Dark rain

the long version

"[S]et in the days after Hurricane Katrina... [t]wo small-time ex-cons with big dreams get the idea that this would be the perfect time to rob a bank. Catch is, the bank is in New Orleans, and they're on parole in Houston. Now, as every sane person tries to get out of The Big Easy, Emmit and Dabny will do whatever it takes to get in. As they journey through a tide of human suffering, Dabny wants to help, and Emmit sees only the money. But a rogue commander of the ruthless security force "Dark Rain" has his sights set on taking down the same bank. If Emmit and Dabny don't outrace him, their last hope for a second chance could be washed away in the floodwaters-- along with their lives" -- from publisher's web site.