Landslides in the Hilly Regions of Bangladesh and Mitigation Measures

Group 3Name of the Student Roll NoName of the Student Roll No.

Anjalina Diana Podder 1101Nazifa Anjum 1103Dilruba Farzana 1104Rowshon Ara 1108Farzana Rahman Lopa 1111Farzana Rahman Lopa 1111Khadija Akhter 1115Protity Rahman 1119Zerin Tasmin 1121Md. Hamidur Rahman 1122Ashfaqur Rahman Asha 1149Ashfaqur Rahman Asha 1149Efaz Ahmed 1150

Contents IntroductionTypology

Context of Chittagongyp gy

Causes of LandslideHotspot

ChronologyHigh risk areaHotspot

Where it occurs High risk areaCase study

mostly in Bangladesh

Effect/ImpactMitigation

Major causes: g

Recommendation

Introduction: What is Landslide?• Definition:

According to United States Geological Survey (USGS), “Theterm landslide includes a wide range of groundterm landslide includes a wide range of groundmovement, such as rock falls, deep failure of slopes, andshallow debris flows. Landslides are mainly caused byexcessive rainfall earthquakes and changes in groundexcessive rainfall, earthquakes, and changes in groundwater and sometimes change of a slope by manmadeconstruction. Not every time it is occurred by natural

f ti it l b i iti t d b dreason, for sometimes it can also be initiated by manmadehazardous actions. Besides, Landslide can also occurbecause of the non-engineered construction, non-engineered excavation and deforestation that lead intosoil erosion.”

What is Landslide (cont.)• A landslide is a downward or outward movement of soil, rock or

vegetation under the influence of gravityvegetation, under the influence of gravity.• Factor of Safety(F);

F = Resisting Force(R)Driving Force(D)

When, F< 1 = landslide occur

R i ti f (R) ti• Resisting forces(R) preventing the mass from sliding down the slope are inverselyproportional to the same hill slope angle and directly proportional to the friction angle ofthe materialthe material.

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• In addition, the resisting forces can beforces can be significantly reduced in case of rain or earthquake vibrations.

• Three distinct physical events occur during a landslide: the initial slope failure theslope failure, the subsequent transport, and the final deposition pof the slide materials.

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Speed of LandslideTh d f h f l id• 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 lessThe speed of the landslide will make an even more or less avoidable and therefore, more or less risky.

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1. Rotational 4. Rock topplingslides

2 T iti l

pp g5.Lateral

di2. Transitional slides

spreading 6 Flow

3. Rock fall6. Flow

Types of movement and materials involved with landslide Types of movement Types of materialsTypes of movement Types of materials

Bedrock Soils

Coarse Grained Fine grained SoilSoil

Falls Rock fall Debris fall Earth fall

Topples Rock topples Debris Topples Earth topplesTopples Rock topples Debris Topples Earth topples

Slides Rotational Rock slide Debris slide Earth slide

Transitional

Lateral spreads Rock spread Debris spread Earth spread

Flows Rocks flow Debris flow Earth flow

Complex: Combination of two or more types of movement

Source: www.usgs.gov

Rotational slidesa) Rotational slides move along a surface of rupture that is curved and concave.

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Transitional slides b) Translational slides occurs when the failure surface is approximately flat or slightly pp y g yundulated

) R k F llRock fall

c) Rock Fall:Free falling of detached bodies of bedrock (boulders) from a cliff or steep slope

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d) R k t li h

Rock toppling d) Rock toppling occurs when one or more rock units rotate about their base and CollapseCollapse.

e) Lateral spreading occurs when the soil massLateral spreading

e) Lateral spreading occurs when the soil mass spreads laterally and this spreading comes with tensional cracks in the soil masstensional cracks in the soil mass.

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Flow f) Flow: Down slope movement of collapsed, unconsolidated material typically along a stream channel.

Causes of LandslidesNatural Factors:Natural Factors:

Gravity: Gravity works more effectively on steeper slopes.Geological factors: GeologyGeological factors: Geology setting that places permeable sands and gravels above impermeable layers of silt andimpermeable layers of silt and clay or bedrock.Heavy and prolonged rainfall:

lid ft ith i t i bslides occur often with intense rain by creating zone of weakness, also water tables rise with heavy rain makes some slopes unstable.slopes unstable.Earthquakes: Ground vibrations created during Earthquakes.

W

Causes of Landslides (Cont…)

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.Fl t ti f t l l d t th tid lFluctuation of water levels due to the tidal action.Deposition of loose sediments in delta areasareas.

Anthropogenic Factors:Causes of Landslides (Cont…)

gInappropriate drainage system: Surface runoff of irrigated water on slopes exposes soil under cultivation to erosion. Cutting & deep excavations on slopes for buildings, roads, canals & mining: causes modification of natural slopes, blocking of surface drainage, loading of critical slopes and withdrawal to toe support promotingwithdrawal to toe support promoting vulnerability of critical slopes. Shifting(Jhum) cultivation.DeforestationDeforestation.Unsustainable vegetation.

