Understanding flood triggering mechanisms and flood risk changes

Floods are caused by the interaction of several physical processes and factors including meteorological conditions, the soil moisture state of the catchment, the type of the dominant runoff generation processes, and river routing (e.g., NIED et al. 2014). Detailed knowledge of the synoptic-scale and meso-scale meteorological conditions leading to the triggering of flood-producing rainfall, information on the antecedent wetness conditions of soils in the catchment, and detailed information of the relevant hydrological processes that lead to runoff formation, all contribute to a better understanding and prediction of floods. The first part of this section (5.2) provides a summary of the current knowledge of both climatic and non-climatic divers of floods in Switzerland and globally. The second part of this section (5.3) discusses anthropogenic influences on flood frequency and magnitude. The third part (5.4) discusses exposure and vulnerability aspects of flood risk. The final fourth part (5.5) summarizes our current knowledge of changes in flood triggering mechanisms and flood risk factors in the recent past.