I’ve been thinking a lot about floodplains lately. Most creeks and rivers in the West are channelized to one degree or another: squeezed into a narrow ditch so that they, and the rich benches where they used to deposit their silt, can be used more efficiently for agriculture. Channelization has had major effects on the riparian systems of the West, which evolved to rely on frequent flood disturbance to create channel complexity and redistribute nutrients. You can see this dynamic at work in the photo at right: here, riparian vegetation (evolved to handle floods) kept the water somewhat contained. The trees and shrubs, meanwhile, benefit from new silt, new seedbeds, new minerals .
Floodplains are dramatic: they are frequently scoured, but the floods make wet meadows, bird and butterfly habitat, side channels, carbon sinks. Perhaps most importantly, a functioning floodplain acts like a sponge, catching water when it’s high and storing it to recharge (and cool) the creek in the dry season. These ecosystem benefits disappear when the creek is channelized: the water simply rushes down, or rushes into its irrigation diversions.
I know one of these channelized creeks well: Camp Creek, in the canyon lowlands of The Nature Conservancy’s Zumwalt Prairie Preserve. This part of the Preserve, below and east of the better-known Prairie, is not open to the public, but TNC owns a house down here, which
various friends of mine have lived in. I’ve visited often to house-sit or hang out, sometimes for weeks at a time. And I used to work for TNC, so I know this creek’s headwaters too, up on the Prairie, where water emerges from springs near the Buttes and descends in lazy meanders through willows I once counted and tended. The creek, as you follow it into its canyon, finds places to rush and places to seep, goes underground and pops back up, makes little pools for tiny trout and for coyotes to drink from. Most of the time, along most of its length, this creek is less than knee deep.
But this spring, and last spring, it flooded. This year, oh boy, it flooded big time.
My friend Heidi (the Preserve’s lead scientist, who lives in the Camp Creek house these days) left me a note when I came down most recently, this May, to house-sit: “I hope you have time to explore the recently remodeled Camp Creek!” The old-timers I ran into on a walk along adjacent Trail Creek, who were looking for mushrooms, called the flood a “blow-out.”
I’ve heard that term—blow-out—before to refer to a flood, but never, until this spring, did I really understand what it means. It’s like a pipe exploding: once the first breach happens, the pipe is done for. The water in a pipe, or a channelized ditch, is pressurized like crazy.
I’d seen the evidence of the blow-out downstream of the house: the creek had clearly come up at least four feet, rushing over the meadow and the road, cutting down—as you see in this photo—not to bedrock but to cobble: this creek used to freely stretch its muscles across this entire canyon bottom. Of course, it was the creek that made this canyon.
But upstream was the real drama. On my first walk up the creek I noticed the road had recently been regraded, and then I began to see debris all over the pastures I know so well, and flattened grass where the water had been. This photo shows a brand new side channel, right alongside the road (the creek proper is a hundred yards farther west). This is where I began to say “Wow, wow!” You see the layers of rounded stone where the water found its way through the thin topsoil and down into the old creek bottom. This is where the creek used to be, and it still wants to be here.
The next pasture was entirely remade. I came over a little rise and looked down and I
shouted. I got a little giddy. I’m not embarrassed to report that I shouted, to this creek I thought I knew well: “Look at YOU! Look at YOU! You are a POWER!”
This channel, this waterfall, this fallen tree, that wide apron of cobble debris in the background? All new. New to me. And OLD: as you can see. This creek has a new old major meander.
I can’t adequately express how delighted I was to see the evidence of this little creek’s power. This water punched out of confinement, threw boulders and trees around, spread out, flexed its muscles, remade itself in its own image. Seeing this flood was such a vivid reminder that these little creeks, hardly more than ankle deep most summers, made these 3000-foot-deep canyons—and not gradually, not necessarily, but sometimes all at once, in great powerful dramatic bursts.
Our efforts to control powers like this are temporary at best.
This made me feel small, and humble, and that’s a feeling that I seek and love. “Look at you!” I said again. “You are a POWER.”