Urban Stormwater Management: Evolution of Process and Technology

Historically, stormwater management focused primarily on controlling the peak rate of runoff to prevent flooding. However, the field has evolved toward the Runoff Reduction Method (RRM), which emphasizes reducing the total volume of stormwater generated at a site. This approach treats stormwater as a resource rather than just a waste product, utilizing natural processes like infiltration, evapotranspiration, and harvesting to manage water before it enters conventional drainage systems.

The RRM utilizes a hierarchical three-step process to achieve compliance with modern environmental standards:

1. Better Site Design (BSD): Minimizing impervious surfaces and preserving natural features like forests and undisturbed soils to prevent runoff at the source.
2. Runoff Reduction Practices: Implementing structural measures such as bioretention, permeable pavement, and vegetated roofs to capture and treat water on-site.
3. Conventional Stormwater Practices: Using traditional methods like detention ponds or filters as a final step to address remaining pollutant loads or volumes that could not be managed in the first two steps.

Because modern stormwater practices are more complex than traditional basins, they require a collaborative effort across multiple disciplines. Successful implementation involves site planners, soil scientists, engineers, and landscape architects working together to ensure that systems are correctly designed, installed, and maintained. This complexity reflects the transition of stormwater management from a purely engineering-focused task to a multidisciplinary field that integrates ecology, horticulture, and urban planning.