What type of impact does a 100% vegetated roof have on storm water management?

A 100% vegetated roof significantly reduces runoff due to its ability to absorb rainwater through the plants and the growing medium. These systems are designed to retain a considerable amount of water, which is used by the vegetation for growth and evaporation. This absorption and evaporation process means that less water reaches the building's drainage system and ultimately reduces the volume of stormwater runoff that would typically occur with traditional roofs.

In addition to minimizing runoff, vegetated roofs also provide other environmental benefits, such as improving air quality, enhancing biodiversity, and aiding in temperature regulation within urban areas. The reduction of runoff is particularly important because it helps to alleviate stress on local stormwater management systems and can mitigate issues like flooding and water pollution by reducing the volume of untreated stormwater entering local waterways.

The other options do not accurately describe the impact of a vegetated roof on stormwater management. For example, increasing runoff and generating heat contradict the principles of green roofs, while additional irrigation may be necessary in some cases but is not a direct impact of the vegetated roof itself on stormwater management. Thus, the role of a 100% vegetated roof in reducing runoff is key to its environmental benefits and stormwater management effectiveness.