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<br />. <br /> <br />5 <br /> <br />. <br /> <br />jmposes on natural alluvial river systems. Variables affecting alluvial <br /> <br />river channels are numerous and interrelated. Their nature is such that, <br /> <br />unlike rjgiu-boundary hydraulic problems, it is not possihle to isolate <br /> <br />and study the role of each individual variable. Because of the complexity <br /> <br />of the processes occurring in natural flows that influence the erosion and <br /> <br />deposition of material, a detached analytical approach to the problem may <br /> <br />be difficult and time consuming. Most relationships describing river process <br /> <br />have been derived empirically. Most factors affecting alluvial stream chan- <br /> <br />nel geometry are: (1) stream discharge; (2) sediment load; (3) longitudinal <br />slope; (4) characteristics of bed and bank material; (5) bank and bed resis- <br />tance to flow; (6) vegetation; (7) geology, including type of sediment; and <br />(8) works of man. <br />Considerable study and analysis of the hydraulics of rigid-boundary <br />open channels provide the required knowledge to assure excellent results. <br /> <br />The steady-state sediment transport of sand-sized sediments is well under- <br /> <br /> <br />stood. Similarly, there is an adequate understanding of stable channels <br /> <br /> <br />formed in noncohesive materials of all sizes. The theory is adequate to <br /> <br /> <br />support design of stable channel systems, or if necessary, designs can be <br /> <br />formulated to assure the stability of otherwise unstable reaches of river. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />2.2 River Morphology and River Response <br />2.2.1 Stream Form and Classifications <br /> <br />Rivers can be classified broadly in terms of channel patterns; that is, <br /> <br />the configuration of the river as viewed on a map or from the air. Patterns <br /> <br />include straight, meandering, and braided systems, or some combination of <br /> <br />these patterns. These typical river channel patterns are shown in Figure 2-1. <br /> <br />. <br /> <br />. <br />