The cross section of a channel in a certain area is shown in the diagram below. The channel has a compound section, with different Manning roughness coefficients for the main deep channel and the high floodplains on both sides. The bed slope of the channel is S=0.02. (1) When the normal depth yn=1.5m, calculate the composite Manning roughness coefficient ( ncomposite) of the channel and estimate the flow rate (cms) for this section. (2) If the Manning roughness coefficients for the high floodplains on both sides are changed to be the same as that of the deep channel, what is the new flow rate for the