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: