Mapping Shallow Zones with Potential for Land Subsidence Around Subsurface Water Channels Using 2D Electrical Resistivity Tomography in Bandung

Abstract

Recurring ground subsidence around the Cikapayang River, particularly near the Bandung Center for Groundwater and Environmental Geology (PATGTL), indicates ongoing subsurface instability despite previous remediation efforts. This phenomenon is associated with backfill soil, rainwater infiltration, and subsurface drainage structures that can reduce soil bearing capacity and promote the formation of weak zones and voids. This study aims to identify shallow subsurface conditions associated with recurring ground subsidence and potential weak zones around subsurface drainage structures. 2D Electrical Resistivity Tomography (ERT) using the Wenner–Schlumberger configuration was conducted along five survey lines, each 52 m long with a 1 m electrode spacing. The datawere processed using Res2DInv, integrated and visualized in Leapfrog Geo, and validated through synthetic forward modeling using Res2DMod. Resistivity values ranged from 4.86 to 339 Ωm. The low-resistivity zone (4–30 Ωm) was interpreted as a water-saturated clay fill layer with low bearing capacity, while the high-resistivity zone (>101 Ωm) was associated with voids and subsurface drainage structures. Land subsidence zones were identified in four sections in the central area, while potential new land subsidence zones were detected at a depth of approximately 1 m in the outermost section. The results indicate that integrating ERT, synthetic modeling, and line merging is effective inidentifying land subsidence-prone zones and supporting urban risk mitigation.