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Ouray National Wildlife Refuge Sites <br />Cross sections throughout the Ouray National Wildlife Refuge reach of the Green River were <br />established in 1995. These cross sections were used to measure water surface elevations at various <br />discharges and develop stage/discharge relationships. Flooding discharges were predicted for the ONWR <br />cross sections, and ranged from 17,400 cfs to 25,300 cfs. The average flooding discharge determined was <br />21,900 cfs. This value was 9% higher than the average determined in 1995. More stage/discharge <br />measurements, on the order of six per cross section bracketing design flows were made in 1996. In 1995, <br />only three stage/discharge measurements were made, two of which were below 5,000 cfs. In addition, more <br />topographic surveying was performed where mapping was questionable for the 1995 study. Thus, accuracy <br />of flooding predictions were increased and field observations were documented to enhance the understanding <br />of the flooding conditions in the ONWR. Several low spots were identified where overbank flooding was <br />initiated at flows of 14,000 cfs to 15,000 cfs. However, man-made dikes along Leota, Sheppard, and Old <br />Charlie Diked prevented overbank flows from connecting to the bottomlands at 22,400 cfs. Only at one <br />location, along Leota-10, in which flows trickled over the dike, did a connection occur. Wyasket and Johnson- <br />4, which do not have the extensive man-made dikes, do flood overbanks above approximately 14,000 cfs and <br />begin to significantly fill the bottomlands around 18,000 cfs. Levee removal designs have been proposed for <br />each of the five ONWR sites. <br />Favorable flooding locations were identified in the field, and the sites were designed to flood at 13,000 <br />cfs. Under existing conditions, none of the sites flooded at 13,000 cfs. Under proposed conditions, 637 acres <br />are flooded at 13,000 cfs. Supplementary topographic data collection performed at the ONWR also identified <br />levee locations and quantified levee heights, which had not been documented in previous analyses. Table <br />13 summarizes existing and proposed flooding conditions for the ONWR sites. <br />The proposed levee removal strategies will increase the opportunities to evaluate the roles of <br />bottomland floodplain habitats to endangered fishes. In addition, the effectiveness of different design <br />configurations may be studied from a hydraulic, geomorphic, and biologic standpoint. The mapping created <br />for the BLM bottomland sites can be used as a tool to quantify biological parameters to depths and/or <br />vegetation locations. Also, erosion and sedimentation processes could be quantified and optimum flow <br />velocities for entraining larval fish identified. Parameters which may favor endangered fish species can be <br />identified and used as guidelines for future restoration activities. <br />LJ <br />61 <br />