1/3036

And By Equn.V = (1/N)R(2/3)S (1/2)

We  Can Decide Slope as per value of  S   OR Bed Material As Per The Value Of  N. That is the way to Design a canal in alluvial  soil or concrete (N = 0.0225).

P.K.Pandey    CITY.....REWA(M.P.)    , INDIA

Ph. 091-7662-58747