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<br />Some areas in Steamboat Springs are subject to sheetflow, that is, broad, shallow <br />overland flooding generally less than 3 feet deep and characterized by unpredictable <br />flowpaths. The water-surface elevations (WSELs) of flooding in these areas are <br />essentially independent of those adjacent streamways and are affected principally by <br />obstructions in flooded areas. <br /> <br />Analyses prepared for this report show that the loo-year flood on the streams under <br />study would result from snowmelt augmented by rain, the 500-year flood on the Yampa <br />River would result from general rain, and the 500-year flood on the tributary creeks <br />would result from cloudburst storms. <br /> <br />The worst flooding known in the Steamboat Springs area occurred in June 1921 and <br />April 1974. Flooding was widespread in the region in 1921, with highway travel cut <br />off and towns isolated. In Steamboat Springs, flow in Soda Creek was too great to be <br />passed by the Lincoln Avenue crossing, and a large lake formed that surrounded several <br />homes and was backed up by the bridge. Floodwater ultimately flowed over the street <br />in a stream that was a half-block wide, the bridge was damaged, and the streambank <br />eroded. Between Lincoln Avenue and the Yampa River, Soda Creek was from 300 to <br />500 feet wide. Along the Yampa River, the railroad was badly damaged at several <br />locations between the depot and the upper end of town. Railroad traffic and power <br />generation were interrupted, masses of debris collected at bridges and had to be <br />removed, and other miscellaneous flood damage occurred. The measured stage of the <br />Yampa River in Steamboat Springs indicated a flow of 7,000 cfs, which was 1,000 cfs <br />greater than any previous flow of record. Flow in Soda Creek was estimated at <br />2,000 cfs, and flow in Walton Creek was measured at 2,800 cfs. <br /> <br />In April 1974, all the streams in the Steamboat Springs area were higher than at any <br />other time in recent history, but damage occurred principally along Butcherknife Creek. <br />Three days of unseasonably warm weather (which accelerated snowmelt) and a heavy <br />rain triggered flooding that began at 6 p.m. on April 25 and lasted until midnight on <br />April 27. Flooding of disastrous levels along the Yampa River and Fish Creek was <br />prevented by 200 to 300 volunteer floodfighters who filled and placed sandbags and <br />built emergency berms at critical locations. However, approximately 50 homes along <br />Butcherknife Creek were surrounded by floodwater, and approximately 300 homes <br />were threatened. A state of emergency was declared on April 26. Flow in the river <br />was approximately 500 cfs above flood stage. There was some structural damage to <br />foundations, floors, and walls of the 50 inundated homes, but the principal flood losses <br />were damage to basement appliances, such as furnaces, water heaters, freezers, <br />washers, and dryers. Other flood losses included the cost of floodfighting and the cost <br />of cleaning rubble-covered streets, lawns, and fields. Photographs of the 1974 flood <br />are shown in Figures 17 through 20. <br /> <br />Routt County <br /> <br />The flood hazard in Routt County downstream of Steamboat Springs results from <br />Yampa River overflows. The Yampa River flows from the southeast to Steamboat <br />Springs and then westerly. Slate Creek enters the Yampa River in the study reach. <br />However, the potential for flood damage along the Yampa River is not great because of <br />the lack of development. <br /> <br />19 <br />