[mapotofu]

I imagine this type of system is not designed for large, sudden and prolonged inundation of water, something New Orleans faces from seasonal hurricanes and their storm surges. Or maybe it is and it’s just a question of magnitude?

[Leonard_of_Q]

Yes, it is a question of magnitude and also of planning for those specific threats. To catch storm surges you'd use catch areas, dry basins and some sacrificial areas - parks come to mind - where storm surge water can be temporarily held until the pumps catch up. There should be extra pump capacity held in spare for these occurrences, both regular pumps as well as mobile units which can be placed where the need is highest. You also don't just use one dike around the whole area but divide it into sections with 'sleeper dikes' - dikes which normally do not border flooded areas but which can catch water which somehow makes it past the main dikes - behind the main ones. There are reams of literature on the subject to be had from places like the Netherlands where all this has been daily life for centuries, it is not a new problem.