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<br /> <br />'. <br /> <br />damsite that were not included in about 42 Bureau items. The follow- <br /> <br />tng preliminary conclusions have been made in the research study of <br /> <br />the above data. <br /> <br />;,; <br />1. A constant value of 0.33 may be used for the exponen1 X in <br /> <br />the lag equation. It was determined by a series of logarithmic <br /> <br />least squares computations. <br /> <br />2. It was found that the broad range in lag time values could be <br /> <br />grouped into 4 sets of data of apout equivalent logarithmic range <br /> <br />of ordinate values. within each set. These sets represent vari- <br /> <br />ations of flood runoff characteristics ranging from very rapid to <br /> <br />relatively slow~ The watersheds associated with each set of lag <br /> <br />time. data tend to have similar identifiable topographical features <br /> <br />and cover conditions. <br /> <br />3. A mean lag curve together with upper and lower limiting curves <br /> <br />for each set of lag time values was computed and accepted as <br /> <br />preliminary basic curves indentified by the C values for the mean <br /> <br />curve. Preliminary descriptive material for topographical features <br /> <br />and runoff characteristics associated with each basic lag curve <br /> <br />was prepared .to assist in selecting appropriate lag curves. The <br /> <br />curves which define limiting values for each set, except the lowest <br /> <br />and highest limiting curves, are common to two sets of data. <br /> <br />These curves are considered applicable to watersheds which have a <br /> <br />combination of the runoff characteristics of the adjacent sets. <br /> <br />8 <br /> <br />.,."'l_ <br /> <br />~....~..~ . <br /> <br />._..~ <br /> <br />- <br />