Future risk pathways for a Southeast Asian megacity: Coupling socioeconomic scenarios and agent-based modelling to integrate exposure, vulnerability, and hazards in Jakarta (Indonesia)

Future risk is expected to rapidly increase in coastal urban areas in Southeast Asia. The case of Jakarta (Indonesia) shows intense urban development, land subsidence, and increased risks of floods and storm surges. Climate adaptation seeking to prevent the impacts of these risks has so far been disconnected from urban planning and land use policies, setting the stage for a largely unchecked real estate market and a highly unequal development process that increases exposure and fosters increased climate vulnerability. In our research, we fill this gap by combining the participatory development of metropolitan-scale shared socioeconomic pathway narratives for the Jakarta metropolitan region (also known as Jabodetabek) with cross-analysis of path dependency factors influencing future urban development. From this primarily qualitative research foundation, we then perform semi-quantitative estimation of key development indicators that are input into an agent-based model of urban development to simulate future urban growth scenarios under each SSP. The results include three SSP narratives for the megacity-sized metropolitan region (with ca. 32 million inhabitants) and estimations for indicators that include population growth, urbanisation compactness, economic inequality, informal and precarious work, and informal and precarious settlements. We also present urban growth simulations for 2050 at 150 m resolution that incorporate the differentiation of socioeconomic profiles based on location preferences and real estate market simulation. We then analyse the growth trends versus known patterns of exposure to riverine flood and coastal storm surge and provide an outlook for future risk in the region. The novelty of this approach is threefold. First, we integrate qualitative, semi-quantitative, and simulation methods to generate future scenarios of urban growth. The potential is to lay out a clear framework for similar future-oriented work in data-scarce and highly complex urban environments in the Global South. Second, we provide medium-term socioeconomic pathways along with estimates of key socioeconomic variables, which are helpful for future risk modelling studies in the region, notably those integrating urban development. Finally, we implement an agent-based modelling approach that is flexible and accessible to scholars focusing on megacities in the Global South. Our methods are based on robust previous research and require only open data (e.g., OpenStreetMap, Global Human Settlement Layer, WorldPop, among others) and local export elicitation for their parameters and inputs. Ultimately, we hope our research supports disaster risk reduction and climate adaptation policies in the complex metropolitan regions of the Global South by reducing uncertainties and integrating risk and urban analysis.