The Rhine reach comprising the Niederrhein and the Upper Rhine Delta is characterized by a long history of engineering interventions. The area is densely populated and the Rhine, the main inland waterway in Europe, justifying the need for such measures. Interventions have had a strong impact on morphodynamic channel characteristics. We use bed level data collected since 1926 to assess large scale bed level change in the Upper Rhine Delta and Niederrhein. The field data show various trends both at the large scale and locally. A reduction of the main channel slope is observed in the Waal and the IJssel branches of the Rhine Delta, achieved through bed degradation. In the Pannerdensch Kanaal-Nederrijn-Lek branch, the morphoynamics are controlled by three weirs, downstream of which degradation has developed. The downstream half of the Niederrhein has degraded, resulting in a slope increase. Most of the domain has remained relatively stable for at least 20 years. The observed trends provide insight on the river response to interventions, which helps to better understand degradation processes, in model calibration, and in anticipating future change of channel geometry. ... Read more

The co-occurrence of storm surge, high tides and heavy precipitation increases flood probability and potential consequences compared to each hazard separately in Delta cities. The Huangpu River (HP) is a tributary of the Yangtze River in China, which drains Tai Lake to the west of Shanghai city, and meanders through downtown Shanghai. During typhoon events, storm surge reverses the river flow and pushes the water level up as far as 100km upstream. If storm surge (1-2 m above msl) co-occurs with high tide (2-3 m above msl), it poses great threats to the HP floodwall (crest level from ~3-5.5m above msl). At the same time, typhoons cause heavy precipitation (up to 70-80mm/hour) in the city, which increases urban drainage discharge in the pipeline system. In order to prevent elevated water levels in the river, stormwater drainage is ceased to effectively work in this situation. Pluvial and fluvial flooding occur simultaneously. The objective of this paper is to develop a hydrodynamic model to simulate simultaneous pluvial and fluvial flooding and to produce inundation maps due to failure of floodwalls and the urban drainage system. We apply the Delft3D FM numerical model to compound flood events in Shanghai. Results raise risk awareness for decision-makers during compound flood events and demonstrate the importance of compound flood modelling at a city scale. ... Read more