CHAPTER I. 



THE PROTECTION OF LAND FROM THE WASTING ACTION OF 



RIVERS. 



Abrading action of rivers, illustrated by the Forth. Winding rivers may be 

 improved by "cuts." Remedial works for checking abrading action of 

 rivers by making the surfaces of the banks smooth and uniform by plant- 

 ing willows and reeds by depositing stones on the face of the banks by 

 timber pile-work and the deposit of fascines of brushwood. Examples of 

 river embankments. 



IN considering the first of the topics to be discussed, which 

 refers to the wasting action of rivers on their banks, the follow- 

 ing general statements may be made : 



1. The scouring or abrading action of a stream is influenced 

 by its velocity. 



2. The velocity again is influenced by the fall or slope on 

 its surface.* 



3. The effect of the scouring action on the adjoining banks 

 is further influenced by their geological formation, experiments 

 having shown that ordinary sandy soil is moved by a current 

 having a velocity of about half a mile an hour, and that a cur- 

 rent of about one mile per hour will move fine gravel, while 

 heavy gravel resists a current of upwards of two miles per 

 hour. 



* When a river is in train also by its hydraulic mean depth. 



