Consider a trapezoidal channel where water flows steadily at a certain depth, with a specified bottom width and side slopes angled to form the channel's cross-section.

The channel bottom has a specified slope, which directly affects the flow velocity.

Using these parameters, the goal is to calculate the flow rate for this channel configuration.

The calculation begins by determining the cross-sectional area, combining contributions from the bottom width and the sloped side sections.

Next, the wetted perimeter, consisting of both the bottom and side surfaces in contact with water, is calculated.

Using these values, the hydraulic radius is obtained by dividing the cross-sectional area by the wetted perimeter.

The Manning resistance coefficient, n, is selected for finished concrete lining to account for surface roughness.

The hydraulic radius, together with the channel slope and other parameters, is substituted into Manning's equation.

After the calculations, the flow rate is determined, representing the volume of water passing through the channel per unit of time.