Design a suitable section for the overflow portion of a concrete gravity dam having the

downstream face sloping at a slope of $0\mathrm{.}75$ H: $1$ V$.$ The design discharge for the spillway is

$4000$ m$3$

$/$s$.$ The height of the spillway crest is kept at RL $190\mathrm{.}0$ m$.$ The average river bed level

at the site is $100\mathrm{.}0$ m$.$ The spillway length consists of $4$ spans having a clear width of $15$ m

each. Thickness of each pier may be taken to be $2\mathrm{.}0$ m$.$ Other data, if required, may be suitably

assumed.