Impact of Land Subsidence and Sea Level Rise Influence Shoreline Change in The Coastal Area of Demak

Abstract

Abstract Climate change has a negative impact on the environment, one of which is the phenomenon of sea level rise. Sea level rise has a devastating effect on marine coastal areas such as shoreline abrasion. Sea level rise has caused a reduction in land, one area on the north coast of Java affected is located in Demak. Demak is a coastal area that has the potential for a shoreline abrasion because of sea level rise and a decrease in the land surface. Monitoring of shoreline changes needs to be monitored in order to find out the magnitude of the shoreline changes and the impact caused by reduced a mainland. One method that can be used to monitor shoreline changes is to use remote sensing technology. Satellite imagery can produce changes in shoreline abrasion without coming to the objects directly. This study aims to assess sea level rise and land subsidence resulting in changes in the shoreline in Demak. The data used are Jason-1 and Jason altimetry satellite data 2, Landsat 7 ETM + satellite imagery in 2011 and Landsat 8 in 2016. Altimetry satellite data is processed to obtain sea level rise on the coast of the Java Sea. Sea Level Anomaly (SLA) data processing uses Inverse Distance Weight (IDW) interpolation. The rise in sea level is determined by the analysis of linear trends from the processing of altimetry satellite data. The separation between water and land boundaries from Landsat satellite imagery uses the band ratio method on Green bands and NIR bands. shoreline changes are calculated using DSAS (Digital Shoreline Analysis System). The results of data processing obtained an average sea level rise in the Java Sea in 2011 to 2016 of + 6.80 mm/year. The highest increase was in Jakarta waters of +11.043 mm / year and the lowest was in Surabaya waters with an increase of +3.85 mm/year. The increase in Semarang waters was + 5.52 mm/year which was used as validation with the tidal data of Semarang. The average change in coastline in the Demak region is -119.08 m. Demak experienced a land subsidence of +2,078 to -8,376 cm/years. The biggest abrasion occurred in Sayung Subdistrict of -691 m. The largest accretion occurred in the District of Wedung + 512.48 m. Based on the results of the increase in water level in the coastal areas of the island of Java and land subsidence that occurred in Demak caused a fairly wide shoreline abrasion.