Major cities now require a stormwater management plan, prepared by a professional engineer, for any project involving significant impervious surfaces — whether for a building, parking area, or urban development.
The increase in impervious surfaces alters the natural behavior of runoff by accelerating flow rates and placing additional demand on existing infrastructure. A stormwater management plan therefore analyzes these impacts and proposes appropriate measures — such as detention, retention, or infiltration — to control peak discharge to the municipal system.
This framework allows municipalities to better protect and plan their infrastructure while reducing the risks of sewer backup, flooding, and downstream property damage.