RIVER DEVELOPMENT 



185 



Sometimes the flood plain of the main river is built up 

 more rapidly than the tributaries can build theirs, so that 

 they are dammed up as they enter the flood plain of the 

 main stream and form a series of fringing lakes along its 

 border. A fine example of this is found in the lower course 

 of the Red River of Louisiana. 



AN OLD RIVER 

 This river has done its work and has completed its activities. 



When a river has graded itself and built its flood plain, 

 its own active work consists largely in carrying off the 

 materials brought to it by its side streams. Although 

 these are now able to appropriate no new territory they 

 continue to wear down the country and round off the divides 

 till the whole region, unless reelevated, is reduced to an 

 almost level plain with its entire drainage system nearly 



