The gradients were found to vary remarkably across the globe and are overall smaller in the upper range of flood magnitudes that in the lower range. We test the applicability of the method on local, national, and global scale by using existing data sets, including flood hazard maps, flood protection standards, floodplain delineation, river network definition, and spatial population distribution. We calculate the normalized gradients of the flood exposure curves, that is, the increase in the exposure and magnitude of the perturbed event relative to the exposure and magnitude of the current scenario. The increase in the impact of a current design flood compared to its counterfactual illustrates the sensitivity to changes in hazard. The method is based on downward counterfactuals, namely perturbations of a selected flood scenario by increasing its magnitude, interpreted in this case as the worsening of a today’s design flood event as a result of climatic changes. To overcome these problems, we propose a method for analyzing and mapping the sensitivity of population exposure in floodplains to changes in flood magnitude. Moreover, uncertainties are expected to propagate through the model cascade. Model results are found to be sensitive to climate forcing, the structure of the underlying models, the choice of methods used for downscaling and bias correction, and the use of extreme value analysis for both current and future climate conditions.

However, this approach is subject to uncertainties. Most studies investigating the impact that climatic change has on flood risk are based on a cascade of global climate model simulations coupled with regional climate models, hydrologic models, inundation models, and flood impact models. However, these areas are commonly exposed to floods, and the increasing population together with the changes in storminess as a result of global warming mean that the risks from flooding are expected to rise. The floodplains of rivers are relevant living spaces for population globally and provide favorable locations for economic development. 2Environmental Fluid Dynamics Group, Andalusian Institute for Earth System Research, University of Granada, Granada, Spain.1Mobiliar Lab for Natural Risks, Oeschger Centre for Climate Change Research, Institute of Geography, University of Bern, Bern, Switzerland.

Flat earth after flood map