tomatically. As a results size, number and setting 
point of dams in the watershed decided. Figure 
3 shows the flowchart of the system. Major 
functions are listed below. 
1) Display and undisplay of analyzing process. 
2) Display of attributes 
3) Conditional access 
4) Computation of designed run-off sediment in 
watershed 
5) Decision of number of soil saving dams. 
6) Display of cross-sectional view of designed 
soil saving dams and its print output. 
4.3 Use of digital elevation map 
We used digital elevation map data (50m mesh) 
to estimate the number and setting place for soil 
saving dam. Geographical Survey Institute of 
Japan has been made the digital elevation map in 
whole country since 1993. Three CD-ROM re- 
leased in 1997. CD-ROM is available at any big 
book store and inexpensive. Map data( CD-ROM) 
was used to calculate some of parameters in the 
system.It is ,for example, run-off sediment de- 
rived by the equation Ve-B*De*Le. Parameters 
B and Le is average width and length of river in 
the stream respectively. Other many parameters 
(2,5) 
«(2 
»(2,4) 
“23),2,2) (2,4 045 2 
(1,1> (1,2) 
    
were derived by digital elevation map data. De- 
rived parameters by 50m mesh elevation data are 
given below; 
A:watershed areas(km2) 
O :slope of river bed 
b:bottom width of soil saving dam 
iO:actual slope of river bed 
Figure 4 shows the relationship between topo- 
graphic feature and parameters. Symbolized SP 
in the center of Figure 4 means Setting Point 
which is the place ofthe first soil saving dam. 
Watershed(dotted line),225 up the river from SP 
and cross section to river were derived by digital 
elevation data. Flow of river which expressed by 
solid line in the Figure 4 simulates another GIS 
software. The software was used to extract the 
watershed from digital elevation map. 
Figure 5 shows relationship between cross-sec- 
tion of soil saving dam and data point of digital 
elevation map. The circular symbols in the Fig- 
ure 5 shows the elevation data point which was 
extracted from 50m mesh digital data( CD-ROM ). 
Average gradient ? 1d bottom width were calcu- 
lated from those e.2vation data. 
5. RESULTS 
Trin un 
Pluy;=( -46448 81 , 472628) 
  
  
Fig.6 The left is relationship between the soil saving dam and watershed. The right is Cross- 
section of soil saving dam. 
612 Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
  
  
  
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