slope safety preparedness in southeast asia for effects … · slope safety preparedness in...

JTC-1 TR3 Forum

Presented by

Harianto Rahardjo

Slope Safety Preparedness in

Southeast Asia for Effects of

Climate Change

School of Civil and Environmental Engineering

Nanyang Technological University

Singapore

Joint Technical Committee JTC-1

17-18 November 2015

• Singapore : Dr. Alfrendo Satyanaga (NTU); Dr. Aaron Sham

Wai Lun, Er. Ong Chang Leng, Kelvin Hoon (BCA)

• Malaysia : Prof. Bujang Bin Kim Huat, Mohammad Hamed

Fasihnikoutalab, Dr. Afshin Asadi (UPM)

• Indonesia : Prof. Paulus Rahardjo (UNPAR)

• Thailand : Prof. Apiniti Jotisankasa (Kasetart University,

Thailand)

• Vietnam : Prof. Trinh Minh Thu, Tran The Viet (Water

Resources University)

Co-Authors

• Intergovernmental Panel on Climate Change (IPCC, 1990,

1995, 2001, 2007, 2013) report

• Kyoto Protocol (Oberthur and Ott, 1999)

• Doha amendment to the Kyoto Protocol (Doha, 2012)

• United Nation Framework Convention on Climate Change

(UNFCCC) report (United Nation, 1993)

90 % human activities cause the increase in CO2, CH4,

NO2, O3 and halocarbons

Reports on Climate Change

• Growing sign of the global climate changes

• If carbon emissions from human activities continue to grow,

climate change will accelerate

• Singapore’s vision following IPCC report:

“Singapore is expected to be a climate resilient global

city that is well positioned for green growth and remains a

vibrant and livable nation for our future generations” – DPM

Teo Chee Hean

Intergovernmental Panel on Climate

Change (IPCC) Report

• Global Platform for Disaster Risk Reduction(Second Session, Geneva, Switzerland, 16-19 June 2009)

Global Climate Change

Ban Ki-moon addressed that

we face a more threatening future

from natural hazards … First by

more extreme weather…

Risk reduction is an investment, it

is our first line of defense in

adapting to climate change.

Climate change could lead to more severe fluctuations in weather patterns, resulting in geo-disaster that are thought to be water-related disasters

Committees and Workgroup (National

Climate Change Secretariat, 2012)

Adaptation for Climate Change Impacts

• 4-fold approach (NCCS, 2012)

Reduce carbon emissions in

all sectors

Be ready to adapt to climate

change

Harness green growth

opportunities

Forge partnerships

Climate Change Studies in Singapore

Effect of Climate Change on Slope Stability

Landslide at Bukit Antarabangsa, Kuala Lumpur,

Malaysia on 6 December 2008


Landslide in Padae-Tak, Thailand


Landslide along

Kuala Lumpur-

Karak highway on

4 November 2015


Landslide in Kennon Road, Mankayan,

Philippine on 22 August 2015


More than 20 slope failures

occurred on 26 February 1995

in NTU campus, Singapore


Slope failure in Bukit Batok, Singapore (2006)

Effects of Climate Change on Unsaturated

Soil Behavior

Negative pore-water

pressures (total suction = matric

suction + osmotic

suction)

Positive pore-water

pressures

Potential evaporation (air temperature, wind

speed, relative humidity, vapor pressure)

Precipitation

Water table

Upward flux (pore-water

pressures less than hydrostatic)

Downward flux (pore-

water pressures greater than hydrostatic)

Hydrostatic

Pressure

equal to zero

Ground temperature

Air vapor pressure

Soil temperature

Soil vapor pressure

Capillary fringe

Unsaturated

zone

Saturated

zone

Mechanism of Rainfall-induced Slope

Failure

Saturated zone

Unsaturated zone

Tension cracks

Wetting front

Transpiration

Infiltration

Ground water table

Rise in water table

Slip surface

Rainfall Rainfall

Potential evaporation = f (air temperature, relative humidity, solar radiation, wind speed)

Actual evaporation = f(potential evaporation, soil temperature, soil suction)

How do we adapt to climate change?

• Investigate main influencing parameters

• Perform a field monitoring and numerical analysis

• Establish preventive measure

Reduction of high risk and/or high impact

Main influencing parameters

• Flux boundary

- Rainfall/runoff

- Ground water level

- Evaporation

• Soil properties

• Slope geometry

Climate change-related parameters

Location of Site Investigation in Singapore (Research Collaboration between NTU and HDB)

26

Location of Instrumented Residual Soil Slope in Singapore (Research Collaboration between HDB and

NTU

Yishun

NTU-CSE,

NTU-ANX

Mandai

Marsiling

Havelock

Ang Mo Kio

Telok

Blangah

Bedok

Tampines

Sedimentary

Jurong Formation

Bukit Timah

Granite

Old

Alluvium

Kallang Alluvial

FormationJalan Kukoh

Pasir RisLorong

Halus

27

Field Instrumentation to Study the Effect of

Climate Change on Slope Stability

P1

P2

P3

Rain

gauge

Tensiometer

Soil moisture

sensor

Temperature

sensor

A B C D

Runoff

boundary

Flume

Weather

station

Rain gauge

Piezometer

Time-domain

Reflectometry

Tensiometer

Weather

station

Data logger

Solar panel

Temperature sensor

Solar panelData logger

Notes:

P = piezometer

A, B, C, D = tensiometer

and soil moisture sensor

at different depth

Instrumented slope

(Rahadjo et al., 2014)

Jurong Formation

Bukit Timah Granite

Old Alluvium

Instrumented slope

(Rahadjo et al., 2003a)

Instrumented Slope

Cut-away view

Slope Responses: Runoff Generation and

Infiltration

Field Installation of a Flume with Water Depth

Probe for Runoff Measurement

31

(1) Rainfall / runoff

Rainfall amount (mm)

0 50 100 150 200 250

Infi

ltra

tio

n (

%)(

as

pe

rce

nta

ge

of

rain

fall

)

0

20

40

60

80

100

120Natural rainfall (Rahardjo et al., 2005)

Simulated rainfall (Rahardjo et al., 2005)

Trend Line (Rahardjo et al., 2005)

Natural rainfall at Jalan Kukoh (5 October 2008

Natural rainfall at Jalan Kukoh (7 October 2008

Field Monitoring

Recorded on 12 Dec 1998

at residual soil slope from

sedimentary Jurong

Formation

Relationship between

infiltration and rainfall

amount (Rahardjo et al.,

2013)

Instruments for Measurement of

Positive Pressures

Piezometer

Porous Stone Piezometer Tips connected to 25 mm Diameter PVC Standpipes

Jet-Fill Tensiometer for Measuring Positive and Negative Pore-water Pressure

Type of Tensiometer used in Residual Soil Slope in Singapore

Jet-fill

tensiometer

manufactured by

Soilmoisture

ICT tensiometer

transducer

(2) Ground water level

Field Monitoring

Residual soil slope from

sedimentary Jurong

Formation (Rahardjo et

al., 2010)

Residual soil slope from

Bukit Timah Granite

(Rahardjo et al., 2010)

Weather Station

Evaporation Pan

(3) Evaporation (air & soil temperature)

Date

16-Oct-98 30-Oct-98 13-Nov-98 27-Nov-98 11-Dec-98 25-Dec-98

Te

mp

era

ture

(o

C)

22

24

26

28

30

32

34

36

38

Air temperature

Temperature of soil (midnight)

Temperature of soil (noon)

Date

0:00:00 4:00:00 8:00:00 12:00:00 16:00:00 20:00:00 0:00:00

Ts -

Ta (

oC

)

0

1

2

3

4

Noon (12:00 pm)

Night (12:00 am) Night (12:00 am)

Field Monitoring

Variations of air and soil

temperature for residual

soil slope from Bukit

Timah Granite (Rahardjo

et al., 2013)

Typical variation of

differences between air

and soil temperature for

residual soil slope from

Bukit Timah Granite

(Rahardjo et al., 2013)

Numerical Model

(Seepage Analysis)

t

h

g

m

y

h

y

k

x

h

x

k

y

hk

x

hk

w

wyx

yx

r

2

2

2

2

2

=+++

Seepage governing equation (two-dimensional)

0

20

40

60

80

100

120

140

160

Rai

nfa

ll in

ten

sity

(mm

/h)

Time, t (hours)0 1 2 3 4

No flow

Total head

No flow

0

Total head

No flow

Jln. Kukoh - Row C (26 September 2008)

Pore Water Pressure (kPa)-30 -20 -10 0 10 20 30 40 50 60

Ele

va

tion

, z (

m)

