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INDIANA UNIVERSITY STUDIES 



The position of the 'highs' and the 'lows' during the period of 

 March 23-27, is responsible for the continuation of the excessive 

 downpour in the Ohio Valley. As nearly as possible, the following 

 is the succession of events that caused the continuous downpour: 

 In advance of the first storm, that formed on the 22nd and centered 

 in the lake district on the morning of the 24th, a great bank of 

 high pressure moved across the United States and settled in and 

 over the Bermudas, remaining there until the 27th. Thus while 

 the second storm was pushing eastward on the 24th, an area of high 

 pressure existed off the Atlantic coast, and another area of high 

 pressure existed north of the Great Lakes, and was spreading 

 eastward. On the evening of March 24th, the two areas of high 

 pressure were separated only by a long narrow trough extending 

 northeast by southwest across the Ohio Valley. This trough con- 

 nected the receding storm with the approaching one, making al- 

 most continuous rainfall. On the morning of March 25th, the 

 trough extended from Texas to New England, with centers over 

 Arkansas and the Ohio Valley. The high pressure in the Canadian 

 region and in the Bermudas kept the area of low pressure over the 

 Ohio Valley from moving on to the eastward. On the 26th the south- 

 ern portion of the trough moved to the eastward and settled over 

 North Carolina. When the southern portion of the trough passed 

 over the drainage areas of the streams that flow into the Ohio 

 River from the south, the latter were also caused to assume flood 

 stages, thus making doubly sure the resultant destructive flood 

 stages on the Ohio River. On the 27th the high pressure over 

 the Bermudas gave away and the area of high pressure in Canada 

 moved over the Atlantic Ocean, thus permitting the areas of low 

 pressure to move on into the Atlantic ocean, relieving the flood- 

 stricken Ohio Valley. 



Thus the two storms passed across the Ohio Valley so close 

 together that the rain areas of the two blended, and the second 

 storm was held back by the two 'highs,' concentrating the rain- 

 fall for two successive days in the same place, while the southern 

 portion of the trough moved across the southern tributaries of the 

 Ohio, flooding them at the same time. At no time in the history of 

 the Ohio Valley had so much rain fallen in a 72-hour period as 

 fell last March 23-27. In many local areas, as large an amount 

 of rain has fallen in an equal length of time, but never has there been 

 such a heavy rainfall over so large an area in so short a time. 



Again it is of special interest that no low temperatures existed 

 immediately before, during or after this period of flood. At no 



