Five months after Hurricane Katrina flooded most of New Orleans, some 80 percent of the “Crescent City” remains unrepaired. Damage is estimated at $35 billion. Most schools and businesses are still closed, and two-thirds of the 460,000 residents have moved out. How many will return remains troublingly uncertain. Municipal leaders only this month began setting up a process to decide which of the city's 73 neighborhoods can be resettled and which would be left uninhabited to soak up future floodwaters. Questions about who will help the city's poorer residents — many of them African-American — hang over the city, along with concern about how much of New Orleans' storied popular culture will survive. Meanwhile, as a new hurricane season approaches, efforts to repair and strengthen the protective system of levees, canals and pumps lag behind schedule.