Unsustainable vegetation Deforestation

Hill cutting for road expansiong p

Hill cutting for brick field

HotspotsAnywhere with steep slopes and weatheringAnywhere with steep slopes and weathering.High mountain ranges, sheer cliffs and steep sided rider valleys where volcanoes erupt and along y p gcoasts.

Where do it occurs mostly in Bangladesh?C & C• Chittagong & Chittagong hill tracts***

• Hill Ranges of Northeastern• Hill Ranges of Northeastern Sylhet

• Hill along the narrow northern strip of Mymensingh.

***Chittagong hill tracks have most frequentChittagong hill tracks have most frequent landslideThe bedrock and soil structure of these hills are not stable, for which ,reason these areas are highly prone to landslide.

MAJOR CAUSES: CONTEXT OF CHITTAGONGCONTEXT OF CHITTAGONG

Natural• Soft (less rocky) soil based hills• Soft (less rocky) soil based hills• Compact high rainfall• Flash-floods are the in hill tracks ofFlash floods are the in hill tracks of

BangladeshManmade• Hill cutting for any causes• Unplanned settlement by cutting hills• Jhoom cultivation without risk

assessment

Chronology of major landslidesDate Landslide Area1968 Kaptai – Chandraghona Road

1970 Ghagra – Rangamati Road

May 30, 1990 Jhagar beel area, Rangamati

July, 1997 Charaipada, Bandarban

August 11 & 13, 1999 Bandarban & Chittagongg , g g

June, 2000 Chittagong University Campus & Chittagong City

J 2007 Chitt Cit d Chitt U i itJune, 2007 Chittagong City and Chittagong University Campus

Recent landslides with consequences in ChittagongDate Location  Consequence 

3 August 2005  Nizam Road Housing Society  2 people killed and 12 injured 

11 June 2007  Mati Jharna Colony of LalkhanBazar

128 people killed and 100 injured 

10 September 2007  Nabi Nagar in Chittagong  2 people killed 18 August 2008 Matijharna in Chittagong 11 people killed and 25 injured18 August 2008  Matijharna in Chittagong  11 people killed and 25 injured 

26 June 2012  Lebubagan Area and Foys Lake  90 people killed and 150 injured 

01 July 2011  Batali hill, Tigerpass intersection  15 people killed and 150 injured 

28 July 2013  Lalkhan Bazar 2 people killed 19 July 2015 Bayezid and Lalkhan Bazar areas of 

Chittagong6 people killed

Landslide Vulnerability in Chittagong City

High Risk Areas1. Lebubagan Area2 Baizid Bostami Area2. Baizid Bostami Area3. Kushumbag Residential Area4. Batali Hill Area5 M tijh A5. Motijharna Area

CASE STUDYCHITTAGONG Bangladesh June 27 2012 (AFP)CHITTAGONG, Bangladesh, June 27, 2012 (AFP) -More than 90 people have been killed inlandslides in southeast Bangladesh after threedays of rains that triggered flash floods

Thousands of poor people in the region live inshanty houses at the foot of the hills, defyingrepeated warnings from authorities about therepeated warnings from authorities about thedanger of landslides, which are common duringthe monsoon season.

According to the state Disaster ManagementInformation Centre, around 50,000 people wereaffected by the flash floods, and many of themforced to take shelter on higher groundforced to take shelter on higher ground.

Post-landslide conditions in Motijharna Area

Statistics• Since 1997, landslides have caused the death

f l 235 l i i i f lof nearly 235 people in various informal settlements within Chittagong city and its adjacent small urban centersadjacent small urban centers.

• Different studies show that approximately 500 000 impoverished people are currently500,000 impoverished people are currently living in informal settlements on the risky foothills of Chittagong city.g g y

EffectsLandslides cause:

• property damage• property damage, • injury and death and adversely

ff t i t faffect a variety of resources. • Water availability, quantity and

quality can be affected by landslides.landslides.

Effects and losses due to landslidesA) Direct Effects:• Physical Damage-Debris may block roads supplyPhysical Damage Debris may block roads, supply

lines (telecommunication, electricity, water, etc.) and waterways.

• Causalities- deaths and injuries to people and animals.

B) Indirect Effects:B) Indirect Effects:• Influence of landslides in dam safety- failure of the

slopes bordering the reservoir, Flooding caused by p g , g ymovements of large masses of soil into the reservoir.

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• Landslides and flooding- Debris flow can cause flooding by bl ki ll d t h l f i lblocking valleys and stream channels, forcing large amounts of water to backup causing backup/ flash flood.

