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28 FLOODS OF SEPT. 1970 IN ARIZ., UTAH, COLO., AND N. MEX. CENTRAL ARIZONA 29 barrier to the flow in the channel and caused the deposition of as much as 6 ft (1,8 m) of sand. The trees diverted part of the flow over the terrace along the left bank, and minor flood damage occurred in a trailer court. The flood of 1970, which was the largest known along Black Canyon Creek according to residents, originated principally in Turkey Creek basin, Residents reported that giant logjams occurred in the headwaters of Turkey Creek and that the sudden breaching of the jams probably caused the high peak flows near Cleator. The peaks were 10-20 ft (3.0-6.1 m) high, depending on the width of the channel. J. W. Williams and T. E. Russell of the U.S. National Forest Service (written commun., 1970) estimated that the peak discharge in Turkey Creek was about 11,000 ft'js (310 m'js). Undercutting of an abutment damaged a concrete bridge east of Cleator. Downstream in the narrow gorge of Black Canyon Creek, flood marks were as much as 35 ft (10.7 m) high. The abnormally high floodmarks probably were caused by log jams. Between Rock Springs and Lake Pleasant, the flow of the Agua Fria River augmented by that of Black Canyon Creek inundated a one-fourth-mi-wide (O.4-km-wide) area of the flood plain. The flood in the Agua Fria River near Lake Pleasant was larger than any that had occurred in recent years but did not approach the magnitude of the flood of 1909. All the floodwater from the Agua Fria River upstream from Waddell Dam was stored in Lake Pleasant. The large amount of rain in the New River Mountains caused extremely high flows in New River-the main tributary to the Agua Fria River below Waddell Dam. The peak discharge in upper New River was the greatest since records began in 1960 but decreased rapidly with increasing distance downstream. The discharge of New River above Skunk Creek was less than the maximum of record; downstream from Skunk Creek, the discharge was about equal to the previous maximum of record but was much less than the estimated 38,000 ft'js (1,080 m'js) for the flood of 1943. One person wss drowned in New River when his car stalled at a road crossing in the Phoenix metropolitan area. HASSAYAMPA RIVER-BASIN The Hassayampa River heads on the west side of the Bradshaw Mountains south of Prescott, and Milk Creek is the uppermost tributary of the several main tributaries that join the river within about 4 mi (6 km) of Wagoner. The peak discharge of the Hassayampa River above Milk Creek was only a few hundred cubic feet per second during the flood of 1970. Downstream, however, large flows were contributed by Milk Creek and its tributaries~Ash Creek and Crooks Canyon-and Blind Indian, Arrastre, Cottonwood, and S pring Creeks. The large flow originated in a well-defined area about 6 mi (10 km) wide and 18 mi (29 km) long, which extends northeastward through Wagoner to the crest of the Bradshaw Mountains. According to Homer Dean (local resident, oral commun., 1971), the flood in Milk Creek was the largest in the last few decades. Milk Creek overtopped 4-ft-high (L2-m-high) terraces one-half mi (0.8 km) upstream from its junction with Crooks Canyon and deposited a mantle of sand and gravel 300 ft (90 m) wide and as much as I ft (0.3 m) thick on one of the terraces; this mantle is the first coarse detritus deposited on the terrace for several decades and perhaps for a few centuries. The configuration of the gravel fan deposited by Ash Creek where it enters Milk Creek and the high-water marks along both streams indicate that the floodflows of the creeks were virtually simultaneous. The gravel bar deposited by Ash Creek had a maximum thickness of 4 ft (1,2 m), and the top of the bar was only slightly lower than the high-water marks of both streams near the confluence. The Hassayampa River deposited a I j 2- to I-ft-thick (0.15- to 0.3-m-thick) layer of sandy detritus in fields in the wide valley below Wagoner. In the valley the river channel is broad and shallow, an<l the flood inundated an area one-half mi (0.8 km) wide. According to R. F. Cooper (local resident, oral commun., 1971), the soil in the fields contained little sand before the flood; the deposition of the sandy material in the fields indicates that the flood of 1970 was a rare event. The 50-year-old Cooper ranchhouse at the confluence of Spring and Cottonwood Creeks 2 mi (3 km) southwest of Wagoner was destroyed by the flood. The house was built ona 9-ft-high (2.7-m-high) terrace and was swept away by the 14-ft-high (4.3-m-high) crest of the flood. Fields and wooded areas were severely damaged in the reach just upstream from Box Canyon. Floodmarks in Box Canyon were 44 ft (13.4 m) above the streambed-the highest floodmarks measured for the 1970 flood. The peak discharge of 58,000 ft'js (1,640 m'js) at the gaging station in Box Canyon (pI. I and fig. 7, No. 138)is more than twice the previous maximum forthe 50 years of record and is the largest flood since at least 1890, when the Walnut Grove Dam near Wagoner failed (Newell, 1891). Although extensive flood damage occurred at Wickenburg, no lives were lost. The sewage plant was flooded, a sewerline was washed away, and raw sewage flowed into the river. Several homes and housetrailers were destroyed, and about 50 persons were left homeless. A few ranches along the river were flooded, and buildings, livestock, vehicles, and trees were swept away. Electricity was cut off in part of the area when powerline poles were washed away. In the reach between 3 and 5 mi (5 and 8 km) downstream from Wickenburg, a trailer park, a few homes, and a roadside park were inundated by 4 to 6 ft (1,2 to 1.8 m) of water. The flood crested 16 ft (4.9 m) above the channel in a wooded area, and many trees were toppled or bent over. At the Hassayampa River near Morristown gaging station (fig. 7, No. 140) 7 mi (11 km) downstream from Wickenburg; the peak discharge was 47,500 ft'js (1,350 m'js), and it had decreased to 39,000ft'js(1,100 m'js) by the time it reached the gaging station near the mouth (fig. 7, No. 141). The flood inundated areas as much as I mi (1.6 km) wide in the reach between the gaging stations (pI. I).