New Orleans, lying on the coast of the Gulf of Mexico, suffers from increasingly frequent hurricanes (on average 11 per year and rising) with storm surges above 6 m high, land subsidence, and coastal erosion aggravated by sea-level risexxxi. The ground in New Orleans has sunk as much as 10 feet (around 3.1 meters) over the past 100 years in some parts of the city, affecting streets, levee and floodwall integrity, and subsurface infrastructures. The land subsidence mainly impacts low-income households located in affected areas.
In August 2015, New Orleans unveiled its Resilience Strategyxxxii with visions for 2050, which proposes 41 actions to build city-wide resilience and address land subsidence. The Strategy proposes developing a comprehensive storm water management program (flood perimeter defence system, storm surge barrier, dykes and levees, restoring coastal wetlands), while aiming to mitigate land subsidence. Specific provisions for better management of subsidence threats are detailed in the Greater New Orleans Urban Water Planxxxiii (2013), including: construction of circulating lowland canals; restoration and building of integrated wetlands; street design with bioswales and pervious pavement (“floating street”) allowing groundwater table recharge; and building of blue-green networks. Blue-green networks (e.g. Lafitte Corridor) utilize vacant city lots that can serve to safely store storm water and help replenish the groundwater table, thus limiting the runoff of freshwater into the sea. Apart from land subsidence mitigation, New Orleans also envisages other adaptation measures such as reducing above-surface utility systems and improving the subsurface ones. Finally, further research on soils infiltration and advanced groundwater monitoring is being carried out. Overall, New Orleans estimates that integrated water management could save property owners up to US$2.2 billion in subsidence-related maintenance costs over the next 50 years.
Reasons for success
New Orleans has been able to undertake a holistic, comprehensive redesign of its water management after Hurricane Katrina revealed vulnerabilities of the previous system ten years ago. Since then, New Orleans has received the attention and assistance from the national government, the state government, and many non-government actors, researchers and philanthropies. New Orleans has therefore been able to serve as a model project for delta cities and has been able to reassess its relation to water from four directions –the sea, the river, the rain and the ground.
C40 Good Practice Guides
C40's Good Practice Guides offer mayors and urban policymakers roadmaps for tackling climate change, reducing climate risk and encouraging sustainable urban development. With 100 case studies taken from cities of every size, geography and stage of development around the world, the Good Practice Guides provide tangible examples of climate solutions that other cities can learn from.
All references can be found in the full guide.