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<br />ARKANSAS RIVER BASIN, COLORADO, KANSAS, NEW MEXICO D5 <br /> <br />storm characteristics, provided other related data, and granted access to <br />private property for indirect measurements of peak flow. <br /> <br />RELATIVE MAGNITUDE OF THE FLOODS <br /> <br />The relative magnitudes of the floods described in this report are <br />evaluated by comparison with maximum floods known and by frequency <br />relations. <br /> <br />COMPARISON WITH MAXIMUM FLOODS KNOWN <br /> <br />Hoyt and Langbein (1955, fig. 20, p. 60) plotted maximum known dis- <br />charges in the United States against drainage area for the period prior to <br />1950 and drew an enveloping curve. They compared it with a similar curve <br />for the known floods prior to 1890 (Creager and others, 1945, p. 126). Hoyt <br />and Langbein (1955, p. 59) stated "The upper curve is about five times the <br />lower curve. This is no evidence that flood conditions are changing. The up- <br />ward shift of the curve in Fig. 20 is due entirely to an increased number of <br />gaging stations and increased period of record." Though they called their <br />curve an enveloping curve, it is only nominally so, as they chose to draw it <br />below six discharges shown on their graph. Matthai (1969) drew a higher <br />curve based on the data used by Hoyt and Langbein and data for five ad. <br />ditional floods. Two of these occurred prior to 1950, but presumably the <br />data were not available to Hoyt and Langbein. Matthai's curve is additional <br />evidence that, to paraphrase Hoyt and Langbein, it is our knowledge of <br />floods that increases, not the size of the floods. <br />The enveloping curves are based on the known top discharge figures for <br />sites in the United States, but the potential floods for some areas of the <br />country are less than for other areas because of differences in potential <br />storm rainfall intensities. Hoyt and Langbein (1955, fig. 24, p. 75) outlined <br />in a rough way the regional variations in flood-discharge potentials. They <br />showed that the potential floods in eastern Colorado and New Mexico are <br />less than one-half those shown by their enveloping curve. Their conclusion is <br />based on admittedly risky generalizations, but it can be used for com- <br />parison. <br />The June 1965 floods on several streams in the Arkansas River basin ap- <br />proached or exceeded the potential floods for eastern Colorado and New <br />Mexico and were outstanding events. The most outstanding event was on <br />Jimmy Camp Creek, where the peak discharge was 2.5 times the potential <br />flood, and its ratio to discharge from Hoyt and Langbein's enveloping curve <br />is 1.24. The floods on Rule Creek, Big Sandy Creek, and Clay Creek also <br />exceeded the potential floods, having ratios to discharge from Hoyt and <br />Langbein's curve of 0.82, 0.66, and 0.65, respectively. The higher discharges <br />in relation to drainage area for the June 1965 floods in the Arkansas River <br />basin and the three enveloping curves mentioned above are shown in <br />fiall,"p 1 <br />