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This is a simplified method which has many advantages over the more com. man practice of drawing the flood boundaries by connecting end points of the flood boundary width at each cross. section. The most important advan- tage is the degree of confidence gained in the interpretation of the 100-year flood boundary. The flood contours become permanent documentation of the engineer's ludgmentln interpreting the flood hazards. . Floodplain Delineations The next step of the floodplain study is the delineation of the flood limits on the topographic maps. Delineation requires the depiction In plan or overnead view of the information whIch is shown In vertical view in the flood water sur- face elevation tables and profiles. The plan view provides a clearer picture of the extent of actual flooding at specific locations along the stream. Maintaining consistency IS very Important to developing a technically and legally acceptable regulatory document which can be incorporated into floodplain regulations and/or zoning maps, Problems may be eliminated through improved reporting and interpretation procedures. . The procedure which the CWCS recommends for delineation of the 100- year floodplain on topographiC maps IS as follows: 1) uSing the hydraulic analysis, the flood elevations at each cross.section are tabulated: 2) the flood profiles are drawn; 3) uSing channel cenlerline slatloning from the water surface profiles. the centerline stations of the whole numbered flood elevations which cor- respond to the base contour Interval elevations of the topographic maps are tabulated to produce the plotting table; 4) the location of all flood contours In the channel is marked at the appro- priate station along the centerline on the base maps; 5) the flood contours are extended by draWing "wiggly." or reference, lines perpendicular to the direction of flow until they intercept their corres. ponding ground contours: thiS pOint IS the edge of the floodplain, (The flood contours should parallel the cross.sections. If the cross.sections were Incorrectly located, however. the flood contours may cross them,); 6) flooded area boundaries are drawn by connecting the ends of each "Wiggly" or reference line; and 7) the flood delineation should be checked for reasonability and conSIS' tency with the cross'sectlon data (top Width of the floodplain). This method is also applicable to approximate floodplain mapping where a water surface profile can be drawn uSing an assumed depth. Once the depth has been assumed, It IS easy to show In plan view which areas would be flooded and which would not. The delineation of the floodplain Will need to be re.evaluated if development activities or other factors cause a suffiCient change In the floodplain to alter the threat. When reevaluation IS necessary. it IS important that previously published information be reViewed and adequately correlated with the new information. Maintaining this continUIty between studies will Improve (he workability of a floodplain management program. .