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Before 1800, the Missouri River was one of North America's most diverse and dynamic ecosystems. Since 1800, it has been transformed into a navigation system regulated by reservoirs and flood control structures. Flooding in 1993 and 1996 has had a profound effect on the physical and political landscape of the lower Missouri River. The purpose of this research is to determine the spatial and temporal distribution of wetlands at Lisbon Bottom in order to develop a model of the distribution of wetlands along the lower Missouri River. The project focuses on three questions: (1) What is the Quaternary history of the lower Missouri River Valley? (2) Can a general model of the lower Missouri River Valley alluvium be developed? (3) What is the relationship between the valley's alluvial architecture and the hydrogeology of its wetlands? A variety of techniques and technologies will be used to answer these questions. Principal among these will be geographic information and image processing systems, which will be used to analyze and interpret photographic, topographic, and geophysical data. INTRODUCTION The Missouri River of the early 1800s was one of North America's most diverse and dynamic ecosystems, with abundant riparian lands, braided channels, chutes, sloughs, islands, sandbars, and backwaters (Laustrup and LeValley, 1998). These river and floodplain habitats were created and maintained by erosion and deposition, which continuously reshaped the channel and the floodplain (Schmudde, 1963; Funk and Robinson, 1974; Nicollet, 1993; Laustrup and LeValley, 1998). Seasonal variation in the river's flow recharged wetlands and backwater habitats in spring. It also exposed nesting habitat and provided slow and shallow aquatic habitat through late summer and fall. Since 1800, the Missouri River has been transformed into a navigation system regulated by reservoirs and flood control structures. These modifications have reduced seasonal flow variability and sediment load, and they have disconnected the river from backwater, off-channel, and flood plain habitats (Funk, 1974; Interagency Floodplain Management Review Committee, 1994; Laustrup and LeValley, 1998). Flooding along the Lower Missouri River in 1993 and again in 1996 provided the opportunity to study the relationship between biologic and geologic processes in a setting that closely mimics the preregulated Missouri River (Jacobson and others, 1999). Flooding during 1993 broke agricultural levees and created scours on both the upstream and downstream sides of Lisbon Bottom, a loop bottom located approximately 10 miles downstream of Glasgow, Mo. These levee breaks and scours were not repaired, and flooding subsequent to 1993 repeatedly inundated the bottom. Flooding in 1996 connected the upstream and downstream levee breaks and created a chute that crossed the bottom. Knowledge of surficial geologic characteristics and processes in an alluvial setting like Lisbon Bottom provides a scientific basis for floodplain management. This knowledge is also vital to a complete understanding of riverine habitat disturbance, recovery, and rehabilitation (Interagency Floodplain Management Review Committee, 1994; Winkley and Schumm, 1994; Berg and others, 1999). A critical component of this knowledge is an understanding of the spatial and temporal relationships between riverine habitat dynamics and fundamental geomorphic processes, and the spatial and temporal relationships between groundwater and surface wetlands. Equally important is the contextual framework within which these processes operate. At Lisbon Bottom, as with other sites along the lower Missouri River, that framework includes the geology of the river valley at both the regional and site-specific scales. Purpose The purpose of this investigation is to determine the fundamental geologic processes controlling habitat dynamics at Lisbon Bottom. The results of this investigation will include a discussion of the evolution of the river, coupled with a general model of the architecture of the valley. This model will illustrate the interdependence of physical and biological processes, as well as the spatial and temporal relationship between ground and surface water along the lower Missouri River. The results of this investigation will aid in the development of goals for habitat rehabilitation projects and will provide a scientific basis for future flood plain management practices along the lower Missouri River. Research Questions This project will address three specific questions regarding the Quaternary geology of the lower Missouri River Valley and the relationship between the geology of the valley and terrestrial habitat along the river: (1) What is the Quaternary history of the lower Missouri River Valley? (2) Can a general model of the lower Missouri River Valley alluvium be developed? (3) What is the relationship between the valley's alluvial architecture and the hydrogeology of its wetlands? Whether Pleistocene glaciers advanced into or south of the modern