RANGE PRESERVATION AND EROSION CONTROL. 5 



most violent period, with rocks containing as much ;is 30 cubic feet 

 of material, the flood destroyed wagon roads, trails, ami water 

 dil dies. 



Another typical example of flood and erosion occurred on July 30, 

 1012, when a flow of torrential violence originated at the head of 

 Becks Canyon. A rain, amounting to 0.55 of an inch, the greater 

 part of which fell within an hour, started at 11 a. m., and at 11.45 

 a. m. a flood was pouring out of a small side canyon which drains 

 into Becks Canyon from an area of less than 1,500 acres, at an ele- 

 vation of about 10,000 feet. This area is virtually treeless and is 

 fan-shaped, the main drainage channel originating at the head of 

 a steep canyon which drops into Becks Canyon at the rate of about 

 1,000 feet in less than a mile. The soil is of a clay-loam type, and, 

 considering the area as a whole, is of fair depth, there being but 

 little outcrop. The slopes are moderately gentle, and because of 

 this fact the area had not been included in the adjacent one which 

 was protected from grazing until late in the season. An examination 

 after the flood showed that the soil had been A^ery densely packed 

 by grazing previous to the storm. The whole of this small water- 

 shed was well marked with gullies. The flood was not observed 

 until it reached the mouth of the side canyon. Here it presented a 

 front approximately 8 feet wide and H feet high. The water was 

 so infiltrated with sediment that it did not run but rolled over and 

 over, picking up small rock and gravel. The flow increased to a 

 front of from 10 to 25 feet wide and from 6 to 8 feet high. The 

 velocity and force of the rolling mass down the steep slope were 

 appalling. The main flow lasted approximately one hour, varying 

 in volume as. had the rain 30 minutes previous. Owing to the enor- 

 mous deposits of debris, the course at the mouth of the channel 

 changed three times. As the stream changed its course from one 

 side to another enormous quantities of material were deposited only 

 to be carried away later. At one time approximately 5,000 cubic 

 feet of the bank was torn out in a few minutes as the old bed filled 

 up with material from above. All these tons of soil, vegetable 

 matter, and other material were carried down by the rushing water 

 in less than two hours after the rain began to fall. 



In addition to the direct loss of personal property, damage to the 

 range itself in the way of decreased forage production and soil de- 

 pletion has a most vital effect on a community. Such loss is seldom 

 fully appreciated until the stockmen must, of necessity, limit the 

 number of animals grazed on the lands. Following the action of 

 a few destructive floods, the productivity of the grazing lands may 

 be so decreased that only the more inferior drought-resistant plants 

 will thrive. Where the farm lands, upon which supplemental win- 

 ter feed is grown, are remote from shipping points, as is true of much 



