Plane length L = 35 m
Plane slope So = 0.008
Manning's n = 0.08
rainfall excess i = 55 mm/hr
Kinematic flow number K = (SoL)/(Fo2ho)
Calculate equilibrium outflow; establish rating; calculate ho from rating; calculate mean velocity vo,
and Froude number.
Equilibrium outflow qe = iL = (55 mm/hr × 35 m × 0.001 m/mm) / (3600 s/hr) = 0.000535 m3/s/m
Rating: qe = b hom
b = (1/n) So1/2 = (1/0.08) (0.008)1/2 = 1.118
Choose m = 5/3 [Manning friction in wide channels (overland flow)]; 1/m = 3/5 = 0.6
Calculate he = (qe/b) 1/m = (0.000535/1.118)0.6 = 0.01 m
ho = he = 0.01 m
Calculate vo = qe / he = (0.000535/0.01) = 0.0535 m/s
Calculate Fo2 = vo2 / (gho) = (0.0535)2 / (9.81 × 0.01) = 0.0292
Calculate K = (SoL)/(Fo2ho) = (0.008 × 35) / (0.0292 × 0.01) = 959 > 20.
The flow is kinematic. ANSWER
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