54 BULLETT-N 1017, U. S. DEPARTMENT OF AGRICULTURE. 



a continuous increase in size of channel of the Red River and a de- 

 crease in the general slope of the channel, broken by short stretches 

 of greater fall (see fig. 2). 



When the water in the river reaches a stage of 23 feet on the gauge 

 maintained by the United States Weather Bureau at Moorhead, 

 Minn., the water starts to overflow the inner banks and reaches some 

 of the lower lying road grades, buildings, and bridges — the channel 

 between the mouth of the Dakota Wild Rice River and the mouth of 

 the Sheyenne River will easily carry 6,000 second-feet. A rise above 

 23 feet causes the overflow of low areas within loops of the river and 

 parts of the city of Fargo which lie but slightly above the banks of 

 the lower-water channel. Even at stages as high as 35 feet at Fargo 

 no extensive areas of land are flooded. Below the mouth of the Shey- 

 enne River the channel of the Red River will carry 12,000 second- 

 feet, and from the mouth of the Buffalo to Grand Forks 15,000 sec- 

 ond-feet can be passed without overflow. Below the mouth of the 

 Red Lake River at Grand Forks the channel is considerably larger 

 than above, and in the stretch between that point and the interna- 

 tional boundary, along which the slope constantly diminishes, are 

 found the sections of maximum area (see figs. 2 and 4) . This part 

 of the channel will carry a volume of 25,000 second-feet without top- 

 ping the outer bank. 



It should not be presumed that the river when flowing at these 

 maximum rates will entirely fill the channel for its whole length, or 

 that greater volumes can not be carried at some points without over- 

 flow. The figures given refer to the approximate maximum volumes 

 that can be passed through the various sections of the channel with- 

 out overflow at any point along the river. Greater volumes can be 

 carried at certain points, but even though the river remains within 

 the banks at these points it will overflow either above or below. When 

 flowing bank-full, on the other hand, the smaller sections pass more 

 water than their size and the slope of the stream as a whole would 

 indicate. This is due to the heading up of the water above the sec- 

 tions of small area, and the ability of the larger sections below to 

 carry the same volume at lower stages, which gives an increased 

 water-surface slope through the restricted portions. The capacity 

 as calculated by Kutter's formula agrees very closely with actual 

 discharge as indicated by stream-gauging records. 



TRIBUTARY STREAMS. 



In some respects the tributary streams are much like the Red River, 

 the fall being slight in the lower parts of the channels. However, in 

 their upper reaches the fall in most cases is much greater than in the 

 Red. These streams rise outside the old lake boundary and flow 

 from the east and west through the old beaches across the flat lake 