102

104

106

108

t = 0 (Numerical)

t = 2.5h (Numerical)

t = 5h (Numerical)

t = 0h (Field Data)

t = 5h (Field Data)

0.64 m depth

1.31 m depth

1.66 m depth2.08 m depth

Pore Water Pressure (kPa)

Ele

vati

on

(m)

Rainfall

Legend for Variables in Figures 11 and 12 kx = water coefficient permeability in the x-direction ky = water coefficient permeability in the y-direction ∂hw/∂x = hydraulic head gradient in the x-direction ∂hw/∂y = hydraulic head gradient in the y-direction m2w = coefficient of water volume change with respect to a change in matric suction

rw = density of water g = gravitational acceleration t = time c’ = effective cohesion W = the total weight of the slice of width “b” and height “h” b = the width of a slice uw = pore-water pressure

’ = effective friction angle

= the angle between the tangent to the center of the base of each slice and the horizontal FoS = factor of safety

Numerical Model

(Slope Stability Analysis)

FoS

mα

bW

m

'w

ub

Wc'

FoS

tansincos;

sin

tan

+=

+

=

Janlan Kukoh slope (Jurong Formation)(rainfall event 26 September 2008)Marsiling Road slope (Bukit Timah Granite)(rainfall event 11 March 2008)

, F

oS

43

• Uniform temperature and pressure, high

humidity and abundant rainfalls.

• Maximum rainfall in one year is usually observed

between December and January.

• The driest month in one year is usually in June.

• On 19 December 2006, Singapore experienced

the third highest amount of rainfall for one day

(366 mm) in 75 years.

Climatic Condition in Singapore

Prediction of Maximum Annual Rainfall in

Singapore (based on Historical Rainfall

Data from 1985 to 2014)

Jurong Pier

Choa Chu Kang (West)

Kranji Reservoir

Mandai

Macritchie Reservoir

Kampong Bahru

Tanjong Katong

Buangkok

Changi

9 weather stations are selected in this study

Prediction of Maximum Annual Rainfall in

Singapore (for 1 Hour Rainfall Duration)

Maximum rainfall intensity (mm/h) = (1.36 * year) - 2625

46

• Seepage and stability analyses were carried out

using Seep/W and Slope/W, respectively to

compare the variations of factor of safety of

residual soil slope from Old Alluvium at Punggol,

Singapore under different rainfall intensities of

80 mm/h (year 1990), 114 mm/h (year 2015),

155 mm/h (year 2040) and 182 mm/h (year

2065) for rainfall durations of 110 minutes.

Seepage and Stability Analyses

Numerical Model of Residual Soil Slope

from Old Alluvium at Punggol

= 20 kN/m3; c’ = 10 kPa; ’ = 30o; b = 15o

SWCC of Residual Soil from Old Alluvium

at Punggol

Matric suction, ua-uw (kPa)

10-2 10-1 100 101 102 103

Vo

lum

etr

ic w

ate

r co

nte

nt,

w

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Air-entry value = 70 kPaFredlund and Xing (1994) fitting parameters:a = 48 kPan = 1.36m = 4.64

Permeability Function of Residual Soil from

Old Alluvium at Punggol

Matric suction, ua-u

w (kPa)

10-2 10-1 100 101 102 103

Co

efi

cie

nt

of

perm

eab

ilit

y,

kw

(m

/s)

1e-4

1e-5

1e-6

1e-7

1e-8

1e-9

1e-10

1e-11

1e-12

ks = 7.9e-6 m/s

Leong &Rahardjo (1997) fitting parameters:a = 19 kPab = 1.11c = 2.67p = 4.10

Variations of Factor of Safety with Year for

Residual Soil Slope from Old Alluvium at

Punggol in Singapore

Current Intensity-Duration-Rainfall (IDF)

Curve of Singapore

Current Intensity-Duration-Rainfall (IDF)

Curve of Singapore

Proposed equation for

best fitting IDF curve of

Singapore

Duration, td (min)

1 10 100 1000

Inte

ns

ity,

I T(m

m/h

)

10

100

1000

Return Period, Tr (years)

2

5

10

25

50

100

d

c

d

trT

b

t

II

+

=

expln

Review of IDF Curve of Singapore (based

on Historical Rainfall Data from 1990 to

2010)

Sedimentary Jurong Formation

Bukit Timah Granite

Old Alluvium

Legend:

