Author(s): Sonke Schriever; Yannik Baulig; Stefan Vollmer; Frauke Konig; Ina Quick
Keywords: Depth erosion rates; Monitoring; Temporal and spatial scales; Hydromorphological classification tool Valmorph; Sediment management measures; Navigable surface waters
Abstract: Depth erosion often occurs along rivers. Erosional tendencies are mainly caused by river training works, course shortenings, flood protection and reduced sediment supply due to dams and weirs. Balanced sedimentation, transport and erosion processes are of utmost importance for the connectivity of rivers and floodplains as well as for human water uses. In order to classify the level of bed incision, investigations were carried out for the case study area of the Lower Rhine in Germany, Europe’s most used waterway, using the hydromorphological classification tool Valmorph. It was developed to capture, quantify and evaluate hydromorphological conditions and changes. Comparative conditions for an evaluation have to be derived predominantly from type-specific historical quantitative data analyses. This paper analyses the Valmorph indicator ‘mean bed level changes’. Data relating to the heights of the river bed levels between the years 1896–2010 were investigated. The classifications show an immense reduction from the previously extremely high erosion rates. Additionally, the monitoring identifies cause–effect relationships between incision rates and implemented sediment management measures. The findings are shown for various temporal and spatial resolutions, reflecting the development of the depth erosion. The knowledge obtained can be used for river basin management, for example for designing large-scale measures to restore river ecosystems with sediment deficits and for monitoring their success.