Bulletin 1486. U. S. Dept. of Agriculture 
Plate 4 
ft 3**- *• 
"<w 
Streams with Unstable Channels and Banks Subject to Erosion 
A. — Streams with insufficient fall to transport material delivered by their tributaries become 
filled with gravel and sand bars. These deflect the current against the banks with 
resulting erosion. In this case the current is being deflected against the left bank and 
the bend is gradually being accentuated 
B.— A typical meandering stream. Flood currents have from time to time deflected against 
the left-hand bank causing marked erosion, as shown, and converting a portion of the 
left bank into an island. Note that the left-hand channel current is nearly at right 
angles to the current in the main channel. Cross currents and eroding tendencies of 
this kind are peculiar to streams in this stage of development 
Incorrect Grade-Line Treatment 
C— The concave vertical curve on the approach in combination with the cambered truss 
gives the optical effect of sag and weakness 
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