The River

June in Boise started with the classic form of summer in south Idaho. Clear sky, bright sun, a cool bite in the dry air. The flotillas of cumulus clouds from two days ago were nothing but a sharp white memory set against a gray, wet May.

It was the second wettest May on record, with 4 and 4 tenths inches of rain, surpassed only by the May of 1896, which had almost 5. A veritable monsoon in this desert corner of the world. 1896 was also the year of historic floods on the Boise river. It remains to be seen what will happen in 1998.

Whatever does happen will be the result of human decision-making, however, not just the whim of winter snow, spring rain and the start of a hot summer. There are now three dams on the Boise river: Anderson Ranch, Arrowrock and Lucky Peak. The dams were an easy sell after the river had scoured out the budding town a few times. We need flood control, damn it! Dam it!

But flood control doesn't take all year, like raising a crop of spuds or wheat or cows. Flood control was the splashy soloist, but irrigation has always been the orchestra. The conductors - in our case the Army Corps of Engineers (and the BLM?) - are more interested in the larger group than the diva.

So at the end of the second wettest May on record, after a more or less average winter (a little warmer and wetter, perhaps, nothing remarkable in the snowpack depths), and the reservoirs are 101%, 100% and 98% full, coming down toward the city. I guess "full" is a term of art, otherwise 101% would be coming over the top, a dreaded last resort in dam management.

And the decision-makers, anticipating perhaps more rain, but inevitably the melting snowpack when June gets hot, decided to send 8,000 cubic feet of water per second down through town, after the 3,000+ cfs diversion to the New York Canal, and other smaller canals downstream. 8,000 cfs laps up on some of the nicest, newest real estate in town; the deluxe homes and businesses that tapped into Boise's number one "amenity," the river's greenbelt.

6,500 cfs or so starts flooding the low spots of the greenbelt path, like the Main street underpass. 8,000 cfs keeps the swallows from darting under the Fairview bridge and somewhere between 9 and 10,000 cfs, the river will tickle that bridge's belly. The decision-makers figure they can turn 9500 cfs loose, but will go over that only for dire need, knowledgeable of the damage, protest and outrage that will follow.

They could have managed the river flow sooner, of course, as the river is always throttled to a trickle in the wintertime. They could have left the three big reservoirs 80% full longer into the spring. But water let past the dams is water "wasted" from the irrigators' point of view, and the irrigators are always the first consideration. If El Niño's rains have finally let up, and June doesn't get hot too suddenly or for too long, they will have succeeded for another year; not too much damage in town and the canals at the "full serving" line for the length of the summer and into fall.

If not, we may get the flood map redrawn the easy way - dial in the prescribed flood, and then trace out the water's edge through new subdivisions, roads, fairways, etc. But how do we decide what a "50 year" or "100 year" flood is with just 100 years of weather and river history, and only a couple decades of 3-dam river management? Curious questions. The influx to the three reservoirs right now, minus the various canals' efflux is a flood on the Boise river through some of our nicest living rooms and toniest landscaping, enough to cover Park Center Boulevard, and overflow the little checkponds adjacent to it.

The news reported that sand was available from a number of local fire stations, BYOB. (Bags, that is.) When the river comes calling, there will be valiant and hopeless attempts to pretend that the flood map doesn't include some of these new developments. The managers will also have to remind some folks that they may not so pretend - as their denial would simply pass the problem on to someone else, downstream.

Of course, downstream from the area of concern, there has been, is, and will be flooding augmented by the city's control and denial. But that's agricultural land, isn't it? At least it's out of sight, and out of mind.

The city's built in a flood plain, after all, plainly marked by multiple river benches to the south, and high water marks on the hills to the north. I commute via Chinden Boulevard, which runs through Boise's ghetto (otherwise known as Garden City) and then up through the first bench right where HP's site marks the once-upon-a-time northwest corner of urbanity. Where it's cut along the bench, there is a new pair of gullies this spring, with raw sand and gravel showing between the spring growth of grass and forbs and sagebrush. An SUV-sized delta fills the drainage way between road and hillside. I smile when I drive by it, happy to see that the oldest form of "growth in Boise" is still proceeding nicely.

June 1, 1998

PS July 18

Another successful year. June was relatively cool, with no sustained rainfall, and without the burst of hot weather we usually get. We're having highs at and above 100 now, but the peak runoff is taken care of, and no houses floated away. There are weeds sprouted out of the talus pile along Chinden. Life goes on.

PPS September 6

The ACHD was not as pleased as I was with the "growth" along Chinden Blvd., aka US Highway 20/26. They got out their Tonka trucks, deleted the delta, filled the gully with graded rock and something like soil, then spray-coated it with something an unnatural green... Stabilizer? Grass seed?

Lucky Peak was left full longer than I can ever remember, almost all the way through August, in spite of an exceptionally hot summer featuring highs in the upper 90s right up to today.

PPPS December

It was grass seed, and came up nicely this fall. The second, smaller gully is still going, though....

We've switched from El Niño to La Niña, and I want a good snow year to justify my Bogus Basin season pass. See ya down by the river, next spring!

Tom von Alten      tva_∂t_fortboise_⋅_org

Monday, 08-Mar-1999 20:45:00 MST
http://www.fortboise.org/the_river.html