Detection of silent subsidence over extensive area by SBAS DInSAR: a case study of Southern Bali, Indonesia

¹ Yamaguchi University, Tokiwadai, 755-8611, Ube, Japan
² Udayana University, Jl. P.B. Sudirman, 80234, Denpasar, Indonesia
³ Centre for Remote Sensing and Ocean Sciences (CReSOS), Udayana University, Jl. P.B. Sudirman, 80234, Denpasar, Indonesia
⁴ Centre for Research and Application of Satellite Remote Sensing, Yamaguchi University, Tokiwadai, 755-8611, Ube, Japan
⁵ Regional Satellite Applications Center for Disaster Management (RSCD), Satellite Applications and Operations Center (SAOC), Space Technology Directorate, Japan Aerospace Exploration Agency (JAXA), 4-1-1 Industrial Technology Institute Asutopia, Ube, Japan

^* Corresponding author: eyastika@yamaguchi-u.ac.jp

Abstract

Numerous cities around the world are facing the problem of land subsidence. In many cases, it is the excessive groundwater extraction to meet human needs that leads to this subsidence. Since land subsidence rates are very slow (a few centimeters per year), the subsidence usually remains unnoticed until it has progressed to the point of causing severe damage to buildings, houses, and/or other infrastructures. Therefore, it is very important to detect the presence of subsidence in advance. In this study, screening for the presence of land subsidence in the city of Denpasar, Bali, Indonesia is conducted. The Sentinel-1A/B SAR dataset, taken from October 2014 to June 2019, is processed using the SBAS DInSAR method. Subsidence is found in the districts of Denpasar Selatan, Denpasar Barat, and Kuta, which falls in the range of -100 mm to -200 mm in an area of about 93.03 ha. All the extracted points of interest show the subsidence having linear behavior. The spatio-temporal behavior of the subsidence in Denpasar is presented clearly. However, the mechanism and the deriving factors of the subsidence remain unclear. Therefore, further studies are needed.