The river rose the way it always did in spring — steadily, one layer at a time from the bottom of the flood plain. By the fourth morning the whole grid was underwater. But the corps had been sandbagging all week, and the levee they threw up that afternoon forced the shallowest water back — the topmost layer, the part that had risen most recently, drained back below the barrier. Everything deeper held. The next rain pushed the water right back up again.