Figure 4. --A typical live stream appears on panchromatic photography as a 



meandering, thin, dark line. 



RECOGNITION OF STREAMS ON AERIAL PHOTOS 



Larger streams, which are easily recognized on the photos, are usually correctly mapped. 

 Many smaller streams, however, particularly in mountainous areas, cannot be identified from a 

 map alone as flowing, dry, or intermittent. A number of these can be correctly classified from 

 photos, and substantial savings over field inventory costs can be made. 



Where live streams are obscured by vegetation, their presence may sometimes be inferred 

 from related photo features. A meandering pattern of dark blotches through a forested area may 

 be made by marshes, springs, seeps, or other riparian vegetation and water. On the other hand, 

 dary drainage channels usually appear on panchromatic photography in light -colored image tones, 

 because the deposits of clay, silt, sand, and rock tend to reflect light. Such indirect evidence 

 as exposed boulders, the absence of riparian vegetation, and lack of springs or marsh areas all 

 suggest that a channel is dry. 



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