President Bush flew into New Orleans shortly after Hurricane Katrina devastated the city. His staff had to fire up giant generators to bathe St. Louis Cathedral and Jackson Square in floodlights as a backdrop for his promise that he would "do what it takes" to rebuild New Orleans.

"There is no way to imagine America without New Orleans," he said, "and this great city will rise again."

Then the lights went out, and the president left. Vast swaths of the city have been in darkness ever since.

It would be unprecedented and indefensible for the federal government to leave an American city to fend for itself in recovery. But when we talk of the federal government's role in rebuilding New Orleans, it's important to understand its direct culpability in the destruction.

At the site of the worst urban disaster in American history, we are a city obsessed. Rebuilding New Orleans is our breakfast-table conversation, our lunchtime chatter, our pillow talk. But while we talk, we also wait. For a settlement on our homeowner insurance policy, for our children's schools to reopen, for a sign that our neighbors will come back.

Above all we are waiting for Congress and the federal government to decide that New Orleans deserves strong levees — stronger than the sorry system, designed and built by the Army Corps of Engineers, that collapsed, wrecking our neighborhoods. We want word from Washington that a great American city will not be left to die.

The miles of federally built concrete floodwalls that were meant to keep Lake Pontchartrain from flooding the city through its drainage canals during a hurricane appear to have been poorly designed and improperly constructed. The floodwall system is a federal project, designed by the Corps and built under Corps specifications. Evidence suggests that metal sheet piles didn't go deep enough into the ground and that the walls were built on peaty soil that did not provide adequate anchorage.

One engineering professor from Louisiana State University called in to investigate the failures said it was the kind of engineering shortfall he'd expect his first-year students to be able to identify.

When several of the federally built floodwall panels gave way on the morning of Katrina, after the worst winds had passed, the storm-swollen lake cascaded into the city. It was a man-made disaster, a federal engineering failure with multibillion-dollar consequences.

Today, when we New Orleanians travel around the country, we are comforted by a tremendous outpouring of sympathy from ordinary Americans. We also hear people talk about how things must be getting back to normal.

Nothing could be further from the truth. New Orleans has become two cities — an enclave of survivors clustered along the Mississippi River's crescent, and a vast and sprawling shadow city where the water stood, devoid of power and people.

The ancient heart — the French Quarter and Uptown — is throbbing with commerce and signs of life from the hardiest returnees. But cross Freret Street, and you enter a dim realm. At night, I drive through darkened and abandoned streets, past acres of housing that marinated in polluted floodwater for weeks, past blocks where I know people died, unable to escape the storm, past the homes of poor, middle-class and affluent New Orleanians — all devastated alike.

When daylight returns, many of those dead blocks come alive with visiting homeowners dragging their soggy belongings to the sidewalk, stopping sometimes to hug and to cry, then going back to work. Our street scene is an endless row of ruined refrigerators, moldy sheetrock, debris and garbage bags.

The vastness of this destruction is almost impossible to fathom.

Our city and state understand that it is incumbent upon them to come up with a plan, sensible and well thought out, for the rebirth of New Orleans. The problem is so vast that it is difficult to harness, and the first steps have been halting. But we're working on it.

When we're ready, we will be expecting, not unreasonably, a commitment from our government to fund a well-designed system of substantial levees, floodgates and other barriers extending into the Gulf of Mexico; a system that will protect us not only from a hurricane like Katrina but from the strongest storm, a Category 5. Such a system would already have been built if anyone had taken into account the billions of dollars the government's failure to protect New Orleans is costing us now.

Can America, having witnessed the loss of well over 1,000 lives to Katrina, not rouse itself? Despite its problems, New Orleans remains one of our greatest cities, beloved of this country and the world. We are at the fulcrum of one-third of the nation's oil and gas and 40 percent of its seafood. We gave birth to much of this country's indigenous culture, and we continue to nourish it. What does it say about our civilization if this unique American metropolis is left to die?

What New Orleans needs is no extravagance. Our city must help itself in rebuilding its neighborhoods and reforming its institutions. What is lacking is political will in Washington and the determination to bring our engineering know-how to bear upon the problem. Without a substantial levee system, homeowners won't muster the confidence to rebuild, and businesses will not see fit to invest.

President Bush was still smarting from the embarrassing federal response to Katrina when he stood in the heart of our city and made his promise to rebuild. It would be a greater embarrassment to an entire nation if that promise went unfulfilled.

Jim Amoss is editor of the New Orleans Times-Picayune. He wrote this commentary for The Washington Post.