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<br />\ <br />~-j <br />( <br />__u__l <br />~ <br /> <br />.. <br />, <br /> <br />The slope of the channel (So) is one criterion used in classifica- <br />tion. A critical slope is one on which critical velocity is sustained <br />by a change in potential energy rather than pressure head. A mild <br />slope is less than critical slope, and a steep slope is greater than <br />critical slope. When the slope is positive, the bed slope is classified <br />as mild, steep or critical; and the corresponding flow profiles are <br />the M, S, or C profiles, respectively. If the slope of the channel <br />is zero. the bed is horizontal. and the profiles are called H profiles. <br />If the bed rises in a downstream direction, the slope is negative <br />and is called an adverse slope. Gradually varied flow profiles on an <br />adverse slope are called A profiles. <br />Another parameter used in classifying gradually varied flow profiles <br />is the magnitude of the water depth relative to normal depth, On' and <br />critical depth. D. (The depth that would exist if the flow IJere <br />c <br />uniform is called normal depth. A type 1 profile exists if the water <br />depth is above the highest "depth" line (fig. 3.03) which may be either <br />the cri ti ca 1 depth 1 i ne or the normal depth 1 i ne depending on the <br />channel slope.) A type 2 profile exists if the water depth is between <br />the normal and critical depth lines, and a type 3 profile occurs when <br />the water depth is below the lowest depth line. It is customary to <br />identify profile type by a letter reflecting.bottom slope and a number <br />reflecting depth type (i.e.. Ml. A2, H3, etc.). Figure 3.04 shows <br />a variety of profile types. <br /> <br />I <br />\, <br /> <br />'. <br /> <br />" <br /> <br />, <br />, <br />,. <br />.. <br /> <br />3.09 <br />