Levee Plans
Written by Katie Pesce
Researched by Team 4

Short Term Fixes

Barrier Across Opening to Lake Pontchartrain

By the time Hurricane Katrina had reached New Orleans, it had shrunken to a category 3 hurricane. One main reason for why the damage was so catastrophic was because Lake Pontchartrain was rising rapidly due to surges that were caused by Katrina when it was still a category 5 hurricane (IPET).

In addition the Lower Ninth Ward was flooded in part due to surges coming down the Intracoastal Waterway connecting the Mississippi River to the entrance to Lake Pontchartrain (IPET).

We propose solving both of these problems by installing large sluice gates across the opening to Lake Pontchartrain just before the opening to the Intracoastal Waterway (see map for exact location). These gates will be modeled after a similar sluice gate (the Weerd's sluice gate) currently in use in Utrecht, Netherlands to help protect their delta. The sluice gates should protect the Intracoastal Waterway, the canal gates, and the levees along Lake Pontchartrain from storm surges (Fischetti).

Sluice gates are moveable gates. Metal plates slide vertically into grooves in the sides of the structure. The operation of our gate would be controlled by a hydraulic mechanism (Fischetti).

This solution has actually been proposed in the past but was shot down by environmental groups. They feared the negative environmental impacts on the Lake and the necessity of the tides in the lake everyday to flush out the sewage. However, the gate would only be closed in times of emergency when rising waters in Lake Pontchartrain and threatening storm surges were an issue. At most we predict this to be about a week per year during the hurricane season, so the environmental effects on the Lake would be minimal (NPR).

The shipping industry will still be able to use the Lake as usual, except for the short periods of time when the gates will be closed due to threats. The amount of safety and security from storm surges provided by these gates would greatly outweigh any economic loss.

The Governance of the Gate would be given to NOAA (National Oceanic and Atmospheric Administration). This federal agency is in charge of providing “data and forecasts for weather and water cycle events, including storms, droughts and floods” (NOAA). The agency would watch the weather forecasts for the Gulf Region and alert the city of New Orleans when a threatening storm surges or water levels would be present in Lake Pontchartrain. The gates would be closed and remain closed until the water levels subsided.

An important first step must be taken before we build the sluice gate is to rehabilitate the land on either side of the opening to Lake Pontchartrain.  The land has been eroded by rising sea levels and storm so more land needs to be brought in; however, the main problem is the quality of the soil there presently. It needs to be replaced with compacted soil of better quality (USACE Levee Construction).

Closing off the Mississippi River Gulf Outlet
Written by Team 9

Team 8/9 is planning to create two main distributaries leading to the east and west of the current channel of the Mississippi River. These distributaries would deposit sediment in the surrounding wetlands to help revitalize them.  The eastern distributary channel will utilize the current Mississippi River Gulf Outlet (MR-GO).  This channel was filled in with an average of about 15 ft of silt by hurricane Katrina and is accessible only by small, shallow draft vessels until dredged (Brown 2005).  Rather than spending extra money to dredge this channel, it should be filled in from its intersection with the Intracoastal Waterway until the southern tip of Lake Borgne. The funnel effect during Hurricane Katrina that flooded much of New Orleans East and St. Bernard Parish and ultimately caused levee breaches along the Industrial Canal initially came up through MR-GO. Closing of MR-GO end the funnel effect that worsened the storm surge from hurricane Katrina. A distributary from the Mississippi river should be directed into the remaining lower section of the MR-GO.  This distributary will redirect a maximum ¼ of the river’s volume, or about 103,000 ft³ of water during normal water levels (General Information About the Mississippi River).  The intersection of the previous MR-GO channel and the new distributary will be marked by a flood gate that will control the amount of water allowed to enter the channel.  This way, during periods of low water, more of the river’s volume can be kept in the main channel to ensure a navigable channel for ships. 

The impact on the industry and shipping of New Orleans should not be very great. Usually the MR-GO is used by commercial ship as a short cut from the ocean to the port of New Orleans, but closing it off will only add about 40 miles into Lake Pontchartrain to their journey. The security from preventing another funnel effect by closing off the MR-GO greatly outweighs the frustration caused to any industry.

Canal Gates and Double Pumps

Unfortunately the very same canals that have successfully drained New Orleans for many years were the reason for much of the flooding in Northern parts of the city. The pumps also were useless because they were unable to pump water out because they were situated in the city below sea level. As a result, the levees along the canals failed and the water was free to flood the city (IPET).

