9612 - Laserfiche WebLink

Home Browse Search

0 DRAFr February 25, 1998 ft3/s. If levees were removed, inundation could be initiated at most locations with discharges of approximately 18,600 ft3/s. This discharge corresponds to a return period of 2.6 years and an average annual duration of 4.4 days. Similarly, if 2 to 3 foot deep side channels were excavated at appropriate locations to connect the bottomlands to the river, flooding could be initiated at all Ouray bottomlands with a discharge of 13,000 ft3/s. The 13,000 ft3A discharge has a return period of 1.5 years and an average annual duration of 11 days. Through a combination of levee removal, side channel excavation and application flooding, it would be practical to flood over 2,185 hectares at discharges on the order of the 1.5 year return period. This would correspond to significant flooding every two out of three years on the average and would provide flooding frequency and duration similar to pre-1963 conditions. The maximum possible area of inundation is approximately 4,050 hectares for a discharge over 37,000 ft3/s (100-year return period). In Canyonlands, flooding of the side canyon backwater areas begins at a discharge of approximately 7,000 ft3/s. Above 7,000 ft3/s, a linear increase in the flooded acreage occurs until bankfull discharge, approximately 39,000 ft3/s, is reached. There is no optimum discharge for the area of inundation of the Canyonlands backwater habitat; a higher discharge results in more floodable acreage. At discharges in excess of bankfull, the floodplain would start to become inundated, resulting in a significant increase in slow velocity, out-of-channel habitat. It was estimated that 200 hectares of floodplain became inundated between 30,000 ft3/s (5-year return period) and 53,000 ft3/s (100-year return period). Temperature Characteristics of the Green River System Background The U.S. Fish and Wildlife Service began a program of monitoring River temperatures on the Yampa and Green Rivers in 1987 (Smith 1997). Thermographs were placed at key locations on the Yampa and Green Rivers (Table 3). The data from these thermographs, along with data from U.S. Geological Survey gauging stations and work done by other researchers were used to describe the thermal regime of the Green River system. The Green River is a snowmelt driven system where winter snows accumulate from October through mid-April. When ambient air temperatures in the basin begin to rise in the March-April period, snowmelt is initiated and runoff begins. As stream flow increases, the cold snowmelt water quickly increases in temperature from interactions with the channel bed, the atmosphere, and direct solar radiation. I1