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<br />15 <br /> <br />(6) Cottonwood Creek (Prasuhn & Sing, 1981) <br /> <br />3. Basic Concepts: <br /> <br />The model was developed to analyze scour and deposition of movable-bed <br />channels by simulating one-dimensional, steady, gradually-varied water and <br />sediment flows. The principal assu~tions employed in the model are as <br />follows: <br /> <br />(1) Flow is one dimensional and hydrostatic pressure prevails at any <br />point in the channel. <br />(2) Manning's n is applicable to gradually-varied flow and is expressed <br />as a function of either water-surface elevation or water discharge <br />(the model incorporates indi rectly the roughness effects of changes <br />in bed forms). <br />(3) The entire movable-bed portion of a cross section is scoured or <br />deposited at the same rate. <br />(4) Channel slope is small. <br /> <br />The following basic equations are employed in the model: <br /> <br />(1) Flow-continuity equation: <br /> <br />~- <br />dx - q,t <br /> <br />.... (2-18) <br /> <br />(2) Sediment-continuity equation: <br /> <br />~+B~=O <br />ax at <br /> <br />.... (2-19) <br /> <br />(3) Flow-energy equation: <br /> <br />Il!L <br />(h + 2)k-1= <br />2gA <br /> <br />Il!L <br />(h + a 2)k + HL <br />2gA <br /> <br />....(2-20) <br /> <br />where <br /> <br />Q = water discharge <br />