Quantitative evaluation of life loss induced by embankment failure with the impact of riverbed deformation

Drastic riverbed deformation caused by intensive human activities will change river hydraulics which may impact the fluvial inundation. The Beijiang River has undergone severe downward incisions due to in-channel human activities, greatly increasing its discharge capacity. This study analyzed flood loss of life induced by dike breaches considering the effects of riverbed deformation. The hydrodynamic model coupled with the embankment failure model was established to simulate floods and provide the basis for mortality evaluation under different scenarios. The results show that the maximum inundation depth decreased by approximately 2 m and the flood arrival time was also delayed due to riverbed undercutting. The flood mortality in most areas in 2020 has decreased by approximately 0.2 compared with that in 1999. The changes in flood hydrodynamics contributed over 80% to the decline in mortality rate in the areas near the breach, while the mortality in the remaining zone that far away from the breach was more sensitive to the flood arrival time. Early warning is an effective measure to reduce loss of life during flood disasters, and a 12-hour advance warning may reduce the mortality rate by more than 50%. This study provides a reference for evaluating the impact of riverbed evolution on flood risk and mitigating losses of flood disasters. • Riverbed deformation and stage-discharge in the past two decades are analyzed. • This study establishes a fluvial inundation model coupled with a parametrized breach development model for hydrodynamic simulations. • The flood characteristics and life loss induced by dike breaches are quantitatively estimated. • The effect of flood arrival time and hydrodynamic parameters on flood mortality is investigated. • The contribution of early evacuation warnings to flood mortality decreasing is explored.