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LANDSLIDES AND THEIR MITIGATION
MEASURES IN BANGLADESH
Prepared By
Md. Arifuzzaman Arif
MSc in Disaster Management
Departm...
Contents
 What is Landslide?
 Speed of Landslide
 Types of Landslide
 Causes of Landslides
 Where does It Occur
Mostl...
What is Landslide?
A landslide is a downward or outward movement of soil,
rock or vegetation, under the influence of gravi...
Speed of Landslide
• The speed of the movement may range from very slow to rapid.
Landslides travel at least over than 260...
TYPES OF LANDSLIDES
a) Rotational slides move along a
surface of rupture that is curved and
concave.
b) Translational slid...
TYPES OF LANDSLIDES
c) Rock Fall Free falling of detached
bodies of bedrock (boulders) from a cliff
or steep slope
d) Rock...
TYPES OF LANDSLIDES
e) Lateral spreading occurs when the
soil mass spreads laterally and this
spreading comes with tension...
Natural Factors
Gravity:
Gravity works more
effectively on steeper slopes.
Geological factors:
Geology setting that places...
Causes of Landslides
Waves:
Wave action can erode the beach or
the toe of a bluff, cutting into the
slope, and setting the...
Causes of Landslides
Anthropogenic Factors:
▸ Inappropriate drainage system
▸ Cutting & deep excavations on
slopes for bui...
Where does it occur mostly in Bangladesh?
▸ Chittagong & Chittagong hill
tracts***
▸ Hill Ranges of Northeastern
Sylhet
▸ ...
Statistics of causalities in Chittagong, Cox’s
Bazar, Bandarban and Rangamati
Chittagong
37%
Rangamati
31%
Bandarban
7%
Co...
Statistics of causalities in CHT over 18 years
0
20
40
60
80
100
120
140
2000 2007 2008 2011 2012 2017 2018
13
127
11
17
2...
Effects of landslide
Landslides cause:
• property damage,
• injury and death and adversely
affect a variety of resources.
...
Effects and losses due to landslides
A)Direct Effects:
• Physical Damage
Debris may block roads, supply
lines (telecommuni...
Effects and losses due to landslides
C) Direct losses:
• Loss of life, property, infrastructure
and lifeline facilities, R...
Effects and losses due to landslides
A damaged house in Rangamati
Part of the Rangamati-Chittagong road collapsed in Manik...
Environmental impact on landslides
Loss of soil fertility, soil degradation.
Erosion, sediment Deposition, flash flood.
...
Possible Measures
Structural measures
• Modification of
slope/geometry
• Drainage
• Retaining Structure
• Internal slope r...
Modification of slope Geometry
Remedial Measures
Applicability in the context
of Bangladesh
1. Reducing
general slope
angl...
Drainage condition
Remedial Measures
Applicability in the context
of Bangladesh
1. Surface
Drains
• alone will seldom corr...
Bio-engineering
Remedial Measures
Applicability in the context of
Bangladesh
Vegetation
Planting
• Initial cost is very lo...
• Choose a safe location to build the home, away from steep slopes where
landslides have occurred in the past.
• Prevent d...
 Detailed analysis should be done across the dangerous hill slopes
 Numerical modeling like Finite Element Method should...
Chisty, K. U. (2014), “Landslide in Chittagong city: A perspective on hill cutting”,
Journal of Bangladesh institute of pl...
Thanks!
