Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Flood routing, hydrological reservoir and channel routing
Question Statement:
The wedge storage in a river reach during the passage of a flood wave is
Options:
(A) positive during rising phase
(B) negative during rising phase
(C) positive during falling phase
(D) constant
Official Answer Key:
A
Step-by-Step Solution & Explanation
In channel (Muskingum-type) flood routing, total storage in a reach is split into prism storage (a function of outflow alone) and wedge storage (the extra storage caused by the difference between inflow and outflow along the reach, which gives the water surface a wedge shape). During the rising limb of a flood, inflow exceeds outflow, so the wedge is positive (water is being added on top of the prism, sloping upward toward the upstream end) — option (A). During the falling limb, outflow exceeds inflow and the wedge becomes negative.
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