The task set before Messrs. Randolph, Cory, Hind and Clarke was one that might well have daunted even engineers of their great ability and experience. As the summer flood approached its maximum, in the latter part of June, the crevasse widened to more than half a mile, and the whole river, rushing through the break, spread out over an area eight or ten miles in width, and then, collecting in separate streams as it ran down the slope of the basin, discharged at last into the Salton Sea through the flooded channel of the New River barranca. Thousands of acres of land, covered with growing crops, were inundated, and thousands of acres more were so eroded and furrowed by the torrential streams that they never could be cultivated again. The works of the New Liverpool Salt Company were buried under sixty feet of water; the towns of Calexico and Mexicali were partially destroyed, and in many places the tracks of the Inter-California Railroad (a branch of the Southern Pacific) and the Holtville Interurban were deeply submerged or wholly carried away. The wooden flumes which carried the irrigating water over the New River barranca were swept down into the Salton Sea, and 30,000 acres of cultivated land in the western part of the Valley became dry, barren and uninhabitable. At the height of the flood, the Colorado discharged through the crevasse more than 75,000 cubic feet of water per second, or six billion cubic feet every twenty four hours, while the Salton Sea, into which this immense volume of water was poured, rose at the rate of seven inches per day over an area of four hundred square miles. The main line of the Southern Pacific was soon inundated, and five times in the course of the summer the company had to move its track to higher ground.
A Flood Waterfall in Imperial Valley, Cutting Back
Nearer View of Flood Cataract in Imperial Valley, Cutting Back
The most dangerous and alarming feature of the situation was the “cutting back” of the torrents into which the flood-water collected as it rushed down the delta slope toward the Salton Sea. The fine silt of which the soil was composed washed out like powdered sugar, and wherever there happened to be a strong current, the flow soon produced a miniature rapid. The rapid then became a cascade, the cascade grew into a fall, and the fall finally developed into a roaring cataract, which “cut back,” upstream, at the rate sometimes of four thousand feet a day, widening as it receded, and leaving below it a deep gorge with almost perpendicular walls. Some of the gorges eroded in the light friable silt by these receding waterfalls were fifty to eighty feet deep and more than a thousand feet across. It was estimated that the channels thus formed during the floods of 1906 had an aggregate length of more than forty miles, and that the solid matter scoured out of them and carried down into the Salton Sea was nearly four times as great as the whole amount excavated in the digging of the Panama Canal. But the damage actually done by these receding waterfalls was unimportant in comparison with the damage that they threatened to do. If one of them should “cut back” far enough to break into the irrigation system of the California Development Company, all the water in the latter’s canals and ditches would instantly flow down into the deep gorge below the cataract, and bring about a disaster almost unprecedented in history. The twelve thousand settlers in the desert oasis were wholly dependent upon the irrigation system for their supply of drinking water, and if that supply should be cut off, they would be compelled by thirst either to camp around the margin of the Salton Sea, which was ten or fifteen miles away from most of them, or else get out of the valley within forty eight hours in a wild precipitate stampede. Paradoxical as it may seem, the danger of being driven out by lack of water was even greater and more immediate than the danger of being drowned out by the rising flood.
The changes in the topography of the Colorado delta brought about by the crevasse and the floods of 1906 were greater than any that had occurred there in the three preceding centuries of recorded history. In referring to them Mr. Cory says:
“The effect of this flood, in a geological way, was of extraordinary interest and very spectacular. In nine months, the runaway waters of the Colorado had eroded from the New and Alamo River channels and carried down into the Salton Sea a yardage almost four times as great as that of the entire Panama Canal. The combined length of the channels cut out was almost forty three miles, the average width being one thousand feet and the depth fifty feet. To this total of 400,000,000 to 450,000,000 cubic yards must be added almost ten per cent for side cañons, surface erosions etc. Very rarely, if ever before, has it been possible to see a geological agency effect in a few months a change which usually requires centuries.”
Channel Cut by the Runaway River on Its Way to the Salton Sea