Causes of landslide in Chittagong hill tracks

1. WELCOME

2. The cause analysis of
landslide
A case study of Chittagong
Presented by;
Group: A
Enamul Haque, Sujon Sutro Dhar, Kazi Mohammed Ikram
Hossain, Tanveer Alam Munshi

3. Geologically, Chittagong is in folded bed area & it has many hills which are steep
in slope. Its a region where landslides occur many times, so Chittagong is a
perfect place for analyzing the causes of landslide.

4. Landslide:
A landslide is a downward or outward movement of soil, rock or
vegetation, under the influence of gravity.

5. Mechanism of
Landslide:
Factor of Safety:
F =
𝑅𝑒𝑠𝑖𝑠𝑡𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒(𝑅)
𝐷𝑟𝑖𝑣𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒(𝐷)
When, F< 1 = landslide occur.
Resisting forces(R) preventing
the mass from sliding down
the slope are inversely
proportional to the hill slope
angle.

6. Causes of Landslide
Natural Causes
• Rainfall
• Steep-Slope
• Soil-Type
• Earthquake
Man-Made Causes
• Hill Cutting
• Deforestation
• Urbanization

7. Rainfall:
When rainfall happens the
porous space will be filled with
water due to infiltration of
water. As a result the weight of
rock mass and the downward
gravitational force will increase
simultaneously. This make rock
slope stability to decrease at
level where landslide may
happen.

8. Steep-Slope:
If the angle of slope
increases, the component of
gravity parallel to the slope
also increases. Which
decreases the stability of the
rock.
In the figure we see that the
left side rock mass is more
stable than the right side
rock mass

9. Hill Cuttings:
Most of the landslide
occurred in Chittagong
region due to indiscriminate
hill cutting. Because of hill
cutting, the slopes become
unstable. Due to hill cutting
the slope angle increases
which will reduce the rock
slope stability. The steep
slope of the hill cannot bear
the mass weight of the wet
soil or mud that results the
landslide

10. Landslide due to hill cutting. Source: Journal of Bangladesh
Institute of Planners, Vol. 7, December 2014, pp. 1-17

11. Causes of landslide according to the survey 2014. Source: J.
Environ. Sci. & Natural Resources, 8(2): 1-5, 2015, ISSN
1999-7361

12. Deforestation:
Deforestation is another
major reason of landslide in
Chittagong region.
Vegetation protects the soil
and makes slope stable
which reduce the risk of
landslides. Large trees
provide strong structures in
the earth that anchor the
soil and protect it from any
erosion.

13. Urbanization:
House construction in the hill or
hill side is another cause of
landslide. In Chittagong so many
people live near or in the hill
side area. The Chittagong city is
a densely populated area. For
accommodation people build
house on the top of the hills or
on slope or on the foot of hills
without following the existing
rules and regulations. The steep
slope of the hill cannot bear the
mass weight of the wet soil or
mud that results the landslide

14. From the pie chart we can see that rainfall & hill cutting are major causes for
Landsliding

15. THANK YOU…