27.6.1. φ-Index

Try these first

1. 1.

   What does the φ-Index signify?

   Hint

   Think of the relationship between rainfall and water that flows over the surface.

2. 2.

   How is the φ-Index calculated?

   Hint

   Focus on the total rainfall and runoff values.

3. 3.

   What is the primary purpose of the φ-Index?

   • To calculate total rainfall
   • To evaluate soil texture
   • To determine runoff potential

   Hint

   Remember its relationship with rainfall and surface runoff.

4. 4.

   Is the φ-Index dependent on initial soil moisture content?

   • True
   • False

   Hint

   Consider how wet soils behave differently than dry soils.

5. 5.

   A rainfall event produces 120 mm of rain and results in 40 mm of runoff over a duration of 3 hours. Calculate the φ-Index, then discuss how varying rainfall intensities might impact this value.

   Hint

   Focus on applying the φ formula first, then analyze intensity impacts.

6. 6.

   Imagine a city that has an average φ-Index of 15 mm/hr. Predict how changes in land use due to increased impervious surfaces might affect this value and potential flooding risks.

   Hint

   Consider urban development impacts on water absorption during rainfall.