A rainfall-induced multi-hazard framework integrating flood, landslide, and their cascading effects: Application to Saint Vincent Island

Multi-hazards pose increasing risks due to complex interconnections and amplified impacts, needing a thorough understanding of their dynamics. Modeling such interactions on a regional scale is difficult, with few frameworks providing simple yet efficient approaches. The present study proposes a novel regional-scale framework for multi-hazard assessment focusing on cascading interactions due to flood and landslide hazards.  

The first step involves a detailed assessment of flood hazards in the study area for a rainfall event. Separately, landslide hazards are evaluated to identify and highlight landslide initiation points. The cascading hazard model uses reach angle to translate landslide hazards into sediment transport within the river network. The sediment transport from the rainfall event is then compared with reference sediment transport corresponding to a specific return period to classify cascading hazards into four levels. The outputs of the flood and cascading models are combined to classify multi-hazard into four levels across the river network. These hazard levels are further aggregated into mapping units such as sub-basins, forming combined hazards.  Finally, a hazard matrix merges landslide and combined hazards to produce the overall multi-hazard assessment.

An initial version of this proposed framework is tested on Saint Vincent Island, focusing on a significant event that resulted in widespread flooding and landslides.  Preliminary results from applying the multi-hazard framework highlight its effectiveness in identifying zones of heightened risk, particularly in areas where landslides and sediment transport significantly affect the river network and surrounding regions. These findings offer critical insights into the interactions and dynamics of rainfall-induced multi-hazards, demonstrating the framework's potential to inform proactive risk management. The initial outcomes highlight the framework's applicability as a practical tool for hazard mitigation planning while contributing to the broader advancement of multi-hazard research and assessment methodologies.