A rectangular channel having a bed slope 0.0001, width 3.0

A rectangular channel having a bed slope 0.0001, width 3.0 m and Manning’s coefficient ‘n’ 0.015, carries a discharge of 1.0 m³ /s. Given that the normal depth of flow ranges between 0.76 m and 0.8 m. The minimum width of a throat (in m) that is possible at a given section, while ensuring that the prevailing normal depth is not exceeded along the reach upstream of the contraction, is approximately equal to (assume negligible losses)

The width of section should be such that specific energy should be critical at contracted section.

E_c =	3		q²		^1/3
	2		g

0.7893 =	3	(1)^2/3
0.7893 =	2	g^1/3(B_min)^2/3

B_min = 0.836 m