Civil Engineering - Irrigation - Discussion

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

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

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.

A Groyne pointing upstream is a repelling one with a angle 10-30° (with the normal to bank).

While a Groyne pointing downstream is an attracting one with an angle 60-80° ( with the bank).

REFERENCE: IRRIGATION ENGINEERING AND HYDRAULIC STRUCTURES BY SANTOSH KUMAR.

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.

What is the best answer?

According to Santosh Kumar book on" hydraulic structure" the gyrones generally, build are repelling types because it creates silt pack which serves the purpose so the majority of the time Gyrones build are of projected towards upstream so the right option is B.

A is the correct answer.

D is the correct option.

If it is B then what about the option A? it also be right.