Land subsidence is a phenomenon of sudden sinking or gradual downward settling of the ground’s surface towards the reference point. This condition is commonly occurs in coastal cities, coastal peat areas and coastal oil and gas exploitation areas.
In Indonesia, at least 21 provinces and 132 districts / cities are now indicated to have land subsidence, even for several locations on the North Coast of Java and East Sumatra Coast, have been recorded for having experience on land subsicence and are exposed to the its impact , i.e Tidal flood. The rough calculation of losses that measured only from the adaptation costs for repairing roads, bridges and settlements in northern coast of Java shows that the potential losses caused by land subsidence for each year is IDR 619 Trillion. Meanwhile, for the potential loss of residential buildings in the subsided peat area is reaching around IDR 158 trillion, this figure have not yet included other economic losses parameters.
The average rate of land subsidence in Indonesia’s coastal lowlands are varies from 1-20 cm / year. In some locations, such as Rangsang island, Riau, subsidence is also followed by coastal erosion at rates 30 meters / year. ITB monitoring results show that in the north coast of Java, at least 16 cities / districts experienced subsidence with impacted total area is reaching 11,500 hectares, while indications of subsidence in the peat ecosystem is reached 2.6 million hectares. High rates of subsidence has hampered conservation and rehabilitation efforts in the Coastal Zone and have the potential to eliminate Strategic Economic Zones, such as the Java North Coast Region, and eliminate tropical peat ecosystems such as the East Coast of Sumatra. For border and outer islands areas, such as Meranti Islands, Riau, this condition creates a weak point in the nation and state defence effort.
MITIGATION AND ADAPTATION ROAD MAP OF LAND SUBSIDENCE IN LOWLAND COASTAL AREAS IN INDONESIA
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