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<br />. <br /> <br />body of flow. Depths and velocities are low in these areas, with their <br />extent being determined by analysis of the topographical mapping and specific <br />land features in the area. Since the shallow flooded areas are not hydrau- <br />1 ically connected to the main channel, the IOO-year water surface elevations, <br />top widths, and divided flow conditions do not necessarily agree with the <br />HEC-2 computer output. <br /> <br />Top Width. The HEC-2 computer output gives the appropriate top width of the <br />flood plain at each cross section. At a few locations there are large dis- <br />crepancies between the width shown on the flooded area maps and the output <br />from the HEC-2 program. <br /> <br />The inconsistency is a result of the computer using areas beyond embankments <br /> <br /> <br />as part of the floodway, when actually, the flows cannot get to these areas. <br /> <br /> <br />This would account for top widths being larger than actually shown on the <br /> <br /> <br />flood plain maps. A good example of this situation is at cross section 21. <br /> <br />. <br /> <br />General Information <br /> <br /> <br />The HEC-2 Users Manual, dated October 1973, was used for all computer <br /> <br /> <br />runs on the Roaring Fork and Fryingpan Rivers. Mannings n values were <br /> <br /> <br />determined by field inspection of the study area. Bridge data was taken <br /> <br /> <br />during the field survey, which was used in the special bridge routine of <br /> <br /> <br />the HEC-2 computer program. No adjusted bridge areas were used to account <br /> <br /> <br />for possible blockage of bridge openings by floating debris. <br /> <br />. <br />