Street inlets, catch basins, storm sewers, municipal separate storm sewer systems, runoff, flooding, curb gutters, outfalls, untreated discharge, trash, oil, sediment, bacteria, and water quality
Storm drains
Storm drains collect rainwater runoff from streets, parking lots, roofs, and other hard surfaces and move it through drainage systems.
What they are
Storm drains are the grates, curb openings, catch basins, and inlets that collect runoff from streets and other paved surfaces. They are the visible pieces of a larger drainage network built to move water away from places where it can flood roads, buildings, and sidewalks.
Where the water goes
The path depends on the city and the sewer type. In a municipal separate storm sewer system, stormwater may travel through pipes or ditches to a nearby stream, lake, harbor, or coastal water. In some older areas, stormwater may enter combined sewers that also carry wastewater.
Not the same as a sink
A household drain normally connects to sanitary sewer or septic treatment. A storm drain is different: it is built for rain and runoff. That is why labels such as “drains to river” matter. They remind people that storm drains are not disposal points.
What runoff carries
Runoff can pick up soil, leaves, fertilizer, pet waste, oil, metals from brake dust, road salt, bacteria, trash, and chemicals from yards or work sites. A small inlet can collect pollution from a much larger area of roofs, curbs, driveways, and pavement.
Flood-control role
Storm drains reduce nuisance flooding by collecting water quickly. That speed is useful during storms, but it also changes streams downstream. Fast runoff can raise peak flows, erode channels, and reduce the chance for water to soak into soil.
Clogs and maintenance
A storm drain blocked by leaves, sediment, ice, or trash can flood a street even when the pipe system has capacity. Cleaning catch basins, sweeping streets, clearing curb inlets, and keeping construction sediment out of drains are ordinary but important maintenance tasks.
Better upstream design
Green infrastructure tries to keep some runoff out of storm drains in the first place. Rain gardens, bioswales, trees, permeable pavement, and detention systems slow water down, filter pollutants, or store runoff before it reaches the inlet.
Why it matters
Storm drains make urban rain disappear from view, but not from the watershed. They connect everyday surfaces to real waterways, which means small choices on streets, lawns, driveways, and construction sites can add up quickly during a storm.