New insights into Moselle River floods revealed by instrumental data

The flood history of the transboundary Moselle River has so far not been analysed at the watershed scale. This study is based on a large collection of historical archives in hydrology dating to the beginning of the instrumental period. Many valuable archives are made available by the authors but data are discontinuous and heterogeneous. We describe homogenization and reconstruction methods leading to an original flood dataset covering the entire Moselle basin over the last two centuries. The flood series show that the basin is predominantly affected by oceanic floods that mostly occur in winter and that severe flooding generally affects the entire basin. A flood frequency analysis shows that the series are stationary and that flood quantiles obtained with short measured record series and reconstructed series are quite similar. However, although long historical series give robustness to the frequency analyses they also highlight bias and uncertainties related to sampling.