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<br />affected streams rise relatively slow; sometimes over a period of <br />several days. The duration of the flood period also is sometimes <br />of considerable length. Because of the large areal extent of <br />rainfall, more tributaries contribute to the peak discharge on <br />the South Platte River. This results in increasing discharge <br />progressively downstream over a considerable length of the South <br />Platte River. However, downstream from the contributing <br />tributaries, the effects of valley storage cause flood discharge <br />attenuation. <br />Erosive effects can be considerable in the event of any <br />flood regardless of its origin. Floods resulting from intense <br />rainstorms typically create severe erosion damages in a short <br />period of time due to the relatively large peak discharge and <br />high velocity of the floodwater. Erosion damages from snowmelt <br />or general rainstorm floods usually result from prolonged <br />exposure of the floodwater because of the long duration typical <br />of these floods. <br />Intense rainstorm floods as well as general rainstorm floods <br />have occurred on the South Platte River. Examples of the intense <br />storms are the 1965 events on Plum Creek and Bijou Creek and the <br />1976 event on the Big Thompson River. Examples of the larger <br />more generalized storms are the 1969 and 1973 events producing <br />flooding on the South Platte River. <br />The following flood accounts are typical of flood events <br />which have occurred along the South Platte River in Colorado, but <br /> <br />2 <br />