The 3 rd International Conference on Coastal and Delta Areas - PROCEEDINGS 353 ICCDA#3 Problem, Solution and Development of Coastal and Delta Areas ANALYSIS OF CHANGE IN THE AREA OF INUNDATION DUE TO LAND SUBSIDENCE IN SEMARANG (A Case Study: Jl. Ahmad Yani, Jl. Erlangga Tengah, Jl. Sugiyopranoto) Pratikso, Rahmat Mudiyono Lecturer of Sultan Agung Islamic Univesity, Department of Civil Engineering Jl. Raya Kaligawe Km.04, Semarang, Central Java, Indonesia pratikso@hotmail.com; rachmatmudi@yahoo.com Dian Indah Permatasari Sultan Agung Islamic University, Department of Civil Engineering Jl. Raya Kaligawe Km.04, Semarang, Central Java, Indonesia permatasaridianindah@gmail.com Abstract - Semarang is located on the north coast of Java island and develops in river flow area which genetically has alluvial materials. The process of precipitation continues until now and as a result a fairly thick layer of clay is founded. The layers of clay and land subsidence are related to each other. Land subsidence causes inundation or locally called rob area becoming increasingly widespread. The process of land subsidence causes a loss for the government of Semarang. The purpose of this study was to analyze the change in the area of inundation due to land subsidence in Semarang, on Ahmad Yani Street, Central Erlangga Street, and Sugiyopranoto Street, and give the best advice for the government to develop the city. Method of analysis used in this study was terzaghi method, GIS software (Geography Information System), and Plaxis software. The results showed that the rates of the land subsidence is getting bigger and the time is getting longer. Keywords: Land Subsidence, Terzaghi, Geography Information System, Plaxis 1. Introduction The growth of people and development in Indonesia is very rapid, particularly in Semarang city which has 1.765.396 people with an area of 373.4 km 2 and 17 sub-districts (Department of Population and Civil Registration of Semarang, 2017). North Semarang is formed by alluvial swamp sediment, the process of land subsidence that occurred in North Semarang causes harm to the Semarang city government, society, and the local industry. This study provides problem limitations, they are: 1) The research location is located in South Semarang Sub-district on Ahmad Yani Street, Central Erlangga Street, and Sugiyopranoto Street. 2) Measuring land subsidence based solely on land consolidation. 3) Analyzing land subsidence on the alluvial plain in South Semarang Sub-district in 2017 until it reaches T90%. 4) Identifying changes in the area of inundation due to land subsidence on alluvial plain in South Semarang Sub-district in 2017 to reach T90%. 2. Research Methodology Experimental research was used on this case study in South Semarang. The research area was generally consisted of alluvium rock system which was still young and having several hundred years age so that keeps it in experiencing compression. The study Proceedings of International Conference : Problem, Solution and Development of Coastal and Delta Areas Semarang, Indonesia – September 26 th , 2017 Paper No. C-26