(Solved): The trapezoidal cross-section river channel has a bottom width of 20 m, side slopes of 2:1 (H:V), an ...

The trapezoidal cross-section river channel has a bottom width of 20 m, side slopes of 2:1 (H:V), and a bed slope of 0.0001, with the bed material composed of sand (n=0.025). We plan to cover a 100 m length of this river with concrete (n=0.012). Calculate the fish habitat area (WUA) of this river when the instream flow is 20 m³/s before covering it with concrete. Discuss the change in habitat area when maintaining the same instream flow after covering the river with concrete. Assume that the habitat suitability index for the bed material is 1 and use the geometric mean for calculations. The habitat suitability index for fish is provided in the following graph (20 pt).