Post-Katrina, New Orleans faces ongoing urban and environmental risks of impact from flooding and increasing subsidence. Despite the area's massive water pumping capacity, heavy downpours overwhelm drainage systems, causing frequent localized flooding; in the longer term, the city must also confront the risks of rising sea levels.
Though a natural phenomenon in southeast Louisiana, increasing subsidence is mainly due to inadequate water management strategies that rely on excessive pumping methods, which dries out organic soils and causes the land to sink. The city also continues to grapple with socioeconomic issues resulting from the frequent interruption of economic activity due to flooding, and also the legacies of Katrina, such as unemployment, increasing insurance rates, and a devalued property market.
In 2010, the State of Louisiana’s Office of Community Development – Disaster Recovery Unit funded Greater New Orleans, Inc. (GNO, Inc.) to develop a comprehensive, integrated and sustainable water management strategy for the east banks of Orleans and Jefferson Parishes and St. Bernard Parish using federal Community Development Block Grant – Disaster Recovery funds from the Department of Housing and Urban Development. And in 2013, the Greater New Orleans Urban Water Plan was announced as being a vision for long-term urban water management in the 21st century, and effectively the first regional urban water plan of its kind in the United States. The plan was developed over the course of two years by a team of local and international water management experts, with the additional input of city, regional and state governments.
The plan follows the innovative “slow, store & use, and drain” model borrowed from the Dutch. Rather than pumping away every drop of water that falls as quickly as possible and thereby increasing subsidence, this approach entails “slowing down” the water using bio-retention and infiltration strategies. This includes rain gardens and bio swales, storing it in the landscape longer by retrofitting canals and finding space for new canals and ponds, and draining it only when necessary.
The specific actions of the plan are broken into three phases:
- Near term (2013-2020): implementation of “smart retrofits”, interventions to reshape legacy infrastructure or ongoing projects to incorporate water management strategies.
- Medium term (2020-2030): improving water flows and connectivity within the scale of the actual project
- Long term (2030-2065): diffusing Urban Water Plan’s strategies throughout Southeast Louisiana.
The Greater New Orleans Urban Water Plan provides a roadmap for mitigating flood risk, limiting subsidence, and improving the quality of water. The additional benefits associated with these three main environmental targets are numerous, for instance, reduced “heat island” effects and enhanced air quality thanks to the planting of new trees; increasing waterways and green spaces that create micro-climates and act as heat sinks. Furthermore, the implementation of slow, store and use strategies will serve to reduce property and infrastructure damages and associated insurance premiums, and is expected to have a positive impact on property values.