This standard provides criteria for the hydraulic design of flumes, which are constricted channel sections in canal systems. It covers the design principles for flumes operating under both sub-critical and super-critical flow conditions, with a major focus on the geometry and energy loss calculations for inlet and outlet transitions.
Provides criteria for the hydraulic and structural design of flumes in canals for flow measurement or crossing obstructions.
Quick Reference Values
Recommended inlet transition splay (sub-critical)1 in 2.5 (22.5 degrees)
Recommended outlet transition splay (sub-critical)1 in 2 (30 degrees)
Minimum recommended freeboard0.5 m to 0.75 m (varies with discharge)
Contraction loss coefficient (Kc) for well-designed transitions0.1 to 0.2
Expansion loss coefficient (Ke) for well-designed transitions0.2 to 0.3
Manning's 'n' for smooth concrete finish0.014 - 0.016
Key Formulas
Freeboard = C * (y)^1/3, where y is depth of flow and C is a coefficient from Table 1
Head loss in contraction: hc = Kc * (V2^2 - V1^2) / 2g
Head loss in expansion: he = Ke * (V1^2 - V2^2) / 2g
Froude Number: Fr = V / (gD)^0.5
Practical Notes
Pay close attention to the design of transitions; improper splay angles can lead to flow separation, eddies, and significant energy losses, reducing the canal's efficiency.
The structural design of the flume barrel and foundations to withstand hydrostatic and earth pressures must be carried out separately according to codes like IS 456.
Ensure adequate freeboard is provided to prevent overtopping of canal banks, especially upstream of the flume, considering potential surges and inaccurate hydraulic calculations.