TWENTY-FIRST ANNUAL YEAR BOOK— PART VIII 



635 



FLOOD OF MARCH-APRIL, 1920, DUBUQUE, IOWA DISTRICT. 



By James H. Spencer, Meteorologist. 



Weather Bureau OflBce, Dubuque, Iowa, May 25, 1920. 



This Mississippi River flood was the worst in this district since 1888, 

 and has been exceeded in the last 50 years only by the floods of June, 

 1880, and May, 1888. It was the earliest spring flood of such magnitude 

 of which there is any record in this section. For rapidity of rise, it is 

 comparable, only with the flood of June, 1880. The total rise in each 

 of these two floods continued over a period of more than two weeks, and 

 was between 13 and 14 feet, but slightly greater in 1920. 



In the flood of June, 1880, the period of maximum rise was 6.0 feet 

 in three days during the first half of the 15-day period, while in the flood 

 of 1920 the period of maximum rise was also 6.0 feet in three days, but 

 occurred during the last half of the 15-day period. There is no previous 

 record of such a rise as occurred in 1920 during the week immediately 

 preceding the peak of the flood. 



Most of the flood waters came from the headquarters of the Mississippi. 

 The Wisconsin River was above flood stage during the same period, a 

 maximum stage of 15 feet being recorded at Portage on March 31. This 

 flood added about 1.5 feet to the peak of the Mississippi River flood be- 

 tween Dubuque and Pr. du Chien. Heavy and general rains on April 1 

 also added 0.5 or 0.6 feet to the peak between Pr. du Chien and La Crosse. 

 With these exceptions the flood waters came wholly from the region north 

 of La Crosse. 



The following table shows the progress of the flood in the Dubuque 

 river district: 



Lansing, Pr. du Chien, Dubuque, Portage 



March 22 8.0 7.2 7.1 10.0 



23 8.3 7.4 7.4 9.8 



24 8.9 7.9 8.2 9.5 



25 9.4 8.5 8.7 9.8 



26 9.7 9.3 9.8 10.2 



27 10.2 9.8 10.5 11.1 



28 10.7 10.2 11.0 12.6 



29 11.3 10.8 11.4 14.0 



" 30 12.5 11.9 11.8 14.8 



31 13.9 13.2 12.4 14.9 



April 1 15.1 15.4 13.5 14.7 



2 16.2 17.2 15.8 14.5 



3 16.9 ' 18.7 18.0 14.2 



4 17.2 19.6 19.5 13.7 



5 17.2 19.6 20.5 13.0 



6 16.9 19.1 20.9 12.4 



7 16.5 18.7 21.0 12.1 



8 18.0 20.7 11.6 



Flood stage at Lansing, Pr. du Chien, and Dubuque is 18.0 feet, and 

 at Portage 14.0 feet. 



In two particulars the floods of June, 1880, and March-April, 1920, were 

 not comparable. The cause in 1880 was exceedingly heavy rains early in 



