OVERFLOW OF RED RIVEB OF THE NORTH. 53 
tance back from the banks. The fall along its course is for the most 
part slight and somewhat variable. Along the Bois de Sioux the 
fall is about 0.3 foot per mile; from Breckenridge to Fargo, about 1 
foot per mile ; and from Fargo to the Canadian line from 0.6 to 0.3 
foot per mile. (See fig. 2.) 
The channel of the upper Bois de Sioux is small and poorly de- 
fined (see fig. -1 and Plate IV, fig. 1), but in the vicinity of Brecken- 
ridge the banks are between 20 and 25 feet high, and from 100 to 200 
feet apart. At this point there is a further increase in size due to 
the entrance of the Otter Tail, and from Breckenridge on for the 
greater part of its length the stream has an inner or low- water 
channel with banks of varying height, with one or more terraces on 
each side which bring the outer banks up to or slightly above the 
level of the adjacent land. The outer banks, in places on the lower 
part of the river, are from 1,000 to 1,200 feet apart. 
The course is extremely crooked for most of its length, with many 
loops, bends, and side channels. The channel often doubles back 
upon its course and flows a considerable distance without gain in the 
general direction of flow. Over the greater part of its length the 
channel — especially the outer flood channel — is badly obstructed by 
trees and brush (see PI. IV, fig. 2) and many buildings, fences, and 
other structures are situated within the outside banks. Many of the 
county wagon bridges have been built on the inner banks, spanning 
only the low-water channel (see PL IV, fig. 3) ; at flood stages these 
are either washed out or completely covered, thus forming addi- 
tional obstruction to flow. 
Owing to the slight fall in the stream bed and the fact that the 
slope decreases downstream as more water is added, the velocities of 
flow are small and channel erosion is comparatively slight. The 
stream under these conditions has not a channel of sufficient capacity 
at all points to carry the volumes of water present at high stages, and 
the situation is rendered the more acute by the obstructed state of 
the channel. As a result, heavy run-off from the watershed causes 
the stream entirely to fill the channel and spread widely over the 
contiguous country. 
The upper part of the Bois de Sioux has practically no channel 
(PI. IV, fig. 1) and at times of high water the adjacent land to the 
west becomes a part of Lake Traverse. The land to the east rises 
sharply a short distance from the stream. Farther down, the chan- 
nel gradually develops until at a point about 10 miles upstream 
from Breckenridge it attains a capacity of 2,000 second-feet (see fig. 
2 and fig. 4). At Breckenridge there is a sharp increase in slope and 
size of channel which gives a capacity of about 4,000 second-feet 
within the inner banks and about 8,500 second- feet for the entire 
channel. From Breckenridge to the international boundary there is 
