Civil Engineering and Infrastructure Repair in New Orleans After Hurricane Katrina - Background

Background

Flooding due to rain and storms has long been an issue since the New Orleans' early settlement due to the city's location on a delta marsh, much of which sits below sea level. The city is surrounded by the Mississippi River to the south, Lake Pontchartrain to the north, and Lake Borgne to the east. Construction of the levees along the River began soon after the city was founded, and more extensive river levees were built as the city grew. The levees were originally designed to prevent damage caused by seasonal flooding. Today, the floodwalls atop the 17th Street and London Avenue Canals are used for drainage, to pump water from the city streets out to Lake Pontchartrain. These floodwalls are one foot (300 mm) wide at the top and widened to two feet (600 mm) at the base. The visible portion is a concrete cap on steel sheet pile that anchors to the wall. Sheet piles are interlocked steel columns, in this case at least 30 feet (10 m) long, with 6 to 10 feet (2 to 3 m) visible above ground; examinations afterward showed that some pilings were not as deep as specified. The wide, navigable Industrial Canal is used for shipping.

The heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. Congress removed responsibility from the state and mandated that the US Army Corps of Engineers have sole authority over the design and construction of the New Orleans area flood protection, although local cooperation was stipulated. This is spelled out in the Flood Control Act of 1965. Forty years later when Katrina struck, the flood protection was between 60-90% completed with an estimated completion date of 2015, despite the initial expectation of completion within thirteen years. As of May 2005, work in Orleans Parish was certified as 90% complete, with "some work remaining" along the London Avenue Canals, and 70% complete in Jefferson Parish.

There were many predictions of hurricane risk in New Orleans before Hurricane Katrina in August, 2005. In 2001, the Houston Chronicle published a story which predicted that a severe hurricane striking New Orleans, "would strand 250,000 people or more, and probably kill one of 10 left behind as the city drowned under 20 feet (6.1 m) of water. Thousands of refugees could land in Houston." Many concerns also focused around the fact that the city's levee system was only designed for hurricanes of no greater intensity than category 3. As it turned out, Katrina was Category 3 when it made landfall and most of New Orleans experienced Category 1 or 2 strength winds. However, due to the slow moving nature of the storm in its pass over New Orleans, several floodwalls lining the shipping and drainage canals in New Orleans collapsed and the resulting flood water from Lake Ponchartrain inundated the city within the two days following the storm, causing costly damage to buildings and resulting in many deaths.

Furthermore, the region's natural defenses, the surrounding marshland and the barrier islands, have been dwindling in recent years due to human interference.

See also: Hurricane preparedness for New Orleans