watercourse has a trapezoidal section $($see figure below$).$ Determine the value of the section area, the wetted perimeter as well as the width of the LV mirror

Below we will find representative data from a river section:

$\backslash$table$[[$Distance $,$Elevation $($m$)],[0,403],[10,403],[30,398],[80,398],[110,403],[120,403]]$

For this part of the river, the Manning roughness coefficient is estimated at $0\mathrm{.}05$ and the slope of the bed is measured at $1$ in $1000.$ a$)$ Assuming that the flow is steady and uniform, estimate the normal depth of this river channel for a measured flow of $310m\frac{3}{s}.$ We know that the flow remains inside the main channel for this flow rate. b$)$ Also estimate the flow of this channel when the water level is just at the top of the main channel.