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<br />(2) All flows are gradually varied with hydrostatic pressure prevailing at <br />all points in the flow, such that vertical accelerations can be neglected. <br /> <br />(3) No lateral secondary circulation occurs. <br /> <br />(4) Channel boundaries are treated as fixed, therefore no erosion or <br />deposition occurs. <br /> <br />(5) Water is of uniform density, and resistance to flow can be described <br />by empirical formulas, such as Manning's and Chezy's equation. <br /> <br />The dynamic wave equations can be applied to a wide range of one- <br />dimensional flow problems, such as: dam break flood wave routing; forecasting water <br />surface elevations and velocities in a river system during a flood; evaluating flow <br />conditions due to tidal fluctuations; and routing flows through irrigation and canal <br />systems. Solution of the full equations is normally accomplished with an explicit or <br />implicit finite difference technique. The equations are solved for incremental times <br />(6t) and incremental distances (6x) along the waterway. <br /> <br />6.2. Approximations of the Full Equations. <br /> <br />Depending on the relative importance of the various terms of the <br />momentum equation (6). the equation can be simplified for various applications. <br />Approximations to the full dynamic wave equations are created by combining the <br />continuity equation with various simplifications of the momentum equation. The most <br />common approximations of the momentum equation are: <br /> <br />7-66 <br />