SUPERVISOR: Helmut HABERSACK

PROJECT ASSIGNED TO: Markus EDER 

Floods are the most frequent type of disasters and affect the largest number of persons (around two billion people in recent decades 1997 to 2017) among all natural catastrophes. One of the reasons why the level of flood damage remains high can be attributed to population and economic growth in flood-prone areas, and generally a lack of attention to flood risk prevention, specifically flood-sensitive spatial planning. Historically, controlling rivers with structural defence measures, such as levees or embankments, was seen as the principal solution to protect vulnerable areas against flooding. However, severe floods have led to overtopping or failure of these structures and therefore showed that technical defences alone are themselves vulnerable, especially against catastrophic events and may result in higher damage in protected areas. In addition, a degradation of riparian and river ecosystems as well as a loss of areas for flood retention led to a significant increase in flood peaks and acceleration of flood waves. Non-structural measures such as the preservation and/or restoration of floodplains were identified as appropriate measures for a sustainable flood risk management at a river-basin scale. Floodplains generally decelerate and reduce the flood peak, and thus contribute towards mitigating the flood hazard potential. . Moreover, river floodplains fulfil important ecological and recreational functions. As highly endangered ecosystems – 90% of floodplains in Europe and North America are impaired by anthropogenic activities – conserving and restoring floodplains have become a priority in environmental and water policy.

In this thesis, the opportunities and constraints of a sustainable flood risk and floodplain management are investigated with the goal to expand an existing methodology for the evaluation of floodplains (Floodplain Evaluation Matrix – FEM). The developed method is based on 2D hydrodynamic-numerical modelling and GIS-analyses. Giving stakeholders and decision makers the opportunity to assess and to compare expected future changes in flood hazard, flood exposure and flood damage due to land use changes (e.g. expansion of settlements) and climatic changes (e.g. increase of discharges) on the level of river stretches. Therefore, quantitative and qualitative research methods from the fields of hydrology, hydraulic engineering, spatial planning and political sciences are used to account for the interactions between these fields within flood risk management, in particular between the policy domains flood risk management and spatial planning. One output of this thesis will be a supportive method for a future-oriented flood risk and floodplain management at a river-basin scale.

In the second part of the thesis, the importance of floodplains along the Danube River for flood risk management, ecology and socio-economics are determined with the Floodplain Evaluation Matrix. For most rivers, there is generally a lack of knowledge about the multiple benefits of their floodplains in regard to flood risk reduction, ecology and socio-economic. Hydrological (e.g. peak reduction), hydraulic (e.g. water level change), ecological (e.g. protected species) and socio-economic (e.g. affected buildings) parameters are used for the determination of the importance of  floodplains along the Danube. The results are assembled in the Floodplain Evaluation Matrix. In addition, these parameters are also calculated and compared with the identified potential floodplains along the Danube.

The findings of this thesis will give stakeholders, decision makers and practitioners tools to foster sustainable floodplain and flood risk management and show them the importance of the remaining floodplains.