Geographia Technica, Vol 21, Issue 1, 2026, pp. 80-94
A GEOSPATIAL ASSESSMENT OF SHORELINE DYNAMICS AND COASTAL VULNERABILITY INDUCED BY THE SEMARANG–DEMAK SEA-TOLL ROAD INFRASTRUCTURE IN CENTRAL JAVA, INDONESIA
Indra HERMAWAN, Sutrisno ANGGORO 
, Suradi Wijaya SAPUTRA , Agus SUHERMAN , Wisnu Arya GEMILANG , Ulung Jantama WISHA
ABSTRACT: The Semarang–Demak sea-toll road, a national strategic project in Central Java, Indonesia, was designed to enhance connectivity while simultaneously serving as a sea dike to mitigate tidal flooding and erosion. However, its construction within a subsiding and geomorphologically dynamic coastal environment raises concerns about long-term sustainability. This study assesses coastline change and coastal vulnerability after the toll road development using a GIS-based Digital Shoreline Analysis System (DSAS) and Coastal Vulnerability Index (CVI) frameworks that integrate nine geologic and oceanographic parameters. Results indicate pronounced spatial heterogeneity: North Semarang and Genuk exhibited high accretion rates (31.54 m/year and 51.64 m/year, respectively), whereas Sayung experienced extreme erosion, with retreat rates up to 654.09 m/year. CVI analysis revealed that 38.01% of the coastline falls under high vulnerability, particularly in the Sayung District, determined by factors such as sea-level rise, land subsidence (up to 8 cm/year), and extensive land use changes. The findings demonstrate that while the toll road enhances short-term protection and connectivity, it also intensifies long-term risks by disrupting sediment dynamics and degrading coastal ecosystems. Therefore, adaptive and ecosystem-based management is crucial to align infrastructure development with environmental resilience in rapidly subsiding deltaic regions.
Keywords: Coastal vulnerability; Shoreline change; Land subsidence; Semarang–Demak Toll Road; Indonesia
Full article here