A dam is built across a wide rectangular river with a bed slope of .The river conveys a specific discharge of 2.833 /s. If the depth of flow just upstream of the dam is 3.5 m, estimate the length of...

A dam is built across a wide rectangular river with a bed slope of

.The river conveys a specific discharge of 2.833

/s. If the depth of flow just upstream of the dam is 3.5 m, estimate the length of the backwater curve. H ow far upstream of the dam will the backwater curve cause a velocity reduction of 18% as compared to the velocity under normal flow conditions? Take Chezy's roughness coefficient as 70 (metric).