REGULARIZATION. 51 



conditions when planning and locating the work. It is not an uncommon thing to 

 see in some of the earlier works of regulation examples where injury instead of benefit 

 has been done to navigation by their faulty location. Another frequent cause of 

 failure has been the lack of sufficient funds with which to properly perform the work. 



Numerous failures have naturally led to bringing the system into disrepute, but 

 it is believed that much good can be done by it where the plans for its execution have 

 been well studied and are based on correct hydraulic principles, and the necessary 

 time taken in which to carry them out. There will be opposition from navigation 

 interests, which naturally demand immediate relief, but permanent results are more 

 advantageous in the long run. 



As has been stated, regularization contemplates the establishment and mainte- 

 nance of a medium and low-water channel. It is important that this channel shall 

 have sufficient depth during the lowest water liable to occur, as well as at ordinary 

 stages, and be of sufficient width to accommodate all navigation. Should it fail in 

 depth, craft must proceed with lighter loads, or stop altogether. The desired depth 

 is obtained by decreasing the section, that is, by narrowing the channel at bars, etc., 

 by artificial works. This contraction of the river-bed increases the current velocity 

 and causes erosion, the material being carried out into deeper water below. This very 

 contraction, however, may defeat the ends of navigation by leaving an insufficient 

 width for navigation, and by increasing the current beyond the limit at which craft 

 can proceed safely and economically. 



The following rates of current for different rivers are given by Sganzin, in his 

 " Cours de Construction " : 



Feet per Second. 



Mean velocity of the Seine, below Paris 2.3 



" " Thames at London, flood tide 3.0 



Low-water velocity of the Tiber at Rome 3.3 



" " Danube at Ebersdorf , 3.5 



" " Loire 4.3 



" " Rhone at Aries 4.9 



" " " " " " Beaucaire 8.5 



" " Durance, below Sisteron 8.5 



Maragnon, S. America 13.0 



Velocity of the Rhine varies from 3 feet 2 inches to about 14.0 feet. 



In Europe, where a depth of three feet is considered sufficient to permit a traffic 

 with barges or canal-boats, it has been found that where the slope of the river exceeds 

 i in 2000, up-stream navigation becomes very difficult for the ordinary methods of 

 towing. On the river Lys, in Belgium, for example, where the slope is i in 2000, the 

 towing is done by horses, and would be very arduous were it not for the presence of 

 the aquatic plants which retard the velocity of the current, and which it is strictly 



44 



II 



