RIVER DEVELOPMENT* 181 



carry less, thus being forced to drop some of its load. As 

 a river flows along its graded stretches, eroding in some 

 places and filling in others, it broadens its valley floor, 

 leaving at the border of its channel a low plain which in 

 time of flood may be covered with water. 



These plains are very fertile and are usually called 

 " bottom lands " by the farmers. They are often unhealthy 



RIVER EROSION 

 Cutting down the outer side of the curve and depositing on the inner. 



because of floods and poor drainage. Where the water in 

 the river rises rapidly and to a considerable height, it is 

 dangerous to inhabit these plains. But sometimes these 

 plains are so fertile that they are densely populated, as 

 the plain of the Ganges. Such a river-made plain is called 

 a flood plain. 



If a river once begins to swing on its valley floor, it con- 

 tinues to do so, since whenever it strikes the bank, it is 

 deflected toward the other side, and is made to move in 

 the direction of the opposite bank as well as downstream. 



