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<br />6. Draw flooded area boundar ies by connect ing the ends of . <br />each "wiggly line." <br /> <br />7. Check flood delineation for reasonability and <br />consistency with cross-section data (top width). <br /> <br />This simple method has many advantages over the common <br />practice of drawing flood boundaries by interpolating between end <br />points of top width computed at each cross section. The most <br />important advantage is the degree of confidence gained in the <br />interpretation of the lOO-year flood boundary by having many llOre <br />plotting points. Often, both large and small islands, which <br />would previously have gone unnoticed, become apparent. Potential <br />erosion problems from high velocity flow will be indicated where <br />flood contours are spaced close together. The flood contours <br />become permanent documentation of the engineer's judgment in <br />interpretating flood hazards. By showing flood contours in plan <br />view, a local administrator can quickly determine flood <br />elevations and visualize flood depths directly from the maps. <br /> <br />The method is also applicable to approximate floodplain <br />mapping where a preliminary water surface profile can be drawn <br />using an assumed depth. If such a map were made initially, it <br />would be useful in deciding where cross sections should be placed <br />for input to the HEC-2 computer program. <br /> <br />. <br /> <br />. <br /> <br />-2- <br />