Select the option that is appropriate regarding
the following two statements labelled Assertion and Reason.
Assertion: A channel should be designed for a velocity that will neither deposit the sediment nor scour the bed and banks. This velocity is known as non-scouring and non- silting velocity.
Reason: If the velocity of flow is too low, the sediment held in suspension will settle down; whereas, if the velocity is too high, the water will scour the bed and sides of the canal.

Correct option is A

• The velocity to be allowed in a channel design should be too low such that the silt flowing in the channel is dropped on the bed . Also the velocity should not be large enough to erode away the bed and sides of the channel. A velocity which will just keep the silt in suspension, without scouring the channel is known as non-silting and non-scouring velocity.
• Many investigators have worked on various existing channels towards the design of non-silting-non-scouring channel section. Notable amongst them are works done by Mr. R.G.Kennedy of Punjab Irrigation Department and Mr. Gerald Lacey, Chief Engineer Irrigation Department U.P.