Question

The spacing between adjacent spurs in river training work is generally kept between ______ times the spur length.

1. 1.5 to 2.5
2. 1 to 2
3.  2 to 2.5
4. 2.5 to 3.5

Answer 1

Correct Answer - Option 3 :  2 to 2.5

Concept:

Groynes or spurs: 

• These are constructed transverse to the river flow extending from the bank into the river.
• This form of river training works perform one or more functions such as training the river along the desired course to reduce the concentration of flow at the point of attack, creating a slack flow for silting up the area in the vicinity and protecting the bank by keeping the flow away from it.
• Each groyne can protect only a certain length and so the primary factor governing the spacing between adjacent groynes is their lengths. Generally, a spacing of 2 to 2.5 times the length of groynes at convex banks and equal to the length at concave banks is adopted.

Groynes or spurs are classified as -

1.  Permeable or impermeable
2.  Submerged or non-submerged
3.  Attracting, deflecting repelling and sedimenting and
4. T-shaped (Denehey), hockey (or Burma) type, kinked type, etc.