Sebastian Roger

A new approach to investigate the interactions between sediment transport and ecotoxicological processes during flood events

Extreme hydrodynamic events such as flood events or dredging activities bear the risk of eroding sediments in rivers, reservoirs, harbour basins or estuaries. One of the key concerns associated with these erosion processes is the re-mobilisation of sediment-bound pollutants in highly contaminated sediments. To date, much research has been conducted to characterise flow and sediment processes associated with hydrological events such as floods. Furthermore, there is a large body of literature describing the interaction of contaminants associated with particulate matter to aquatic biota. However, there is little knowledge regarding interactions between hydro-sedimentological and ecotoxicological processes. Understanding of the ecotoxicological consequences and associated risks to aquatic wildlife associated with hydraulic events can provide critical information to regulatory bodies or managing authorities. Specifically, it will aid in assessing risks associated with current management practices and will aid in developing more sustainable future management practices for waterways or harbours. Therefore, a combined experimental methodology between hydraulic engineers and ecotoxicologists was developed to investigate the ecological and toxicological relevance of sediment re-suspension and transport during erosion. An overview of this methodology is given in the present paper.

Dike-Break Induced Flows: a Simplified Model

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a macroscopic control volume. A proper definition of the shape of the control volume enables to take the main characteristics of the flow into account and thus to compensate for the extreme simplification of the spatial representation of the model. At the breach, a relation derived from the shallow-water equations is used to determine the direction of the flow. Developments have been guided by numerical simulations and results have been compared to experimental data. Both the accuracy and the domain of validity of the simplified model are found satisfactory.

Hybride Modellierung deichbruchinduzierter Strömungen

Experimentelle Modellversuche und numerische Simulationen erganzen sich gegenseitig in einem hybriden Untersuchungskonzept fur deichbruchinduzierte Stromungen. Unter Berucksichtigung der deichbruchspezifischen Randbedingungen werden in Laborversuchen charakteristische Stromungsfeldgrosen mit hochgenauer Messtechnik detailliert aufgezeichnet. Die korrespondierenden numerischen Modellierungen werden auf Basis der zweidimensional tiefengemittelten Flachwassergleichungen sowie der Reynolds-gemittelten Navier- Stokes-Gleichungen durchgefuhrt.