For
Your Worthy Patience
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LANDSLIDES AND THEIR MITIGATION MEASURES IN BANGLADESH
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LANDSLIDES AND THEIR MITIGATION MEASURES IN BANGLADESH

Prepared By
Md. Arifuzzaman Arif
MSc in Disaster Management
Department of Geography and Environment
University of Dhaka
BSc in Forestry & Wood Technology Discipline
Khulna University

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LANDSLIDES AND THEIR MITIGATION MEASURES IN BANGLADESH

  1. 1. LANDSLIDES AND THEIR MITIGATION MEASURES IN BANGLADESH Prepared By Md. Arifuzzaman Arif MSc in Disaster Management Department of Geography and Environment University of Dhaka BSc in Forestry & Wood Technology Discipline Khulna University
  2. 2. Contents  What is Landslide?  Speed of Landslide  Types of Landslide  Causes of Landslides  Where does It Occur Mostly in Bangladesh?  Statistics of Causalities  Effects of Landslide  Effects and Losses Due to Landslides  Environmental Impact on Landslides  Possible Measures  Recommendations  References
  3. 3. What is Landslide? A landslide is a downward or outward movement of soil, rock or vegetation, under the influence of gravity.  A geological phenomenon  Under the effect of gravity a wide range of ground movements  Deep failure of slopes  Shallow debris flows  Often promoted by large accumulation of soil water from rainfall, spring or melting snow  Hilly areas are vulnerable to landslide
  4. 4. Speed of Landslide • The speed of the movement may range from very slow to rapid. Landslides travel at least over than 260 feet per second. • The speed of the landslide will make an even more or less avoidable and therefore, more or less risky.
  5. 5. TYPES OF LANDSLIDES a) Rotational slides move along a surface of rupture that is curved and concave. b) Translational slides occurs when the failure surface is approximately flat or slightly undulated
  6. 6. TYPES OF LANDSLIDES c) Rock Fall Free falling of detached bodies of bedrock (boulders) from a cliff or steep slope d) Rock toppling occurs when one or more rock units rotate about their base and Collapse.
  7. 7. TYPES OF LANDSLIDES e) Lateral spreading occurs when the soil mass spreads laterally and this spreading comes with tensional cracks in the soil mass. f) Debris Flow Down slope movement of collapsed, unconsolidated material typically along a stream channel.
  8. 8. Natural Factors Gravity: Gravity works more effectively on steeper slopes. Geological factors: Geology setting that places permeable sands and gravels above impermeable layers of silt and clay or bedrock. Heavy and prolonged rainfall: slides occur often with intense rain by creating zone of weakness, also water tables rise with heavy rain makes some slopes unstable. Earthquakes: Ground vibrations created during Earthquakes. Causes of Landslides
  9. 9. Causes of Landslides Waves: Wave action can erode the beach or the toe of a bluff, cutting into the slope, and setting the stage for future slides. Volcanoes: volcanic ash deposits are prone to erosion and subjected to mud flows due to intense rainfall.  Fluctuation of water levels due to the tidal action.  Deposition of loose sediments in delta areas.
  10. 10. Causes of Landslides Anthropogenic Factors: ▸ Inappropriate drainage system ▸ Cutting & deep excavations on slopes for buildings, roads, canals & mining. ▸ Shifting(Jhum) cultivation. ▸ Deforestation. ▸ Unsustainable vegetation.
  11. 11. Where does it occur mostly in Bangladesh? ▸ Chittagong & Chittagong hill tracts*** ▸ Hill Ranges of Northeastern Sylhet ▸ Hill along the narrow northern strip of Mymensingh. ***Chittagong hill tracks have most frequent landslide The bedrock and soil structure of these hills are not stable, for which reason these areas are highly prone to landslide.
  12. 12. Statistics of causalities in Chittagong, Cox’s Bazar, Bandarban and Rangamati Chittagong 37% Rangamati 31% Bandarban 7% Cox's Bazar 18% Sylhet 5% Other 2% Casualities due to landslide (Districtwise)
  13. 13. Statistics of causalities in CHT over 18 years 0 20 40 60 80 100 120 140 2000 2007 2008 2011 2012 2017 2018 13 127 11 17 28 26 3 TOTALDEATH YEAR
  14. 14. Effects of landslide Landslides cause: • property damage, • injury and death and adversely affect a variety of resources. • Water availability, quantity and quality can be affected by landslides.
  15. 15. Effects and losses due to landslides A)Direct Effects: • Physical Damage Debris may block roads, supply lines (telecommunication, electricity, water, etc.) and waterways. • Causalities deaths and injuries to people and animals. B) Indirect Effects: • Influence of landslides in dam safety- failure of the slopes bordering the reservoir, Flooding caused by movements of large masses of soil into the reservoir. • Landslides and flooding- Debris flow can cause flooding by blocking valleys and stream channels, forcing large amounts of water to backup causing backup/ flash flood.
