For the flood modeling we use observed weather data from the time period 1971-2010 to drive a series of global hydrological models (GHMs). We use an ensemble of 46 combinations of weather data sets and GHMs, all participating in the The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) phase 2a. On the basis of these weather conditions, the GHMs are then able to calculate the runoff in each location of the world on a 0.25 x 0.25 degree resolution on a daily basis. In order to derive flooded areas and the flood depth, we use this runoff to force a river routing model that includes topographical information and the exact river routes. In this way we produce annual global maps of flooded areas and flood depth (example for Bangladesh in Figure 7 of the main article). In this modeling approach we can be sure that changes in these areas over time are only caused by atmospheric changes, as the hydrological models assume fixed urbanisation and river regulation patterns.
Modeled flooded fractions of each gridcell.
FIG 1 / Image source: Sauer et al. (2021)
1 Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany