High Water at Black Cliffs

We break out a new rope and enjoy it on a few easy climbs at the Black Cliffs outside Boise. The weather is about perfect, but the interesting thing in the canyon today is the state of the river. We climb just above a diversion dam that marks the beginning of the big New York irrigation canal, and both the river and the canal are full to the brim:

Ann above diversion dam

There has been a large amount of late-season snow falling in the mountains, bringing an already deep snowpack way above average. With temperatures rising earlier in the spring, large and sudden runoffs are possible. The big Lucky Peak dam a couple of miles upstream is now draining as fast as possible in anticipation of this runoff, filling the river to just below flood level. The race is on to see if the reservoir can be emptied enough to catch the runoff without flooding Boise when temperatures rise. The pleasant 60’s we’re enjoying on the cliffs may not be welcomed by everyone. So far the forecast predicts no change in flow over the next few days.

Boise begins to flood at 7,000 cubic feet per second (CFS), and today it hits 6,800.

Before the Lucky Peak dam was completed in 1955, a big spring runoff would often let well over 20,000 CFS rip through town. But the river looked different back then. The floods scoured a large rocky area where there was no development, both because of the danger and because people thought the area was unattractive. Since the dam was built, no floods more than 10,000 CFS have reached town. The river banks became more appealing, covered with trees and grass, and they were slowly developed. Now the area contains many homes and businesses.

In 1983 there was a combination of deep snowpack and high temperatures in May, and Lucky Peak wasn’t ready. Flows peaked over 9,800 CFS, and there was some damage, but many of the developments were protected by defensive trenches and sandbags. I’m guessing that the full river we’re seeing now is an attempt to prevent a repeat of that event. Much more history of the river is available in When the River Rises by Susan M. Stacy.

I must admit when I imagined living in Boise, the riverfront developments looked nice. Right there on the bike path. Having learned a bit more, I’m not sure I’d like the feeling of Lucky Peak above me all summer long, holding back water that would quickly sweep everything around me away if let loose…

But nothing dramatic happens today, we just enjoy a few climbs and get primed for more good climbing weather to come. Routes:

  • Loaded Gun 5.7
  • Tidy Up 5.10a TR
  • Little Boots 5.8
  • Almer Casile Memorial Buttress 5.8 TR

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