rb1957 is correct. In this case, the pumps were useless because it was a Lake Ponchartrain levee (via the canal) that was breached, and the pumps push the water into the lake.
==> Who's responsibility is it to install, maintain and manage the flood defences for New Orleans?
That depends on who you ask, and when you ask. The levees were originally built just after WWII in the late 1940's and after Hurricane Betsy (category 4) in 1965, a 10-year federal project was approved to build up the levess. Every administration and congress since then has gradually eroded funds form the US Army Corps of Engineers, and now, 40 years later, the 10 year project was about roughly 75-80% complete before Katrina. The low water mark (no pun intended) was in 1995 when President Clinton refused all federal monies for the Corps, stating that flooding concerns were strictly local issues. He was talked out of that position, but at late as 1999, President Clinton cut the Corp's budget request for southeaster Louisiana flooding control projects in half. President Bush turned an equally blind eye to warnings of New Orlenas vulnerability. No one president or political party is to blame for the complancy that put New Orleans in the position it is now. This is the result of 40 years of bi-partisan neglect.
With respect to this particular disaster, there is plenty of blame to go around between Mayor Nagin, Governor Blanco, and President Bush for the preparations, or lack thereof, in the days and hours prior to landfall, and even more damning, the lack of coordinated and timely response thereafter. They all screwed up.
I also think the major news networks, especially FOX and CNN, both reporting live from downtown New Orleans, need to accept some degree of responsibility because in the first few hours after Katrina moved north of New Orleans, they were all reporting that New Orleans had been spared, that the storm had turned east at the last minute and that New Orleans again dodged a bullet. They were reporting that this was not "the big one". But I'll bet you'll never hear them say that.
Good Luck
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As a circle of light increases so does the circumference of darkness around it. - Albert Einstein