Remote sensing of environment and disaster laboratory

Institute of Industrial Science, the University of Tokyo, Japan

Detection and Calculation of Peatland Subsidence in Indonesia
by using Interferometric Synthetic Aperture Radar!"#$#
!"#$#Sho Tsunoda1), Wataru Takeuchi1)1) IIS, The University of Tokyo, Japan
ABSTRACT Peatland is a kind of wetlands with a thick waterlogged organic soil layer storing large amount of carbon. In recent years, peatland in the world has been
destroyed due to drainage or fire for agricultural use. When peatland is affected by such human activities, its organic carbon is decomposed into the air as greenhouse gases,
and the ground level goes down. This phenomenon is called “peatland subsidence”. In this study, peatland subsidence in Jambi, Indonesia, was assessed with time-series of
ALOS/PALSAR data based on InSAR technique. Firstly, PALSAR raw data was converted into SLC data, and interferometric processings were conducted to generateinterferograms from SLC images. Secondly, a group of time-series interferograms was created thorough PS-InSAR analysis. Finally, subsidence distribution, subsidence
amount, and subsidence velocity were calculated spatially. As a result, significant land surface deformation originated from peatland subsidence was observed from 2007 to2011.

BackgroundPeat is composed of accumulated vegetation or organic matter that is partially decayed.
Peatland, an area where peat can be found, plays an important part in the environment since it has aunique ecosystem and can effectively store large amount of carbon. Recently, peatland in the world
has been rapidly decreasing mainly due to the land use change for agriculture.
Indonesia, one of the largest peatland owners, suffers from peatland subsidence derived frominappropriate maintenance of peatland. Farmers near the seashore have experienced serious floods
caused by tidal effect and heavy rain during the rainy season. In 2005, peatland emission was estimatedto be about 772 Mt CO2eq that accounted for 38 % of total Indonesia’s annual GHG (DNPI, 2010).
Thus, under such circumstances, appropriate management of peatland is an urgent issue. To mitigate
peatland emission and peatland subsidence, many research works have been ongoing in Indonesia. ObjectiveMethodologyĐÈTo detect the distribution of peatland subsidence and to calculate the extent ofsubsidence in the study site by using InSAR techniqueĐ To assess the subsidence velocity for the past few years in the study siteÈÈ

Fig 1. The mechanism of peatland subsidenceFig 3. Data processing
flowchart with
StaMPS software(Hooper et al., 2012)

Fig 2. Study site (Jambi, Indonesia)

Results and Discussions Interferomerograms

PS InSAR analysis

Subsidence velocityThis shows a mean velocity in the line-of-sight (LOS) direction projected on Google Earth. In the southeast part of study area (colored blue), the subsidence had developed
rapidly from 2007 to 2011 with the maximum velocity of 142.8 mm/year. In the southwest part of study area (colored red), the tendency of moving up was detected whichcorresponding to the result of Figure.4.
Figure.4.
The interference patterns (fringes) can be seen in all These pixels represent PS points extracted by StaMPS. In the southeast part of study area (coloredinterferograms, particularly in the image taken in December 87347 points were analyzed in this study area. As time blue), the subsidence had developed rapidly
2008 due to the short time difference of two observations. goes by, the whole ground seems to move down (from from 2007 to 2011 with the maximum velocity
Although topographic errors were successfully removed with green to blue) gradually. A large expansion deformation of 142.8 mm/year. In the southwest part of
SRTM data, orbital errors and the influence of ionosphere still (or shifting to the east) was also observed in the study area (colored red), the tendency of
exist besides surface deformation.
southwest part of the images.
moving up was detected.

Summary

ReferencesĐ PS-InSAR analysis was conducted to monitor pattern of subsidence phenomenon
in Jambi, Indonesia, with StaMPS software.
Đ Subsidence distribution and subsidence amount were calculated spatially, andsubsidence velocity was visualized.
Đ This study revealed that the subsidence had developed rapidly from 2007 to 2011
with the maximum velocity of 142.8 mm/year in the southeast part of study area.

Dewan Nasional Perubahan Iklim (DNPI), Indonesia, 2010. Indonesia’s greenhousegas abatement cost curve.
Hooper, A., Bekaert, D., Spaans, K., Arikan, M., 2012. Recent advances in SARinterferometory time series analysis for measuring crustal deformation.
Tectonophysics 514-517, pp.1-13.

For further details, contact: Sho Tsunoda, Ce-506, 6-1, Komaba 4-chome, Meguro, Tokyo 153-8505 JAPAN (URL: http://wtlab.iis.u-tokyo.ac.jp/ E-mail: tsunosho@iis.u-tokyo.ac.jp)