Subsidence and flooding in New Orleans: Space geodesy

A subsidence map of the city offers insight into the failure of the levees during Hurricane Katrina. Countdown to disaster A new subsidence map of the city of New Orleans, generated from space-based synthetic aperture radar measurements, reveals particularly rapid subsidence in the three years before Hurricane Katrina struck. One area that sank significantly lies near the canal southwest of Lake Borgne, and it was badly affected when the levees failed in several places during the hurricane. It has long been recognized that New Orleans is subsiding and is therefore susceptible to catastrophic flooding. Here we present a new subsidence map for the city, generated from space-based synthetic-aperture radar measurements, which reveals that parts of New Orleans underwent rapid subsidence in the three years before Hurricane Katrina struck in August 2005. One such area is next to the Mississippi River–Gulf Outlet (MRGO) canal, where levees failed during the peak storm surge: the map indicates that this weakness could be explained by subsidence of a metre or more since their construction.