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Rants from the Hill: Watching the desert flood

When the ghost rivers rage in Nevada.

“Rants from the Hill” are Michael Branch’s monthly musings on life in the high country of western Nevada’s Great Basin Desert and originally posted at High Country News.

Photo credit: ShutterstockTo say that conditions here in the western Great Basin are extreme hardly does justice to the apocalyptic weirdness we often experience out in this remote, high desert place. Since making our home on the Ranting Hill more than a decade ago, we've seen temperatures close to 110 degrees on the top end and 20 below at the bottom, while day-night swings of 40 degrees are not uncommon. We've had high winds blow up into impenetrable sandstorms of whipping alkali dust, while other periods have been so breathless and stultifying that it seemed the earth had ceased to turn on its axis. There have been wildfires on the nearby public lands almost every year, and we have twice been subject to fire evacuation. Earthquakes have on occasion rattled books off our shelves, and smaller tremors are fairly common. A number of blizzards have snowed us in up on our hill, with one memorable series of massive snowstorms forcing us to snowshoe up to our house during the better part of an entire January. One year hordes of shieldbacked katydids (a large, sagebrush country insect often called the "Mormon cricket") invaded, blanketing these hills so thickly that their mushed guts rendered the paved roads slick as ice, even causing some major thoroughfares to be temporarily closed.

As all Westerners know, the apocalypse du jour in our region is drought, and I confess that even in these extremely arid lands, where desiccation is a condition to which we're well accustomed, this drought has been especially severe and troubling. Recently, though, we've had the opposite problem: not too little water but far too much of it, and in too little time. A series of unusual summer thunderstorms has hammered our area, fueling flash floods. You might think that a lot of rain is a good thing in a place that receives so little of it, and perhaps an ennobling metaphor like "quenching the land's thirst" might come to your mind. Once you've seen a flood in the desert, however, a different metaphor suggests itself. Imagine being so parched that dehydration is a real threat, and then being offered a sip of water from a forestry hose blasting at 450 psi; you'll get your water, but it will likely take your face off with it. Needless to say, this choice may cause you to ask yourself: "Am I really that thirsty?" As fellow High Country News writer Craig Childs puts it in his book The Secret Knowledge of Water, "There are two easy ways to die in the desert: thirst and drowning." According to the USGS, in American deserts, more people drown than die of dehydration, which puts the immense power of flash floods in humbling perspective.

In weather nerd parlance, a "flash flood" is distinguished by speed as well as volume: it is an event in which geomorphic low-lying areas are inundated in less than six hours. This event can be triggered by torrential rains or accelerated snowmelt, or by the collapse of an ice dam—or an artificial dam, as when 2,200 people were swept to their deaths in the 1889 Jonestown Flood. While we don't tend to associate deserts with floods, flash flooding is not only surprisingly common but also especially dangerous in desert areas. The unstable temperature and pressure gradients that characterize weather patterns in arid lands can create a lot of water in a short time. Desert soils, both sand and clay, are ill-equipped to slow and absorb water, and in an open, mostly treeless landscape like ours there is little vegetation to help the cause. While heavy rain falling on a forest is much like water pouring onto a sponge, a torrent in the open desert is more like water dropping onto a rock.

Because this landscape does not have regular rains to help keep ditches, culverts, and drains clear, floods here tend to be heavily laden with debris, which creates blockages that exacerbate water damage. This effect is clearly visible on our rural road here in Silver Hills, where the recent flash floods uprooted sagebrush, Russian thistle, and tumble mustard, jamming them into the mouths of culverts, where they formed a mesh that captured mud, clogging the heads, impeding water flow, and causing the runoff to jump the ditch and rip across the road surface, where it sliced through the roadbed, rendering it impassable. Perhaps most surprising and hazardous, flash floods in the desert often occur beneath clear skies. Localized thunderstorms somewhere above release the water load, which gathers force as it tumbles downslope through canyons, arroyos, and washes, eventually blasting into areas where no rain may have fallen.

 

Beauregard the dog relaxes in the shade of a cutbank created when the roadbed was swept away by a recent flash flood.
Michael Branch

I had a memorable experience of this kind of flood twenty years ago while backpacking in the Escalante Canyons of southern Utah. If you've never seen this magnificent country, it is perhaps best imagined as an immense labyrinth of fissures carved into the exposed face of a vast tableland of mesas and plateaus. For the hiker, navigating these canyons means meandering through a maze of narrow slots, beneath sheer walls of Navajo sandstone painted with carbonate patina and streaked with desert varnish. The narrowness and depth of these sinuous canyons creates their undulating beauty, but also ensures that those of us walking within them have little idea what might be going on beyond the slice of sky we're able to see between the canyon walls.

On the day I witnessed the surprise flood, bright sun illuminated the red cliffs of the canyon I was following, while the sliver of sky visible above me remained pure azure, save for an occasional, puffy cloud drifting innocently across it. Despite these ideal conditions, by mid-afternoon I heard the distant rumbling of thunder, which was my cue to peel a weather eye and devise contingency plans. After hiking for another hour I reached a bottleneck in the canyon, and I knew that in entering it I would risk being trapped without an escape route in the unlikely event there was water running somewhere above me and beyond my sight. Instead, I decided to wait it out, remaining in a wide amphitheater of the canyon bottom, through which the small creek slid first against one wall, then snaked gracefully across the cobble of the broad wash to run gently against the other. I sat down on a sandy bench that seemed safely elevated above the creek, leaned back against my pack, and enjoyed the beauty of the place.

After a half hour I noticed the little creek begin to rise, and rather quickly. Within minutes, water that had been only inches deep—so shallow that I had simply walked through it perhaps twenty times that day—rose to a foot deep, while also quickening its pace. Then, around the bend of the canyon, came the aptly-named "snout," the leading wave that is pushed before a flash flood. It was several feet high, viscous and brown, loaded with debris, and barreling into the canyon with a volume and force that far exceeded anything the little creek could contain.

I grabbed my pack and clambered up to a broad notch higher in the cliff side. From there I watched as the coffee-colored snout led a wave that swept the canyon bottom, overrunning the shallow creek bed and spreading out over rocks and sand, tearing through reeds and bushes, encircling boulders and swirling around the trunk of a cottonwood tree that had formerly stood thirty feet from the creek. I watched in amazement as the canyon of dry cobble became a cliff-to-cliff river, shallow but roiling, spitting brown foam and ploughing forward with a tumbling load of upcanyon debris.

 

 

In the next moment something equally remarkable and surprising occurred. The sky darkened as I heard the wind rise and felt the temperature begin to drop. And then the rain that had been heralded by the flood exploded above me in a cloudburst so sudden and intense that it hammered the cliffs in deafening sheets. Water also began to run down the canyon walls and spout from their tops. Within moments the canyon bottom was being pounded by a series of spontaneous waterfalls, as the mesa lands above gathered the runoff and shot it over the canyon's sandstone brow. Squinting through the blast I counted eleven simultaneous waterfalls, one of which was launching from the cliff beneath which I had taken shelter, catapulting itself over me and into the canyon-wide torrent below.

Read the rest at High Country News