336 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



raised the level by 0.1 foot. The hazard of wind action is not so great 

 as on a lake of similar dimensions, because the flood waters are usually 

 shallower and projecting trees and buildings serve to reduce both the 

 wind velocity and the disturbance of the water. 



When so enormous a quantity of water is involved, spread out over 

 the lowlands, the passage of even great masses downstream lowers 

 the upstream stages but slowly. The quantity of water represented 

 by one foot when the flood is at its height is equal to that represented 

 by several feet at lower stages. So great was the discharge of the Ohio 

 relative to the Mississippi at the junction of the rivers that in this 1937 

 flood the flow of the Mississippi above the mouth of the Ohio was 

 reversed. This means that all the run-off of the Mississippi above 

 Cairo was stopped for a time and that even moderate rains plus the 

 water from the melting of the great quantity of snow in the upper 

 Mississippi and middle Missouri valleys might have raised the levels 

 of these rivers above flood stages before the flood waters of the Ohio 

 passed on. Frankenfield found the damming effect of a flooded Ohio 

 nearly to St. Louis. Similarly the great discharge of the Arkansas 

 and other streams into the Mississippi below Cairo created a water 

 dam. It is obvious why the period of high waters in the lower 

 Mississippi is protracted. 



Table 3. — Maximum flood stages, Ohio and lower Mississippi, January and 



February l 



1 Data from U. S. Weather Bureau gage records. 

 1 Beale St. gage. 



WESTERN COLD THE ACCOMPANIMENT OF EASTERN FLOODS 



The flood so eclipsed all else in weather news that the extreme cold 

 in the West received little general attention. Throughout January 

 polar air masses were just as persistently covering the West as tropical 

 ones were deluging the East. Oranges were freezing in southern Cali- 

 fornia while they were ripening too fast in Florida and early fruit 

 trees were blossoming in southern South Carolina. Figure 1 shows 

 temperatures more than 20° F. below normal in the central and south- 



