ABSTRACT
The 1927 flood revealed the imprudence of the long-standing levees-only policy for river flood control and demonstrated the need to accommodate the will of the river. Afterward, spillways, which are essentially controlled crevasses, were installed at Bonnet Carré and Morganza to serve as safety valves during flood stage. Riverfront levees today form the single most influential man-made feature in the deltaic landscape, protecting people, creating value, and encouraging urban development even as they cause soil subsidence and coastal erosion. They held fast when Hurricane Katrina's residual Category 5 surge raised the river's stage from four feet to 16 feet above sea level. The same cannot be said of the slender levees and floodwalls lining the city's intricate network of drainage and navigation canals. Their failure formed the proximate, though not the ultimate, cause of the city's worst flood ever.
