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eGov Services • 1300 Perdido St, New Orleans, LA 70112 • (504) 658-4000
Home » Hazard Mitigation » Stormwater
Taking measures to slow down and absorb rainwater on individual properties can help reduce small scale flood events. Storing or absorbing water runoff during storm events decreases the amount of water on streets, in storm drains, and on private property. Many of these measures also improve the quality of stormwater runoff, resulting in less pollution. All stormwater that enters the City's drainage system eventually ends up in local water bodies, such as Lake Pontchartrain.
Rain barrels temporarily store runoff from roofs, preventing it from collecting on your property or in the street. The water collected in a rain barrel can later be used for gardening, washing cars, or other non-potable uses (this water is not safe for drinking).
Example of a Rain Barrel, Image Courtesy of Steve Piccou
Rain gardens are landscaped areas that store and filter stormwater. They are typically built slightly lower than the surrounding area and are made of mulch and plants. Rain gardens are good for residential, commercial, and municipal spaces.
Example of a Rain Garden, Image Courtesy of Steve Piccou
Permeable pavement (also called porous or pervious pavement) contains many small holes, allowing water to pass through into the ground. It can be interlocking pavers or can be poured like regular concrete. Because of the soil in New Orleans, an under-drain is typically necessary. Permeable pavement is good for driveways and sidewalks.
Example of Permeable Pavement, Image Courtesy of Steve Piccou
Green roofs are roofs of buildings that are partially or completely covered with vegetation. They effectively reduce stormwater runoff by absorbing rainwater. Green roofs can reduce stormwater runoff, which would otherwise contribute to street flooding and pollution. Green roofs can also increase energy efficiency, lowering electric bills.
Image courtesy of Lisa J from panoramio.org
Infiltration trenches are long, narrow, gravel-filled areas. They are located in small drainage areas and are used to direct and store stormwater. They have the added benefit of reducing stormwater pollution before it enters local bodies of water. They work effectively when positioned at building downspouts and around building foundations.
Image courtesy of sustainablestormwater.org
Planter boxes can be filled with plants that absorb large amounts of water and can be placed directly below the edge of the roof to catch runoff. These planter boxes can help absorb some of the water during rain events and prevent damage to building foundations.
Image courtesy of the Environmental Protection Agency (EPA) from epa.gov
There are a range of measures that neighborhoods can implement to make communities safer from flooding. Most of the actions recommended for neighborhoods involve either storing or absorbing runoff during storm events. This page explains actions that help prevent the neighborhood drainage system from being overburdened. Please note: some neighborhood level mitigation actions require appropriate permits from the city, especially if located on public property.
Often leaves, branches, and trash may collect around the drains which block water from flowing into the drain. Street flooding can be reduced by cleaning and maintaining storm drains. Neighbors can easily clear out the drains and the areas around drains with shovels or rakes.
Image courtesy of Steve Piccou
People often clog drains with debris and dump harmful pollutants down drains. The City’s storm drains are pumped into canals which flow directly into Lake Pontchartrain. Dumping can increase flooding and pollute Lake Pontchartrain. Labeling storm drains with warnings can be an effective method for deterring these actions. Marking storm drains also reminds workers repairing streets to not cover the drains with construction debris.
Image courtesy of the Environmental Protection Agency (EPA)
Retention areas are areas designated for stormwater storage. They allow neighborhoods to hold water in a safe spot until it can drain. This reduces the amount of water that the drains must accommodate during a storm event, which decreases the risk of flooding.
Detention areas are similar to retention areas; however, detention areas hold water for a significantly shorter period of time. In New Orleans stagnant water can be attract mosquitos. Because of this, detention areas are often preferred.
When plants absorb water, that reduces the amount of water flowing into the City’s drains. Many native plants are able to store and absorb greater amounts of water than non-native plants. The Louisiana State University Agricultural Center's Website provides a list of plants which are well suited for Louisiana and New Orleans
Bioswales are depressed narrow channels that are used for temporarily holding runoff. They often contain plants and/or gravel designed to remove pollution and other sediments from stormwater. It is important for bioswales to be drained after a few days (24-72 hours), or they may attract mosquitoes.
Image courtesy of the Lake County Illinois Stormwater Management Agency
The City's drainage system requires regular maintenance and upgrades.
The Federal, State and City governments have implemented a range of actions designed to protect the City from flood events. These actions include making grants available for drainage improvement projects and home elevation, offering flood insurance, constructing levees and floodwalls, and planning coastal restoration. These large-scale mitigation actions that provide benefit across the city and region require coordination between multiple levels of government and affected stakeholders.
Levees are earthen or concrete structures that are constructed to protect the city from flood events. Levees are located along the Mississippi River, Lake Pontchartrain and in the eastern sections of the City.
Image courtesy of the Federal Emergency Management Agency (FEMA)
Floodwalls are manmade structures used to contain water. They are usually constructed out of concrete or metal and can be found along the Mississippi River and outfall canals. Floodwalls are also used in places where levees are unable to be built, such as along roadways.
Storm surge barriers block storm surge that could flow up water ways and threaten communities. A series of storm surge barriers have been built across the Mississippi River Gulf Outlet and the Intercostal Waterway to protect New Orleans from such a threat.
Image from the United States Army Corps of Engineers (USACE)
Canals are manmade waterways, which New Orleans uses to store and drain water. Canals are frequently blocked off from neighborhoods by floodwalls and levees.
Greenspace is vacant, undeveloped land. The land is left in a more natural state, which allows for better stormwater absorption. This results in less water entering the drain pipes. Greenspaces can range in size from individual lots to large parks.
Certain ordinances can be put in to place to promote better flood protection. These can include requiring new homes to be raised to a certain height and restricting development in hazard prone areas.
If a city wishes to participate in the National Flood Insurance Program (NFIP), which is administered by the Federal Emergency Management Association (FEMA), then the City must adopt and enforce minimum building restrictions to minimize flood damage.
Wetlands provide a crucial protective barrier against winds and storm surge from tropical storms, but Louisiana is currently losing 16-25 square miles of coastal wetlands every year. Over the last several decades this has added up to an area larger than the State of Delaware. This loss has occurred throughout Southeast Louisiana, including in and around New Orleans. The majority of the wetlands in the area have declined as the result of levees, development, and the construction of the Mississippi River Gulf Outlet.
Image Courtesy of United States Fish and Wildlife Service
Last updated: 8/17/2016 1:42:14 PM