Land subsidence characteristics of Bandung Basin as revealed by ENVISAT ASAR and ALOS PALSAR interferometry

In this work, land subsidence in Bandung Basin, Indonesia between 2002 and 2011 was mapped using the C-band ENVISAT ASAR and L-band ALOS PALSAR data. Twenty four ALOS PALSAR and thirty ENVISAT ASAR images acquired between 2002-2008 and 2007 - 2011, respectively, were analysed. Several locations that were experiencing land displacement were identified including Cimahi, Dayeuh Kolot, Rancaekek, Solokan Jeruk and Gedebage. The subsidence rates in the basin range from −240 mm/year to 40 mm/year. The comparison between the ALOS PALSAR and ENVISAT ASAR measurements, which showed good agreement, suggested the subsidence in many areas of the basin were steady between 2002 and 2011, except south Bandung. Acceleration of subsidence in south Bandung was observed between the measurements from the two datasets, likely as a result of increasing population and industries. The subsidence in the basin was expected mainly as a result of excessive groundwater extraction and soil consolidation caused by surficial loading. GPS survey data collected between 2002 and 2010 were used to validate the ALOS PALSAR and ENVISAT ASAR measurements. Good correlations were observed between InSAR and GPS measurements. The comparison between the land subsidence measurements and the groundwater level information showed there were some correlations between them. For every 1 m reduction in groundwater level per annum, ground subsidence of 20-23 mm per annum has been observed. The comparison results suggested that there was no evidence showing the aquifer in the basin is being recovered.