Semarang – Semarang City has reaffirmed its status as the area most affected by land subsidence in Central Java. The latest data shows that from 2015 to 2019, the city’s subsidence rate reached 9.85 cm per year.
The main contributing factors are groundwater exploitation and infrastructure load in densely populated areas.
“Semarang is one of the cities most severely affected by land subsidence. About 20% of the city is affected, especially in alluvial and densely populated areas,” said the Assistant for Economy and Development of the Regional Secretary of Central Java Province, Sujarwanto Dwiatmoko, at the Indonesian Journalists for Climate webinar titled ‘The Future of 112 Regency/City Frequent to Coastal Flooding’, Saturday, September 7.
Based on monitoring conducted by the Energy and Mineral Resources Agency of Central Java Province, seven spots in Semarang City have experienced land subsidence. According to Sujarwanto, the subsidence is mostly caused by groundwater exploitation, contributing up to 82%, while infrastructure loads cause the rest.
“Excessive groundwater extraction accounts for 74-82% of the decline, while the rest is caused by the weight of buildings, which reaches 18-26%. In addition, natural geological factors are also influential, especially in the Pantura region located in the back-arc basin,” explained Sujarwanto.
This land subsidence is further exacerbated by industrial development activities in coastal areas, which put additional burden on the soil and accelerate the compaction process. Apart from Semarang, other coastal cities in the Pantura, such as Pekalongan, Tegal, Brebes, and Demak, are also experiencing similar problems.
Revision of Java north coast spatial planning
To overcome the problem, the Central Java provincial government has made various efforts, one of which is to revise the spatial planning in the Pantura region to not burden the land subsidence-prone areas with industrial or residential development. “We have banned groundwater use in areas such as Semarang, Pekalongan, and Kendal, towards the target of zero groundwater use,” said Sujarwanto.
The government is also working to strengthen public access to clean water by optimizing the performance of Regional Drinking Water Companies (PDAMs) and building Drinking Water Supply Systems (SPAMs), including in West Semarang and Petanglong.
“We also continue to increase the construction of infiltration ponds to help stabilize groundwater,” he added.
Meanwhile, academic and researcher Heri Andreas from the Bandung Institute of Technology highlighted that land subsidence in Semarang is part of a larger disaster in Indonesia’s coastal areas. In addition to land subsidence, coastal areas are vulnerable to sea level rise and tidal flooding.
“Three major coastal disasters continue to occur: land subsidence, sea level rise, and tidal flooding. All of these have a major impact on 112 regencies and cities in coastal Indonesia,” said Heri.
According to him, the solution to this problem cannot be generalized.
“Each region has different characteristics, so the solution must also be specific, ranging from embankment construction and relocation, to infrastructure elevation. Everything must be done with a comprehensive approach, including water management from upstream to downstream,” Heri concluded. (Hartatik)
