Section 4: Soil and Water Conservation Engineering
Soil and Water Erosion
Subtopic: Gully control structures – drop, drop inlet and chute spillways
Question Statement:
Which of the following statements regarding permanent gully control structures is/are correct?
Options:
(A) Drop spillways are generally installed for hydraulic drop heights less than 3 metres.
(B) Chute spillways are well suited for high drop structures and steep gullies.
(C) Drop inlet spillways consist of a vertical conduit or riser connected to a horizontal barrel through an earthen embankment.
(D) Drop spillways require an auxiliary vegetative emergency spillway when designing for total peak design flood.
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
• Straight drop spillways are economical and structurally stable for drops typically up to 3 m (A is correct).
• Chute spillways convey flood flows down steep slopes up to 5–6 m or more (B is correct).
• Drop inlet spillways convey water through a vertical riser pipe to a nearly horizontal barrel buried beneath an embankment (C is correct).
• Drop spillways are usually designed as the principal spillway to safely convey the design peak discharge without necessarily needing an emergency vegetative spillway unless specified for extreme floods.