Missouri River Valley between Kansas City, Mo. and the confluence near St. Louis has not been satisfactorily resolved. There is evidence that ice did advance south of the modern Missouri River near present day Kansas City, Mo. (Simms, 1975; Colgan, 1992; Kelly and Blevins, 1995). There is also evidence that ice advanced into the Missouri River Valley near present day Miami, Mo. (Baker, 1993). However, there appears to be little or no evidence that ice advanced into or south of the modern valley either between these sites or at any others along the river. Determining the architecture of the river's alluvium and the relationship between that architecture and the hydrology of the valley's wetlands will provide a more complete understanding of the relationship between the geology of the river valley and the dynamics of its terrestrial habitats. This will lead to a more complete understanding of habitat disturbance, rehabilitation, and restoration along the lower Missouri River. REVIEW OF LITERATURE Regional Setting The Missouri River flows nearly 2.350 miles from the confluence of the Gallatin, Madison, and Jefferson Rivers at Three Forks, Mont., to its confluence with the Mississippi River near St. Louis, Mo. Its basin encompasses more than 500,000 square miles (fig. 1). From its headwaters in southwestern Montana, the Missouri River flows north then east across Montana and into North Dakota, where it turns southeast and crosses South Dakota. Leaving South Dakota, the river turns east and forms part of the boundary between South Dakota and Nebraska before turning south again to form the boundaries between Nebraska and Iowa, Nebraska and Missouri, and Kansas and Missouri. At Kansas City, the river turns east, crosses Missouri, and enters the Mississippi River approximately 20 miles north of St. Louis. Broadhead (1889) divided the Missouri River Valley into three general areas: the upper or mountain district, the plains, and the lower valley region. Today, the river can still be subdivided into three major sections. However, unlike Broadhead's more geographical classification, today's subdivisions are based on the degree to which each section has been modified by mainstem reservoirs or bank stabilization and flood control structures. These three divisions include the free-flowing upper section, the impounded middle section, and the channelized lower section. The free-flowing upper section extends from the confluence of the Gallatin, Madison, and Jefferson Rivers in southwestern Montana to Fort Peck Lake in central Montana. The impounded middle section extends from Fort Peck Lake to Gavins Point Dam near Yankton, S. Dak., and includes Fort Peck Lake, Lake Sakakawea, Lake Oahe, Lake Shaipe, Lake Francis Case, and Lewis and Clark Lake. The channelized lower section extends from Gavins Point Dam to the confluence near St. Louis. This study is focused generally on the channelized section of the lower Missouri River Valley between Glasgow, Mo. and the confluence with the Mississippi River near St. Louis (fig. 2). The Missouri River Valley between Glasgow and the confluence is a bedrock trench filled with 60 to 120 feet of alluvium. This alluvium consists of highly permeable basal glacial outwash (sand, gravel, and boulders) overlain by postglacial sand and gravel, which in turn are overlain by postglacial interbedded sand, silt, and clay (Dahl, 1961; Schmudde, 1963; Emmett and Jeffery, 1969; Simms, 1975; Interagency Floodplain Management Review Committee, 1994; Jacobson and others, 1999). This segment of the valley is relatively narrow (less than 3 miles wide) with steep sides. Within this relatively narrow valley, the meandering course of the river frequently approaches the valley sides, partitioning the alluvial surface into separate pieces enclosed by a loop of the river and the side of the valley. These distinct, nearly level partitions of the floodplain are locally referred to as bottoms. Schmudde (1963) defined two types of Missouri River bottoms: long and loop. Long bottoms are much longer than they are wide. Long bottoms are terminated where the river cuts diagonally across the valley. Conversely, loop bottoms are relatively small and partly enclosed by a single, curving, meander-like loop of the river. Between Glasgow and the confluence, Schmudde (1963) identified eight long bottoms, five wellformed loop bottoms (where the length and width within the enclosing meander loop are approximately equal), four less well formed loop bottoms, and several bottoms that have shapes and sizes intermediate between long and loop types. This project focuses specifically on Lisbon Bottom, a well-formed loop bottom located 10 miles downstream from Glasgow, Mo. The lower Missouri River Valley at Lisbon Bottom is nearly 2 miles wide and is incised 200 feet into the surrounding terrain. The channel meanders from valley wall to valley wall, enclosing approximately 3 square miles of flood plain (fi

The evolution of the lower Missouri River; a discussion of the geology and a proposal for research at Lisbon Bottom