Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [264]
The throng on College Hill watched speechlessly as the wall of water washed their town away, burning it down as it went. A big white frame house floated over to the base of the hill below them and settled down in shallow water in the middle of a street. The water itself, moving only ten miles an hour now but engorged with a cubic quarter mile of topsoil, had force enough to separate homes from their foundations, but the real damage to Rexburg was done by Sugar City and Wilford. Reduced to giant pieces of flotsam—silos, walls, automobiles, telephone poles, pianos, trees—Wilford and Sugar City were a battering ram afloat, smashing Rexburg to pieces. When the flood passed after dusk, it had left six inches of silt on everything, as if it had snowed mud. A Greyhound bus sat on someone’s lawn.
A hundred miles downriver on the Snake was American Falls Reservoir, holding four times as much water as Teton had held. American Falls was one of the Bureau’s oldest dams. The dam was, in fact, unsafe—something the Bureau knew as early as 1966, but hadn’t bothered to correct. (In 1967, chief engineer Barney Bellport wrote Floyd Dominy that “the need for replacement of American Falls Dam is largely governed by structural reasons, although the deterioration of the concrete due to alkali-aggregate reaction contributes to the poor condition of the structure. The lack of bond between constriction joints and the fact that the dam was not designed for ice pressures are of great significance.” By 1976, however, the dam had been neither replaced nor fixed.)
If the dam was too weak to withstand the strain of the Teton flood coming on top of high flows in the Snake, the resulting calamity could only be guessed at. Instead of spreading out, the water would remain largely confined by the canyon of the Snake until it hit the Boise. Below, beyond Hells Canyon, the dams were lined up like dominoes: Ice Harbor, Little Goose, Lower Granite, Lower Monumental; then the Columbia River and McNary, The Dalles, John Day, and Bonneville dams. The bigger Columbia dams would have seen such a flood before, perhaps, but those on the Snake, unless their reservoirs could be emptied in time, might meet flows they were never designed to handle. There was only one course of action: empty American Falls. Over two days, the archaic dam would have to release more water than it ever had before, and its reservoir would receive more at one time than it ever got.
By nightfall on Saturday, Rexburg was a silhouette of wreckage, carnage, and flaring fires. The lower half of the town was a total loss. As Rexburg finally became a vast, slowly shrinking pool of standing water, the flood was washing up against the Menan Buttes, some low hills off to the west. Now six miles wide, it split suddenly into two streams. The one veering northward around the buttes struggled upward against the inclined plain and fell back into a channel it quickly dug down to bedrock. Within minutes, it was a replica of the chocolate-brown Colorado River at high water. Then, beyond the buttes, the two channels rejoined, and the flood went into Idaho Falls.
Two things saved Idaho Falls. One was the geologic bedrock and soil which had made Teton such a bad project, physically and economically. By the time the flood poured itself into the Snake River twenty miles above the town, a lot of it had drained off into the porous soil and deeply fractured bedrock beneath it. The other salvation