Stormwater Management

The planning, design, and implementation of systems to control the quantity and quality of rainwater runoff from developed sites, as required by local, state, and federal regulations.

What is Stormwater Management?

Stormwater management encompasses the systems, practices, and regulations designed to control the flow, volume, and quality of rainwater runoff from developed land. When natural landscapes are replaced by impervious surfaces (buildings, parking lots, roads), rainwater can no longer infiltrate the ground naturally, leading to increased runoff that can cause flooding, erosion, and water pollution. Stormwater management systems address these impacts.

Regulatory Framework

Stormwater management is regulated at multiple levels. The federal Clean Water Act requires municipalities to obtain National Pollutant Discharge Elimination System (NPDES) permits for their stormwater systems, which in turn impose requirements on private development. State and local regulations add site-specific standards for detention, retention, infiltration, and water quality treatment. Most jurisdictions require a stormwater management plan as part of the building permit or grading permit application.

Common Stormwater Systems

Development projects may incorporate: detention basins (which temporarily store runoff and release it slowly), retention basins (which permanently hold water), bioswales and rain gardens (which filter and infiltrate runoff through vegetation), permeable pavement, green roofs, underground storage chambers, and manufactured treatment devices. The appropriate system depends on local regulations, site conditions, and available space.

Impact on Development

Stormwater requirements significantly affect site design, particularly on tight urban lots where space for detention or infiltration facilities is limited. Stormwater compliance costs can be substantial for large developments. Early integration of stormwater management into site design is essential to avoid costly redesigns later in the permitting process.