LAYOUT AND CONSTRUCTION OF CANALS
CANALS
A canal is an open-air waterway along which water flows unassisted.
The two main characteristics of every canal are:
- Geometric characteristics and
- Hydraulic characteristics
These are illustrated below.
Geometric characteristics (Fig. 1)
b = inner border
B = Canal bed
B’ = Top base of the canal
b’ = outer border
h = Depth of the canal
ø = Angle of the canal slope
A’ = Cross-cut section of the canal (it can be rectangular,
circular, trapezoidal or triangular)
Hydraulic characteristics (Fig. 2)
Q = Water flow (litres/second)
V = Water velocity (m/second)
A = Area of the cross-section of the mass of water conveyed by the
canal (m2). Its shape will depend on the cross-section of the canal
S = Slope or inclination of the canal bed, expressed in percentage
terms or in so much per thousand
d = Water stress or depth
R = Hydraulic radius. R = A/P
P = Wet perimeter, the sum of two banks and the canal bed
which are in contact with the water
n = Rugosity coefficient. Its value depends on the material the canal
is made of (earth, concrete, stone, etc.).
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