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Executive Summary The floodplain is considered to be an important component of riverine ecosystems. In the upper Colorado River basin, much of the floodplain has been removed from the system because of reduced spring flows and flood prevention measures. Loss of floodplain habitat is believed to be a factor which has contributed to the decline of the endangered fish species of the Upper Basin, especially the razorback sucker. To counter this decline and assist in recovery, efforts are underway to restore or enhance floodplain habitats by enhancing floodability via excavation and/or levee removal. Public lands are being targeted where there are floodability enhancement opportunities, and owners of private lands are being contacted to see if they are interested in participating. In an effort to quantify the floodability of bottomland habitats, floodability assessments were conducted on eight privately-owned bottomland sites along the Green, Gunnison and Colorado Rivers in -1997. The objectives of the study were to determine: 1) The discharge at which each of the bottomlands flood; 2) Areas of inundation for each bottomland for different flood levels; 3) Flooding enhancement strategies to flood the bottomlands at a more historical frequency, timing, and duration. This information was provided to Fish and Wildlife Service land acquisition personnel to help the Recovery Program identify what they would get for their money if they choose to pursue acquisition, If the site is determined to be valuable to the program, the negotiation of an easement or the purchase of these private properties could be pursued. These objectives were met by performing the following: • Cross section monitoring for each reach to detect and quantify any changes to channel morphology. • Cross section surveys and water surface elevations at various discharge levels to develop stage/discharge relationships. • Identifying flooding discharges for each bottomland. • Topographic surveys to create mapping, estimate and show areas of inundation at different flood levels, and identify levee removal strategies to enhance floodability. • Comparing historical versus existing flow magnitudes, frequency, duration, and inundation conditions for the bottomlands. • Proposing restoration alternatives to enhance the floodability of the bottomlands while avoiding the overwintering of non-native fishes. A brief summary of the floodability analysis results at each site follows. By request, site codes have been used in place of property names.. For example, GRSN303W, GR indicates the Green River, SN is a property code, 303 is the river mile and W stands for West, i.e. the west side of the river. Green River GRSN303W Site -Located approximately one mile upstream of the Jensen Bridge, near Jensen, Utah, a 100-acre wetland area is located partially on the SN (Stuntz Valley Ranch) and IM properties. Located mostly on the SN property, the wetland area receives water year-round from offsite drainages. During runoff season, overbank flooding provides fish access to this site when water flows through a small lateral ditch when Green River flows exceed approximately 17,000 cfs (2 out of 5 years, based on post-1963 hydrology). floodplain enhancement could increase the frequency of flooding at this site to 2 out of 3 years, if the existing ditch were lowered and widened. This would, however, also increase the flooding frequency of the downstream property owner's land that is connected to the SN wetland by a culvert through a levee that separates the properties. No structures would be affected by flooding enhancement activities, but an access road down to the site that currently floods at high flows would flood more frequently.