Green infrastructure provides multiple techniques that cities and regions can employ to help mitigate the risk of flooding from climate change or other natural occurrences. By storing and draining water into the ground naturally, green infrastructure can help prevent flooding. The increase of pavement and hard surfaces like roads and rooftops interrupt the natural ‘water cycle’ in urban areas, which prevents water from infiltrating into the ground or being used by trees and plants. Green infrastructure counteracts this impact, by slowing down runoff and capturing and infiltrating rainwater where it falls, therefore preventing flooding.
According to the American Rivers report, “Banking on Green,” Federal Emergency Management Agency (FEMA) estimates that 25% of the $1 billion in annual damages from caused by flooding are linked to stormwater. Therefore, by increasing infiltration and retention, green infrastructure can substantially reduce the overall amount of water entering local storm sewers or surface waters and reduce flooding-related impacts, including decreased property values and tax revenues associated with flooding, damages to public infrastructure and associated repair costs and damages to private and public property.
Some examples of how cities have used green infrastructure techniques to mitigate flood risks include Greenseams in Milwaukee. This program makes voluntary purchases of undeveloped, privately owned properties in areas expected to have major growth in the future. This land will remain undeveloped, therefore protecting and providing the ability to naturally store rain and melting snow.
Toledo, Ohio rebuilt a block of a street using green infrastructure techniques that captured rainfall in rain gardens, porous pavement and street edge swales. After the project was completed in 2012, residents experienced no basement flooding, even when a major storm dumped seven inches of rain on the city.