What is an advantage of vegetated rooftops regarding stormwater?

Vegetated rooftops, often referred to as green roofs, provide a unique benefit in stormwater management by temporarily capturing and storing stormwater runoff. This capability is primarily due to the soil medium and plant life that absorb rainfall. When it rains, the vegetation and underlying soil system soak up a significant portion of the water, which helps to reduce the volume of water that directly enters the stormwater drainage system.

This temporary storage helps mitigate peak runoff flows, allowing for a slow release of water over time, which can ease the burden on drainage systems and reduce the risk of flooding. Additionally, the vegetated layers help to filter pollutants from the stormwater, improving water quality when the runoff eventually does leave the rooftop. Unlike options that suggest complete elimination of runoff or permanent storage, the key feature of vegetated rooftops is their ability to manage stormwater dynamically, enhancing both urban biodiversity and the effectiveness of urban drainage systems.