On the Roles of Geospatial Information for Risk Assessment of Land Subsidence in Urban Areas of Indonesia

Land subsidence is a silent hazard that may occurs in large urban areas, and usually caused by combination of excessive groundwater extraction, natural consolidation of alluvium soil, load of constructions and tectonic activities. Geospatial information is useful for studying the characteristics, causes, impacts and cost of land subsidence. This paper concentrates on the roles of geospatial information for risk assessment of land subsidence in three large cities in Indonesia, namely Jakarta, Bandung and Semarang. Geodetic based results show that land subsidence rates in all three cities generally have spatial and temporal variations, and their magnitude is in average about 5-10 cm/year and can reach up to about 20 cm/year at certain locations and times. The impact of land subsidence can be seen already in the field in forms of the buildings and infrastructure cracking, the wider expansion of (coastal) flooding areas, and increased inland sea water intrusion. Land subsidence has a strong linkage with urban development process. Urban development increases the built-up areas, population, economic and industrial activities, and also groundwater extraction, which can then lead to land subsidence.