The purpose of this research is to assess the future flood risk in rapidly urbanizing cities under climate change. A flood inundation model and a flood damage costs model were employed to project the future flood risk. We employed the combinations of eight global climate models (GCMs) and three representative concentration pathways (RCPs) for precipitation to represent the climate change. Land-use change and land subsidence information were employed to represent the urban development effects. The expected annual damage costs (EADC) were also calculated to explain the severity of the flood risk. In addition, a global approach was used to estimate the asset values by comparing the common parameters (e.g. gross domestic production (GDP) or population). As a result, the combination of climate change and urban development amplified the mean future flood risk by 322% to 402% in 2050, with a 95% confidence interval. The results also show a large uncertainty of the future flood risk due to the future scenarios. These findings will assist policymakers in determining the investment for future flood prevention and mitigation. KEYWORDS damage cost; flood inundation model; land-use change; land subsidence; climate change

Jakarta has experienced many floods in the past, and those floods resulted in not only human casualties but also economic damages. In this paper a rainfall runoff and flood inundation model was applied to the 2013 flood event of the Ciliwung River basin and Jakarta by using radar rainfall information as the input. The applied model relatively well reproduced the flood inundation situation in Jakarta. As the results of analysis, we concluded that the shortage of capacity flow in the lower Ciliwung River contributed 6.7%, the shortage of capacity flow in other rivers 72.9%, and the urbanization and the land subsidence 20.4% of the total flood inundation volume in Jakarta. Furthermore, it was found that the land use change from 1983 in the target areas contributed 38% of the total flood inundation volume.

Floods are considered to be one of the major natural disasters in Indonesia. Jakarta in Indonesia has experienced many floods in the past, such as those in 1996, 2002, 2007 and 2013. In this paper, land subsidence problems contributing to flooding in Jakarta were described and historical and future land subsidence situations in Jakarta were reconstructed and projected using a simple linear extrapolation method. Also, those land subsidence impacts were analyzed by using a flood inundation model. As a result of analysis, it was found that the land subsidence in Jakarta contributed by 17.6% to increase of the total flood inundation volume from 1983 to 2013. Also, it was estimated that the land subsidence situations for the future period of 2050 would increase the flood inundation volume by 10.3% compared to those of 2013. However, impacts from land use/cover changes on the flood inundation were found to be much greater than those from land subsidence in Jakarta. It should be noted that the land subsidence affects flooding from the coast when high waves and surges occur but those effects were not considered in this paper.

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River Basin Organization of Cidanau-Ciujung-Cidurian (RBOC3) is a water authority in Banten Province that has the planning of six rockfill dams in development planning, i.e Karian, Pasir Kopo, Tanjung, Cilawang, Sindang Heula, and Cidanau Dam. Regarding to the emergency response plan, it is necessary to have an inundated area estimation due to a dam break. The objective of this study is to develop a flood hazard map based on dam break analysis in selected dams in Banten Province so that the flood situation can be understood. HEC-RAS software was utilized to simulate the two-dimensional flood propagation. The result shows that the total of inundation due to all dam failure is around 152 km 2 . The effect of this Karian Dam submerges 46% of the total area and volume of inundation from six rockfill dam failure. Also, Sindang Heula Dam and Cilawang Dam were considered as the second and third biggest impact on flood volume compared to the others dam break. This study can be used as the initial flood hazard map information in order to reduce flood damage in the future period under the massive construction. Furthermore, the result of this simulation could be applied to emergency response plans as the requirement of dam operation.