Author(s): W. Putuhena; D. Legono; A. Setiaji
Linked Author(s): Djoko Legono
Keywords: Jakarta Flooding; Underground Tunnel; Hydraulics Simulation
Abstract: The urban city flooding of Jakarta is actually a common problem since the long term history due to the condition that the area is majority located in the low land area. At the same time, the low permeability of majority soil and the tendency of the increase of the rainfall intensity are factors those contribute more significant causes of the flooding in Jakarta. Such natural physical condition is therefore obvious that Jakarta area is very potential to flood occurrence. Unfortunately, due to the rapid growth of population and demand of people to increase their social welfare, the flooding problems (frequency and intensity) due to various activities made by the community (such as land occupation for settlement, ground water pumping for industries, and others) have been increasing significantly. Moreover, both sea level rise and soil subsidence phenomena have also become issues those affect the increase of inundation intensity. An idea to mitigate the negative impacts of the Jakarta flooding is then adopted through the introduction of multipurpose deep tunnel to reduce the flood disaster risk of Ciliwung River. The term multipurpose means that the utilization of the tunnel is not only as a flood way during the flood season, but also as a tall road during the normal season. This paper presents the result of hydraulics simulation of the multipurpose deep tunnel to evaluate the hydraulics performance of the flow applying SOBEK software. The discussion is focused on the evaluation of hydraulics effectiveness of the multipurpose deep tunnel at certain geometry, (approximately 12.00m diameter, 45.00m depth, and26.00 Km long) to reduce peak flow along Ciliwung River at downstream of intake structure. The 2007 flood hydrograph of Ciliwung River at Balekambang control point is used as upstream inflow boundary condition. The results show that the system may reduce the peak of flood hydrograph of Ciliwung River at Balekambang from 626 m 3 /sec to 450 m 3 /sec. The simulation also performed the reduction of flood inundation at the surrounding Ciliwung River system from 15.85Km2 into 12.33 Km2, compare with that occurred in 2007 Jakarta flooding, which is relatively ineffective. Further analysis shows that the operation and maintenance of the multipurpose deep tunnel may be extremely complex and inefficient.