Disaster risk reduction strategies for cold lahar-induced flash floods at Mount Marapi, Indonesia

Cold lahar-induced flash floods represent a recurrent and complex disaster in volcanic regions, particularly in Indonesia, where interactions between volcanic activity, extreme rainfall and watershed characteristics intensified disaster risk. Despite repeated events, disaster risk reduction at the local level has remained fragmented and weakly informed by spatial risk evidence. This study aimed to analyse the impacts of the 11 May 2024 cold lahar flash flood in Agam Regency, assess spatial disaster risk potential and develop disaster risk reduction strategies to support local disaster risk governance. This study applied a mixed-methods approach, combining spatial analysis using Geographic Information Systems with multi-criteria decision-making techniques. Disaster impacts were assessed at the nagari level based on human, economic and physical indicators. Spatial risk analysis integrated flash flood hazard maps, volcanic hazard zones and land-use patterns. Interpretive Structural Modelling (ISM) was used to identify and structure disaster risk reduction strategies. The results showed that disaster impacts were highly localised along river corridors originating from both Mount Marapi and Mount Singgalang, indicating a multi-source hazard system. Spatial risk distribution was strongly influenced by land-use patterns and watershed configuration. Disaster-mitigation-based land-use control, relocation of communities in high-risk areas and the development of alternative livelihoods emerged as the main driving strategies.

The findings highlighted the importance of integrating spatial risk assessment with local planning and socio-economic interventions to reduce disaster risk. This study contributes practical insights for strengthening locally grounded and community-oriented disaster risk governance in volcanic regions of developing countries.