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Horseshoe Bend. Different strategies are proposed in order to identify which configurations might favor endangered fishes and/or stabilize more successfully over time, reducing or eliminating the need for operation and maintenance. Where possible and consistent with the flooding strategy selected for a site, the restoration involved using existing inlets or low areas to enhance or restore historic flooding patterns. All the BLM bottomlands sites studied act as depressions, which retain water after flood flows recede. It is assumed that these bottomlands will not retain sufficient water to sustain a fish population after flows recede. Currently, with the exception of Above Brennan, water seeps back to the river after flows recede through seepage connections and the bottomlands completely dry or contain less than one to two feet of water prior to recharge from the next runoff season. Areas of inundation were determined for the BLM bottomlands under existing and proposed conditions. Under existing conditions, total bottomland flooding by surface flow is limited to 50 areas at one bottomland for flows up to 18,000 cfs. Under proposed conditions, approximately 140 acres of flooded bottomland habitat at five sites would be available when flows exceeded 13,000 cfs and up to 173 acres would be flooded at 18,000 cfs. ONWR Bottomland Sites For the ONWR bottomland sites, more acreage is available for flooding than at the BLM sites. The Ouray sites are characterized by low floodplains which begin to flood at 14,000 cfs to 15,000 cfs. These surface flows, however, are prevented from reaching the Leota, Sheppard, and Old Charlie Diked bottomlands by man-made levees. Discharges of approximately 24,000 cfs and higher, well over the 5-year storm event, would be necessary to overtop these levees and flood the extensive bottomlands behind them. The Johnson- 4 and Wyasket bottomlands do not have the man-made levees which inhibit the surface flows from reaching the extensive bottomland areas. Flows in excess of 18,000 cfs for a duration of several days to a week are required to establish a significant surface flow connection which would fill these bottomlands and allow fish • passage. The 18,000 cfs discharge, at which Johnson-4 and Wyasket Bottoms allows fish passage, has a return period and flow duration of 2.5-years and 5.4 days, respectively, based on post-1963 hydrology. Floodplain restoration designs have been proposed at the ONWR sites. Proposed levee removals are typically 100 feet to 600 feet wide and located at the lower ends of the bottomlands. Flooding elevations will be set 50' to 100' back from the banks and armored with existing cottonwood logs. The banks will be cut to 1' to 2' lower than the flooding discharges to allow some of the anticipated sedimentation processes to occur before flows reach the flooding elevation set back from the bank. Sites were designed to flood at 13,000 cfs. This discharge corresponds to a 1.5-year return period and 11 day flow duration based on post-1963 hydrology. The Johnson, Leota, and Sheppard bottomlands have several ponds which are separated by interior dikes. Interior dike raising is required to isolate J-4, L-7A, and S-2 ponds from adjacent bottomlands. Without interior dike raising, hundreds to thousands of acres would be flooded in these bottomlands. Monitoring of fish usage in these expansive areas would be difficult. By removing the levees, the flooded acreage would be expanded by 637 acres once flows exceed 13,000 cfs. Currently, only application flooding using refuge inlets, most of which do not function properly, is possible at this discharge under existing conditions. The existing condition does not provide sufficient fish access to the bottomlands. Therefore, no flooding conducive to fish passage occurs at the ONWR until flows of approximately 18,000 cfs, when Johnson-4 and Wyasket are connected to the Green River by significant overbank flows. The proposed levee removal strategies allow fish passage to the bottomlands close to an assumed historic frequency and duration. Limited data are available to accurately determine the value of the flooded bottomland habitats to endangered fish species. The proposed restoration activities will make biologic, geomorphic, and hydraulic data collection efforts feasible to analyze these habitats. •