How does a green roof help in terms of stormwater runoff?
The natural cycles of the environment are interrupted when changes to the landscape are made. The development and expansion of cities significantly, if not completely, changes the natural environment. Constructions such as roadways and buildings create a seal over the ground and prevent rainwater from being absorbed. As a result, rainwater runs along the sealed surfaces picking up contamination in its path before reaching the sewer system and eventually being dumped directly into water bodies. Sewer systems are often stressed or flooded as a result of such large quantities of water arriving in a short period of time. Green roofs help restore aspects of the natural water cycle by absorbing and recycling rainwater. Runoff water can be reduced from 10-90%, depending on the green roof build-up. Plants can then use the retained water for natural processes and consequently, acclimatize the surrounding environment. Excess water can be collected into cisterns or other collection devices. Even
