More than just fast flowing water: the landscape impact of the July 2021 west Germany flood

Rain driven flash floods have severe impacts on society and landscape functions. The July 2021 flood in the Eifel region, west Germany, was one drastic example of such impact. While media and scientists rightfully highlighted the meteorological and hydrological aspects of this flood, it was the concurrent reorganisation of important landscape conditions and the debris carried by the fast flowing water that made this flood so devastating and unpredictable.Here, we take a process-based impact perspective and systematically ask, which were the specific roles of non-hydraulic but geomorphic dynamics that implemented the damage, caused flood non-linearities and amplified the landscape deterioration. We combine insights from field mapping campaigns during, right after and within the relaxation phase of the flood with high resolution geophysical and LiDAR surveys to discuss the role of hillslopes, vegetation, fluvial sediment mobilisation and the legacy of anthropogenic landscape reorganisation. We conclude that some of these elements emerged as the flood event evolved, causing either transient effects or persistent landscape features, thus modifying the response of the landscape to future events, also to less intense precipitation events.Our findings not only support more tailored recovery efforts for the flood affected Eifel catchments, but should also inform landscape development trajectories and potentially crucial factors in other Central European regions.