31.8. Comparison Table: φ-index vs W-index

Try these first

1. 1.

   What does the φ-index measure?

   Hint

   Think about how we assess rainfall contribution to runoff.

2. 2.

   What does the W-index take into account that the φ-index does not?

   Hint

   Recall the definition of initial abstraction.

3. 3.

   What does φ-index represent?

   • Initial losses
   • Average rate of infiltration
   • Total runoff

   Hint

   Consider what we discussed about its definition.

4. 4.

   The W-index accounts for initial losses. True or False?

   • True
   • False

   Hint

   Remember the key difference between the two indices.

5. 5.

   Given a storm event with 150mm of rainfall, where 90mm of runoff was recorded and initial losses measured to be 30mm, calculate both the φ-index and W-index.

   Hint

   Use the formulas correctly and think about each component.

6. 6.

   Design a scenario where using φ-index would mislead stormwater management in a town. Discuss the outcomes if W-index were used instead.

   Hint

   Consider the importance of initial losses in real-world applications.