314 Anderson — Stream. Piracy of Provo and Weber Rivers. 



Art. XXV. — Stream Piracy of the Provo and Weber Rivers, 

 Utah / by G. E. Anderson. 



The Provo River is one of a series of streams which 

 have cut deep canyons into the Wasatch Range and drain 

 westerly into the Great Basin. Of these may be men- 

 tioned the Ogden, Weber, Little and Big Cottonwood, the 

 American Pork, the Provo and the Spanish Pork all having 

 steep gradients and picturesque canyons. Two of these, the 

 Weber and the Provo, have cut entirely through the Range 

 and have contiguous drainage basins east of the Wasatch and 

 now their head waters drain the west end of the Uinta Range. 

 The Weber was the first to cut through the Range and is the 

 master stream of the whole system. It had in fact developed 

 the whole drainage basin east of the Wasatch before the Provo 

 had cut through that range and the head waters of the present 

 Provo as far down as Rhodes Valley was then a south fork of 

 the Weber — the two forks of the Weber uniting at what is now 

 the village of Peoa. 



Between Peoa and Rockport the Weber River erodes its 

 channel in the resistant and nearly vertically dipping partly 

 metamorphosed sandstones and conglomerates of Triassic age 

 with the direction of the river channel at right angle to the 

 strike of the sandstones, causing channel erosion over them to 

 be very slow and the gradient of the Weber thereby held up 

 at this point until the south fork of the Weber became a some- 

 what mature river valley immediately above its junction with 

 the north fork, with a sluggish and meandering stream, which 

 widened its valley to a width of two and one-half miles and 

 for a distance of eight miles up stream to the south. This 

 valley is the present Rhodes Valley. It has a gradual north- 

 ward slope from an elevation of 6500' in the south end to 

 6300' at the north end of the valley. A slight amount of 

 aggradation has taken place in the valley by the small streams 

 draining the hills from the east and west sides. This, however, 

 has not materially changed the gradient or filled up sufficiently 

 to cause any well-defined erosion through the valley since it 

 was formed by the south fork of the Weber. 



While Rhodes Valley was being formed the Provo was 

 cutting down its barrier — the Wasatch Range. Channel 

 erosion through the Wasatch was slow, however, so that the 

 head waters of the Provo on the east side had time to widen 

 out the valley in which the town of Heber is now located. 

 Seven miles above Heber, at Hailstone, the Provo head erosion 

 divided into two tributaries, one reaching out in a northerly 



