How do green roofs reduce urban flooding and moderate city temperatures?

Green roofs, also known as landscaped rooftops, serve as effective tools in civil engineering for managing urban environmental challenges by utilizing vegetation to interact with water and heat cycles.12

Stormwater Management

Green roofs reduce urban flooding by acting as a natural sponge. The vegetation and soil layers absorb and retain rainwater, which significantly decreases the volume of storm runoff that enters a city's drainage system. By capturing this precipitation, green roofs alleviate pressure on aging storm sewers, helping to prevent the overflow and flooding often associated with heavy rainfall in urban environments.12

Temperature Moderation

Green roofs help mitigate the urban heat island effect—a phenomenon where cities experience significantly higher temperatures than surrounding areas due to the prevalence of heat-absorbing materials like asphalt and concrete. They moderate city temperatures through several mechanisms:1
* Natural Insulation: The layers of soil and plants provide thermal insulation for buildings, reducing the need for artificial cooling systems and lowering energy consumption.12
* Evapotranspiration: Vegetation releases moisture into the air, which cools the surrounding environment.1
* Reduced Heat Absorption: By covering surfaces that would otherwise absorb and reemit solar energy, green roofs lower the overall ambient temperature in urban settings.1