What hydrologic design criterion does a 100-year storm represent and why is it used?

What hydrologic design criterion does a 100-year storm represent and why is it used?

• A. It represents a storm with a 50% annual probability; used for planning.
• B. It represents a storm with a 1% annual probability; used to size drainage and prevent flooding.
• C. It represents a storm with a 5% annual probability; used for rough hydrology checks.
• D. It represents the maximum observed flood event; used as a safety margin.

Answer: (B)