Drainage is the planned movement of rainfall and snowmelt away from buildings and vulnerable areas. Stormwater management goes further by controlling runoff quantity, quality, erosion effects and water balance before water reaches a sewer, watercourse or other outlet.
Drainage focuses on safe conveyance
A drainage design establishes slopes, swales, catchbasins, roof outlets and overland routes. It prevents unwanted ponding, protects entrances and accessible paths, and avoids sending water onto neighbouring property. The grading plan is a primary tool for showing this system.
In a park, drainage also keeps play areas, sports fields, dog off-leash surfaces and paths usable. The design must distinguish ordinary rainfall drainage from wash-down water or other operational discharges, which may be subject to different sewer-use rules.
Stormwater management focuses on impacts
Stormwater management asks what changes when the site is developed. Controls may limit peak discharge, store water temporarily, treat pollutants, preserve infiltration or direct exceptional flows safely. Measures can include controlled roof drains, surface ponding, tanks, ponds, oil-grit separators and LID features.
A site can drain quickly but still fail stormwater criteria if it sends too much water downstream. It can also meet a release-rate target yet have poor local drainage around a building. Both layers need to work together.
Bous Engineering’s Stormwater Management Report service coordinates calculations with the grading and servicing plans. Related references explain major storm flow routes and what a site grading plan shows.
Key takeaway
Drainage solves where water travels on the site; stormwater management addresses how development affects the receiving system and environment. A complete civil design usually needs both perspectives.
Bous Engineering supports servicing, stormwater, grading and municipal approval assignments across Eastern Ontario.