OVERFLOW OF RED RIVER OF THE NORTH. 49 



In preparing reports upon drainage projects in the Red River Val- 

 ley, J. T. Fanning 7 (in Minnesota) , and John T. Stewart 8 (in North 

 Dakota) , estimated run-off by a method in which the size of water- 

 shed is the principal variable considered. Their conclusions, as re- 

 corded for areas up to 200 square miles, are shown in Table 12. 



CONCLUSIONS REGARDING RUN-OFF. 



Relative to seasonal variations of run-off, the study made by the 

 Bureau of Public Roads indicated two important conclusions as fol- 

 lows : 



1. No combination of storm and monthly precipitation is likely to 

 occur from May to October which will cause the Red River to over- 

 flow below Wahpeton. 



2. No storm precipitation will cause excessive run-off and floods 

 in any portion of the watershed from November to March, when the 

 prevailing temperature is low. 



These two negative conclusions may be stated positively thus : Ex- 

 cessive precipitation may cause floods on any of the streams from 

 May to October except along the channel of the Red River below 

 Wahpeton. Rapidly melting snow, or a combination of precipitation 

 and melting snow, may cause floods along any of the streams in the 

 Red River watershed during March or April. 



There is nothing to indicate that conditions as to rate or volume of 

 run-off are undergoing any permanent change in the Red River Val- 

 ley. Rather it seems probable that the future run-off during any 

 long-term period will be subjected to seasonal and periodical fluctua- 

 tions as great as any that have occurred in the past. 



THE FLOOD SITUATION. 



Serious floods caused by rapid melting of snow and rain occur in 

 early spring at intervals of from 1 to 15 years along the Red River 

 below Wahpeton, N. Dak. These floods affect land and property in 

 North Dakota and Minnesota, and in Manitoba, Canada. 



During the period May to October local floods are caused by local 

 storms which may cause very heavy rainfall over areas of 6,000 

 square miles or less. 



SPRING FLOODS. 



Just after the annual spring thaw the run-off is sometimes sufficient 

 to overflow the outside high banks of the channel. At such times ex- 

 tensive areas of land are flooded. As the land along the stream is flat 



7 Report of Commissioners, " Red River Valley Drainage," Crookston, Minn., 1886 (out 

 of print). 



8 Bulletin 1S9, Office of Experiment Stations, U. S. Department of Agriculture, May, 

 1907 (out of print). 



70352°— 22 1 



