Civil Engineering - Irrigation - Discussion

You are right @Maria saeed.

The groynes are generally aligned either perpendicular to bank or pointing upstream. Here written generally means normal groynes. This point to be noted. So, Only Option A is correct.

Ocean groynes are generally found perpendicular to the bank. So, why not A?

What is the best answer?

The given answer is right.
Repealing groynes toward upstream at 30 degree.
Attractive is downstream at 60 to 70 degree.
Deflecting is 90 degree.

A, B is right.

C is wrong since attracting groynes has 45-60 degree d/s.

1. Repelling groynes-(60°-80° inclination from bank, pointing upstream).

2. Attracting groynes-(45°-60° pointed downstream).

3. Deflecting groynes- (made perpendicular to the bank only deflect the flow without repelling the flow, it only gives local protection).

4. Denchey T-headed Groyne-(a special type of Groyne- in which earthen embankment projecting from a marginal bonds, T shape,spaced 800m apart ,head of the Groyne- has a slope on both sides and are heavily protected by stone).

All of the above is the correct answer.

Repelling groynes are built with their head towards upstream with an inclination of 60 to 80 degrees with the bank. They repel the water flow towards the bank on which it is located.

Repelling Groyne.

The head portion of repelling groynes is under the main attack by the flow. Hence, it should be built with strong protection. The sediments carried by the water gets deposited in the silt pocket which is formed at the upstream side of repelling groyne. These groynes are more advantageous than attracting groynes and are used widely for river training and bank protection.

Upstream is for repelling groyne.