Gundam, I talked to my wife (who's been at a flood conference coincidentally) and she said make some noise, find out who the contractor is, make noise with them, and most importantly find the plan specifications, which should detail plans in an event that something like happens, and as long as the rainflow wasn't outside of typical intensity they should have been prepared. She said either the city will just cave, pay you and sue the contractor, or fight it because they're dicks. If you have any more detailed technical questions just lemme know and I'll pass them along to her. Also did you take pictures of the conditions of the storm drain inlets? how they were blocked etc?