The Philadelphia Water Department maintains stormwater pipes, inlets, and treatment facilities to capture rainwater, decrease flooding and combined sewer overflows, and to reduce pollution.

Stormwater Wetland

Stormwater wetlands are shallow systems that collect runoff and store it in permanent pools. They are populated by marshland vegetation that help treat the water and allow pollutants to settle at the bottom like they do in natural wetlands, which allows them to support wildlife.

Stormwater Trees

Stormwater trees look like typical street trees, but these specially designed systems include a deep stone pit that holds excess water during intense rainstorms and as snow melts.

Tree Trenches

A tree trench is a system of trees that are connected by an underground infiltration structure. On the surface, it looks like a row of ordinary street tree pits, but underground there is a system to manage incoming runoff.


A swale is a grassy depression that controls stormwater velocity and infiltrates runoff where feasible. Swales are typically used to channel stormwater from a street or sidewalk to a rain garden or basin.

Subsurface Trenches

A storage trench is a subsurface rectangular bed cut into the street or sidewalk. The storage areas are designed to infiltrate stormwater or slow its flow into the sewer system.

Rain Gardens

A rain garden is vegetation designed to collect runoff from impervious surfaces, allowing water to infiltrate the ground. Rain garden plants are generally robust native species that can thrive in extremely wet and dry weather.

Stormwater Planters

A stormwater planter is a specialized sidewalk system that captures runoff from streets and sidewalks. The planter is lined with permeable fabric, filled with gravel or stone, and topped off with vegetation.

Permeable Paving

Permeable or porous pavement allows water to soak through the surface rather than flow over the surface and into storm drains. This system provides the structural support of conventional pavement but also has an underground stone reservoir.

Green Roofs

A green roof is a roof fully or partially covered in plants and waterproof media that helps reduce the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater release, and promoting evaporation.

Green Gutters

Green gutters are narrow, shallow landscaped strips along a street’s curb line that are designed to allow stormwater runoff from both the street and the sidewalk to flow directly into the system.

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