**Data sources**

Before starting risk assessment the area of investigation has to be well defined and rainfall runoff modelling as well as hydraulic simulations have to be accomplished. Additionally, some economic pre-calculations like the determination of asset values have to be carried out.

Basis of each risk related consideration is the area of investigation as the size of this area determines the scale which is relevant for further analysis. Related to flood risk this area is normally smaller than a watershed which defines the catchment area. Mostly, the area of interest is the inundated area. But nevertheless data related to the catchment area are necessary for pre-processing. Therefore influences caused by floods can predominantly be analysed within the respective catchment area.