In January and February 1937 the Ohio and mid-Mississippi Rivers experienced floods which, over reaches many hundreds of miles in length, exceeded all previously recorded stages. When measured by the loss of life and property, extent of damage, and general disruption of human activities, these floods constituted a major catastrophe.

The floods were caused by a succession of heavy rainstorms that began late in December 1936 and continued nearly to the end of the following January. Although the storms covered a considerable part of the lower Mississippi River Basin and almost the entire Ohio River Basin, the center of heaviest precipitation was in the middle and lower portions of the Ohio River Valley.

The total storm period can be subdivided into several individual storms, which were more or less clearly demarked by short intervening periods of little or no precipitation. Although the individual storm periods were the same or nearly the same over wide areas, their subdivisions were somewhat different in the most widely separated parts of the affected areas, with intermediate gradations in the intervening areas. The heaviest rainfall--that of January 20 to 25--was centered in the lower Ohio Valley, and, falling as it did upon a region with soil saturated and waterways already running full, it had the effect of producing extreme floods.

The small quantity of snow on the ground over the higher eastern parts of the area at the beginning of the storm period disappeared in a short time. Some of the precipitation occurred in the form of snow, but this snow and the associated cold weather were much less significant in their influence on the floods than in the misery and discomfort they caused to ill-sheltered flood refugees and flood-bound people.

Sequence and time of the storms were such that in the upper and smaller tributary basins the associated flood rises tended to clear to a notable degree before the-next flood rises came; hence many of these tributaries were at no time in extreme flood. In the lower reaches of the largest tributaries, and especially on the middle and lower reaches of the Ohio River, there were extreme and almost continuously increasing accumulations of run-off, which culminated in the region of Louisville, Ky., in stages 10 or 11 feet higher than any previously known.

The precipitation was heaviest in the Ohio River Basin, and the flood in the Mississippi River, like other notable floods of the past, was caused largely by the extraordinary contributions from the Ohio River. The river stages exceeded those previously recorded for the lower 700 miles on the Ohio River and for 250 miles .on the Mississippi River below the Ohio. At Cairo, Ill., at the mouth Of the Ohio River, the river stage was higher for a period of 19 days, from January 24 to February 11, than at any previous time on record. The height above previous flood stages diminished materially as the flood progressed down the Mississippi.

The mean precipitation ever the Ohio River Basin during the storm period was. 12.85 inches. The snow on the ground at the beginning of the period is estimated to have been equivalent to a mean depth of 0.10 inch of water over the basin. Out of the total precipitation 8.9 inches appeared as flood flow. On January 26 the computed volume of water in the stream channels of the Ohio River Basin was 56,000,000 acre-feet, equivalent to a depth of 5.1 inches over the drainage basin. The maximum discharge of the Ohio River at its mouth was 1,880,000 second-feet on February 1. On February 2, the day of the crest stage at the mouth of the Ohio, the computed volume of water on the surface channel system was equivalent to a depth of 3.7 inches over the drainage basin, of which 2.4 inches was in the 337-mile reach of the Ohio River between Louisville, Ky., and the mouth.

This water-supply paper presents records of stage and discharge for the period including the floods at about 250 measurement stations, records of stage and discharge for the period including the floods at about 250 measurement stations, records of storage in many reservoirs, a summary of peak discharges with comparative data for other floods at about 470 measurement points, and tables
showing crest stages along an aggregate length of stream channel for 5,000 miles. The report also includes basic information in regard to the
weather associated with the floods, results of detailed studies of the rainfall and run-off, analyses of the volume of flood waters'in the surface
channel systems during the progress of the floods, and many other kinds of flood information.

Following the main flood report is a brief report entitled "Flood" deposits of the Ohio River, January-February 1937, a study of sedimentation."
An abstract of that report is presented on page 693.