I recently floated the Willamette from Oaks Park to the Sellwood Bridge. Soon after, I found myself in a vicious bar argument with a friend who swears I couldn't have floated north to south, against the current. The map says he's right. Am I insane?

—Standing My Ground

I have to admit, Standing, that my first inclination after hearing your question was to check the ground you're standing on for that little plastic rose that comes with the convenience-store crack pipe.

You are, after all, talking about the river running backward, which is right up there with the sun rising in the west on the list of Things That Aren't Supposed to Happen. What's next? Dogs and cats getting married? The seas running red with blood? A new show from Tony Danza? Damn you, Obama!

Let's be clear: The Willamette does generally run from south to north through Portland. Otherwise we'd be talking about a river that leaps up Willamette Falls like a trout and disappears into the here-be-dragons hinterlands of greater Oregon as a series of ever-smaller creeks.

So what the hell? Clearly, this was a job for the rippling thews and beetling brow of the Riverkeeper. By day, Travis Williams is director of the environmental NGO Willamette Riverkeeper—but it's well-known that by night he patrols the watery depths on the back of a giant sturgeon, trident in hand, fighting crime and communicating telepathically with fish.

With a toss of his algae-flecked locks, Williams dished: "The Willamette is tidal up to Oregon City. With low summer flows, this effect could be more pronounced, sending the current gently in the upstream direction."

Aha! The tides! Rising ocean tides can push river flows backward, and the Oregon Department of Environmental Quality has actually measured reverse flows at Ross Island, a stone's throw from where you were. You may well be insane, but this probably isn't a symptom.

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