The Emerald Mile by Kevin Fedarko is a really good book subtitled The Epic Story of the Fastest Ride in History Through the Heart of the Grand Canyon. Fedarko details both a 1983 wooden dory trip 277 miles down the Colorado River, one intended by Kenton Grua and two others to set the mark for fastest float through the Canyon, and the potentially cataclysmic events at the dam upstream that made the speed run possible.
Huge El Niño rains in 1983 causing the water level at Lake Powell, held back from the Colorado River by the Glen Canyon Dam, to rise to within feet of its top. Lake Powell holds some nine billion gallons of water and the dam supplies power for many parts of the west. The book also details the harnessing of water for electricity, citing that dams covered almost every major river except the Yellowstone, including twenty-nine on the Mississippi, thirty-six on the Columbia, and forty-two on the Tennessee.
The Glen Canyon Dam was built with spillway tunnels on either side, but it was discovered that cavitation had occurred in the tunnels, with repeatedly high water pressure straining the concrete, causing water to go into the bedrock. Rocks and dirt then further damaged the tunnels and were tossed into the river.
It was never said in the book that the dam at risk of failing, like in the Johnstown tragedy of 1889 where thousands died, but even lesser possibilities included things that could have been calamities, ranging from overtopping of the dam to the bedrock eroding so much that water from Lake Powell make its way around the dam. Engineers had plywood put up to raise the height of the dam by several feet while the spillway problem could be worked on, and released huge amounts of water into the Colorado River.
This created the largest flow of water down the river in a generation, making conditions dangerous for rafters, and tantalizing for Grua and the two others on The Emerald Mile. The trip down the river is typically several weeks and they finished in just over thirty-six hours, breaking the prior speed record by more than ten hours.
Fedarko provides a detailed and interesting account of the float down the river, events at the dam, including the engineering experts who worked the crisis, and the Grand Canyon itself. He writes of how remarkable it is, and how river trips often feature side hikes, with guides talking about the geology of the Canyon.