Question

A sloping apron is provided partly above the river bed and partly below the river bed in case of ____________________________

(a) when TWC coincides with the JHC at all discharges

(b) when TWC lies above the JHC at all discharges

(c) when TWC lies below the JHC at all discharges

(d) when TWC lies above the JHC at low discharges and below the JHC at high discharges

The question was asked in an international level competition.

Question is from Energy Dissipation Below Overflow Spillway topic in division Spillways, Energy Dissipators and Spillway Gates of Irrigation Engineering

Answer 1

The correct choice is (d) when TWC lies above the JHC at low discharges and below the JHC at high discharges

The best explanation: At low discharges, the jump will be drowned and at high discharges tail-water depth is insufficient. When TWC lies above the JHC at low discharges and below the JHC at high discharges, the solution is the provision of sloping apron partly above and partly below the river bed. The horizontal apron and end-sill are also provided.