Landslide Risk Reductionin Sri Lanka

Eng (Dr.) Asiri Karunawardena,
Director General,
National Building Research Organisation
Sri LankaLandslides in Sri Lanka• Landslides have become a frequent natural hazard in central
highlands of Sri Lanka, which disturbs its life, causes damage toproperty, 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.
250No. of Deaths

200150
100
50

2000
2001
2002
2003
200420052006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017

0

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

Landslides in Sri Lanka

Mulhalkele 1986

Watawala 1991-92

Paradeka - 2006

Ladupita,Kiriwanella- Nuwara Eliya District 2007

Landslides in Sri Lanka

Peradeniya 2006
Kalawana 2003

Ratnapura 2003
Ratnapura 2003

Padiyapelella 2007

Reactivation of Beragala Landslide (BadullaDistrict) 2009

Landslide along major roads

Kahagolla Landslide

Outer Boundary

Damages due to Unplanned Construction

Pilimathalawa 2007

Nildandahinna - 2007

Non Engineered Construction Leading toCutting Failures Along Main Roads

Recent Cutting FailuresLandslides in Sri Lanka
Main triggering factor- Rainfall
2014-10-29,
Meeriabedda

2014-06-01

2014-12-26

Our Strategies In Landslide Risk
Management• Landslide identification and hazard zonationmapping• Integrate from Hazard to Risk management• Landslide monitoring and early warning andawareness• Landslide risk assessment for development andconstruction projects• Landslide Special Investigations• Structural mitigation works• Related policy development and planningMapping Process

Landslide Identification & HazardZonation Mapping
KeyMapFormer Landslide*
Ground Surveys*
Field Investigations*

Slope range andslope category
Bedrock geology andStructure
Colluvium andResidual soil

Available Maps*
Unpublished materials

Landform andErosion

Attribute
Terrain factors & WeightingsMaps••••••

BEDROCK GEOLOGY- 20
SOIL COVER- 10
SLOPE RANGE & CATEGORY - 25
HYDROLOGY & DRAINAGE - 20
LAND USE & MANAGEMENT - 15
LAND FORM- 10

Allocated weights for attributes andfactor maps according to the statisticalanalysis and experts knowledge

Hydrology andDrainageRainfall
Human Settlements &Infrastructure
Landuse &ManagementFinal ProductLANDSLIDEHAZARD MAP

Landslide Hazard Zonation Maps
Landslide Hazard Zonation Maps at different levels,Regional, District & Local Authority level

Map of Kandy Municipal area

Mapped Area

A typical hazard zonation map

Map of Nawalapitiya Urban Council area

Development of Flow pathsDay

2016.5.17＿17:00
2016.5.18＿ 0:00
Damage 28dead,99missing

12

DEVELOPMENT INTEGRATED LANDSLIDE HARZED MAPSBUILDING FOOTPRINTSINTEGRATED LANDSLIDE HAZARD ZONATION MAPBUILDINGS EXPOSURE TO LANDSLIDE HAZARDDATABASE ON ELEMENTS AT RISK – Data BaseSearch
option in different
levelsRetrieve datafrom selected area orbuildingDetails of the Risk Levels of thelandslide prone locations at alldistricts#Province

1 Uva

Investigation andIdentification of
Vulnerable
Communities andHigh Risk Settlements

2 Central

3 Sabaragamuwa
4 Southern
5 Western

BadullaNumber ofHouses inHigh Risk
6,418

Kandy

1,292

Nuwara Eliya

3,496

District

Matale210

Rathnapura

757

Kegalle824

Matara591

Hambantota

343

Kalutara929

Real Time Landslide Monitoring & Early Warning• 100 automated rain gauge stations in preselected catchments in landslide prone
districts

DMC
DynamicModelDOM

NBRO

Standard threshold limitsof the Rainfall forlandslides
Kalawana

EarlyWarning

Pelmadulla

Elapatha

Kahawatta

Nivithigala

Warning andEvacuation

Automatic Rainfall
Measurement System

AlertWarning

75 mm/day
100mm/day

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

Rainfall data is used in computer simulation and early warning is issued
depending on threshold limitsSite specific/CB Monitoring, Forecasting and Early Warning

Schematic diagram of the socio-technical management system onlandslide early warning

Extensometer

Tilt Sensor

Data Logger for tilt sensor

Instrumentation and Monitoring
Protection Box

Invar Wire

Extensometer
Protection Pi pe
Crack, Scarp

Landslide Movement
Movable Pile
Protection Pipe40

15.7mm/3days(7.6mm/day)

20

10-10

2016/09/01

2016/10/01

2016/11/01

2016/12/01

2016/10/01

2016/11/01

2016/12/01

2016/08/01

2016/07/01

2016/06/01

2016/05/01

2016/03/01

2016/02/01

2016/09/01

600

2016/01/01

2015/12/01

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

15- 27 Dec. 2014
Cumulative rainfall: Total 652mm
24 Dec 2014
218mm/day

4002002016/08/01

2016/07/01

2016/06/01

2016/05/01

2016/03/01

2016/02/01

2016/01/01

2015/12/01

2015/11/01

2015/10/01

2015/09/01

2015/08/01

2015/07/01

2015/06/01

2015/05/01

2015/04/01

2015/03/01

2015/02/01

2015/01/01

0

2014/12/01

Cumulative Rainfall (mm)Cumulative Rainfall (mm)800

2015/11/01

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

Rainfall (mm/day)
1000

2015/10/01

2015/09/01

2015/08/01

2015/07/01

2015/06/01

2015/05/01

2015/04/01

2015/03/01

2015/02/01

2015/01/01

2014/12/01
1200

2016/04/01

2016/7/6 Fire Incident(SB-3,4)
2016/8/1 Re-installation-20

Railfall (mm/day)

SB-1
SB-2
SB-3
SB-40

2016/04/01

Displacement (mm)30

Extensometers and Groundwater Level for Badulla Landslide
10.0mm/2days(5.8mm/day)Thankyou