the average lake level. Navigable commercial waterways extended from the lake into the interior of the city to promote waterborne commerce. After the construction of the Inner Harbor Navigation Canal in 1940, the state closed these waterways causing the town's water table to lower drastically. In 1965, heavy flooding caused by Hurricane Betsy brought concerns regarding flooding from hurricanes to the forefront. That year, Congress passed the Flood Control Act of 1965 which, among other issues, gave authority for design and construction of the flood protection in the New Orleans metropolitan area to the United States Army Corps of Engineers, subject to cost sharing principles, some of which were waived by later legislation. The local municipalities were charged with maintenance once the projects were completed. After 1965, the corps built a levee system around a much larger geographic footprint that included previous marshland and swamp. Many new subdivisions were developed to cater to those who preferred a more suburban lifestyle but were open to remaining within the city limits of New Orleans. Historians question why the area farthest east was developed, since it was viable wetlands and because ringing this region with levees did nothing significant toward protecting the city. What expansion accomplished was to increase the amount of land that could be developed, and it was a reason for the Army Corps to expand the size of its project. In addition the structures caused subsidence of up to in some areas due to the consolidation of the underlying organic soils. A 1999–2001 study, led by Richard Campanella of the Tulane School of Architecture, used LIDAR technology and found that 51% of the terrestrial surface of the contiguous urbanized portions of Orleans, Jefferson, and St. Bernard parishes lie at or above sea level, with the highest neighborhoods at above mean sea level. Forty nine percent lies below sea level, in places to equivalent depths. When authorized, the flood control design and construction were projected to take 13 years to complete. When Katrina made landfall in 2005, the project was between 60 and 90% complete with a projected date of completion estimated for 2015, nearly 50 years after authorization. Hurricane Georges in September 1998 galvanized some scientists, engineers and politicians into collective planning, with Scientific American declaring that "New Orleans is a disaster waiting to happen" in October 2001. However, even the most insistent calls from officials to evacuate ahead of