Fig. 3 
Fig. 4 
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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
as to frequency and magnitude of flooding, and evidence of shifting channels 
and possible undercutting of the proposed line by stream action. 
Several illustrations show how photo interpretation helps in drainage assess 
ment. Fig. 2 shows a location in Alaska on the Bering River Highway where an 
area of complex drainage caused by beaver dams (indicated by arrows) was 
encountered. Fig. 3 shows a river crossing at a narrow point where the bridge 
abutments would be protected by boulder moraines (B.M.). 
Study of borrow materials and aggregates sources is a photo interpretation 
function most useful in the final location and construction stage. This type of 
analysis is illustrated in fig. 4, a side-by-side borrow and waste situation on the 
Quebec Cartier Mining Railway in Canada. 
Location and assessment of potential and existing slide areas is an important 
special problem that lends itself well to photo analysis. Examples of the results 
of this type of analysis are shown in fig. 5, wherein a large alluvial fan was 
deposited over lake clays and the latter’s weakness has been a cause of slides. 
Permafrost, soil flow, muskeg, stream icing and frost-susceptible soils identi-