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<br />REGIONAL FLOOD-FREQUENCY RELATIONS <br /> <br />Flood-frequency relations at streamflow-gaging stations are well <br /> <br />documented. However, flood characteristics also are needed at ungaged <br /> <br />sites. This information can be obtained using the flood-information <br /> <br />transfer techniques discussed in the "Introduction". Past applications of <br /> <br />these techniques have failed to adequately describe the flood hydrology of <br /> <br />foothill streams (McCain and Ebling, 1979). Although there are limited <br /> <br />precipitation and streamflow data, investigators have assumed that the <br /> <br />total basin area contributes runoff during rainstorms. However, rainfall <br /> <br />floods in the foothill region of Colorado are caused by intense short- <br /> <br />duration thunderstorms or cloudbursts of very limited areal extent. <br /> <br />Because there is very little rainfall data for such storms for the foothill <br /> <br />region, and because transfer of rainfall data from other nonsimilar hydro- <br /> <br />meteorologic regions may lead to inaccurate and overestimated floodflows, <br /> <br />transfer techniques at this time need to be based on streamflow and paleo- <br /> <br />flood data. One of the problems in determining flood-frequency relations <br /> <br />in the foothills in Colorado has been that when rainfall-runoff techniques <br /> <br />have been applied at long-term gaged sites (50 or more years), the rainfall- <br /> <br />runoff relations are much larger than those based on frequency analysis of <br /> <br />the recorded annual peak-flow data. Users of deterministic methods believe <br /> <br />that the gaged record is not representative of the flood hydrology of the <br /> <br />site. Our belief is that the synthetic rainfall-runoff methods have not <br /> <br />been calibrated for this region, that rainfall was transposed from a <br /> <br />different hydrometeorologic setting, and that the storms are improperly <br /> <br />applied over the e~tire drainage basin above and below 7,500 <br /> <br />..35"* <br />