As the Louisiana Spillway is opened to relieve potentially catastrophic flooding on the Mississippi River, it highlights some of the strategies that will have to be used more often to deal with the increased flooding expected under climate change.
The floodway is one of four, and has only been used once, in 1973. Its opening is designed to relieve pressure on the levee system protecting Baton Rouge, New Orleans and a host of chemical plants and oil refineries downstream. Hundreds of thousands of acres of farmland and thousands of homes will be flooded in the Atchafalaya River basin. As I wrote in last week’s Listener cover story on climate change, massive floods of this kind are the sorts of events for which we will have to sharpen our planning.
American author Mark Hertsgaard expects that in some locations new floodways or “sacrifice zones” will have to be planned for as we find ways to live with climate change. In his new book Hot: Living Through the Next 50 Years on Earth, Hertsgaard argues that even if dramatic action is taken to avert climate change, there is already plenty of trouble in the pipeline in the way of rising sea levels and wild, energetic weather. And he argues it is time to start planning for that. In the Netherlands, that has meant the delineation of two new sacrifice zones for the flooding of the Rhine on the outskirts of the city of Nijmegan, areas where settlement has already taken place.
In New Zealand, local authorities are beginning to think through other cases in which land might have to be sacrificed, rather than protected. Environment Waikato has carried out a research project on what “managed retreat” might mean, in which vulnerable coastal land would be abandoned. In New Zealand, planning for increased flooding is in its infancy, with little detailed understanding yet on which areas might be most badly affected. That means Dutch-type initiatives are premature. But one major research project funded by the government which is looking at community vulnerability, resilience and adaptatation to climate change includes a case study looking at future flooding risk in the Hutt Valley and how that might affect the community there. Its results are due later this year.
NB: Bryan Walker at sciblogs has posted this response to my article.