Question

based on figure 3, which of the pmw or pbm types of barriers was as effective in reducing runoff at a height of 38 mm as it was at a height of 19 mm?
a. pmw, because for that type of barrier the amount of runoff at both heights was the same.
b. pmw, because for that type of barrier the amount of runoff at the 38 - mm height was less than the amount of runoff at the 19 - mm height.
c. pbm, because for that type of barrier the amount of runoff at both heights was the same.
d. pbm, because for that type of barrier the amount of runoff at the 38 - mm height was less than the amount of runoff at the 19 - mm height.

Explanation:

Step1: Analyze PMW

For PMW, at 19 - mm height, the runoff is about 4.5. At 38 - mm height, the runoff is about 5. So the runoff at 38 - mm height is more than at 19 - mm height.

Step2: Analyze PBM

For PBM, at 19 - mm height, the runoff is about 7. At 38 - mm height, the runoff is about 4. So the runoff at 38 - mm height is less than at 19 - mm height.

Step3: Analyze SCM

For SCM, at 19 - mm height, the runoff is about 3. At 38 - mm height, the runoff is about 3.5. So the runoff at 38 - mm height is more than at 19 - mm height.

Answer:

D. PBM, because for that type of barrier the amount of runoff at the 38 - mm height was less than the amount of runoff at the 19 - mm height.