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

The objective of the Floodsearch project - which is funded by the Excellence Initiative of the German Federal and State Governments - is to combine the traditionally separated disciplines of hydraulic engineering and ecotoxicology in a single experimental approach in order to investigate the bioavailability and hazard potential of sediment-bound contaminants to aquatic organisms under simulated flood conditions. Depending on the flow velocity, sediments can either be eroded from or settle down in high and low flow sections in rivers, reservoirs and in harbour basins, respectively. In industrialised regions rivers and estuaries often contain large volumes of old cohesive sediments that can be polluted with toxic agents. Thus, the deposited sediments become a potential risk for the environment due to their ability to bind contaminants [1-3]. The behaviour of such contaminated materials during extreme hydraulic events is of particular interest because toxic fractions of eroded and newly suspended material can be re-suspended, and thus, become bioavailable in the water column again. Former investigations (cf. [4-6]) confirmed the bioavailability of previously immobilised particle-bound contaminants and concluded that re-suspension of sediments may have a major impact on aquatic biota. Unfortunately, no research is available combining hydraulic stresses, sedimentological response and resulting bioavailability of re-suspended contaminated sediments.The Floodsearch project combines hydraulic and ecotoxicological (hydro-toxicological) methodologies in a joint experimental study [7]. The interaction of hydraulic processes, contaminated sediments and aquatic organisms is investigated under controlled laboratory conditions. The main advantage of these experiments is the simulation of the important processes in a single model set-up (hydraulic processes, sediment erosion, transport and deposition, bioavailability of the sediment bound contaminants and the ecotoxicological effec