President's Address. 57 



is no longer capable of cutting its channel deeper. Water contin- 

 ues flowing through it, however, and a process of meandering is as 

 absolutely necessary as it is that the stream exist. This meandering 

 of the channel is a most important point, particularly in connection 

 with all river improvements. As cutting continues under this new 

 set of conditions, the so-called ox-bow curves are formed, such as 

 can be seen along the course of any stream. 



Let us suppose that we could straighten the channel of a stream 

 throughout a distance of a hundred miles, building an entirely new 

 channel. Would this new channel remain straight for any consid- 

 erable length of time? It certainly would not unless extra precau- 

 tions were used. If the water be encased in walls of masonry, the 

 channel would remain straight as long as the masonry walls re- 

 mained intact. If a less pretentious protection were given and the 

 walls were riprapped, using the term in the ordinary way, mean- 

 dering processes would be hindered, but sooner or later the ten- 

 dency would become so great that the riprapping would be worn 

 away in places, after which its existence elsewhere would only assist 

 and intensify meandering processes. This same fact may be stated 

 in another way. Any channel of a river may be kept in its present 

 position by a sufficient interference on the part of man so long as 

 this interference is maintained. If the people in a given community 

 wished to retain a river channel in its present position for a thousand 

 years, they could do so by a sufficiently strenuous effort in the way 

 of preventing the stream from cutting its banks. The converse of 

 this is also true. A stream which has already ceased cutting its 

 channel deeper may be made to shift its channel at the will of man, 

 provided suflBcient influence is brought to bear upon it, the energy 

 of the running water being used entirely for the execution. 



When a stream has reached a certain degree of meandering or 

 of crookedness, the same stream has a tendency to straighten its 

 own channel. This tendency is manifested principally in two ways, 

 one by cutting its banks during mild floods until the necks of the 

 ox-bow curves are destroyed; the other by excessive floods when 

 the water spreads from bluff to bluff and the current, ignoring the 

 ordinary channel, flows in an approximately straight line between 

 the bluffs. This new current often cuts a new channel deep enough 

 to hold the current after the flood has subsided. A river, therefore, 

 makes crooked its own channel, apparently in order to have the 

 privilege of straightening it, but in reality when working under 

 the inflexible laws of nature. 



