Laserfiche WebLink
<br />sections should not all be parallel to each other. It is important <br />to have a solution technique that can calculate a representative <br />reach length in order to insure that one set of cross sectional data <br />can be used for the entire range of discharges. <br />Ilydraulic roughness values. for example Manning's n-values, are <br />a third important property that can vary greatly across a section. <br />Manning's n-values also often vary in the vertical. A general solu- <br />tion technique for solving the energy equation must accommodate such <br />variations. <br />All of these requirements can be satisfied by subdividing the <br />flood plain into strips having similar hydraulic properties in the <br />direction of flow. Figure 5.02 illustrates this concept with three <br />strips: (1) = left overbank. (2) = main channel and (3) = right <br />overbank. <br />In this figure the left overbank strip begins at the limits of <br />the flood plain on the left and extends to the top of the bank on the <br />left side of the main channel. The right overbank strip begins at the <br />top of the right bank of the main channel and extends to the limits <br />of flood plain on the right. All flow is conveyed within the boundary <br />geometry defined by these three strips. The boundary between strips, <br />however, is hypothetical, and flovl is permitted to pass freely from <br />one strip to another without a penalty for energy losses or an award <br />for energy transfer. That is, both the water surface elevation and <br />total energy elevation are assumed to be constant across the cross <br />section. <br /> <br />5.04 <br />