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<br />It is possible to standardize many elements of flood frequency analysis. <br />This guide describes each major element of the process of defining the flood <br />potential at a specific location in terms of peak discharge and exceedance <br />probability. Use is confined to stations where available records are ade- <br />quate to warrant statistical analysis of the data. Special situations may <br />require other approaches. In those cases where the procedures of this <br />guide are not followed, deviations must be supported by appropriate study <br />and accompanied by a comparison of results using the recommended procedures. <br />As a further means of achieving consistency and improving results, <br />the Work Group recommends that studies be coordinated when more than one <br />analyst is working currently on data for the same locationo This recom- <br />mendation holds particularly when defining exceedance probabilities for <br />rare events, where this guide allows more latitude. <br />Flood records are limitedo As more years of record become available <br />at each location, the determination of flood potential may change. Thus, <br />an estimate may be outdated a few years after it is made. Additional <br />flood data alone may be sufficient reason for a fresh assessment of the <br />flood potential. When making a new assessment, the analyst should incor- <br />porate in his study a review of earlier estimates. Where differences <br />appear, they should be acknowledged and explained. <br /> <br />II. Summary <br /> <br />This guide describes the data and procedures for computing flood flow <br />frequency curves where systematic stream gaging records of sufficient length <br />(at least 10 years) to warrant statistical analysis are available as the <br />basis for the determination. The procedures do not cover watersheds where <br />flood flows are appreciably altered by reservoir regulation or where the <br />possibility of unusual events, such as dam failures, must be considered. <br />The guide was specifically developed for the treatment of annual flood <br />peak discharge. It is recognized that the same techniques could also be <br />used to treat other hydrologic elements, such as flood volumes. Such <br />applications, however, were not evaluated and are not intended. <br /> <br />2 <br />