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.' . ~ ( - 9 - '.' The Grand Junction area is served by U. S. Highl'1ay 50, U. S. High 6-24, and several major state highways, as well as an excellent system of county roads. Both the main and bypass routes of Highway 6-24 cross the lower part of the watershed. Grand Junction is the main freight center on the Denver and Rio Grande Western Railroad between ,Denver and.S.alt Lake City. In 1952 the railroad completed construction of a ~3,500,000 classification y~rd, most of which lies within the watershed boundaries. The Grand Junction municipal airport is located west of the watershed above the High Line Canal. Two airlines, United and Frontier, operate daily flights to Denver, Salt Lake City, and other points. ... \<lATER3HED PROBIDfS ( The principal problem in the watershed is the extensive floodwater and sediment damage to irrigated cropland, irrigation facilities, residential and commercial property, streets, highways, bridges, and railroads in and adjacent to the City of Grand Junction. This damage is caused by floods originating primarily fram localized, high intensity thunderstorms over the steeply sloping desert rangelands in the upper two-thirds of the watershed. In general, rainfall amounts and intensities in this type of storm became higher with the increase in elevation between the High Line Canal and the steep escarpment of the Little Book Cliffs at the north edge of the watershed. Runoff in this area is also more rapid~ and sediment production is greater than in the more gently sloping lower one-third of the watershed. . .. Amounts of runoff and sediment originating in the area below the High Line Canal are seldom great enough to constitute a major source of damage in themselves. However, the runoff from thi s area adds to the overall problem of floodwater disPosal through existing channel facilities whenever this runoff occurs in conjunction with heavy flood flows originating in the upper part of the watershed. The areas subject to significant d~~ages are shown on the Damage Area Map, Figure 1. Estimates of average annual damages are presented in Table 7. Floodwater Damage ... l Intense thunderstorms occurring over the upper part of the watershed during the summer and early fall have been the most frequent cause of damaging floods on Indian Wash. InforL~tion obtained fram local residents indicates that damaging floods have occurred in the watershed on the average of once every six years. However, very little factual information is available concerning dates and amounts of monetary damage of these floods. Records of precipitation at the Grand Junction U. S. Weather Bureau Station indicate that large storms occurred in the area on the following dates: September 23, 1896; Hay 24, 1906; October 16- 18, 1908; and August 20-25, 1921. It should be noted, however, that a large stonn can occur in the upper watershed area with little or no precipi- tation being recorded at the weather station. Storms of this t)~e produced dama.ging floods on Indian \lash in August 1938, June 1954, and liay 1955.