1

2

3

4

56

7

8

9

10

11

12

13 14

15

Note: 1 = Kranji Reservoir; 2 = Tengah; 3 = Choa Chu Kang; 4 = Jurong West;

5 = Jurong Pier; 6 = Jurong East; 7 = Bukit Panjang; 8 = Sembawang;

9 = Macritchie Reservoir; 10 = Queenstown; 11 = Tanjong Pagar; 12 = Seletar;

13 = Serangoon; 14 = Paya Lebar; 15 = Changi

Prediction of Modified Intensity-Duration-

Rainfall (IDF) Curve of Singapore

Frequency distribution function (Gumbel, 1958):

SKPP TaveT +=

Amount of rainfall for certain rainfall duration, PT (mm):

Pave = the average of annual maximum rainfall for certain

rainfall duration (mm)

S = standard deviation of annual maximum rainfall for

certain rainfall duration (mm)

Prediction of Modified Intensity-Duration-

Rainfall (IDF) Curve of Singapore

Frequency distribution function (Gumbel, 1958):

+=

1lnln5772.0

6

r

rT

T

TK

Gumbel frequency factor, KT :

d

TT

t

PI =

Rainfall intensity, IT (mm/h):

td = rainfall duration (h)

Modified Intensity-Duration-Rainfall (IDF)

Curve of Singapore

Duration, td (min)

1 10 100 1000

Inte

ns

ity,

I T(m

m/h

)

10

100

1000 Best fitting

2

10

50


Modified Intensity-Duration-Rainfall (IDF)

Curve of Singapore

Duration, td (min)

1 10 100 1000

10

100

1000


5

25

100

Best fitting

58

• Seepage and stability analyses were carried out

using Seep/W and Slope/W, respectively to

compare the variations of factor of safety of

typical residual soil slope from Bukit Timah

Granite, Singapore under different rainfall

intensities of 22 mm/h (original IDF curve) and

36 mm/h (modified IDF curve) for rainfall

durations of 10 hours.

Seepage and Stability Analyses

No flow (Q=0)

Total head (H)

No flow (Q=0)

Total head (H)

Slope angle = 27o

Rainfall (q)

Numerical Model of Residual Soil Slope

from Bukit Timah Granite

= 20 kN/m3; c’ = 16.5 kPa; ’ = 26o; b = 13o

SWCC of Residual Soil Slope from Bukit

Timah Granite

Matric suction, ua-uw (kPa)

10-2 10-1 100 101 102 103 104 105 106

Vo

lum

etr

ic w

ate

r co

nte

nt,

w

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Residual soil from Bukit Timah GraniteAir-entry value = 1 kPa

Permeability Function of Residual Soil

Slope from Bukit Timah Granite

Matric suction, ua

-uw

(kPa)10-1 100 101 102 103 104 105 106

Co

efi

cie

nt

of

pe

rme

ab

ilit

y,

kw

(m

/s)

1e-4

1e-5

1e-6

1e-7

1e-8

1e-9

1e-10

1e-11

1e-12

1e-13

Residual soil from Bukit Timah Granite

ks = 7e-5 m/s

Variations of Factor of Safety with Year for

Residual Soil Slope from Bukit Timah

Granite in Singapore

Time (Minutes)

0 5 10 15 20 25

Fa

cto

r o

f S

afe

ty,

Fo

S

1.0

1.1

1.2

1.3

1.4

22 mm/h for 10 hours (Original IDF curve)

36 mm/h for 10 hours (Modified IDF curve)

Rain stopped

Time (Hours)

Preventive measures

• Horizontal drain

• Vegetation or green technology

• Capillary barrier system

Preventive Measures to Maintain

Unsaturated Zone in Slope

64

Effect of Vegetation on Slope Stability at

Tampines, Singapore

Tensiometers

TE4TB4TA4

TE5TB5TA5

Notes:

TE4, TE5 =Tensiometers with 0.3 m depth

TA4, TA5 = Tensiometers with 0.6 m depth

TB4, TB5 = Tensiometers with 1.2 m depth

Rain GaugeSolar Panel

Data Acquisition

System (DAS)Green Technology

using Shrub

(Orange Jasmine) Green

Technology

using Grass

(Vetiver)

Vetiver

characteristics

It has massive fine

structured root system

which can grow very fast.

In some cases the root

system can grow up to 2-4

meter in depth.

Factor of Safety Variations for Slope with

and without Vegetative Cover (Rahardjo et

al., 2014)F

ac

to

r o

f S

afe

ty, F

oS

1.0

1.5

2.0

2.5

3.01

Au

g 1

0

8 A

ug

10

15

Au

g 1

0

22

Au

g 1

0

29

Au

g 1

0

5 S

ep

10

12

Sep

10

19

Sep

10

26

Sep

10

3 O

ct 1

0

10

Oc

t 1

0

17

Oc

t 1

0

24

Oc

t 1

0

31

Oc

t 1

0

7 N

ov 1

0

14

No

v 1

0

21

No

v 1

0

28

No

v 1

0

5 D

ec

10

12

De

c 1

0

19

De

c 1

0

26

De

c 1

0

2 J

an

11

Date

Ra

infa

ll In

te

ns

ity, m

m/h

0

50

100

150

200

Original Slope without vegetation

Slope with Vetiver grassSlope with Orange Jasmine

Capillary Barrier System (CBS) for

Minimizing Rainwater Infiltration

Construction of Coarse-grained Layer

69

Construction of Fine-Grained Layer

Constructed Capillary Barrier for Slope

Repair

Tensiometers for Studying the

Effectiveness of Capillary Barrier in the

Field

CBS with recycled

concrete aggregate

for coarse grained

layer

CBS with

geodrain for

coarse

grained layer

Green Technology

using Shrub

(Orange Jasmine)

Green

Technology

using Grass

(Vetiver)

Depth of Tensiometers:

TA1 = 0.63 m TA2 = 0.61 m TA3 = 0.67 m

TB1 = 1.18 m TB2 = 1.23 m TB3 = 1.29 m

TC1 = 1.48 m

TD1 = 1.76 m TD2 = 1.81 m TD3 = 1.84 m

TA1 TB1 TC1 TD1 TA2 TB2 TD2

Tensiometers

Capillary Barrier System at Tampines

TA3 TD3TB3

Original slope

Factor of Safety Variations for Slope with

and without Capillary Barrier System

Fa

cto

r o

f S

afe

ty,

Fo

S

1.0

1.5

2.0

2.5

3.0

3.5

Slope with capillary barrier system

Original slope without capillary barrier system

1 J

un

10

8 J

un

10

15

Ju

n 1

0

22

Ju

n 1

0

29

Ju

n 1

0

6 J

ul 1

0

13

Ju

l 1

0

20

Ju

l 1

0

27

Ju

l 1

0

3 A

ug

10

10

Au

g 1

0

17

Au

g 1

0

24

Au

g 1

0

31

Au

g 1

0

7 S

ep

10

14

Se

p 1

0

21

Se

p 1

0

28

Se

p 1

0

5 O

ct

10

12

Oct

10

19

Oct

10

26

Oct

10

2 N

ov 1

0

9 N

ov 1

0

16

No

v 1

0

23

No

v 1

0

30

No

v 1

0

7 D

ec 1

0

14

De

c 1

0

21

De

c 1

0

28

De

c 1

0

4 J

an

11

Date

Ra

infa

ll In

te

ns

ity, m

m/h

0

50

100

150

200

Slope Safety Preparedness in Singapore

Singapore Land Authority (SLA)

• SHARES – Slope Hazard Analysis & Repository System

Combination of geospatial tools and analytical Hierarchy

Process (AHP)

Capturing of data from past

slope failures

Displaying captured past slope

failure

Resultant map classified into

different categoriesProximity-impact analysis

SHARES

Development of Landslides Susceptibility

Model for Singapore

Rainfall Triggered Slope Failure

Zone 2 Zone 3

Zone 4

Building and Construction Authority (BCA)

• Building Control Regulation

• 3-stage slope management system


Pro-active initiatives:

1. The mandatory periodic structural inspection (PSI) regime is one that is proactive and unique to Singapore.

2. BCA conducts public seminars to communicate with the public highlighting regular inspection and maintenance are critical as the slope stability


• Response to dangerous slope incident


Summary for Singapore

Slope failures occurred during or after rainfall

Singapore government uses a combination of geospatial

tools and analytical hierarchy process (AHP) to create a

slope hazard analysis and repository system (SHARES)

Vision of SHARES: identification of susceptible locations,

and implementation of slope protection and crucial

preventive measures

Development of Landslide Susceptibility Model for

Singapore

Slope Safety Preparedness in Thailand

Landslide at Padae Tak, Northern Thailand

Landslide occurred after 3 continuous days of rainfall (total

amount of rainfall = 300 mm)

Landslides and rainfall history

Padae Tak, Northern Thailand Natum, Surathani, Southern Thailand

Relationship between Rainfall Pattern and

Landslides in Thailand

Departments of Highways, Water Resources, Mineral

Resources and Petroleum are active in mitigation of

landslide risks including use of bio-engineering technique.

Kasetsart University has been active in understanding the

hydro-mechanical properties of unsaturated residual soils

and interaction between climate and slope stability.

Monitoring Granitic Fill Slope (covered with

Vetiver and local grasses) at Doi-intanon,

Chiangmai using tensiometers

2.606.80

7.70

10.80

-0.500.80

4.90

2.50

2.501.40

5.40

-1.40

0.00

Plot A-

Pore water pressure contour, kPa

27-02-11

-7.70

-5.40

0.30

-11.70

-10.50

-12.80

-9.20

-9.10

0.00

0.30

3.80

-1.40-0.30

27-02-11

15-09-11

10 m

Shallow failure occurred at Maximum daily rainfall of 100 mm with 3-day antecedent rainfall of 180 mm

Field Instrumentation at a Reinforced Slope

in Mae-Lana, Thailand

Pore-water Pressure Distributions within 10

m Depth of Soil at a Reinforced Slope in

Mae-Lana, Thailand

Adaptive measure

• Soil bio-engineering (use of vegetation)

Bamboo Slope grating with vetiver grass

Installation (14/Dec/12) 5/Apr/13 (4 months) 3/Aug/13 (8 months) 16/Dec/13 (1 year)

Vetiver grass :

- very dense fine vertical root system

- making it very effective for slope stabilization

- reduction of runoff erosive energy and sediment trap

Technology for landslide warning system

Simple cylinder raingauge Telemetry weather station

Several attempts have been made to develop hazard map, low-

cost landslide warning box.

However, most local communities still rely on daily rainfall as

measured by raingauge based on rainfall envelope concept.

Summary for Thailand

Rainfall is the key triggerring factor of landslide in Thailand

Characterization of unsaturated soil properties were carried

out to understand the effect of rainfall on slope stability

Slopes were instrumented to monitor the changes in pore-

water pressures within residual soil slope during and after

rainfall as well to provide landslide warning system

Bio-engineering (i.e. vetiver grass) was used as slope

preventive measure

Slope Safety Preparedness in Vietnam

Climate change & Sea level rise in Vietnam

• Temperature (1951-2000)

- Annual temperature has increased by 0.7°C

- Overall temperature in 2100 is likely to increase by 2.1 -

3.6°C in the high emission scenario. (Nguyen, 2009)

• Rainfall (1911-2000)

-The most common amount of rainfall recorded is about 1400

to 2400mm.

- The precipitation will increase, generally around 2% - 10%.

• Sea level riseScenario Time

2020 2030 2040 2050 1060 2070 2080 2090 2100High (cm) 12 17 24 33 44 57 71 86 100

Medium (cm) 12 17 23 39 37 46 54 64 74

Rainfall-induced landslides

Number Time Location of Landslide Rainfall Intensity

1 11 – 1964 Que Son, Quang Nam 300 – 1000 mm

2 10 – 1969 Quan Cay, Thai Nguyen 600 – 700 mm

3 12 – 1986 Son Tra, Quang Ngai 500 – 1227 mm

4 08 – 1996 Muong Lay, Lai Chau 300 – 400 mm

5 11 – 1999 Phu Loc, Thua Thien Hue Approximately 1000 mm

6 09 – 2002 Huong Son, Ha Tinh 500 – 700 mm

7 09 – 2005 Van Chan, Yen Bai Approximately 300 mm

Sliding along the national highway (8/2005) Lanslide in Bat Xat – Lao Cai in 27/09/2005

Rainfall-induced landslides

• It is expected that climate change will bring more rainfalls to

Vietnam with higher intensity and longer duration.

• Vietnam has 75% of the land in mountainous areas

• Analysis of slope along highway at Tam Ky – Tien Phuoc

considering the saturation of the initially unsaturated zone during

rainfall.

Rainfall-induced Dykes Problem

Hai Hau sea dyke broke due to

Storm (27 Sep 2005)Effect of overtopping at Haiphong

dyke after Typhoon (2005)

If the sea level rises by 0.2 and 0.6 meters, 100 – 200 thousandhectares of Vietnamese plains are predicted to be submerged.

A one meter rise of sea level would result in 0.3 – 0.5 million hectaresof the Red River Delta will be under water and 90% of the MekongDelta will be flooded.

Adaption to sea level rise

• Vietnamese government approved a program to upgrade sea

dykes.

• The 13 provinces involved have reinforced 272km of sea

dykes, renovated or built 42 sluices and planted more than

130 ha of wave blocking trees.

• In Ha Tinh province alone, 100 km of sea dykes have been

improved.

• Vietnamese government is planning on constructing 6

embankments and commencing 13 projects on constructions

of sea dykes.

Summary for Vietnam

• Significant impact due to climate change: significant

rise in sea level and heavy rainfall

• Rainfall is the main factor affecting landslides

• Safety preparedness: construction of sea dyke,

numerical analyses to observe the variations of

factor of safety during and after rainfall

Slope Safety Preparedness in Malaysia

Mean Annual Maximum Temperature Trend

in Malaysia (oC / 10 years)

Key Features of Landslides in Malaysia

• Landslides are a big problem in Malaysia

• Increased rainfall has also affected water level, resulting in serious problem in slope stability

• Annual rainfall intensity: over 2500mm

• Shallow failures: less than 4 m deep

Landslides in Malaysia

• 80 landslides occurred along the road from the main

highway to Genting Sampah since 1993 (some of

them were observed after continuous rain for more

than 72 hours on 30th June 1995)

• 21 Landslides in Hulu Kelang between 1990 and

2011

• Major landslides in Bukit Gasing and Paya Terubong

in 2013

Landslides in Paya Terubong, Malaysia

(2013)

Adaptive Measure using Live Pole

Live pole technique Trial steps for live pole

The influences of Ht/Ds roots on the slope FS increased from 0.93 to 1.11 (20%) (Mafian, 2009)

Adaptive Measure using Hibiscus Tiliaceus

(Ht) and Dillenia Suffruticosa (Ds)

Bending strength of Ds and Ht Live pole treated slope in 2014

Summary for Malaysia

• The significant effect of climate change is in the

increase in rainfall intensity and groundwater table

• Rainfall is the most important factor triggering

landslides

• Slope safety preparedness: vegetative cover (i.e.

live pole)

Slope Safety Preparedness in Indonesia

Climatic Condition in Indonesia

Trend of precipitation in West Java

Indonesia is analyzing the historical data in order to predict the rainfall intensity in the future.

Climatic Condition in Indonesia

Climate change prediction from AR4

2080

The annual change of average temperature in 2080 will be about 2.49°C and the increase of precipitation will be about 5.1%

Key features of Landslide in Indonesia

• Java is composed of clayshale and expansive soils

Distribution of landslides in Java area and its geomorphology

More than 250 landslides occurred in Indonesia (2003-2007).

More than 56% were in West Java.

Statistics of Landslides in Indonesia

between 2003 and 2007 (LIPI-Geoteknologi)

West Java15856%Central Java

6021%

East Java145%

North Sumatera124%

West Sumatera124%

North Sulawesi 8

3%

West Sulawesi 3

1%

Central Sulawesi3

1%

NTT9

3%

East Kalimantan3

0%

Papua2

1%

Aceh1

0%

South Sulawesi1

0%

KEJADIAN GERAKAN TANAH DI BEBERAPA PROVINSI DI INDONESIA

2003 - 2007

Reactivation of old landslides

Volcanic breccia was deposited on top of clayshale very long time

ago as lahar flows after volcano eruption.

Clayshale is material that is degrading fast due to exposure.

The inclination of clayshale boundary with the breaccia enable

creep or even sliding of the breccia over clayshale.

Clayshale and severe rainfall can cause foundation movement.

Summary for Indonesia

• Significant effects of climate change is the increase in

temperature and rainfall

• Rainfall is the main factor causing landslides

• 56 % Landslides occur in West Java since this area

consists mostly of clayshales and expansive soils

• Reactivation of old landslides is commonly occurring

• It is likely that land use change and human activity will

have a greater impact on landslide frequency than

climate change over the next 80 years

Conclusions

1. Climate change results in the increase in rainfall intensity in

Southeast Asia.

2. Many slope failed during or several days after rainfall in

Singapore, Indonesia, Vietnam, Malaysia and Thailand.

3. Characterization of climatic data (rainfall, wind speed,

temperature, relative humidity) is necessary for

assessment the effect of climate change on slope stability.

4. Characterization of unsaturated soil zone, which is in direct

contact with the environment, is required for understanding

the effect of climate change (infiltration and evaporation) on

the dynamic factor of safety of slope.

Conclusions

5. Appropriate characterization of unsaturated soil properties

(soil-water characteristic curve, permeability function) is

necessary for accurate seepage and stability analyses.

6. Singapore is developing landslide susceptibility map

(SHARES) to address the effect of climate change on slope

stability.

7. Thailand is developing early warning system and landslide

hazard mapping for adaptation and preparedness against

the effect of climate change on slope stability

Conclusions

8. Vietnam is developing a software that can predict slope

failure due to climate change. In addition, they are also

constructing dykes to address the problem on the sea level

rising due to climate change.

9. Malaysia is adopting green solution (vegetation) to address

the problem on rainfall-induced slope failures due to

climate change.

10. Indonesia is analyzing the historical data in order to predict

the rainfall intensity in the future.

Thank you

Comparison between Predicted and

Measured Rainfall Intensity at Penggaron

Bridge, West Java, Indonesia

Rain

fall

in

ten

sit

y (

mm

)

800

700

600

500

400

300

200

100

0

Actual

Predicted

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb

2011

2012

2013

• Intergovernmental

Panel of Climate

Change (IPCC,

1990, 2013)


• Kyoto Protocol (Oberthur and Ott, 1999)


• Kyoto Protocol (Schiermeier, 2012)


• The impact of climate across nations and sectors: food,

increase in groundwater table , ice melting, extreme weather

(high rainfall, high temperature, strong winds & floods) –

Stern (2007)

• High rainfall intensity in: United States (Kunkel, 2003);

Australia (Groisman et al., 2005); South Africa (Mason et al.,

1999); United Kingdom (Osborn et al., 2000); Europe

(Forland et al., 1998); China (Zhai et al., 2005); Japan

(Fujibe, 2008)

Studies on Climate Change

• Modification of IDF curve is necessary for future climate

scenario (Mirhosseini et al. 2013)

• Development rainfall model using spatial and temporal

variability in West Africa (El-Hadji & Singh, 2002); United

Arab Emirates (Sherif et al., 2011)

• Analyses of changes in rainfall pattern to define the design

parameters of water sensitive urban design in Australia

(Chowdhury & Beecham, 2010)

Studies on Climate Change


• Majority of slope failures occurred during rainfall

Slope failures in Naples (Evangelista et al.,

2008; Papa et al., 2008)

Hong Kong (Brand, 1992)

Malaysia (Liew et al., 2004)

Singapore (Pitts, 1985; Tan et al., 1987;

Chatterjea, 1989; Lim et al., 1996; Toll et al.,

1999; Rahardjo et al., 2001)


• In UK, Glendinning et al. (2009) set up the BIONICS

project (biological and engineering impacts of climate

change on slopes).

Vegetation contributed to the sustainability of slope

infrastructure.

Climate changes are followed by changes in weather

patterns.

Longer dry season and higher intensity of rainfall

during wet season.


• In Switzerland, Springman and Teysserie (2001) and

Springman et al. (2003) instrumented several slopes to

study the effect of climate change on slope stability.

Rainfall and snowmelt were the most important

triggering factors for slope failures in Switzerland.

Majority of slope failures are deep seated failures.


Landslide in Seoul, South Korea


Landslide in Taiwan on 26 April 2010


Landslide near Daning River, Wushan

county, Chongqing, China on 24 June 2015

Field Monitoring

P1

P2

P3

Rain

gauge

Tensiometer

Soil moisture

sensor

Temperature

sensor

A B C D

Runoff

boundary

Flume

Weather

station

Rain gauge

Piezometer

Time-domain

Reflectometry

Tensiometer

Weather

station

Data logger

Solar panel

Temperature sensor

Solar panelData logger

Notes:

P = piezometer

A, B, C, D = tensiometer

and soil moisture sensor

at different depth

Instrumented slope

(Rahadjo et al., 2014)

Jurong Formation

Bukit Timah Granite

Old Alluvium

Instrumented slope

(Rahadjo et al., 2003a)

• To clarify and investigate the effects of flux boundary


Slope failure in NTU campus, Singapore (2012)

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