Eigenverlag/Self

Abstract:
Extreme floods in Austria of the years 2002, 2005, 2006, 2009, 2013 and 2018 demonstrate the vulnerability of mankind against such events. River geometry responds to heavy flooding with massive morphological rearrangements. Houses and infrastructure in the affected areas are thus at risk. Therefore, an improved understanding of sediment transport processes is crucial for the analysis of morphodynamics and thus for flood risk management. Also the success of river restoration projects depends on sediment transport and morphodynamics as boundary conditions, but there is a significant lack of knowledge regarding these processes and the connected ecosystem. Sediment monitoring is intended to close these knowledge gaps, but their analysis has so far focused primarily on the sections of the river where the respective data were collected. The RAISE project now aimed to combine long-term and short-term sediment research (such as extreme flood events) in order to relate and integrate this data for the first time. An important step could be taken by the integrative consideration of the sediment monitoring stations in Austria. The understanding of sediment transport processes could be increased and occurring phenomena could be explained. The term sediment forensics was introduced and describes well the level of detail that is sometimes necessary to get more clarity about the transport processes in a catchment area. Sediment intrusion or higher availability was identified as a source of increased bed load and the importance of the catchment area and anthropogenic influence was determined. However, it could also be shown how important a functioning sediment management is and that such a management is often lacking on Austrian rivers. It is often necessary to react after damage instead of acting before it occurs. It could be shown that only by an extreme event, on a river that basically suffers from a sediment deficit, a sediment surplus suddenly leads to problems. An integrative sediment management should therefore promote a certain sediment resilience of the river so that extreme events can take place without the recent very high damages. The analyses of the various catchment areas have shown how different the problems and approaches to solving them are in the individual rivers. With the developed questionnaire, an instrument was created that enables the transdisciplinary identification of problems and weaknesses of sediment management in a river. Now it is a task for the upcoming years to establish concepts for sediment management on Austrian rivers, which are supported by measurement data.