Environmental Hazards
Storm Surge Induced Flooding in New Orleans

Chris Below, Chris Dierich, Keith Erickson, and Rachel Kjos

 

Home

Abstract

What is a Storm Surge?


What Happened During Hurricane Katrina?

Why New Orleans is Vulnerable?

The Future of New Orleans

Additional Resources

Photo Gallery

Reference

Back to Our Class Index Page

 

 

The Future of New Orleans

The future of New Orleans is currently unclear. It will take a combination of various elements to truly protect the city from future storm surge induced flooding. There are several options available for the city, some more reasonable than others. There are however many factors that inhibit the utilization of these ideas. Cost is a major factor to consider when implementing such projects; other socioeconomic issues also come into play.

Restoring current structures to pre-Katrina protection is engineers’ first goal. The hurricane season officially starts June 1st, but as trends have shown it is likely that hurricanes could strike sooner, since ocean waters [including the Gulf of Mexico] have not cooled because of a mild winter.


Source: http://ap.lancasteronline.com/5/new_orleans_levees

Work continues, Wednesday, Nov. 30, 2005, at the 17th Street Canal floodwall that was breached after Hurricane Katrina in New Orleans. Government engineers performing sonar tests at the 17th Street Canal found exactly what independent investigators said they would, that steel reinforcements barely went more than half as deep as they were supposed to, a U.S. Army Corps of Engineers official said Wednesday. (AP Photo/Cheryl Gerber)

Sea gates are another option that have proven very affective in other areas of the world such as Holland, Britain, and Venice, which is also below sea level and has a large number of canals. Sea gates are simply giant air-filled walls that cut off water flow. These gates would most likely be placed on Lake Pontchartrain’s two narrow outlets and would be only be closed if a storm was approaching. Such structures have been considered since the 1960’s, but the idea was crushed in the late 1970’s because people feared the gates would disrupt marine life and sediment transportation. However this should not be an issue since the gates are open the majority of the time. The main hurdle is cost, ranging from $500 million to 1 billion.


Source: http://www.alumni.northwestern.edu/travel/holland-belgium-photos.html?action=viewPhoto&photoID=1115312046

The Delta Project - Holland

Closing or covering certain canals is an option that would help prevent storm surges from reaching so far inland. Currently canals and channels can give storm surge direct access to inland neighborhoods. The Mississippi River Gulf Outlet [MRGO] is one of the canals that has caused major problems in the past. Where MRGO meets the Intracoastal Waterway there is a major area of funneling. The two fronts met at a narrowing point that forms the Industrial Canal and the water height is amplified 20-40%, putting intense pressure on floodwalls causing them to burst. After Hurricane Katrina hit the narrow strip of wetlands between MRGO and Lake Borgne got even smaller, bringing to reality the fear that the two waters might merge into one. MRGO has less than five ships navigating its channel per day; often times only one ship uses the outlet. MRGO has also amplified the wetland loss in the area, allowing salt water to intrude and kill off native vegetation. By keeping only heavily used channels open and turning the rest into trails or parks, flood damage could be reduced.


Source: http://www.louisianasportsman.com/stories/2003/paradise-lost/future-of-mrgo.htm

Today, only a slim line of broken marsh lies between the MRGO and Lake Borgne (top of frame).

Adding a subterranean drainage system to the city is another idea that engineers have come up with. This would include turning some canals into culverts (covering them with trails and parks) and then having heavy duty pumps (located on high ground) to pump the water fully out of the city. The culverts would help channel the water and get it out quickly in times of flood. This is a simple technology, but it is costly running about $1 million per mile of canal.


Source: http://rst.gsfc.nasa.gov/Sect14/Sect14_10a.html

Draining the city after flooding is a major issue. The lack of drainage allows water to sit for long periods of time, causing severe damage to homes and greatly increasing the chances of disease.

Moving the pumping stations is a relatively simple way to help prevent New Orleans from being overwhelmed. Installing heavy-duty pumping stations on high ground or in areas where they can act as damn-like buffers would allow water to be pumped out even when the city is overwhelmed. During Hurricane Katrina, once the pumping stations were flooded the low areas just continued to rise in water level.

Wetland rehabilitation is another plan that could help protect New Orleans from storm surge. Wetlands act as natural barriers against wind-driven waters, but wetlands are being destroyed by saltwater intrusion everyday. Hand planting is very costly and time consuming, making it hard to implement.


Source: http://www.pbs.org/journeytoplanetearth/images/1la2.jpg

Rehabilitation of shrinking barrier islands is another way to better protect New Orleans. The damning of the Mississippi and Missouri rivers has reduce the amount of sediments that reaches the gulf. Today even the sediment that does reach the delta is often lost into the deep gulf because of constant dredging for ship navigation. This was proposed in the Coast 2050 plan, but funding was never granted.


Source: http://www.coast2050.gov/barrier_island.htm

The proposed rehabilitation for the Coast 2050 plan.

Along with restoring the barrier islands, connecting barrier islands with additional levees or sea gates to create a continuous rim around the delta is another option. The sea gates would open to allow normal flow and close for protection during storms. This would be similar to the Netherlands Delta Works. Senior engineer, Joop Weijers, who oversees Delta Works estimates that the whole system for the Mississippi Delta would cost between $15-16 billion.

Containing neighborhoods, similar to aircraft carriers or submarines is another way to prevent the spreading of flooding in New Orleans. Currently there is not internal management if levees fail. These structures would resemble barriers that flank highways and include steel floodgates for surface streets. This would take 2-3 years to implement and cost approximately $1 billion. These floodwalls will also block light and change the appearance of neighborhoods, possibly causing segregation, which makes them hard to sell to communities.


Source: http://www.globalsecurity.org/military/facility/new-orleans-flooding-pics.htm

Better internal management of flood waters [in case of levee failure] would help protect New Orleans. In Katrina's case, once the levees failed all low-lying neighborhoods flooded, with no way to stop rushing water from overcoming the streets.

There has also been talk of converting the lowest lying areas into parks. This would allow the area to flood during high waters, without destroying homes and neighborhoods. However this is controversial since most of the low areas in New Orleans are currently home to poor African American’s who cannot afford to relocate or simply don’t want to leave. This has many questioning whether it’s best to sacrifice some parts of the city to save the remainder.

There is not a lack of ideas to protect New Orleans from future storm surge induced flooding, the biggest hurdle is deciding what plans to implement and who is going to foot the bill. As the hurricane season quickly approaches the need for a decision will intensify. Many of these plans will take years to finish completely, leaving New Orleans vulnerable for yet another year.