  16. 16. Effects and losses due to landslides C) Direct losses: • Loss of life, property, infrastructure and lifeline facilities, Resources, farmland and places of cultural importance. D) Indirect losses: • Loss in productivity of agricultural or forest lands, Reduced property values, Loss of revenue, Increased cost, Adverse effect on water quality and Loss of human productivity.
  17. 17. Effects and losses due to landslides A damaged house in Rangamati Part of the Rangamati-Chittagong road collapsed in Manikchhari, some 6 km off Rangamati town. Workers salvage furniture from a house in Manikchhari of Rangamati after the area was hit by a landslide
  18. 18. Environmental impact on landslides Loss of soil fertility, soil degradation. Erosion, sediment Deposition, flash flood. Loss of aesthetic beauty. Loss of biodiversity, destruction of ecosystem. Loss of habitats of natural wildlife that exist on the earth’s surface
  19. 19. Possible Measures Structural measures • Modification of slope/geometry • Drainage • Retaining Structure • Internal slope reinforcement • Bio engineering Non- Structural measures • Community based risk reduction • Land use vulnerability assessment and zoning • Relocation of foot hill settlements • Controlling hill cutting • Real time monitoring and early warning Two type of approaches
  20. 20. Modification of slope Geometry Remedial Measures Applicability in the context of Bangladesh 1. Reducing general slope angle • suitable only for cuts into deep soil where rotational landslides may occur. • additional modification of the land is needed. 2. Adding lightweight material • a lot of earth works need to be done. • not suitable
  21. 21. Drainage condition Remedial Measures Applicability in the context of Bangladesh 1. Surface Drains • alone will seldom correct an active landslide 2. Sub drainage • Effective in the case of presence of groundwater, cut areas and under proposed embankments 3. Hydrological effect of vegetation • Most effective drainage method • both natural and environment friendly.
  22. 22. Bio-engineering Remedial Measures Applicability in the context of Bangladesh Vegetation Planting • Initial cost is very low compared to the other techniques • Mostly suitable for Bangladesh
  23. 23. • Choose a safe location to build the home, away from steep slopes where landslides have occurred in the past. • Prevent deforestation and vegetation removal. • Avoid weakening the slope. • Plant ground cover on slopes (grasses, plants, etc.) and build retaining walls • In mudflow areas, build channels or deflection walls to direct the flow around buildings. • Support the establishment of landslide insurance. • Capacity building of local firefighting defense and community through training in order to respond to landslide impacts. • Legislation to direct a governmental or private program to reduce landslide losses should be strengthened. Recommendations
  24. 24.  Detailed analysis should be done across the dangerous hill slopes  Numerical modeling like Finite Element Method should be done with necessary field and model laboratory tests  Small scale model test should be conducted in order to understand the phenomenon of landslides  Warning system relating with rainfall should also be developed Recommendations
  25. 25. Chisty, K. U. (2014), “Landslide in Chittagong city: A perspective on hill cutting”, Journal of Bangladesh institute of planners, 7, 1-17. Galli, M. and Guzzetti, F. (2007) “Landslide vulnerability criteria: A case study from Umbria, central Italy”, Environmental management”, 40, 649-664 Islam, M. A.; Khan A. J.; Siddique A.; Saleh, A. M.; Nasrin, S. (2014), “Control of Erosion of Hill Slope Top Soil Using Geojute and Vegetation”, National Seminar on Jute Geotextiles, Dhaka, Bangladesh. Mia, M. T.; Sultana N.; Paul A. (2015) “Studies on the Causes, Impacts and Mitigation Strategies of Landslide in Chittagong city”, Bangladesh. J. Environ. Sci. & Natural Resources, 8(2): 1-5. Rahman, T. (2012) “Landslide risk reduction of the informal foothill settlements of Chittagong city through strategic design measure”, M. Sc. Thesis, BRAC University, Dhaka, Bangladesh. Sarker A. A. and Rashid A. K. M. M. (2013). “Landslide and flashflood in Bangladesh”, Springer, Japan. Schuster, L. R. and Highland, L. M. 2007. “Urban Landslides: socioeconomic impacts and overview of mitigative strategies”, Bulletin of Engineering Geology and the Environment, 66(1), 1-27. References
  26. 26. Thanks! For Your Worthy Patience
  27. 27. Ice Breaking Session

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