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e CHAPTER I. INTRODUCTION Historically, flooded bottomlands were an important component of the life history and the propagation of endemic fishes in the Green River system. Naturally functioning flooded bottomlands provided highly variable habitat conditions, diverse and prolific food sources, warmer water temperatures, low velocity habitat, and cover from predation (Stanford, 1993). The flooded bottomlands have been identified as important nursery habitat for the endangered razorback sucker and are a critical component of the Habitat Restoration Program in the Recovery Program for the Endangered Fishes of the Upper Colorado River Basin. The goal of the Habitat Restoration Program is to restore or enhance natural floodplain functions that support recovery of endangered fishes in the Upper Colorado River Basin (as outlined in Final Conceptual Framework for the Habitat Restoration Program). . This document presents the results of an investigation to determine the magnitude, duration and.frequency of bottom lands flooding along two reaches of the Green River. The first reach is located in the vicinity of Ouray National Wildlife Refuge, near Vernal, Utah and the second study reach is located in Canyonlands National Park near Anderson Bottom. These two reaches represent distinctly different flooding scenarios and serve as general models for assessing current flooding conditions and the ability to restore channel and floodplain interaction. Inundation of the Ouray reach results in extensive flooding of wetland or bottomland areas. In Canyonlands, the focus of the investigation was backwater areas created by flooding side canyon channels. The Canyonlands backwater areas are much less extensive than the Ouray bottomlands but may represent the only significant flooded backwater habitat in the confmed reaches of the Green River in Canyonlands. The project consisted of hydrographic data collection at the two sites during the 1995 high flow season, an analysis of USGS stream gaging data for the period of record at the Green River gages at Jensen and Green River, Utah, hydraulic simulation of flood levels using the Corps of Engineers (COE) HEC-2 step backwater profile model and evaluation of potential measures to restore the channel/floodplain interaction to these important endangered fish habitats along the Green River. This report discusses project goals, site descriptions, site geomorphology, river hydrology and hydraulics, flooded bottomland hydrology and provides recommendations for enhancing bottomlands flooding. The hydrographic data collection reports were submitted to the Fish and Wildlife Service. Project Goals and Objectives . The project goal was to conduct bottomland site hydrology and channel morphology investigations at selected historical floodplain areas in the Green River system to determine the flows or physical changes required to hydraulically reconnect the floodplain with the river. This 1