Landsat RBV camera data. 
In this paper, indicated are water surface phenomena near the 
coast and effects in not only coastal area but also fields after 
Typhoon 8115 which landed in Hokkaido, northeast one of four main 
islands of Japan, on August 23 in 1981. In the analysis of the 
phenomena and the effects, Landsat MSS data of August 25, two days 
after the typhoon,were mainly utilized. 
The water surface phenomena and the effects in coastal area 
concerned are on a front of muddy river water in the sea, counter 
currents to the ocean current, bay current variation in a small bay 
and a clear water flow through a swamp into a muddy lake. 
II. Analysis of Coastal Phenomena as Revealed by MSS Data 
It is recognized that in the imageries of Landsat MSS band 4 
and 5. of August 25, radiance of sea water near the coastal line is 
greater than those of September 30, 1981 and the high radiant area 
is much more widespread (See Photo 1 and 2). The high radiant pat- 
tern in the coastal area is thought to be mostly muddy river water 
into the sea after the heavy rainfall caused by Typhoon 8115. 
The following four phenomena are observed in Landsat MSS image- 
ries of August 25 and also of September 30; 
A front of muddy water 10 to 35 kilo-meters at sea along the 
coastal line 
Water flows along the coast of the Tokachi Plain (Indicated in 
Fig.l) and mixing with the flows of the opposite direction 
near Kombumori (Indicated in Fig.l also) 
Muddy water pattern in Akkeshi Bay (Indicated in Fig.l) sug- 
gesting clockwise flows 
Water flows into Lake Akkeshi at the river mouth 
The results of analtsis of phenomena listed above are describ- 
ed in the following paragraphs. 
II.l Front of Muddy Water 
-— 
  
According to the sea truth data, a sharp change of salinity 
from 24 % to 32 % takes place at off the mouth of the Tokachi River 
(Indicated in Fig.1) where deapth is in the range from 50:to+120 
meters (See Fig.2 and 3). 
Also according to the measurement data of water volume of the 
Tokachi River at the points A and B(indicated in Fig.1), water a- 
mount of the river remarkably increased on 23 and 24 of August (See 
Fig.4j. 
Judging from the two facts above, the pattern of water is con- 
sidered to be that by rivers in the Tokachi Plain. 
It is recognized from the imageries of MSS band 4 of August 25 
that a front of muddy water coincides with the iso-line of around 
200 meters" depth (PHoto 1 and Tig.2). 
On the other hand, the front of muddy water on September 30 
approximately coincides with a 70 meters depth contour line.  There- 
fore the front of muddy water move forward or backward in accordance 
with volume of discharged river water into the sea, where an ocean 
current must have some effect on the formation of the front. 
II.2 Water Flows along Coast 
  
The ocean current flows from northeast to southwest off both 
Akkeshi Bay and the coast of the Tokachi Plain(See Fig.5). On the 
other hand, the water flows around the river mouth prove that the 
direction of current along the coast near the Tokachi Plain is from 
southwest to northeast. Therefore a meso-scale counter current is 
  
    
  
  
     
   
    
   
   
    
    
    
    
    
   
    
    
   
   
    
   
   
    
    
   
   
   
   
    
   
   
   
    
    
    
  
    
     
   
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