It is truly a daunting task. And, I'm afraid, a low priority task that will take backseat to rescuing people that are able to request it. If they have to come and find you in the attic of one of 100,000 flooded homes, you are probably in for a painfully, if not prohibitively long wait. Anybody who can neither get out nor get word out that they are there is in a grave circumstance.
On the other hand, there are a crapload of boats hitting the streets today for rescue. I believe the Louisiana state wildlife department has over 200 boats by itself that are being launched. Add to that the military, municipal, and volunteer watercraft and you certainly have a sizeable armada for waterborne SAR. The key to success will be coordination. If authorities approach the mission as a classic SAR and assign crews by grid, they can efficiently insure that all neighbourhoods are covered adequately. But if you just have 600 boats all running helter skelter across the city with no tactical plan, then you are going to have huge holes in coverage, as well as oversaturation of other neighbourhoods.
Not only does the strategy of the search have to be professionally coordinated, but the method of the search is equally important. Are they going to just motor up to each home, pound on the gable and wait for a reply? Or are they going to make entry to each attic to positively ensure that there is nobody inside? The former is a faster and easier method of covering every home in a timely manner. However, it also leaves the possibility of persons being overlooked too, which would be tragic. On the other hand, chopping your way into each and every rooftop along the Gulf Coast is so prohibitively time consuming that more people will die while waiting to be found.
I know that LA and MS have very professional EM agencies who spend an enormous amount of time preparing contingency plans for exactly this sort of disaster. But I have also experienced first hand on many occasion how the best laid plans fall apart on day one. And with no reliable communications, keeping any organized plan in effect is going to be a formidable challenge.
