At a given location, under normal conditions a river flows with a Manning coefficient of 0.030 , and a cross section as indicated in Fig. P10.47a. During flood conditions at this location, the river has a Manning coefficient of 0.040 (because of trees and brush in the floodplain) and a cross section as shown in Fig. P10.47b. Determine the ratio of the flowrate during flood conditions to that during normal conditions.

Figure P10.47

Transcribed Image Text:

-800 ft- (a) 800 ft- 12 ft +20 ft (b) 1000 ft 8ft