FLOOD10337 - Laserfiche WebLink

Home Browse Search

20 smaller than either the ,I DO-year or 500-year floods are much more common. Large floods, however, can happen; this was clearly demon- strated by the Denver area floods of 1965, the Black Hil Is, South Dakota area floods of June 1972, and the July 1976 floods in the Big Thompson Canyon near Loveland, Colorado. Hazards of Large Floods The extent of damage caused by any flood depends on the topography of the area flooded, depth and duration of flooding, velocity of flow, rate of rise, developments on the flood plain, amount of debris in the floodwater, and ice conditions, if ice is a problem in that particular area. A 100-year flood or a 500- year flood on the South Platte River in the study reach would result in the inundation of and subsequent damage to primari Iy agricultural properties and associated developments as wel I as public utilities and public roadways. Deep floodwater flowing at high velocity and carrying floating debris would create conditions hazardous to persons and vehicles attempting to cross flooded areas. In general, floodwater 3 or more feet deep and flowing at a velocity of 3 or more feet per second could easily sweep an adult person off his feet, thus creating definite danger of injury or drowning. Rapidly rising and swiftly flowing floodwater may trap persons in homes that are ultimately destroyed or in vehicles that are ultimately submerged or floated. Isolation of areas by floodwaters could create hazards in terms of medical, fire, or law enforcement emergencies. Study Results The results of this study are presented in the form of flooded areas, plates 3 through 22; water surface profiles, plates 23 through 30; and elevation-discharge curves, plates 31 through 35. Water surface elevation data was computed through the use of the Corps of Engineers computer program,HEC-2 "Water Surface Proft les".