Uncertainties in flood risk mapping: a case study on estimating building damages for a river flood in Finland

In our review of recent flood risk mapping approaches in Europe, we noted that the sources of uncertainty were rarely questioned. We demonstrated potential sources of uncertainty in flood risk mapping of buildings using a case study of a spring flood in 2005, in Kittila, Finland. One-and two-dimensional hydraulic models of the flood corresponded well with the actual inundation. The initial modelling result of the inundated buildings differed considerably from reality, but this could be improved through modelling performed with more diverse building elevation data. The accuracy of the digital terrain model is a key determinant in the accuracy of flood hazard modelling. An exposure analysis of buildings is often utilized by an overlay analysis of map layers representing both the flood and the buildings. However, we indicated that the analysis may be partly hindered by the characteristics and inaccuracies of the building datasets used and the modelled flood. In flood damage modelling, the average damages calculated from the database were used, as empirical damage data were too general for a detailed flood damage assessment. Damage modelling with empirical and synthetic damage data could be made more reliable through better archiving of actual flood damages and by performing more diverse damage estimates of standard buildings.