524 



SCIENCE 



[Vol. LVI, No. liZi 



fl-ater flon-ing out from this basin. What more 

 natural than that he should assume a hole in 

 the ground through which the river poured its 

 waters into the bowels of the earth? 



But of particular interest, because of its 

 bearing upon the jDresent discussion, is the 

 main fact that periodically, say for a period 

 •of 500 to 1,000 years, the Colorado River had 

 ■an outfall into the Salton Basin, that is, down 

 the northern slope of its delta cone and again 

 for a similar period of time the river has dis- 

 charged into the ocean through the Gulf of 

 California. 



With this fact in mind let the boundary line 

 be traced fi'om the .south boundary of Arizona 

 i:ol!oA\-ing up the Colorado River for some 20 

 miles to Pilot Knob, and thence a little south 

 ■of west in a straight line to the Pacific Ocean. 

 This boundary line leaves a part of the Colo- 

 rado River delta, Yuma Valley, in Arizona. 

 It leaves the head of the Gulf of California 

 .and the main south slope of the river's delta 

 ■cone in Mexico; and it leaves the major por- 

 tion of the north slope of the delta eone, in- 

 cluding what is now knoAvn as Imperial Valley 

 .and also the Coaehella Valley, which was once 

 ■deeiD under the waters of the ancient sea, in 

 California. 



From the earliest studies made of this re- 

 gion by citizens of the United States it is 

 known that the Colorado River originally 

 flowed from near Yuma to the Gulf of Cali- 

 fornia in a meandering channel, having un- 

 stable Ijanks, and inadequate capacity to carry 

 ■all the Avater presented at flood stages. The 

 ■distance in an air line from the head of the 

 river's delta to the Gulf is in round figures 80 

 miles. In this distance the river falls 100 

 feet. It is about the same distance from the 

 head of the delta to the loAvest portions of 

 Salton Basin but as the lowest part of the basin 

 is over 280 feet below sea-level the fall in this 

 ■direction is nearly 400 feet. If the river should 

 be permitted to flow into the ibasin it would 

 take 20 or 30 years to fill it up. There was no 

 immediate danger of the river making a change 

 in its course under the natural conditions that 

 prevailed 50 to 75 years ago 'because at each 

 flood stage the river banks were overtopped; 

 they were well watered far back from the edge 

 ■of the stream, and carried a luxuriant growth 



of trees, brush and grass and they wei-e being 

 constantly warped up by the sediment whieli 

 the muddy water of the river spread out over 

 the land. 



But as soon as human activities modified 

 these natural conditions, as soon as a small 

 dredger cut invited the river down the steep 

 northern delta slope, the river broke from its 

 channel and temporarily abandoned its course 

 to the Gulf. This happened in 1905 and it 

 took a little more than a year to put the river 

 back into its old channel. But while this was 

 being accomplished the delta channels went 

 dry. The vegetation on the jjarched bank land 

 died out and fire destroyed the plant growth in 

 large part which had, theretofore, protected the 

 ai-ea nearest the river against erosion. And so, 

 at the subsequent high stages of the river, there 

 was more overbanic floAV and greater concentra- 

 tion of water in the swales leading away from 

 the river and therefore increased danger of the 

 river breaking out of its original channel. 1907 

 and 1908 passed Avithout this happening, Ibut 

 in 1909 the river broke a new channel toward 

 the west following the course of what was 

 ]^;nown as the Rio Abejas or Bee River. The 

 point where this abandonment of the ori'ginal 

 river channel occurred was about opposite the 

 south boundary line of Arizona. 



The river has ever since, except for a i,«\^ 

 weeks while checked by a levee, been sending 

 its water southwesterly in a round about way, 

 through ^'^oleano Lake and the Hardy Colo- 

 rado into the Gulf. But its flow westerly was 

 on or near the crest line of the river's very 

 flat delta eone. Its channel is a broad shallow 

 bed of sand of irregular alignment. At flood 

 stages its water submerges broad stretches of 

 country. Its flood waters would preferably 

 drop oft' the delta cone to the north but have 

 been prevented from doing this by levees. 

 Herein lies the purpose of this statement of 

 physical facts. The levees along the river and 

 along the crest of its delta were and are re- 

 ciuired for the protection of property in the 

 United States. All of Imperial Valley and of 

 Coaehella Valley are menaced. This does not 

 mean that if a breach in the levees occurred 

 and the river again discharged into Salton 

 Basin that all of these valleys would be flood 

 swept. Not at all. The river would simply 



