150 sandbags, each weighing 1360kg, were dropped into the levee breach to try to plug the hole that had let waters from Lake Ponchartrain enter the Louisiana city. Reports say that the level of the lake has dropped about 75cm in the last two days.

Repairs are also underway to a breach in the city’s main canal, with contractors building retaining walls to cut off the opening to the lake.

However, these are merely temporary measures. USACE will need to repair the city’s huge pumping system, which is able to pump 3M litres of water per minute, to clear New Orleans of flooding.

Meanwhile, USBR engineers have developed an options paper for USACE to help with the levee breach repair. It is also preparing to deploy some of its employees to the city to provide quality assurance and control for debris removal, housing and temporary roofing missions. The deployment will probably occur within seven to fourteen days and last at least 30 days, with additional deployments in the future.

In addition, USBR has said it is prepared to send a water purification unit that can provide drinking water for people in the disaster area. Depending on the quality of the water, such a unit can produce 450,000 to 900,000 litres per day.

Geographically, New Orleans has always been at risk from a disaster such as this. The city is situated below sea level, sandwiched between Lake Pontchartrain to the north (which at 64km wide is more than twice the city’s size) and the Mississippi river to the south. The Gulf of Mexico is roughly 80km away.