Developing a Stochastic Multi-Hazard Environmental Risk Framework for Coastal Megacities in Sub-Saharan Africa: Application to Lagos

This dissertation develops an original stochastic multi-hazard environmental risk framework for assessing and managing compounding environmental risks in sub-Saharan African coastal megacities, with Lagos as the primary case application. Coastal megacities in sub-Saharan Africa face simultaneous environmental hazards including sea level rise, storm surge, urban flooding, air pollution, and industrial contamination, yet risk assessment methodologies developed for temperate developed-country cities do not adequately address the compound risk interactions, data scarcity, and governance fragmentation characteristic of these cities. The theoretical contribution of this dissertation is a novel probabilistic framework that explicitly models hazard co-occurrence dependencies using copula functions, translates multi-hazard physical loads into compound exposure distributions for the urban population, and propagates governance and adaptive capacity uncertainty using Bayesian belief network structures. Empirical inputs include a fifteen-year air quality dataset, coastal tide gauge and storm surge records, urban flood damage records, industrial facility emissions inventories, and demographic vulnerability mapping for Lagos. Framework outputs are validated against historical multi-hazard event records. The framework is used to quantify the risk reduction achievable under alternative policy portfolios combining coastal protection investment, air quality regulation, flood infrastructure upgrading, and environmental health investment. Original contributions include the compound hazard interaction modelling methodology, a contextually adapted vulnerability indicator system for African megacity conditions, and a risk-informed policy prioritisation framework that accounts for equity in distributing risk reduction across Lagos communities. The dissertation provides a generalisable methodological contribution to multi-hazard risk assessment science. Keywords: multi-hazard risk, compound hazards, coastal megacity, Lagos, stochastic framework.