SOMEHOW A BEAM OF SUN has pierced the quilted sky and follows me like a searchlight.

Forty or so miles northwest of New Orleans in St. John the Baptist Parish, I ride through the backyard of a scrap-metal plant, where a backhoe is clangingly sculpting a drumlin of flood-ruined cars. Thirty miles out, I lose the levee at the Bonnet Carré Spillway, which shoots me down onto the shoulder of Highway 61. For the next few miles, I jockey for lane space with semis, navigating fan belts, hubcaps, and sprays of safety and nonsafety glass while praying against ruptured tubes—and experiencing very little of the wayfaring romance that inspired Bob Dylan and others to sing about this road.

At the far side of a causeway, in the suburb of LaPlace, I flag down a cop for directions back onto the levee. He wants to know where I've come from, and I tell him. He looks at me and says, "Son, that's a hell of a long way to ride on that old bike you got."

At 20 miles out, in the home stretch, the levee's dirt lane turns to asphalt. The going should be easier here, but a headwind sweeps in from the river and tries to bully me back upstream. I feel a sudden temptation to turn around, but I have to make New Orleans. Riding down into Jefferson Parish, I see lots crammed with FEMA trailers, blue-tarped roofs. A tide of damp spirits washes over me—and, as I pass beneath the ductwork of an Archer Daniels Midland plant, so does a silver chemical mist that smells like manure boiled in rancid wine.

I finally creak into view of the city, panting, my water bottles dry. I round a curve and there's the spartan Huey P. Long Bridge. It's a vista that once meant a lot to me, but today it doesn't do a thing to lift my mood. The levee itself has gone to seed. Its banks are shaggy with tall brown weeds, the mowing crews engaged with more dire problems. The city's pervasive silence has overtaken the levee path as well. It's Saturday afternoon, a time when, pedaling past the stilt houses on the riverbank, you used to catch the scent of a crab boil or sausages sizzling on the grill. The houses are all empty now. The private strip of land between the river and the levee used to teem with high school kids sullenly necking or smoking furtive joints, but it's bare this afternoon. No cyclists, either, or the packs of Tulane and Loyola coeds who used to jog up here in little more than underwear. At this moment, I feel a sudden empathy for a man I read about in The Times-Picayune yesterday. Another denizen of the levee for whom, perhaps, the restorative magic of the place gave out, he came up here recently—depressed about Katrina, according to the paper—and killed himself.

My bike has slipped into a terminal funk as well, its gears rasping with clotted mud and skeins of grass, and I have to stand on the pedals to get it to move. I catch sight of the spot where the path ends, but the cold wind redoubles itself and I can only creep forward. On the river, a casketlike barge slides up behind me, bound for the Gulf and beyond—places far from here. It overtakes me at a glacial clip, so I start to give chase. But just then the sky falls apart, and the rain pours down in the worst sort of way.