Engineering Wonders of the World
Volume III

THE COLORADO RIVER CLOSURE. 117 point is half that of the Niagara River at the famous falls. Furthermore, the Gila River, which enters the Colorado just above Yuma, is subject to heavy spates caused by cloud- bursts, and in a few hours swells from a trickle into a raging torrent discharging almost as much water as the main stream itself. An- other feature of importance is the character of the Colorado’s bed—deep silt unfathom- able by borings and piles, and so fine that flowing water disintegrates it with the greatest ease. Having acquainted themselves with the peculiarities of the river, the engineers made a third attempt to stop the breach. They drove piles obliquely across the stream to the upper end of an island—fitly called Dis- aster Island, as it was subsequently washed The Third Attempt- away—hoping thus to turn the waters into the channel to the left of the island, and cause the formation of a sandbank at the entrance of the crevasse. But a sudden rise of the river undermined and removed the piles, and August 1905 saw this at- tempt aban- doned. The engi- neers did not despair, how- ever. A brush and pile dam (3 in Fig. 1) was stretched across the Mexican or right channel to the upper end of the now partly de- stroyed island. It had been almost com- pleted when WATER EATING ITS WAY THROUGH THE RIVER BANKS. an exceptionally high flood of the Gila swept down on and destroyed the works. So ended effort num- the , , Fourth. ber tour. Two days before the disaster a contract had been signed for the construction of a steel reinforced concrete headgate near the intake at the upper end of the canal, about 1,500 feet from the Concrete , , ± .1 Headgate. river bank. The gate was de- signed to pass 10,000 cubic feet of water per second, and enable all the river to be diverted through it at low water into the old canal and allow the breach opposite the island to be dammed. The canal itself also required widen- ing ; and as this work could not be effected quickly, it was decided to construct simul- taneously a wooden headgate (5a in Fig. 1) beside the breach, and afterwards dam the breach opposite this headgate. Owing to un- avoidable delay the wooden gate was not completed soon enough to permit opening the by-pass leading to it, and building the dam, before the occurrence of the ensuing summer floods (1906), which were p articularly severe, and extended the width of the crevasse from 600 to about 2,600 feet, de- positing a sandbank 1,500 feet long in front of the headgate (see Fig. 2). This c o mplicated matters seri- ously. The en- gineers deter- mined to erect a darn 3,000