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. the Cache la Poudre River just downstream from Fort Collins. Other tributary flood plains in the plains region are substantially narrower. The flood plains of Sheep Draw and Fossil Creek, for example, average a few hundred feet wide or less. Flood Depths and Velocities. Detailed flood plain studies com- pleted prior to this study are available only for the Cache la Poudre River in the plains and for the Poudre Park area in the mountains. Available information indicates major floods in the plains reaches would range from 8 to 15 feet deep above the channel bed. Channel velocities range from 2 to 5 feet per second. Depths on the overbank are generally 5 feet Dr less, although occasionally deeper. Overbank velocities are generally about 1 to 2 feet per second, but velocities could be higher at certain points. In the narrow mountain canyon at Poudre Park, the 100-year flood averages about 15 feet deep above the streambed and the 500-year flood averages about 20 feet deep. Channel velocities can be 15 to 20 feet per second or greater with overbank velocities of about 5 to 10 feet per second, In general, floodwater 2 or more feet deep and flowing at a velocity of 3 or more feet per second could easily sweep adults from their feet, thus creating definite danger of injury or drowning. FLOOD HAZARD POTENTIAL This section presents information on the development that is subject to flood hazards. PLAINS REGION In the plains section of the basin, most of the flood plain lands are used fDr irrigated or dry cropland, pasture, or rangeland. There is, hDwever, some sand and gravel mining and there are numerous highway and railroad structures. Portions of several urban areas are also located within these flood plains. Along the main stem, these include . 31