Land Subsidence of Java North Coast Observed by SAR Interferometry

Land subsidence in Pekalongan city has affected almost the entire municipality for at least ten years. Land subsidence has occurred in almost all Pekalongan city areas at 2-12 cm/year rates. The direct and indirect environmental impacts of land subsidence are enormous. We aim to map the environmental impacts of land subsidence in Pekalongan city and evaluate the severity of the impacts with the subsurface condition of the affected area. We employed site investigation using resistivity and CPTu soundings at representative sites to reveal the subsurface soils and site survey to map the environmental impacts. Resistivity measurements using a Schlumberger array were carried out at 24 sites, along with 12 CPTu measurements up to 30 m deep. Results show that the subsurface condition up to the depth of 30 m consists of alluvial sediment of clay, silt, and organic soils intercalated with lenses of sand. The alluvial sediment in the southern part is dominated by sandy soils and has a higher stiffness with cone resistance of 1-2 MPa and a friction ratio of 50-200 kPa. The subsurface soils in the northern part are dominated by clay, silt, and organic soils with low cone tip resistance of <0.5- 1 MPa, and friction ratio of <0.25-100 kPa. These values indicate that the sandy soils in the southern part are more compact and have higher bearing capacity than the soft, fine-grained soils in the northern area. The visible impacts of land subsidence include flood and inundation, settlement of buildings and roads, and cracks in houses and infrastructure. The severity of impacts worsens from South to North of the city. This condition is related to the subsurface stratification and engineering properties, where lower bearing capacity occurs in the north.

Section: Direct Impact Of Land Subsidencementioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Mapping the environmental impacts from land subsidence hazard in Pekalongan City and its correlation with the subsurface condition

Sarah¹,

Soebowo²,

Sudrajat³

et al. 2023

“…Among these three cities, study of land subsidence in Pekalongan has not been done in the same attention as Jakarta and Semarang. Although the size of Pekalongan may not be as large as the other two cities, but the rate of land subsidence in Pekalongan is significantly large with some areas can reach up to 11 cm/year [6] [7].…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, urban areas situated within the region are susceptible to the hazards resulting from environmental fluctuations, including but not limited to coastal inundation, depletion of mangrove ecosystems, and erosion along the coast. Several studies have also indicated that land subsidence is prevalent in this particular region, including cities such as Jakarta [1] [2], Semarang [3] [4], and Pekalongan [5] [6]. Among these three cities, study of land subsidence in Pekalongan has not been done in the same attention as Jakarta and Semarang.…”

Section: Introductionmentioning

confidence: 99%

Long term subsidence rate in Pekalongan city observed by SAR Interferometry

Sidiq,

Adiwijaya,

Nugroho

et al. 2023

Land subsidence occur in some large cities in Java Island, Indonesia. Among those cities, Pekalongan suffer relatively large and consistent rate of land subsidence compared to other cities. Impact of this long-term land subsidence manifested as worsen of flood, infrastructure damage, and decline of ground water quality. To see the continuation of land subsidence in Pekalongan, we use Sentinel-1 data from 2016 to 2023 from both ascending and descending direction to spatio-temporaly mapped both magnitude and rate of the land subsidence. Persistent Scatterer InSAR (PS-InSAR) method is used to process the SAR data, also use DEMNAS and Generic Atmospheric Correction Online Service (GACOS) to reduce topographic and atmospheric error consecutively. We use CPKL CORS station, which managed by Badan Informasi Geospasial (BIG) for control point for the final subsidence rate calculation. Our result show that the area of subsidence does not change significantly for the last 7 years, with the maximum rate reach 16 cm/year of subsidence occur in the western side of Pekalongan City. However, the land subsidence also occurs in the coastal part with lower rate of 5 cm/year. The subsidence rate in most of the places are constant, with exception during 2020-2021 period.

“…The northern coast of Java is an area that has a high population density and has many industrial areas, such as Jakarta, Bekasi, Karawang, Cirebon, Tegal, Pekalongan, Semarang, Gresik, and Surabaya [1]. However, the northern coast of Java also has problems with massive coastal degradation [2], such as abrasion and accretion [2-4], inundation [2], and subsidence [5][6][7]; as well as tidal flooding [2,8]. Of the approximately 1687 km long coastline of Java, 745 km (44%) experience abrasion with an erosion rate of around 1950 ha per year [4].…”

Section: Introductionmentioning

confidence: 99%

Thirty years of change of Pekalongan coastline based on Landsat imagery

Chulafak¹,

Khomarudin²,

Ardha³

et al. 2022

The northern coastal area of Java Island is where many economic and industrial centers are located. Many big cities are located in this area, such as Jakarta, Semarang, and Surabaya. One of the problems in this area is the occurrence of tidal flooding. One of those affected by the tidal flood is Pekalongan, where the city also experienced land subsidence which is more severe than other big cities in Indonesia. One of the impacts of tidal flooding is the occurrence of coastal abrasion, where land areas are increasingly disappearing. This research objective is to see how big the coastline changes occurred in the Pekalongan area for 30 years through remote sensing data. Landsat image was used to see changes in coastlines from 1988 to 2021 on an annual basis. NDWI (Normalized Difference Water Index) was used to clarify the difference between land and water areas. Moreover, to reduce subjectivity, Otsu’s method was used for thresholding. The results show that most Pekalongan area is subject to abrasion, with the most severe conditions up to around 232 m. In addition, there are also problems related to tidal flooding, whose conditions are increasingly widespread every year.