Impacts of Global and Climate Change Uncertainties for Disaster Risk Projections: A Case Study on Rainfall-Induced Flood Risk in Bangladesh

Future risks linked to extreme events and options for managing them are receiving increasing attention in the research and policy arena, where uncertainty is considered to be one of the most challenging aspects in regard to disasters triggered by natural hazards. To shed more light on this issue, this study conducts a detailed uncertainty assessment of a forward-looking country level catastrophe risk model for extreme flood events in Bangladesh and identifies how various sources of uncertainties contribute to the variability in modeling results. Alternative assumptions of climate, exposure and vulnerability parameters show that scenario uncertainty regarding socio-economic development — and exposure in particular — seems to dominate other sources of uncertainty. Importantly, this trend is particularly notable for the estimate of extreme events rather than annual average losses and for the prediction over the longer-time horizons rather than near future. It is concluded that there is ample need to better understand how future vulnerability and exposure will develop as they found to be core determinants of risk, apart from climate change, for increases in extreme losses. One viable way is the incorporation of bottom-up assessment of exposure asset build-up and further analysis of vulnerability drivers, which could reduce epistemic uncertainty regarding projection of catastrophic economic losses into future. It is suggested that the concept of “iterative risk management” may provide a feasible way to achieve reduction of these uncertainties in a step-by-step basis.