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<br />- 20 - <br /> <br /> <br />0"02',7 <br />'- ~ .J <br /> <br />" <br /> <br />In addition to the direct floodwater damages, there are indirect <br />damages such as loss of business, depreciation of property, <br />interruption of travel, rerouting of traffic, and interruption of <br />municipal water supplies. For this evaluation 15 per cent of the <br />direct floodwater damages to commercial property, roads, bridges, <br />and utili ties was taken as a conservati ve estimate of the annual <br />indirect floodwater damages resulting from flooding by Fishers <br />Peak Arroyo. For Carbon Arroyo 20 per cent of the direct floodwater <br />damages to commercial property and to roads,. bridges, and utilities <br />was used to estimate indirect floodwater damages because of the <br />probability of damage to exposed water mains in the arroyo which <br />would result in interruption of the muniCipal water supply. <br /> <br />Hydraulic and Hydrologic Investigations <br /> <br />The effects of present and future watershed conditions on <br />flood discharge were determinect through procedures in Supplement A <br />(Soil Conservation Service) National Engineering Handbook on <br />Hydrology, hereinafter referred to as the hydrology handbook. The <br />type of land treatment measures to be applied will have only a <br />minor effect on runoff. <br /> <br />The area range and soil specialists prepared, from existing data <br />and by field inspection, a soils map with a complete description <br />of the range site and hydrologic conditions. These data were <br />reviewed by the Assistant State Soil Scientist, Colorado State <br />SCS Office, with representatives of the Watershed Planning Party and <br />the Colorado Water Consetvation Board. The hydrologic soil grouping <br />and soil-cover complex conditions were established and approved <br />at this time. The composite soil-cover complex curve numbers of <br />73 and 78, respectively fbr the area above and the area below dam <br />site FPC-I for present conditions, and a composite curve number of <br />77 and 78, respectively for the area above and area below dam site <br />FPC-2, were determined. <br /> <br />" <br /> <br />Since there are no streamflow records on the watershed, newspaper <br />files '~re inspected and local residents interviewed to obtain infor- <br />mation suitable for flood frequency determinations. This watershed <br />had damaging floods on the following dates: 1874, September 1901, <br />1904, 1907, 1909, 1918, June 1937, July 24, 1941, 1942, 1948, and <br />1958. It is known that serious overbank flow occurred in the 1874, <br />1901, 1918, and 1941 floods with minor amounts of overflow in other <br />floods. The flood in 1958 caused damages to the closed conduit on <br />Fishers Peak Arroyo but did not produce overbank flow. In general, <br />it was concluded that for Fishers Peak Arroyo bankfull stage (1,000 <br />c.f.s.) occurred about once in 10 years and the one per cent chance <br />flood could be about 2,000 c.f.s. <br />