To solve this problem we propose installing strong gates at the front of the 7^th Street, London Avenue, and New Orleans Avenue Canals. They would basically be single sluice gates that slide vertically. This has actually already been implemented in New Orleans. Temporary gates are in place already with plans to put in permanent ones. These gates will remain open most of the time to allow the canals to serve their usual function of draining the city, but when there is the threat of a storm surge, the gates would be closed to prevent water from pouring into the canals and putting pressure on the floodwalls and levees. Pipes on both sides of the floodgates will allow the pumps to continue draining the city of water even though the gates are closed (USACE Hurricane Protection System Improvements).

The same system that will control the opening and closing of the sluice gates on Lake Pontchartrain will control the canal gates.

There is currently work in New Orleans to rebuild the pumping stations and increase their capacity. The pumps are designed to drain the city of water. They were not built to operate during hurricanes (USACE). To fix this problem we propose implementing a double pump system, in which pumping stations are present at both the lake shore and in the interior of the city where the canal ends. This would increase the pumping capacity and redesign the city so that it could handle both normal drainage and hurricane floods.

For all the pump stations in general around New Orleans, we will install back-up power generators and raise all the critical equipment feet off the ground to help insure that they will continue working when the flood rate surpasses their pumping rate (USACE Hurricane Protection System Improvements).

Levee Re-Construction

The engineering failures and inadequate heights of the levees were major factors that caused the flooding of the city. The levee system in the New Orleans area includes about 450 miles of levee. The map above shows the heights to which we plan to build the levees or maintain them. We plan to rebuild all of the pre-Katrina levees at heights adequate to withstand storm surges from a Category 5 hurricane. We are also lengthening the levee in Jefferson Parish so that it extends all the way to the west to the Mississippi River.

Among our improvements are replacing all I-walls with T-walls. I-walls in many place including in the 17^th Street Canal and London Avenue Canal levees and along the Ninth Ward. T-walls are a much more structurally sound. They are less likely to be pushed over because of the wider, heavier foundation (ASCE Instrumentation of Embankment Dams and Levees). Floodwalls are rated according to a factor of safety. They should have a factor of safety of 1.3, meaning that they are 33% stronger than they need to be to deal with the water pressure. However, it was found that 17^th Street Canal had only a factor of safety of 1, so there was little question that they would fail (NPR).

To protect against subsidence, we have our maintenance and monitoring program that will be described later. We will also look at the subsidence rates at each individual levee site on a small scale. Part of the previous problem was that the Army Corps took the average of the subsidence rate along very long lengths of levees. This system puts the whole levee in danger because it disregards very extreme, dangerous subsidence rates (NPR). From now on, however, subsidence rates will be dealt with on an individual basis, instead of averages.

Poor soil quality was another huge issue. The 17^th Street Canal levees were built on top of sand that caused the foundations to be unstable. Also, many of the floodwalls were anchored in soft clay, allowing rising water to push the wall horizontally and a gap to form at the base of the floodwall and failure from spreading to occur. If the quality of the soil is poor at the locations of the levees, we will replace it with suitable, compacted soil. Although this is an expensive solution, it is the only way to ensure the stability of the levees and floodwalls. Extensive evaluation of the geology of the levee locations is essential (IPET).

To protect against erosion from the levees along the 17^th Street, Orleans Avenue, and London Avenue Canals and the Industrial Canal will be armored with concrete on the backside so that overtopping will not erode the backside of the levee and cause a levee failure. They will also be armored on the water-side of the levee at the base of floodwalls so that gaps can’t form at the between the base of the floodwalls and the soil. Transition points, for example between floodwalls and levees, would be armored because during Hurricane Katrina those spots proved especially vulnerable (USACE Hurricane Protection System Improvements).

Levee Maintenaince and Monitor Boards

Levee Management – The Levee Board

The current, ineffective levee board system in New Orleans is partly what led to the levee failures. The levees are controlled by local levee boards, and there is little interaction or communication between them. The safety standards vary greatly from district to district, and there was no set plan for the maintenance of the levee system. The levee boards are also involved in many other interests, such as real estate and economic ventures. This also causes corruption to be a hindering factor in the levee boards (Eichenseher).

