Landslide Risk Reduction in Sri Lanka

Eng (Dr.) Asiri Karunawardena, Director General,

National Building Research OrganisationSri Lanka

Landslides in Sri Lanka

• Landslides have become a frequent natural hazard in central

highlands of Sri Lanka, which disturbs its life, causes damage to

property, constructed facilities and infrastructure.

• Nearly 20% of the land area from 65,000 sq. km of total area in

Sri Lanka is identified as landslide prone. Nearly 30% of total

population live in these areas.

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No. of Deaths

Number of lives lost due to landslides/slope failures:2000-2017

Landslide Potential Area

Landslides in Sri Lanka

Ladupita,Kiriwanella- Nuwara Eliya District 2007Paradeka - 2006

Mulhalkele 1986 Watawala 1991-92

Kalawana 2003

Ratnapura 2003

Ratnapura 2003

Padiyapelella 2007

Peradeniya 2006

Reactivation of Beragala Landslide (BadullaDistrict) 2009

Landslides in Sri Lanka

Landslide along major roads

Outer BoundaryKahagolla Landslide

Pilimathalawa 2007 Nildandahinna - 2007

Damages due to Unplanned Construction

Recent Cutting Failures

Non Engineered Construction Leading to Cutting Failures Along Main Roads

Landslides in Sri LankaMain triggering factor- Rainfall

2014-06-01

2014-10-29, Meeriabedda

2014-12-26

Our Strategies In Landslide Risk Management

• Landslide identification and hazard zonation mapping

• Integrate from Hazard to Risk management

• Landslide monitoring and early warning and awareness

• Landslide risk assessment for development and construction projects

• Landslide Special Investigations

• Structural mitigation works

• Related policy development and planning

Former Landslide

Slope range and slope category

Bedrock geology and Structure

Colluvium and

Landform and Erosion

Hydrology and Drainage

Rainfall

Human Settlements & Infrastructure

Landuse & Management

LANDSLIDE HAZARD MAP

*Ground Surveys

*Field Investigations

*

Available Maps*

Unpublished materials

Residual soil

Key

Map

Attribute

Maps

Final Product

Mappin

g P

rocess

Terrain factors & Weightings

• BEDROCK GEOLOGY - 20

• SOIL COVER - 10

• SLOPE RANGE & CATEGORY - 25

• HYDROLOGY & DRAINAGE - 20

• LAND USE & MANAGEMENT - 15

• LAND FORM - 10

Allocated weights for attributes and

factor maps according to the statistical

analysis and experts knowledge

Landslide Identification & Hazard Zonation Mapping

Mapped Area

A typical hazard zonation map

Landslide Hazard Zonation Maps at different levels,

Regional, District & Local Authority level

Map of Kandy Municipal area

Map of Nawalapitiya Urban Council area

Landslide Hazard Zonation Maps

Development of Flow paths

12

Day 2016.5.17＿17:00

2016.5.18＿ 0:00

Damage 28dead,99missing

DEVELOPMENT INTEGRATED LANDSLIDE HARZED MAPS

BUILDING FOOTPRINTS

INTEGRATED LANDSLIDE HAZARD ZONATION MAP

BUILDINGS EXPOSURE TO LANDSLIDE HAZARD

DATABASE ON ELEMENTS AT RISK – Data Base

Searchoption in different

levels

Retrieve datafrom selected area or

building

Investigation and Identification of

Vulnerable Communities and

High Risk Settlements

Details of the Risk Levels of the landslide prone locations at all

districts

# Province DistrictNumber of Houses inHigh Risk

1 Uva Badulla 6,418

2 Central

Kandy 1,292

Nuwara Eliya 3,496

Matale 210

3 SabaragamuwaRathnapura 757

Kegalle 824

4 SouthernMatara 591

Hambantota 343

5 Western Kalutara 929

DMC

NBRODOM

Pelmadulla

Elapatha Kahawatt

a

Nivithigala

Kalawana

Dynamic

Model

Early

Warning

Automatic Rainfall

Measurement System

Alert 75 mm/day

Warning 100mm/day

Evacuation, Off limit 75 mm/hour or 150mm/day

Warning and

Evacuation

Standard threshold limits

of the Rainfall for

landslides

Rainfall data is used in computer simulation and early warning is issued depending on threshold limits

Real Time Landslide Monitoring & Early Warning

• 100 automated rain gauge stations in pre-selected catchments in landslide prone districts

Schematic diagram of the socio-technical management system on

landslide early warning

Site specific/CB Monitoring, Forecasting and Early Warning

Extensometer

Data Logger for tilt sensor

Tilt Sensor

Protection Box

Extensometer

Invar Wire

Crack, Scarp Protection Pi pe

Movable Pile Protection Pipe

Landslide Movement

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Disp

lacem

ent (

mm)

Extensometers and Groundwater Level for Badulla Landslide

SB-1

SB-2

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SB-4

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Railfa

ll (mm

/day

)

Rainfall (mm/day)

Cumulative Rainfall (mm)

15- 27 Dec. 2014Cumulative rainfall: Total 652mm

8 Aug. -21 Dec. 2014Cumulative rainfall: Total 873mm

24 Dec 2014218mm/day

Cumu

lative

Rainf

all (m

m)

Horizontal Drainage Drilling 2016/6/15-Surface Drainage Ditch 2016/6/24-

2016/7/6 Fire Incident(SB-3,4)2016/8/1 Re-installation

15.7mm/3days

(7.6mm/day)10.0mm/2days

(5.8mm/day)

Instrumentation and Monitoring

Thank

you