Linda Bergmann (Germany) 1; Regina Patzwahl (Germany) 1; Alexander Kikillus (Germany) 1; Nils Huber (Germany) 1
1 - Federal Waterways Engineering and Research Institute - Germany
The effects of climate change on the functionality of waterways are yet not clear. A possible shift in water levels, especially intensified low water periods, due to climate change has a major impact on inland waterway navigability and transport. In the past decades, river training structures were built to improve the flow conditions and dredging was applied to increase water depths. With regard to the oncoming climate change it presents the challenging task of assessing impact and defining appropriate measures for adaption.
Within the German research program ‘Network of Experts’, the robustness of the German transport infrastructure is examined in regard to oncoming climate change. This research program also aims to ensure the reliability of our waterways and maintain their central role in the complex European transport network. In order to generate hydrological data for a wide range of climate scenarios, a modelling chain consisting of an ensemble of global and regional climate and hydrological models is used. The predicted hydrographs allow the assessment and prioritization of measures in subsequent steps.
To investigate the effects – including flood neutrality – of a planned river training measure, it is common practice to use two dimensional hydrodynamic numerical models. But this alone is not sufficient, because when assessing their suitability for the field of climate change, several more considerations must be taken into account. When it comes to assessing the efficiency of a measure, a severe limitation of a pure hydro-numeric model is the fixed river bed, as the morphological reaction of the river to the measure is not taken into account.
The workflow presented here contains a four-step process. First, flow velocities and water levels, among other outputs, are calculated using a steady-state two dimensional hydrodynamic numerical model. These results are then input into a second model which evaluates the navigability of a river from a weighted set of relevant parameters. In a third step the measures’ effects on the river bed will be estimated with a single grain size sediment transport model. The modeled future river bed is then looped back into the hydro-numeric model and eventually evaluating the forecasted navigability. Finally, a comparison in regard to the waterway’s performance under climate change conditions between the actual state and the adapted state allows profound decision-making.
The workflow will be demonstrated using the example of the Lower Rhine in Germany and the experiences made with it will be presented.