STUDY OF PUMP AND RETENTION BASIN REQUIREMENT FOR SEMARANG-DEMAK COASTAL DIKE PLAN, CENTRAL JAVA

Semarang city in East Java, Indonesia, is frequently inundated on its northern side due to coastal flooding which is mainly caused by land subsidence. A study by the government to prevent this coastal flooding was started in 2014 and resulting comprehensive solution that ultimately will make 8 km of Semarang coastal area protected by the coastal dike. This leaves the area behind the coastal dike as a polder and hydraulic analysis is critical to ensure the polder areas will not be flooded when extreme rainfall occurs in the area. This study analyses the pumping capacity and retention basin configurations based on the official watershed agency (BBWS Pemali Juana) by performing hydraulic simulations and the result shows that the current configuration is relatively minimalist compared to the solutions suggested to other urban areas in the world. Recommended pump and basin configurations with higher flood-draining performance are given in this study based on the past design experience from the capital city of Jakarta as well as similar cases from other urban areas.