What does the term "10-year/24-hour storm" refer to in stormwater design?

The term "10-year/24-hour storm" refers to a statistical estimate used in stormwater management to determine the volume and rate of runoff that a drainage system is expected to handle during a significant rainfall event. Specifically, it represents the amount of rainfall that is statistically expected to occur over a 24-hour period, with a return frequency of once every ten years.

In practical terms, this means that if the design intends to manage a "10-year/24-hour storm," it is focused on preparing the drainage system to accommodate a rainfall event that has a 10% chance of occurring in any given year (though it may not happen every ten years exactly). This estimate is critical for engineers and planners as it informs the sizing of drainage facilities, ensuring that they can effectively manage runoff without leading to flooding or erosion.

Understanding this concept is essential for creating resilient stormwater designs that can handle significant storm events, taking into account the historical data of rainfall patterns in a given area. This makes option B the correct answer, as it accurately describes the purpose and application of the 10-year/24-hour storm in the context of stormwater design.