7.15. A stream bed has a rectangular cross Section 5 m wide and a slope of 0.0002m/m. The rate of flow in the stream is 8.75 m'/s. A dam is

built across the stream, causing the water surface to rise to 2.5 m just upstream of the dam. (See Fig. P7-15.) Using the step method illustrated in Example 7-5, determine the water surface profile upstream of the dam to a point where y = y, ± 0.1 m.Assume n = 0.015. How far upstream does this point occur?