Laserfiche WebLink
<br />Draft Fmal Completion Report to UDWR for Contract #93-1070, Amendment 3 <br /> <br />9 <br /> <br />Meandering Rivers <br />Self-formed channels have been classified as straight, meandering, braided. or anastomosing; each planform <br />type is a response to the interaction of discharge, sediment size and availability, and bank and bed characteristics <br />(Rosgen. 1994; Leopold and others, 1964). While these classifications describe distinct forms, these forms actually <br />describe end-members of a continuum of channel patterns (van den Berg, 1995). Braided streams typically have high <br />sediment loads in relation to transport capacity, straight rivers have low sediment loads, and meandering rivers have <br />. !Jproximately equal sediment loads and transport capacity (Leopold and others, 1964). The Green River, with <br />approximately equal sediment load and transport capacity (Andrews, 1986), is a meandering river through the central <br />Uinta Basin. <br />Much controversy has surrounded the origins of flow meandering. Is meandering caused by the deflection of <br />current around alternate bars, causing. additional deposition on the bars and erosion on the exterior of the bend, or are the <br />bar forms determined by the flow patterns? What physical properties control meander wavelength and amplitude? <br />Rhoads and Welford (1991) noted that no universal theory of meandering initiation has emerged, although the most <br />promising developments have come from themodeling of fluid dynamics and sediment transport (for example, Seminara <br />and Tubino, 1989; Nelson and Smith, 1989a,b). <br />Leopold and others (1964) noted that the form of meanders varies greatly, and that the amplitude of meanders <br />was probably related to the erosional characteristics of the bank sediments. Ikeda (1989) investigated the sedimentary <br />controls on river form and classified meandering rivers into four types: (1) meanders fixed by cohesive deposits, (2) <br />meanders restricted by older deposits, (3) confined free meanders, and (4) true free meanders. The meanders of the <br />Green River through the central Uinta Basin and Ouray NWR are restricted by resistant older deposits (Schmidt, 1994). <br />Ikeda (1989) determined that bar form and characteristic in restricted meander reaches are products of the meandering <br />flow rather than causing the meandering flow. <br />The Green River within the Uinta Basin is, at high flow, a meandering, single-threaded channel between two <br />well defined banks. In some years, the Green River at low flow is multi-threaded, with flow divided by emergent mid- <br />channel bars. Consequently, the Green River exhibits characteristics of both meandering and braided rivers. <br /> <br />Bars <br /> <br />There are two research approaches for investigating bars: describing the features of different systems, and <br />