What is the requirement for natural channels to ensure stormwater does not cause erosion?

The requirement for natural channels to ensure that stormwater does not cause erosion is based on the need to analyze the channel's behavior during a specific storm event. Analyzing natural channels with a 2-year storm event allows for an understanding of how the channel will handle runoff and whether it can accommodate normal variations in flow without experiencing erosion. This return period is significant because it represents a common interval for rainfall that can occur frequently, providing insight into the channel's resilience against erosion under typical conditions.

In contrast, a 5-year storm analysis might be appropriate for assessing larger, more extreme events where flooding and increased erosion potential are concerns; however, it does not address the routine capacity needed to prevent erosion from more frequent, lower-volume events. The other options, such as negating vegetation in the channel and modifying it to increase capacity, do not align with best management practices focused on sustainable and natural solutions for stormwater management, which prioritize maintaining ecological integrity while effectively managing water flow.