Diagnosing long-term divergence in Build Back Better outcomes in low- and lower-middle-income communities

Low-income communities in disaster-prone regions face persistent challenges in translating post-disaster recovery investments into sustained resilience, as they navigate trade-offs among engineering objectives, policy constraints, and evolving socio-economic needs. Despite the widespread adoption of Build Back Better (BBB) principles, evidence on the long-term sustainability of outcomes remains limited, particularly in low- and lower-middle-income contexts. This study examines the sustainability of BBB outcomes in two Indonesian case studies: Banda Aceh (approximately 18 years after the 2004 Indian Ocean tsunami) and Central Sulawesi (approximately 4 years after the 2018 earthquake, liquefaction, and tsunami). Drawing on structured housing assessments, household surveys, semi-structured interviews, and stakeholder consultations, the study evaluates how risk-informed design, zoning controls, and recovery governance mechanisms persist or erode over time. Across both cases, five recurring divergence pathways are identified: spatial non-compliance and location persistence, incremental housing adaptation, functional erosion of risk-informed design features, reversion to non-engineered construction practices, and institutional memory decay. These pathways reflect interacting institutional, socio-economic, and technical barriers whose influence evolves across recovery phases. Central Sulawesi illustrates medium-term feasibility challenges linked to relocation delays and livelihood dependency, while Banda Aceh reveals longer-term institutional drift, coastal re-encroachment, and erosion of risk-informed practices. To address these dynamics, the study develops and applies a temporal multi-barrier lever framework that conceptualizes BBB as a path-dependent process shaped by evolving cross-domain interactions. The framework is operationalized through a logic matrix linking divergence pathways to coordinated, time-sequenced levers across recovery phases. The findings show that sustaining BBB requires continuous alignment among governance, livelihoods, adaptable design, and institutional capacity. The study contributes longitudinal evidence and a practical framework for governments and NGOs to sustain resilience gains beyond reconstruction.