Green & Gray Infrastructure
Green and gray infrastructures are structures that manage water. In New Orleans they are combined to mitigate flood risk.
Gray infrastructure is used to keep water out or force it out. It has been used in New Orleans since the early 1700's when the first levee, at 3 feet high, was built to protect the city from the Mississippi River.
Traditional methods of gray infrastructure for stormwater management include: dams, levees, sewers, pumps (pump stations), and floodgates.
Green infrastructure focuses on the detention, retention, and filtering of water. Instead of keeping water out and getting rid of it as fast as possible, which is an overwhelming and impossible task during major flooding events, green infrastructure manages flood risk by redirecting and/or making use of the water.
Structures that detain hold water for a short period of time. Those that retain hold the water, allowing it to saturate into the ground and recharge the water table. Structures that filter purify the water by filtering out pollutants. Methods of green infrastructure can also combine detention, retention, and filtering capabilities.
Green infrastructures for stormwater management include: rain gardens, green roofs, bioswales, basins, french drains, planter boxes, rain barrels, permeable pavement, and native plants.