Tree size map: The possibility of landslide occurrence increases as the wood diameter decreases

 

 -   Very small diameter: wood diameter is below 6cm and timbers occupy less than 50%

-   Small diameter: wood diameter is 6-16cm and timbers occupy less than 50%

-         Medium diameter: wood diameter is 16-28cm and timbers occupy less than 50%

 

 

         

 

          Tree age map: The possibility of landslide occurrence increases as the trees are younger

 

-         1st age:    more than 50% 1-10 years old timber

-         2nd age:   more than 50% 11-20 years old timber

-         3rd age:   more than 50% 21-30 years old timber

-         4th age:   more than 50% 31-40 years old timber

-         5th age:   more than 50% 41-50 years old timber

 

 

         

          Slope: The possibility of landslide occurrence increases as the slope increases

 

-         Higher landslide occurrence rate when slope is greater than 22 degree

-         Landslide can possibly occur even under 15 degree during heavy rainfall period

 

 

     

          Drainage: The possibility of landslide occurrence increases as the land drains better

 

-         Well drained land has larger grains

-         High drainage rate increases water content, therefore increases the unit mass

-         Poorly drained land has smaller, finer grains

              -         Low drainage rate cause the land slowly absorb water, therefore eventually

         increase the unit mass

-         Increased unit mass increases the risk for landslide

 

         

          Tree kind: The possibility of landslide occurrence varied depending on the type of tree present

 

-         Coniferous tree dominated land has high landslide occurrence

-         Deciduous and needle and broad leaf tree dominated land all have significantly

          less landslide occurrence

-         Due to lack of data, the significance and slide occurrence of ranch, cultivated land

          and field could not be determined

 

         

 

          Tree density: The possibility of landslide occurrence decreases as the tree density increases

-         Loose:      Less than 50% timber area

-         Moderate:        Less than 51 – 70% timber area

-         Dense:     More than 71% timber area

-         The landslide occurrence rate dramatically decreases

-         if the land is populated by more than 70%

 

          Geology: Granite and mica ademelite has the highest landslide occurrence

-         About 66% of geological strata in Korea was molded in the Cenozoic Era

-         70% of all mother rock is comprised by granite and gneiss

     The soil is very susceptible to erosion owing to the changeable

     climate and torrential rain

 

         

 

          Material (soil): Soil made of granite residuum shows the highest landslide occurrence

-         Granite residuum and alluvial-colluvium has the highest landslide occurrence

 

 

 

 

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