We plan to consolidate the levee boards into one body in which the each district would be represented. The Levee Governance Board would be in charge of overseeing the rebuilding of the levees to and their maintenance at the specifications and standards we set up earlier. The members of the board would be appointed by the governor and it would include engineers of technical expertise. All the land currently held by the levee boards would be property of the state. The Levee Governance Board would be responsible for the safety and upkeep of the levee system and would have to report to the governor on it activities and budget.

National Levee Safety Program Act of 2006 is a bill in Congress that sets up standards and protocol for the inspection and inventory of the levees, an interagency committee on levee safety with a National Levee Safety Advisory Board, and a National levee safety program (H.R.4650 National Levee Safety Program Act of 2006). This is obviously a very important measure that would not only help ensure the safety of New Orleans, but many other port cities as well.  

Monitoring and Maintenance
Written by Dan Beauboeuf

The levee system pre-Hurricane Katrina had been very poorly maintained. Because of subsidence many of the levees had sunk below where they were supposed to be, and the levee heights are extremely inconsistent from region to region (IPET). As mentioned above, the Levee Governance Board would be in charge of overseeing all levee maintenance.

The Board would require a yearly inventory of the levee system. Any damage that is found would be fixed according to safety priority before the next hurricane season, or if on the river before the next high water. Subsidence would be taken into account every year by raising the levees to account for unacceptable sinkage.

Part of ensuring the safety of the levees is informing and involving the community and making sure that they don’t get complacent. One way in which we plan to do this is by involving the local universities, such as Tulane and University of New Orleans, in the levee monitoring program and research.

 Lack of knowledge about the state of levees protecting New Orleans was a major reason for failure.  Subsidence had changed the heights of levees in the city by feet in certain neighborhoods (IPET). 

To have a more systematic approach to levee monitoring, we are going to put electronic sensors in all the levees. Our plan includes the use of a Differential Global Positioning System that will monitor the relative positions of points along the levee system.  The DGPS system recommended by the United States Army Corps of Engineers for Levees and Groins has a horizontal movement tolerance of 1-2 ft. and a vertical tolerance of .5-1 ft. We believe that this level of accuracy is not precise enough to protect New Orleans.  The levee system protecting New Orleans needs to be much more closely monitored.  We suggest using equipment with Feature Position Tolerance approaching that used in structure site plans.  Such sensors have horizontal tolerances of .01-.5 ft. and vertical tolerances of .01-.5 ft.  Operating with smaller tolerances would allow for engineers to detect the deformation of levees sooner (Engineering Manual). The readings will be transmitted by satellite to monitoring stations at the local universities. This system will be useful in the overall maintenance of the levees and for emergencies. If people at the monitoring stations see that the water pressure on the levees along the Mississippi River is too great, they could inform the Levee Governance Board who could then evacuate areas in danger.

A side benefit to the improved monitoring and maintenance of the New Orleans levees is all the skilled, well-paying jobs it will create. The maintenance of the levees will be a year-round task that will require a constant crew of workers. 

One of the lessons learned after Hurricane Katrina was that proper maintenance and monitoring is imperative to public safety.  We envision the monitoring system to be the first step in a levee maintenance program.  The decision to use small tolerances in our system was made keeping in mind the various subsidence rates throughout the city.  The fear is that some of the highest subsidence rates per year (6-10mm per year) are not larger than the tolerances of the USACE specified sensors.  Therefore, there was the danger of waiting years before being able to conclusively verify problems.  With the smaller tolerance engineers will be notified much sooner of issues.  We suggest that after such notification, that the levees in question be surveyed and adjusted as needed. 

Army Corps

Instead of involving the Army Corps, we have decided to hire private contractors to rebuild the New Orleans flood protection system. The Army Corps is presently understaffed and underfunded. Many reports have surfaced that saying that the Army Corps had not built the levees up to the standards of the projected plans and had done an extremely inadequate job maintaining the levee system (Bordeau). The Corps knew that the flood protection system in place would not hold up to a strong storm (Shwartz). Misinformation was also rampant. The steel pilings in the 7^th St. Canal levee should have been many 15-30 feet deep according to the records of the Army Corps; however, they were only a few feet deep (IPET). The Army Corps of Engineers needs to be help accountable for its failures in protecting New Orleans. Until the Corps reorganizes itself into a more efficient and productive body, we have decided to keep them out of the rebuilding process.