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Ii~ MaIrix~r,,"nh; 'v -..-'.....- .z:-~ Page 10 July 24,2000 l~jl~~~ ~" -- Page 11 July 24, 2000 Floods on the Roaring Fork result from snowmelt and occur principally during the month of June. The flood of July 1, 1957 had an instantaneous peak discharge of 18,700 cfs at the Glenwood Springs gage. This flood was the maximum of 49 years of record, and its magnitude has an estimated frequency of occurrence of once in approximately 60 years. In compliance with the requests, an inspection of the problem areas on the Roaring Fork River was made by Corps representatives on 12 and 13 December 1957. The inspection covered a 14- mile reach beginning 2 miles above Basalt, Colorado, and ending at Carbondale, Colorado, 12 miles below Basalt.. The following excerpts from He stated that a couple of agricultural fields along the Roaring Fork were washed out and also that the entire valley where the KOA Campground is now located had been completely flooded several times in his memory. Mr. Lucksinger also said the Fryingpan River does not flood very often but during the 1957 flood, it washed out a road 60 feet from the river. the Corps of Engineers letter report also described the July 1957 flood. The 18,700 cfs instantaneous peak discharge referred to in the Corps of Engineers letter report has been revised to 19,000 cfs by the U.S. Geological Survey. This is the maximum instantaneous peak discharge recorded at the Glenwood Springs gage on the Roaring Fork River through 2000. Mr. Richard Lucksinger of Basalt, was an Eagle County Commissioner during the July of 1957 flood and was inteT1Jiewed by the Corps of Engineers. Mr. Lucksinger said that around July 4, 1957, a heavy rain melted large volumes of snow, which still remained due to an unusually cold spring and late summer. He remembered thatthe river rose rapidly to flood height in about 15 minutes and stayed up for three days. According to Mr. Lucksinger the Roaring Fork River rose high enough to wash against the bottom of the Emma Bridge, which washed out and had to be replaced. Pilings for the new bridge were about 60 feet deep. During the flood, the river changed course several times; sometimes going under the bridge, sometime to one side or the other. The areas now occupied by trailer parks in the floodplain in Basalt were several feet deep in water. More than one-half of the known damages in the 1957 flood were caused to roads and bridges in the area, with nearly $24,000 of damages being caused to three bridges and their abutments. Two of these were public bridges and have since been restored. A third bridge, which 'was private was completely destroyed and has not been replaced. A substantial percentage of the total damages were due to overtopping of the low banks and the inundation of pasture and croplands. The banks in most instances range form 2 to 5 feet in height. In two locations, where old channel areas have been reclaimed, considerable volumes of overflow and widespreadflooding resulted from bank overtopping at the upper ends of the areas. Information pertaining to interviews with long time investigation of Flood Problems the older local flood history of the study area came form two main sources; residents and a U.S. Army Corps of Engineers letter report entitled on Roaring Fork River, Colorado, "March 7, 1958 A common type of damage from the 1957 flood was bank erosion. The slope of the stream ranges from 65 feet per mile above Basalt to 40 feet per mile below Basalt. Velocities probably in excess of 10 feet per second occurred during the 1957 flood. The banks are composed largely of sand, gravel, and cobbles overlain by a comparatively thin mantle of soil, and are quite erosible. Spoil-type dikes, constructed by local interests with material bulldozed in the process of channel clearing, proved to be very erosible. 3.3 Summar The Corps of Engineers estimated that the operation of Ruedi ReseT1Joir to fill the operating storage, the Boustead Tunnel diversion and Turquoise Lake prevented $1,770,000 of flood damage in the Colorado River Basin during 1995. of Historical Floods No urban areas are affected by floods. The principal items damaged by the 1957 flood were the agricultural lands and roads and bridges adjacent to, or over, the river. A few farm buildings were flooded. The total known damages in all categories in this reach amounted to slightly more than $45,000. No call was placed on the Colorado River at the Cameo gage by senior water right holders due to high flows in the Colorado River throughout the irrigation season. Because of that, there were no releases made for either Project depletions or for depletions caused by Ruedi ReseT1Joir water contract holders during the 1995 water year. Highflows in the Colorado River also eliminated the need to release any water to augment the habitat of endangered aquatic species in the Colorado River downstream of the Grand Valley Diversion Dam and above the confluence with the Gunnison River. The total April through September inflow was 154,235 acre-feet, which was 130% of average and greater than the reasonable maximum forecast inflow. The high inflows were due, in part, to waters left in the Fryingpan River Basin which normally would have been diverted to the East Slope but were not because the reseT1Joirs on the East Slope hadfilled during the spring runoff. The river in the problem area is characterized by low banks, braided channels, and a considerable amount of gravel, cobbles, and snags deposited on gravel bars. The river carries a large bedload of gravel and cobbles, some of the latter being more than 6 inches in diameter. The capacity of the channel has been reduced by this sediment. In some instances, where channel changes took place during the flood, the original channels were so filled with sediment that nearly all of the present flows are discharging through the "new" channels. Generally, however, the "new" channels are old watercourses abandoned by the river in previous year. The littered condition of the channels, and the increased danger of bank erosion, inundation, and additional channel changes resulting from this condition, constitutes the present flood problem. ort Town of Basalt, Ea le & Pitkin Counties, Colorado ort Town 0 le & Pitkin Counties, Colorado