Author(s): Sven Wurms; Bernhard Westrich
Linked Author(s): Bernhard Westrich
Keywords: Flood retention reservoir; Numerical modelling; Sediment transport; Contaminants
Abstract: The Water Framework Directive (2000/60/EC) of the European Parliament requires the removal of toxic matters from surface waters. Using green flood retention reservoirs for the active trapping of flood induced released contaminated sediment could be one method to improve the aquatic environment. In this case study flow and sediment transport are simulated for both the filling and emptying phase of a green flood retention reservoir by using the 2Dhydrodynamic numerical simulation tool TELEMAC-2D and the numerical transport model SUBIEF. The retention effect regarding contaminated suspended sediment of a conventional green flood retention reservoir during a 100-years flood event with different sediment inflow conditions as well as varying operation rules is investigated. Due to the affinity of toxicants such as heavy metals to sediment particles in the range of few micrometers, a representative particle diameter of 20 um was chosen for the investigations. The numerical simulations have shown that the retention efficiency regarding released contaminated sediment can be increased by the extension of the residence time by decreasing the outlet discharge during the reservoir operation. This option becomes the more effective the bigger the portion of the contaminated water body containing the highest sediment concentration is which gets influenced by the extended residence time. To get an impression of the settling behaviour of different grain fractions, an additional simulation is performed with grain diameters of 20 um and 40 um.
Year: 2007