452 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Discussion 
Mr. Tremolieres (France) asked the speaker if he was of the opinion that aerial photographs 
taken at sufficiently close intervals during a period of inundation and retreat of the water, 
could replace a sufficiently detailed topographic map in establishing a management plan for 
a watershed. Dr. Nakano answered that as the length of the rivers in Japan is generally short 
with a steep gradient, the plains are frequently flooded. The alluvial plains have been built up 
by repeated flooding. Conversely, if we analyse micro features of the alluvial plains, we can 
determine the areas which will be easily flooded. For this purpose photographs on scales of 
1 : 10,000 to 1 : 40,000 are being used. Besides these, there are maps on scales 1 : 25,000 and 
1 : 50,000, which are also used for geographical surveys, but all information regarding land 
surface such as landform, hydrography, land use etc. is obtained by interpretation of aerial 
photographs.