Urban Green Stormwater Infrastructure (GSI) is an alternative to gray infrastructure (storm pipes, gutters, etc.) that incorporates engineered systems and the natural environment, with the goal of reducing stormwater runoff by increasing infiltration and evapotranspiration.

GSI can be categorized as natural, enhanced, and engineered. Natural GSI includes wetlands, forests, grasslands, parks and gardens. Enhanced GSI includes rain gardens, bioswales, green roofs, and urban trees. Engineered GSI includes rain barrels, permeable pavement, cisterns and infiltration trenches. Natural and Enhanced GSI uses vegetation and soil to help manage stormwater runoff by allowing stormwater to infiltrate into the ground and be used and evapotranspired by vegetation. Engineered GSI can be used to collect and reuse stormwater or to help to infiltrate stormwater back into the ground.

Natural landscapes like forests, grasslands, and everything in between play an incredibly important part in shaping our landscapes. As our landscapes change over time with new expansion, natural factors need to be considered for infrastructure to function properly in varying conditions. As our landscapes change over with new expansion, natural factors need to be considered for infrastructures functioning properly in varying conditions.

Intense rainfall events are increasing in frequency and severity in many urbanized communities throughout the United States. According to future climate prediction models, extreme rainfall and flood events are expected to increase. Green spaces in urban environments greatly reduce the amount of flooding that takes place on the streets, highways, and sidewalks that we travel on. Vegetation and soil in urban environments help to infiltrate stormwater ino the ground and evapotranspire it back into the atmosphere, which helps to reduce strain on urban drainage systems. Additionally, stormwater runoff often contains pollutants that can be filtered by the soil and vegetation as it passes through into the ground.