C) Di t lC) Direct losses:• Loss of life, property, infrastructure and lifeline facilities,

Resources, farmland and places of cultural importance.esou ces, d d p ces o cu u po ce.

D) Indirect losses:• Loss in productivity of agricultural or forest lands• 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.

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Environmental impact on landslides• The topography of the earth’s surface• The character and the quality of rivers andThe character and the quality of rivers and

streams and the groundwater flowThe forest that co er m ch of the earth’s• The forest that cover much of the earth’s surface

• The habitats of natural wildlife that exist on the earth’s surface

Landslide Issues at National Level1. Absence of Early Warning System2 L k f St t l M2. Lack of Structural Measures3. Lack of Organizational Coordination4. Absence of Policy implementation

Landslide Mitigation in Chittagong

• Landslide mitigation refers to lessening the effect of l d lid b t ti i dlandslides by constructing various man made projects at slopes vulnerable to In addition to shallow erosion or reduction of sheer strengthshallow erosion or reduction of sheer strength caused by seasonal rainfall, causes triggered by anthropic activities such as adding excessive weight a t op c act v t es suc as add g e cess ve we g tabove the slope, digging at mid-slope or at the foot of the slope, can also be included.

• Volunteers using loudspeakers warned people about the danger of heavy rainfall and landslides in Cox's Bazaar, officials say, but local people and

till l ft h l l h fl d trescuers were still left helpless when floodwater suddenly inundated dozens of villages and severely disrupted communicationsdisrupted communications.

• Chittagong has been hit repeatedly by monsoon rain and landslides in recent years. As a result, the government has tried to tighten rules on wheretried to tighten rules on where development can take place but with littllittle success.

• Retention walls need to be built in landslides areas in Bangladesh, otherwise every time a landslide occurs, loss of life will be seen.

Mitigation and Prevention MeasuresLandslide may be prevented by stabilization of slope. There are

three basic approaches:• Geometric methods, in which the geometry of the hillside slope is , g y p

changed. Rock slope and soil slope geometric modifications will require different techniques.

• Hydrogeological methods in which an attempt is made to lower• Hydrogeological methods, in which an attempt is made to lower the groundwater level or to reduce the water content of the material.

• Mechanical methods, in which attempts are made to increase the shear strength of the unstable mass or to introduce active external forces (e.g. anchors, rock or ground nailing) or passive external forces (e.g. structural wells, piles or reinforced ground) to oppose the destabilizing forces.

Recommendations• 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

wallswalls• In mudflow areas, build channels or deflection walls to direct the flow

around buildings.• Financial Mechanism: Support the establishment of landslide insurance.• Capacity building of local firefighting defense and community through

training in order to respond to landslide impacts. g p p• Legal and Policy: Legislation to direct a governmental or private program

to reduce landslide losses should be strengthened.

Recommendations (Cont.)( )• Awareness generation: Educate the public about signs that a

landslide is imminent so that personal safety measures may be taken. Bring education to school children at root level so that they are aware of the consequences and that they can disseminate knowledge among their community members.disseminate knowledge among their community members.

• Inclusive Approach in DRR: Ensure that the members of community are seen as inclusive in terms of participation, decision making, recognition of diversity, tailored approach and removal of barriers. Recognize the capabilities of the community and identify the community resources to preventcommunity and identify the community resources to prevent any incident.

Conclusion• Hill cutting and heavy rainfall are prime factors for landslides in

Chittagong that causes death to hundreds people with a greatproperty loss. This catastrophe could be checked by controllingth l d bbi f t l d d b d t di ththe land grabbing of government land and by understanding therainfall pattern and its true relationship with landslide in theregion. Detailed land use planning of the city, a landslidedatabase landslide mapping and geophysical analysis of thedatabase, landslide mapping and geophysical analysis of thecity is essential to minimize landslides and its impacts in theregion. In addition, a landslide contingency plan should bein place that would direct proper coordination of the needs ofin place that would direct proper coordination of the needs ofcrisis period. Furthermore, incorporating international resourceswithtotal plan and actions will enhance the capacity of concernedtotal plan and actions will enhance the capacity of concernedorganizations in dealing the hazard.

References• Landslide and its preparedness in Hilly areas of• Landslide and its preparedness in Hilly areas of

Bangladesh, www.adpc.net• Landlisde early warning system for Chittagong y g y g g

Metropolitan area, www.icimod.com • Heavy rains, landslide kills 94 in Bangladesh-

B l d h/ R li f W bBangladesh/ Relief Web• Landslide Tragedy of Bangladesh by Md. Golam M.

Sarwar – Academia EduSarwar Academia.Edu• News by The Daily Star• Landslide by Banglapedia, en.banglapedia.orgy g p , g p g• Landslide, www.wikipedia.com

Landslides are killers. This has to be stopped now.

L t b Let us be aware,

Let us stand together Let us stand together.

Our response must start Our response must start now!now!