2.5. Calculating Area and Wetted Parameter

Try these first

1. 1.

   What is Manning's equation used for?

   Hint

   Think about the factors affecting flow.

2. 2.

   Define hydraulic radius.

   Hint

   What is the relationship between area and perimeter?

3. 3.

   What does the term 'wetted perimeter' refer to?

   • A. The total area of flow
   • B. The length of the channel in contact with water
   • C. The channel's slope

   Hint

   It’s about the surface area in contact with the liquid.

4. 4.

   True or False: Manning's n value decreases with rougher channel surfaces.

   • True
   • False

   Hint

   Think about how friction affects flow.

5. 5.

   A trapezoidal channel has a bottom width of 5 m, side slopes of 1:2, and a depth of 2 m. The bottom slope is 0.0015, and n = 0.01. Calculate the flow rate Q.

   Hint

   Break down the channel dimensions step by step during your calculations.

6. 6.

   For a channel with variable roughness (n1 = 0.02, n2 = 0.025), find the effective Manning parameter if the sections have areas of 4 m² and 6 m² respectively.

   Hint

   Consider how each rough section contributes to the total resistance.