47.3.4. Design Procedure using Lacey’s Theory

Try these first

1. 1.

   What is the formula to calculate the silt factor?

   Hint

   Consider the relationship between sediment and flow.

2. 2.

   What does discharge (Q) represent?

   Hint

   Think about water flow rates in a channel.

3. 3.

   What is the first step in designing a channel using Lacey’s Theory?

   • Calculate the wetted perimeter
   • Determine discharge (Q) and sediment size (d)
   • Find the slope (S)

   Hint

   Think about what information is needed for further calculations.

4. 4.

   Is the formula for the silt factor, f = 1.76 × d, true or false?

   • True
   • False

   Hint

   Recall how sediment influences flow.

5. 5.

   Consider a channel with a discharge of 20 m³/s and sediment size of 1 mm. Calculate the silt factor and subsequent channel characteristics, including velocity, area, wetted perimeter, and slope.

   Hint

   Break down each component step-wise to tackle the problem efficiently.

6. 6.

   Discuss how different sediment sizes can affect the slope estimation in Lacey’s design procedure, providing specific examples.

   Hint

   Consider how the flow dynamics change with sediment size!