FLOODS in New Orleans following hurricane Katrina were made worse by a channel dug by a US government agency, according to testimony heard by a federal court. The hearing, in which the government is being sued for allowing the channel to be built, could lead to payouts to hundreds of thousands of flood victims. It may also lead to massive reforms in flood protection.
The evidence comes from the most detailed modelling of Katrina鈥檚 storm surge to date. 鈥淪cience is the most critical factor in this courtroom,鈥� says , lead attorney for the plaintiffs. 鈥淭o win the day, one side has to provide the judge with a more compelling scientific case than the other.鈥�
The court case is being brought by two residents of the Lower Ninth Ward, a resident and a business in St Bernard鈥檚 Parish and one resident of New Orleans East.
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The US government cannot be sued for the failure of flood protection measures. This (pdf format), got the (pdf format) because it concerns a channel, called the Mississippi River Gulf Outlet (MRGO, or 鈥淢ister Go鈥�) dug by the (USACE). The channel was built in the 1960s to bring shipping into the city.
鈥楬urricane highway鈥�
That MRGO might exacerbate flooding is not a new idea 鈥� it is known as a 鈥渉urricane highway鈥� by many residents of New Orleans.
Shortly after Katrina struck in 2005, a computer model run by coastal ecologist Paul Kemp, then at Louisiana State University, and colleagues indicated that MRGO combined with another waterway to create a V-shaped trap that funnelled Katrina鈥檚 storm surge, causing the levees to be overtopped and breached (see map). However, other reports have concluded that this funnel effect made a minimal contribution to flooding compared to the other dynamics of the hurricane.
Another factor is that vegetation and marshes were lost when MRGO was built. The channel鈥檚 construction sliced through fresh water marshes and destroyed trees and other vegetation that coastal scientists claim would have otherwise provided a key natural barrier against Katrina鈥檚 surge. But others say the effect of such vegetation in mitigating a storm surge is still poorly understood.
Sharpened model
Since then, Kemp and other researchers have created an improved model which accurately simulated the timing of the flooding and levee breaches, as well as the magnitude. They claim it provides the best estimates yet of storm surge, waves and currents during Katrina.
They plugged their storm figures into the new model, which was similar to the original except MRGO was filled in with marshes and vegetation known to have been there before 1958. 鈥淲e wanted to see what Katrina looked like with a GO and without a GO,鈥� says of the University of California, Berkeley, who was part of the team.
The results showed that without MRGO, the storm surge which battered levees protecting the neighbourhoods concerned in the court case led to fewer breaches and less overtopping.
In the model, flooding of the plaintiffs鈥� properties was reduced by almost 9 feet (2.7 metres). In St Bernard鈥檚 Parish, flooding was reduced from 11.5 feet to 3 feet in plaintiff Tanya Smith鈥檚 home, and from 10 feet to 5 feet at the Lattimore and Associates business. In New Orleans East, it was reduced from 9.5 to 2 feet. And in the Lower Ninth Ward, it was reduced from 11 feet to 3 feet in the home of Anthony and Lucille Franz.
鈥淲e have shown that MRGO spelled the difference between survivable flooding and catastrophic flooding,鈥� O鈥橠onnell claims.
鈥楲ong overdue鈥�
The team began presenting its evidence on 20 April. 鈥淔inally, we are having our day in court,鈥� says Kemp. If the plaintiffs win, others in their neighbourhoods should be able to claim damages too. O鈥橠onnell says that more than 200,000 people and groups have already filed such claims.
As New 杏吧原创 went to press, the USACE had yet to present its defence and did not want to comment. In a brief filed to the court, it maintains that 鈥渢his catastrophe would have occurred regardless of the MRGO and regardless of the way the channel was maintained prior to the flood鈥�.
Many New Orleans residents are convinced that such a court case is long overdue. , a law professor at Tulane University in New Orleans says: 鈥淭his opens the door to the government doing what it should have done in the first place 鈥� a massive reconciliation and compensation programme.鈥�
Other coastal scientists are reserving judgement about MRGO鈥檚 role. The decision in the case will rest with district judge Stanwood Duval. 鈥淚t is fascinating to see what will happen,鈥� says at the University of New Orleans. 鈥淚n my experience, Duval is a pretty smart guy.鈥�
