twelve-year landslide risk assessment in villa de independencia, bolivia… · 2020-05-06 · villa...

Twelve-Year Landslide Risk Assessment in Villa de Independencia, Bolivia, with Sentinel-1 and

ALOS-1/2 InSAR Observations

Chuang Song, Zhenhong Li, Stefano Utili, Chen YuNewcastle University

Study Area

Villa de Independencia, Bolivia

There were observed cracks in the downtown walls and wall collapse at the eastern bus station.

Data

2015 2016 2017 2018 2019Time (year)

-200

-100

0

100

Spat

ial B

asel

ine

(m)

2015 2016 2017 2018 2019Time (year)

-100

0

100

200

Spat

ial B

asel

ine

(m)

(b) Sentinel-1 descending

(c) Sentinel-1 ascending

2008 2010 2012 2014 2016 2018Time (year)

-2000

-1000

0

1000

2000Sp

atia

l Bas

elin

e (m

)(a) ALOS-1 and ALOS-2

ALOS-1 ascending

ALOS-2 ascending

ALOS-2 descending< ALOS-2 images are too few to apply timeseries InSAR, so interferometry only >

Flowchart of Time Series InSAR

LOS velocityand

time series

Selectedinterferograms

SLCimages

ResampledSLC images

Coregistration Grouping pairsRemoval of DEM

GACOS troposphericdelay correction

Correctedinterferograms

First-roundcoherent pixels

Dispersionof amplitudePhase noiseSecond-round

coherent pixels estimation

Phase correction forspatially-uncorrelated noise

Wrappedphase images

Unwrappedphase images

3D phaseunwrapping

Correct spatially-correlated noise

StaMPS

/SBAS

Results | Displacement velocity maps

-66.84 -66.82 -66.8 -66.78

-17.11

-17.1

-17.09

-17.08

-17.07

-17.06

-17.05

-50

-40

-30

-20

-10

0

10

20

30

40

50mm/yr

-66.84 -66.82 -66.8 -66.78

-17.11

-17.1

-17.09

-17.08

-17.07

-17.06

-17.05

-50

-40

-30

-20

-10

0

10

20

30

40

50mm/yr

(c) Sentinel-1 descending (2014 to 2019)

-66.84 -66.82 -66.8 -66.78

-17.11

-17.1

-17.09

-17.08

-17.07

-17.06

-17.05

-50

-40

-30

-20

-10

0

10

20

30

40

50mm/yr

-66.84 -66.82 -66.8 -66.78

-17.11

-17.1

-17.09

-17.08

-17.07

-17.06

-17.05

-50

-40

-30

-20

-10

0

10

20

30

40

50mm/yr

(d) Sentinel-1 ascending (2014 to 2019)

(a) ALOS-1 ascending (2007 to 2011) (b) ALOS-2 ascending (2015 to 2017)

Town Centre

Highway 25

Town Centre

Highway 25

Town Centre

Highway 25

Town Centre

Highway 25

Risky Area Risky Area

Risky AreaRisky Area

A landslide risky area below Highway 25, with the displacement velocity of about 30 mm/yr in the Line of Sight (LOS), is detected.

The town centre needs a further check usingSentinel-1 results in high temporal resolution.

Results | InSAR time series in the Risky Area

2008 2010 2012 2014 2016 2018Time (year)

-200-100

0100

LOS

(mm

)

ALOS-1 AscendingSentinel-1 DescendingSentinel-1 AscendingALOS-2 Ascending

The temporal behaviour in descending and ascending LOS coincides well illustrating a

slowdown process from mid 2017.

The detected landslide risky area below Highway 25 is in a lower failure risk than before, but

the low risk may be temporary considering the same slowdown process from 2008 to 2010.

2008 2010 2012 2014 2016 2018Time (year)

-200

-100

0

100

LOS

(mm

)

2020

slowdown

the same slowdown process but accelerated after 2010

Mid 2017

Results | Cumulative LOS displacements in the Downtown

The spatial distribution of Sentinel-1 LOS displacements in descending and ascending

modes suggests that the town centre and its upper block move with different east-west

sliding due to different slope aspect.

Town Centre

Upper Block

Sentinel-1 descending Sentinel-1 ascending

Town Centre

Upper Block

Town Centre

Upper Block

Slopeaspect

Slope aspect

Results | InSAR time series in the Downtown

2008 2010 2012 2014 2016 2018Time (year)

-40

-20

0

20

40

LOS

(mm

)

0

50

100

150

200

250

30-d

ay a

cc. p

reci.

(mm

)

2008 2010 2012 2014 2016 2018Time (year)

-20

0

20

40

60

LOS

(mm

)

0

50

100

150

200

250

30-d

ay a

cc. p

reci.

(mm

)

Acceleration

Note: The daily precipitation data wascollected from NASA GPM and convertedto 30-day accumulated precipitation totals.LOS deformation in descending andascending modes have differentsensitivities to the slope geometry.

• The deformation time series from Sentinel-1 present acceleration in early 2018 and 2019, which is cross-validated by ALOS-2 measurements.

• The two accelerations have similar initiating time and durations, in response to increase precipitation in the late rainy season.

Note: The upper block holds too few coherent pixels byALOS-2, so no ALOS-2 results for it.

(a) Town Centre

(b) Upper Block AccelerationWe thought the acceleration is a signal of landslide activation in the downtown.

2008 2010 2012 2014 2016 2018Time (year)

-200204060

LOS

(mm

)

0100200

30-d

ay a

cc. p

reci.

(mm

)

ALOS-1 AscendingSentinel-1 DescendingSentinel-1 AscendingALOS-2 AscendingALOS-2 DescendingPrecipitation

Ø Displacement velocity from Sentinel-1, ALOS-1 and ALOS-2 data spanning

twelve years revealed a landslide risky area below Highway 25.

Ø Combining InSAR measurements in descending and ascending modes helps

identify two sub-blocks of landslides in the town.

Ø The activation of landslides from 2018 in Villa de Independencia was found,

possibly being related to the increased precipitation in the late rainy season.

Thanks!Email: c.song4@newcastle.ac.uk

Conclusion