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<br />. <br /> <br />. <br /> <br />. <br /> <br />6. Hvdroloqv and Flood Problems. <br /> <br />~ <br /> <br />Flooding problems on the Colorado River in the study area <br />are historically the result of snowmelt. The drainage area is <br />approximately 17,000 square miles. The worst flood occurs when <br />the melting of the mountain snowpack is augmented by rain. The <br />snowmelt flood is characterized by sustained periods of high flow <br />and marked daily fluctuations with the peak flow occurring <br />sometime during April, May, or June. General rains (without <br />snowmelt) have not produced serious flooding in and around the <br />Grand Junction area. <br /> <br />Colorado River floodflows in Grand Junction and Mesa County <br />have inundated streets, lawns, and gardens; deposited sand, silt <br />and debris; and flooded basements and lower floors in the <br />residential areas in the flood plain. The Colorado River below <br />Grand Junction has an average annual flow of 6,l33 cfs. The <br />maximum flow of record at the Colorado-Utah state line gaging <br />station, 69,800 cfs, occurred on 27 May 1984. The minimum flow <br />of record, 960 cfs, occurred on 7 September 1956. The earliest <br />recorded Colorado River flood in Grand Junction occurred in l884 <br />and, with an estimated discharge of l25,000 cfs, is considered <br />the most severe known in the Grand Junction area. The 1921 flood <br />had an estimated discharge of 81,000 cfs. Floods also occurred <br />in 19l7, 1920, 1935, 1952, 1957, 1964, and 1983. <br /> <br />There are eight stream gaging stations between Dotsero and <br />the state line, as shown in Table 1. These stations were used to <br />develop the statistical relationships used in this study. Other <br />statistical studies have been conducted in this area for flood <br />insurance purposes, and their results also compare favorably. <br /> <br />The flow-frequency relationship for the Colorado River at <br />Riverside (from Plate 3) is shown in Table 2. <br /> <br />7. Other Water Resources Needs. <br /> <br />Flood Control is the primary focus of this investigation. A <br />significant related opportunity in the Grand Junction area is <br />recreation. <br /> <br />Grand Junction and other communities in Grand Valley are <br />attempting to revitalize the riverfront area along the Colorado <br />River. Although concern about the dilapidated state of the <br />riverfront and the need for its revitalization has existed for <br />some time, only in recent years has an effort been made to <br />reclaim this valuable community resource. The riverfront project <br />being planned and executed in segments by local and state efforts <br />would continue its momentum whether or not a flood protection <br />project would be installed. <br /> <br />, 5 <br />