Thursday, June 4, 2009


A drop has been defined to be a work designed to secure lowering of water surface in a channel and safe destruction of surplus energy so liberated. The velocity in channel is a function of slope and there is a limiting velocity which can be allowed in a channel depending upon the nature of soil through which it passes without causing it to scour its bed and sides. It follows therefore that there is a limiting slope which cannot be exceeded without causing any harm to the channel. The slope of the country which a channel has to irrigate is usually steeper than the slope required in the channel. To absorb their differential head, the introduction of drop at intervals becomes inevitable. The introduction of drop is required to protect from the ill effects such as erosion on the upstream, side and bed due to increased velocity because of the drawdown effect, to protect below the drop from impact force of falling water at the toe of the drop and to prevent the sides from erosion and bed from scouring due to the turbulent flow.

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