The Hurricane Funnel

The Mississippi River Gulf Outlet is known around New Orleans as "Mr. Go." The ship canal, which the Army Corps of Engineers built in the 1960s, has long been derided as a hurricane highway by locals who suspected the channel would funnel storm surge into the city. Turns out they were right. The BBC reports that:

According to new modelling and field observations from Louisiana State University, the MRGO may have made the storm surge 20% higher, and two or even three times faster as it crashed into the city.

St Bernard Parish, which lies just south of the canal, was one of the most devastated by the storm. Without the funnel effect of MRGO, says one expert, there would have been "maybe 2 to 3 feet of flooding at the max, but not everybody's house underwater. It's still flooding, but one is significant and one is catastrophic."