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<br />FLOODS OF 1965 IN THE UNITED STATES
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<br />According to U.S. Weather Bureau data, losses ITom floods in the
<br />United States during 1965 ($788 million) were 1.2 times those in 1964
<br />($652 million) and 4.5 times those in 1963 ($176 million). The 1965
<br />flood losses were the highest since those of $995 million in 1955 and
<br />were about 2.3 times the national annual average of $340 million, based
<br />on the 10-year period 1951-60, adjusted to the 1960 price index.
<br />The number of lives lost due to floods in 1965 was 119 compared
<br />with 100 in 1964 and 39 in 1963 and was considerably greaterthan the
<br />national annual average of 80 lives lost during the 41-year period,
<br />1925-65,
<br />. Many of the flood reports give the amount of rainfall and the dura-
<br />tion of the storm causing the flood, Recurrence intervals of these
<br />storms may be determined ITom the U.S. Weather Bureau (1961) or
<br />IToma simplified set of isopluvial maps and charts contained in a
<br />report by Rostvedt (1965).
<br />Continuing investigation of $UITace-water resources in the areas
<br />covered by this report is performed by the U.S. Geological Survey in
<br />cooperation with State ageooies, the U.S. Army Corps of Engineers,
<br />the U,S. Bureau of Reclamation, and other Federal or local agencies.
<br />Some data were obtained from Weather Bureau publications.
<br />Coilection of data, computations, and most of the text were made by
<br />the district offices in whose district the floods occurred,
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<br />DETERMINATION OF FLOOD STAGES AND DISCHARGES
<br />
<br />Data of peak stages and peak discharges at disoharge stations in
<br />this report are those which are obtained and compiled in regular pro-
<br />cedure of surface-water investigation by the Geological Survey,
<br />The usual method of determining stream discharges at a gaging
<br />station is the application of a stage-discharge relation to a known
<br />stage. The relation at a station is usually defined by current-meter
<br />measurements through as much of the range of stage as possrble. If the
<br />peak discharge at a station is above the range of the computed stage-
<br />discharge relation, short extensions may be made to the graph of rela-
<br />tion by logarithmic extrapolation, by velocity-area studies, or by use of
<br />other measurable hydraulic factors.
<br />Peak discharges that are greatly ..bove the range of the stage.dis-
<br />charge relation at gaging stations and peak discharges at miscel-
<br />laneous sites (which have no defined stage-discharge relation) are
<br />generally determined by various types of indirect measurements. Dur-
<br />ing major floods, adverse conditions often make it impossible to obtain
<br />current-meter measurements at some sites. Peak discharges are then
<br />measured, after the flood has subsided, by indirect methods based on
<br />
<br />SUMMARY OF FLOODS
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<br />detailed surveys of selected channel reaches. A general description of
<br />the indirect methods used by the Geological Survey is given by Corbett
<br />and others (1943), Johnson (1936), and Dalrymple and others
<br />(1937). More detailed information concerning the la,test techniques is
<br />& vailable in recent reports by Kindsvater and others (1953), Bodhaine
<br />(1963), and Tracy (1957).
<br />
<br />EXPLANATION OF DATA
<br />
<br />The floods are described in Chronological order. Because the type
<br />and the amount of information differ for the floods, no consistent form
<br />can be used to report the events,
<br />The data for each flood include; a description of the storm, the
<br />flood, and the flood damage; a map of the flood area showing flood-
<br />determination points and, for some storms, precipitation stations <>r
<br />isohyets; rainfall amounts and intensities; and peak stages and dis-
<br />charges of the streams affected. When considerable rainfall data are
<br />available, they are presented in tabular form and show daily or storm
<br />totals. When sufficient data are available to determine the pattern and
<br />distribution of rainfall, and isohyetal map may be shown. .
<br />A summary table of peak stages and diooharges is given for each
<br />flood unless the number of stations in the report is small, and then the
<br />information is included in the text description. In the summary table
<br />the first column under maximum floods gives the period of known
<br />floods prior to the 1965 floods, This period does not necessarily cor-
<br />respond to that of gaging-station operation, 'but the period may extend
<br />.back to an earlier date. More than one period of known floods is shown
<br />for some stations. A period is shown whenever it can be associated with
<br />a maximum stage, even though the corresponding discharge may not
<br />be known. A second shorter period of floods is then given in which
<br />maximums of both discharge and stage are known,
<br />The second column under maximum floods shows the year in which
<br />the maximum stage or discharge occurred, within the period of known
<br />floods, prior to the 1965 flood being reported. The third column gives
<br />.he -date of the peak stage or discharge of the 1965 flood.
<br />The last column gives the recurrence interval for the 1965 peak dis-
<br />charge, The recurrence interval is the average interval, in years, in
<br />which a flood of a given magnitude (the 1965 peak) will be equaled or
<br />exceeded once as an annual maximum_ A flood having a recurrence in-
<br />terval of 20 years can be expected to occur, on the average, once in 20
<br />years, or it is one that has a 5-percent chance of occurring in any year,
<br />The recurrence intervals in the tables were obtained ITom Geological
<br />Survey reports on flood magnitude and frequency. In nearly all flood-
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