Reconstruction of the 1374 Rhine river flood event around Cologne region using 1D-2D coupled hydraulic modelling approach

Reconstructions of the most severe historic flood events contribute to improved quantification design discharges corresponding large return periods. Reducing uncertainty has a great significance in constructing proper defences protect hinterland from future flooding. However, reconstructions peak such are generally associated with uncertainties, which arise accuracy topography, hydraulic roughness river channels and floodplains, hydrograph shape. This study sets up one dimensional-two dimensional (1D-2D) coupled model, stretching upstream Bonn at Remagen downstream Düsseldorf, Germany, length 113 km reconstruct maximum discharge 1374 event (Qmax,1374), is considered be largest last millennium Lower Rhine catchment. An analysis was performed by adopting different bed levels values order estimate influence these uncertainties on reconstructed discharge. The wave varied wide range 12,000 24,000 m3/s. resulting Qmax,1374 determined between 14,400 18,500 m3/s, were then used frequency determine Compared computed previous estimations discharge, we found significant reduction 2,000 m3/s 100,000 year period, safety standard adopted Dutch water policy for some dike sections.