Most urban infrastructure was not designed for shorter duration storms that yield torrential downpours. Hard surfaces including roofs cause stormwater to pool rapidly, creating floods. Green roofs can mitigate some of this effect, and a similar approach known as “blue roofs” can accomplish the same without using vegetation.
A blue roof system stores rainwater and slowly releases it using flow-control devices or structures including customized trays and existing building risers that cause water to dam up. Together, they collect and then slowly release rainwater, allowing municipal drains and stormwater piping to keep up with heavy volume pressure.
Blue roofs typically retain more water than green roofs and are particularly beneficial in commercial/industrial zones. Stored water also provides buildings with a cooling effect through evaporation, and the collected water can be made available for reuse.