32.4. SCS-CN Method of Estimating Runoff

Try these first

1. 1.

   What does SCS stand for in the SCS-CN method?

   Hint

   Look for the origin of the term in the name.

2. 2.

   What does the curve number (CN) indicate?

   Hint

   Think about how land use and soil type affect runoff.

3. 3.

   What is the main purpose of the SCS-CN method?

   • To estimate soil erosion
   • To estimate direct runoff from rainfall
   • To manage irrigation

   Hint

   Think about what direct runoff means in water resource management.

4. 4.

   True or False: The Curve Number (CN) can range from 10 to 100.

   • True
   • False

   Hint

   Recall the guideline numbers provided in handbooks.

5. 5.

   Given a rainfall depth of 70 mm, an initial abstraction estimated at 10 mm, calculate the expected runoff if the Curve Number is 80.

   Hint

   Carefully follow the steps in the SCS-CN calculation.

6. 6.

   Discuss the implications of changing land use from agricultural to urban on the Curve Number and consequently the runoff estimation.

   Hint

   Consider how land characteristics directly affect runoff.