New Orleans, as it once existed — as a city of half-a-million people built below sea level in a flood-prone area in the path of hurricanes — was never a natural phenomenon. It was a triumph of human ingenuity, of the feats of engineering that gave it the levees and flood walls and pumps to keep it dry enough to support its charming, but politically, socially and economically dysfunctional, existence on the edge of the deluge.

A year ago, the deluge came. Republicans, nervous about a political catastrophe for their party this fall, often wonder what accounts for the sour public mood, despite robust economic growth. The answer, at least symbolically, is Katrina. The hurricane and its aftermath stand for this sullen chapter in our national life when human ingenuity confronted vast uncontrollable forces, and lost.

The heroic phase of President Bush's presidency was in the immediate post-9/11 period. It was marked by national unity in the face of a horrific terrorist attack; by a celebration of the self-sacrificing heroism of New York City firefighters and policemen; by the toppling of a terrorist-coddling regime in Afghanistan within a matter of weeks, in a demonstration of the reach and tactical brilliance of American power.

Katrina has been an exact counter-point to all of that. The major players in Katrina couldn't keep from political finger-pointing even in the midst of the disaster. Even if there was plenty of heroism (the Coast Guard saved tens of thousands of people), many New Orleans police officers disappeared off the job, and some were accused of participating in looting. The federal, state and local governments couldn't quickly re-establish order in the city, as its poor presented a picture of Third World abjectness despite a decades-old federal "war on poverty."

Leadership is the great intangible in such crises, and it was nowhere to be found. Mayor Ray Nagin was an ineffectual loose canon, who — depressingly enough — has now managed to win re-election despite being manifestly overmatched by his job. Louisiana Gov. Kathleen Blanco dithered and wept as New Orleans sank, and has done nothing to distinguish herself since. The director of the Federal Emergency Management Agency, Michael Brown, thought that the way to strike back on behalf of his neglected agency was to not talk to top Department of Homeland Security officials during the storm's immediate aftermath. President Bush was slow to realize how Katrina was ripping the political guts out of his administration and has during the past year repeatedly made laughably implausible promises of how the Gulf Coast will come back bigger and better.

The levees were supposed to check nature's destructive power in New Orleans, and the Army Corps of Engineers has said that they failed due to unforeseen circumstances. This is cold comfort, since the world specializes in producing the unforeseen. One engineering expert who has studied the levee failure has said he personally wouldn't live in New Orleans, because it is simply too risky. This represents human ingenuity's white flag.

Half of the city has heeded it, and not returned. It doesn't help that a squabbling New Orleans officialdom still doesn't have a rebuilding plan, or that it has been unable to control gangland violence that has necessitated the return of the National Guard to the city. Federal aid has been slow to flow to the city, and the rental-assistance checks FEMA did rapidly hand out have been ripped off to the tune of $1.4 billion.

The Gulf Coast disaster exists against the backdrop of the Iraq War, where America has been seemingly powerless to impose order on the country's warring factions or rebuild a country devastated by 30 years of tyranny and now a budding civil war. If there were a theme to the past two years it would be Ralph Waldo Emerson's "events are in the saddle, and ride mankind." Nothing is so damaging to a political leader. Bush's presidency will remain diminished until he finds a way to vindicate human ingenuity's power over events, and show that he again is in the saddle.