Online BMP captures how much of the runoff?

The concept of Best Management Practices (BMPs) in the context of stormwater management is designed to effectively manage and treat runoff to mitigate its impacts on the environment. When referring to selected BMPs that are employed online, it signifies that they are directly integrated within the flow's path, typically designed to capture and treat the entirety of the runoff generated from a specific area during a storm event.

When a BMP captures all of the runoff, it means that the design effectively redirects, filters, and manages the flow to ensure pollutants are significantly reduced before the water re-enters the natural hydrology or drainage systems. This level of effectiveness is crucial for reducing sedimentation and preventing erosion, as it addresses water at the point of generation, helping to maintain water quality.

In contrast, capturing only a portion, a small percentage, or none of the runoff would indicate an incomplete or ineffective BMP, which does not meet the goal of fully treating stormwater to protect water quality and mitigate erosion and sedimentation issues. Therefore, the expectation from effective online BMPs is that they serve to capture, treat, and manage 100% of the runoff they are designed for, leading to the conclusion that they are intended to capture all runoff.