(A) Slope classification for the landslide frequency (B) Landslide frequency for the slope classification 
100 
(z) 
90 
   
100 
(x) 
90 
80 80 
70 70 
60 60 
50 50 
40 40 
30 30 
20 20 
10 10 
  
123456 12345 123456 1234 1234 123 123 (Srate) 1234567 1234567 1234567 12345 1234 123 (Frate) 
1(38X) 2(40%) 3(14X) 4(4Z)  5(22)  6(1X) 7(1%) (Frate) 1(332) 2(31X) 3(27%) 4(72) 5(1% 6(1%) 7 8 9 (Srate) 
* Frate (Landslide frequency); 
1: 0-5 %, 2: 5-10%, 3: 10-15%, 4: 15-20%, 5: 20-25%, 6: 25-30%, 7: above 30% 
* Srate (Slope angle); 
1: 0-10, 2:10-20?, 3: 20-30° 4: 30-40° 5: 40-50°, 6: above 50? 
Fig.3 Relationship between slope and landslide frequency in the study area. 
Table 1. Landslide susceptibility categories idenfied on isopleth map and assigned 
rating for landslide frequency in the study area 
  
  
  
  
  
  
  
  
  
  
landslide suscep- area covered by landslide evaluation 
tibility categories |deposits in percent rating| guidelines 
I (landslide frequency) 
negligible 0-5 (X) 1 (DeGRAFF, 
very low 5 — 10 2 1985) 
low TO —.15 3 
moderate 15 — 20 4 
high 20 — 25 5 
very high 25 — 30 6 
extreme above 30 7 
Table 2. Summary of stability rating system in the study area 
Factors Weight |Rating 
1. Topographic slope (Tw, Tr) 5 1-6 
2. Landslide frequency(Lw,Lr) 4 1-7 
3. Groundwater level(Gw,Gr) 3 1-3 
4. Vegetation (Vw,Vr) 2 1-4 
5. Rainfall (Rw,Rr) 2 1-4 
6. Soil texture (Sw,Sr) 1 1-3 
7. Geology (Qw,Qr: weathering or faults) 1 1-2 
8. Condition of bedrock (Cw,Cr:fractures or hardness) 2 1-3 
9. Bedding dips in the direction of potential farre 3 1-32 
Bw,Br 
  
  
  
  
  
Table 3. Data layers for analysing stability rating system 
  
Topographic map; topographic contours, roads, streams 
Inventory map of landslide deposits 
Landslide frequency map 
Isopleth map of landslide deposits 
Soil map (texture) 
Soil depth 
Land cover/use map 
Geologic map 
Boring data maps; Sel,Wel,Gel,Sth,Wth,Th (6 layers) 
Point map; wells, schools.. 
  
Od 006-10) 01 QN = 
  
I 
  
676