Question

What is the U.S.B.R recommended value for freeboard when the height of the dam is more than 60 m?

(a) 2 m to 3 m

(b) 2.5 m above the top of gates

(c) 3 m above the top of gates

(d) More than 3 m

This question was addressed to me by my college director while I was bunking the class.

This interesting question is from Design Criteria of Earth Dams topic in chapter Earthen and Rock Fill Dams of Irrigation Engineering

Answer 1

Right choice is (c) 3 m above the top of gates

To explain I would say: For controlled spillway, if the height of the dam is less than 60 m, the minimum recommended freeboard value is 2.5 m above the top of gates. If the height of the dam is more than 60 m, the minimum freeboard value is 3 m.