12 



TRANSPORTATION OF DEBRIS BY RUNNING WATER. 



than in stream transportation. Capacity is 

 reduced by roughness of bed. 



Vertical velocity curve. The vertical distri- 

 bution of velocities in a current is controlled 

 by conditions. The level of maximum velocity 

 may have any position in the upper three- 

 fourths of the current. In loaded streams its 

 position is higher as the load is greater. In 

 unloaded streams its position is higher as the 



slope is steeper, as the discharge is greater, 

 and as the bed is rougher. 



Pilot tube. The constant of the Pitot veloc- 

 ity gage the ratio between the head realized 

 and the theoretic velocity head is not the 

 same in all parts of a conduit, being less near 

 the water surface and greater near the bottom 

 or side of the conduit. 



