12.4.2. Isohyetal Method

Try these first

1. 1.

   What is an isohyet?

   Hint

   Think of it as a 'rain fall' line.

2. 2.

   What do we calculate between isohyets?

   Hint

   Focus on the area concept.

3. 3.

   What is the main purpose of the Isohyetal Method?

   • To measure temperature
   • To calculate areal average rainfall
   • To forecast weather

   Hint

   Focus on rainfall and hydrology.

4. 4.

   True or False: Isohyets are only used in urban settings.

   • True
   • False

   Hint

   Think about where rainfall data might be collected.

5. 5.

   Given a scenario with three isohyets of 20 mm, 30 mm, and 40 mm within a certain storm area, calculate the total volume of rainfall over the area, assuming each isohyet covers 5 km².

   Hint

   Convert mm to meters when calculating volume.

6. 6.

   Critically analyze a situation where isohyetal mapping was incorrectly performed. What were the potential outcomes for urban drainage design?

   Hint

   Think about how poor predictions affect planning and safety.