CASE STUDY 1 Submerged neighbourhood: compounding impacts of subsidence and sea-level rise, Muara Baru, Jakarta, Indonesia Localized areas of Muara Baru, a low-lying area in northern Jakarta, has been reported to experience subsidence rates of 60mm per year. When combined with sea-level rise, this area has experienced frequent and worsening floods, especially during high tides. Notably, landmarks such as the Waladuna Mosque have submerged over recent decades. Since 2009, rising water levels have rendered parts of neighbourhoods unusable, forcing businesses and residents to relocate. The challenges have been associated with subsidence, sea- level rise and inadequate water management. The situation in Muara Baru highlights the urgent need for comprehensive resilience strategies to protect communities and local economies from the escalating risks associated with subsidence and the broader climate crisis. Sources: Bott et al. (2021). Land subsidence in Jakarta and Semarang Bay – The relationship between physical processes, risk perception, and household adaptation. Ocean & Coastal Management, vol. 211, no.105775. https://doi.org/10.1016/j.ocecoaman.2021.105775; Kompas. (2022, 28 November). Menengok Masjid Wal Adhuna, saksi bisu tenggelamnya pesisir Jakarta. https://megapolitan.kompas.com/ read/2022/11/28/18415841/menengok-masjid-wal-adhuna-saksi-bisu- tenggelamnya-pesisir-jakarta?page=1.Subsidence generates both direct and indirect impacts. Direct losses encompass damage to critical infrastructure, such as roads, buildings, railways, ports and utilities, resulting in increased maintenance expenditures and declining property values.17,18 These vulnerabilities risk being exacerbated by ageing infrastructure, much of which was designed for past conditions, and may now be inadequate to withstand current and future climate-related and other shocks. Land loss from subsidence constrains housing availability, economic development and agricultural productivity. Additionally, as coastal land sinks and sea levels rise, saltwater intrusion into freshwater resources intensifies, threatening water security for households, industry and agriculture alike.19,20,21 Subsidence alone can increase flood risks, and when combined with rising sea levels and more frequent extreme weather events, the likelihood of flooding and infrastructure failures is significantly amplified. These impacts can strain emergency response systems, disrupt public services and supply chains, and undermine local economies and livelihoods.The true burden of land subsidence is likely underestimated, as cascading social, health, environmental and economic interdependencies, particularly in the context of the climate crisis, are not yet fully captured. Impacts are likely to be most severe in cities with limited monitoring capabilities and resources to fully assess the issues, carry out risk assessments and implement response measures. Social and health implications The social and health ramifications of land subsidence are equally significant, as sinking amplifies vulnerability to flooding and acts as a risk multiplier when combined with sea-level rise or extreme weather.22,23 In severe cases, flooding can displace residents and businesses, disrupt livelihoods and limit access to essential services. Large-scale displacement places additional pressure on governments and local economies, with marginalized communities often lacking resources for adaptation and relocation.24 The Waladuna Mosque submerged in water due to tidal flooding: Muara Baru, Jakarta, Indonesia Resilient Economies: Strategies for Sinking Cities and Flood Risks 7

Resilient Economies Strategies for Sinking Cities and Flood Risks 2025