Different than the river levees, hurricane protection levees were started much later. When the 1947 hurricane made a direct hit on New Orleans there were no hurricane protection levees to speak of. As a result of that storm, efforts were begun to protect the lakefront and the drainage canals from surge related to storms.

When Betsy passed just west of the city in 1965 widespread damage suggested an improvement was needed. Congress authorized the Corps of Engineers to build a system that  that would protect New Orleans from the "most severe meteorological conditions that are considered reasonably characteristic of the region." The Corps used this authorization to build the system of levees, flood walls, pumps and gates in place at the time of Katrina.

To translate the legislation into engineering terms the Corps developed a model they called the Standard Project Hurricane, much like the Project Flood definition they use in river flood control. They used data available at the time, including a 1959 weather service study of hurricanes from 1900 to 1957 in the New Orleans area.  In today's terms the Corps claims the project hurricane is a fast moving category 3. (The design standard they actually used as recently as 1984 was a 100 mph storm or a Category 2.)  Applying local geography they then computed storm surge at various locations and used this as the basis for their designs.