As global disaster losses keep rising in the early 21st century, global disaster risk management continue to move away from top-down emergency response approaches, towards the transfer of responsibilities, powers, and resources to regional and local levels, in efforts to decentralise disaster risk management. Over the same period, researchers began to question the idea of disaster as a linear ‘cause-and-effect’ process, instead proposing that disasters are better understood as the cascading effects of non-linear interactions between environmental triggers and social-technical vulnerabilities. Theories of these interactions as ‘disaster cascades’ focused on interdependent environmental and critical infrastructure systems, which include disaster risk management teams and facilities as critical nodes within those systems. Attempting to account for the complex mix of contributing factors and feedback loops involved as disasters unfold, the concept of ‘disaster cascades’ provides the opportunity for more holistic, interdisciplinary and nuanced approaches to disaster risk assessment and management.

This interdisciplinary doctoral project uses scenarios to apply the concept of ‘disaster cascades’ in a spatiotemporal assessment of interacting environmental triggers and points of vulnerability in critical disaster risk management and development systems, using Mindanao, in the Philippines, as a case study. The Philippines is exposed to a range of geological and meteorological hazard cascades due to its position on the Pacific Ring of Fire, on an active tectonic plate boundary, in the Typhoon Belt. It was also one of the first nations to adopt the decentralised disaster risk management system recommended in the Hyogo Framework for Action (HFA) 2005- 2015. The Republic Act 10121 (RA 10121; Philippine Disaster Risk Reduction and Management Act of 2010) aimed to increase national disaster risk management capacity by decentralizing powers, responsibilities, and resources to regional and local levels. The Mindanao Island group is farthest from the national capital, has the highest levels of socio-economic vulnerability in the nation, and experienced a series of damaging disaster cascades in the decade that followed RA 10121. Using geospatial and physical science data gathered during and after multi-regional disaster events in Mindanao, statistical government data, and qualitative data from semi- structured interviews with a purposeful selection of DRRM officers (n=44), the research reconstructed the timelines and mapped the interacting hazard cascades and points of vulnerability during selected disaster cascades that occurred between 2011 and 2018. Focusing on the interactions between hazards and aligned vulnerabilities in socio-technical systems provided a rich picture not only of these vulnerabilities, but also of the spatiotemporal evolution of the Disaster Risk Reduction and Management (DRRM) system in Mindanao since RA 10121. The outputs of these retrospective research phases were then used as the basis of cascading disaster impact scenarios that integrate future development projections over the next 25 years.

Key findings with respect to the Mindanao case study were that this island group is likely to continue to experience disasters triggered by extreme meteorological events, while exposure to geological hazards related to massive volcanic eruptions and earthquakes is also likely to increase, especially those from cascading hazards like lahars, tsunami, and disease outbreaks. Social vulnerability appears to have contributed to cascading infrastructure failures, and through this to the severity and extent of disaster impacts. The rate of implementation of the decentralised management of disaster risk required by RA 10121 was found to be socially and spatially differentiated Larger, wealthier LGUs were more likely to be ahead in building the capacity of their DRRM Offices. The formalisation of the DRRMOs was also reactive and in many cases was accelerated by the natural and anthropogenic hazard events that have impacted Mindanao since 2010. LGU officers reported struggling to formalise DRRM offices and roles, and to focus on long- term plans for disaster prevention and mitigation, rather than short-term response and preparedness. Mainstreaming DRRM into development and land use planning had also proved challenging, even in areas recently severely affected by hazard cascades, due to concurrent roles, lack of local expertise and the non-prioritization of land-use planning by local chief executives and legislators. Key factors found to affect the mitigation and prevention of disaster impacts in Mindanao were (A) direction setting and knowledge transfer across government levels and political boundaries, (B) essential partnerships linking national oversight and local legislation, and (C) the development and maintenance of hazard monitoring, communication, transport, power, and local social networks. Recommendations to improve DRRM systems in Mindanao include: 1) prioritise funding for LGUs in deprived regions to implement RA 10121; 2) require greater accountability at local government level for the implementation of RA 10121, particularly with regards to the formalisation of DRRM offices; 3) increase the integration and alignment of the activities of relevant government agencies responsible for different aspects of the new DRRM system; 4) improve access to DRRM science and technology at the local level; 5) invest in systematic DRRM training and education; 6) improve the national DRRM data management system.

Key findings with respect to the use of the concept of ‘disaster cascades’ were that this concept allowed the development of hazard and impact assessments that were geophysically and geospatially rigorous, while at the same time identifying the contribution of aligned vulnerabilities in critical infrastructure (including management and planning functions). Synthesising interdisciplinary data in hazard, impact, and vulnerability assessments, and to build scenarios based on the concept of disaster as cascading interactions between complex environmental and socio-technical systems can provide a valuable spatiotemporal picture of the complex mix of disaster vulnerabilities, exposure, and resilience to cascading hazard events over time and across scale, in a particular region. Like all interdisciplinary research projects, this research entailed trade-offs and associated scope restrictions, particularly with respect to in depth reviews of discipline-specific literature. The emphasis on geophysical and geospatial science meant that qualitative research was restricted to gathering data to identify the aligned vulnerabilities in DRRM and development and land use planning that contributed to particular disaster cascades. The use of the disaster cascades concept, however, is open to applications with a different disciplinary balance. If, for example, the primary discipline was one of the social sciences, scope restrictions would be required with respect to incorporation of geospatial and geophysical data. Although scope restrictions are necessary, they are compensated for by the broad picture provided by spatiotemporal assessments of the interaction of DRRM and cascading hazards in the recent past, and the application of those findings to develop future scenarios that incorporate climate and population projections, rates of decentralised DRRM, integrated development planning and different kinds of cascading disasters. The use of the concept of disaster cascades to inform interdisciplinary hazard and impact assessments that identify the contribution of aligned vulnerabilities is widely applicable, and likely to be of particular value for those involved in planning for DRRM, climate change adaptation and development.