SedTrans

Transport of Particle-Bound Contaminants in the Middle Elbe River

(From Moshenberg 2013:)
Chemical contamination of waterways and floodplains is a pervasive environmental problem that threatens aquatic ecosystems worldwide. The Elbe River is the third largest river in Central Europe, starting in the Czech Republic and running through Dresden and Hamburg before empting into the North Sea. Due to extensive historical contamination and redistribution of contaminated sediments throughout the basin, the Elbe River transports significant loads of contaminants downstream, particularly during flood events. The high mobility of the fine-grained sediments within the basin means that sections of the Elbe River are unlikely to achieve the goals of the Water Framework Directive by 2015 (Zebisch et al., 2005). This study focuses on transport of cohesive suspended sediment and Hexachlorobenzene (HCB), a contaminant of concern in the Elbe River Basin.
Sediment-sorbed concentrations of HCB significantly exceed environmental quality criteria and the Elbe River Community (FGG Elbe) has stated that a reduction of 98 % of the sediment-bound HCB load (relative to 2006) would be necessary to achieve all management objectives (FGG Elbe, 2009). To better understand the fate and transport of cohesive sediments and sediment-sorbed HCB, a hydrodynamic and sediment transport model for the reach of the Elbe River basin between Dresden and Magdeburg was developed. An evaluation of impact of the numerous groynes, or spit dykes, along the Elbe, was integrated into the modeling effort.
BuhnenfelderA quasi-2D model, which includes both a 1D representation of the Elbe between Dresden and Magdeburg and the Elbe’s floodplains between Torgau and Magdeburg, was  developed. The model was calibrated and validated for hydrodynamics, cohesive suspended sediment and sediment-sorbed HCB. A 2D flexible mesh model was developed between Aken and Barby to evaluate the impacts of groyne fields. The 1D and 2D flexible mesh model allowed for quantification the impact of groyne fields on sediment travel time. Simulations were run to evaluate sediment travel time during high water events.
The impact analysis of Elbe groyne fields showed that they reduce transport times of cohesive material and associated sediment sorbed contaminants approximately 15 % during average hydrodynamic conditions. The quasi 2D model was run under a variety of discharge scenarios to calculate the extent of transport of sediment and sediment-bound HCB to the floodplains (337 km2) between Torgau and Magdeburg during nine high water events exceeding mean high discharge (MHQ) between 1998 and 2011. Results for sediment and HCB accumulation on floodplains are presented and discussed. A discussion of uncertainty and issues in model development is included. In addition, ample evidence that extreme high water events, such as the August, 2002 floods can have long-term implications on the suspended sediment transport regime and contaminant loads is provided.
A worst case analysis of HCB uptake by dairy cows and beef cattle indicate that significant, biologically relevant quantities of sediment-sorbed HCB accumulate on the Elbe floodplains following flood events. Given both the recent high frequency of floods in the Elbe Basin, and the potential increase in flood frequency due to climate change, an evaluation of source control measures and/or additional monitoring of floodplain soils and grasses is recommended.

Projekt Information

Funded by: Bundesanstalt für Gewässerkunde, Koblenz
Project duration: 2009-2013
Coordinators: Dr. Peter Heininger (BfG), Dr. Daniel Schwandt (BfG), Prof. Susanne Heise
Team Members: Dr. Kari Moshenberg

Publications

Moshenberg, K. & Heise, S.: HCB Transport in the Elbe River Basin: Assessing Climate-Change Impacts. Poster, HAW

Moshenberg, K., Calmano, W. & Heise, S.: Fate and Transport of Cohesive Sediment and HCB in the Middle Elbe River Basin. Vortrag, EGU, Wien 2014 (Abstract)

Moshenberg, K. (2013): Fate and transport modeling of cohesive sediment and sediment-bound HCB in the middle Elbe river basin / Modellierung des Transports kohäsiver Sedimente und des Verbleibs sedimentgebundenen Hexachlorbenzols (HCB) im Einzugsgebiet der mittleren Elbe. Dissertation an der TU Hamburg Harburg.
http://doku.b.tu-harburg.de/volltexte/2013/1248/pdf/K.Moshenberg_FinalDissertation.pdf