The German Universities of Hanover and Lunenburg have worked together to adapt CARPA to address the problem of pollutant transportation and land use management at the Elbe Riverland in Germany.

Numerical models of hydrodynamic and sedimentation processes are referred to as coupled if they run simultaneously and interactively on a computer. The two models are uncoupled if the hydrodynamic model's results are used as input to the sedimentation model. Often it is more economical to run uncoupled models, especially if different dimensional and temporal resolutions occur in both models. For example, often the temporal resolution of hydrodynamic models has to be higher than of sedimentation models. On the other hand, uncoupled models are unacceptable if the concentration of dissolved or suspended material causes a variation in the fluid density big enough to substantially affect the flow.

Relating to the Elbe River, one- and two-dimensional models can be used for hydrodynamic studies of the stream. For modeling the influences of different vegetation types and formations on hydrodynamic processes of floodplains, at least two-dimensional models are required because one-dimensional models cannot describe occurring transversal currents.

Model Parameters

Attention has to be paid to accurately estimated roughness parameters of both river bed and floodplains as well as vegetation parameters like trunk diameter and distance. In addition, topographical input data has to be accurate. Up to now, only a digital terrain model with a grid spacing of 12.5 m and an elevation accuracy of ± 0.5 m (LGN, 2006) exists of the test site. Especially for the evaluation of sedimentation processes more accurate input data are necessary. According to the responsible authorities in Lower Saxony, a more accurate digital terrain model shall be available by midyear 2007.

To obtain numerical model results with high resolution and good quality, it seems to be necessary to use at least 2D-models, which need a lot of calculation capacity. Consequently, the size of the considered area must be limited. Therefore, we should focus on two or three representative investigation sites of some 5 to 10 river-km each.

For the development of a DSS a functional scheme is needed to couple data base information and model results. The DSS is based on three tools, which have to be combined with each other: hydraulic tool for water levels and currents, statistical tool for soil contamination, and sedimentation tool for estimating the development of soil quality and considering the interactions of hydraulics and sedimentation processes.

References

• ABRE, 2006: Website of Authority of the Biosphere Reserve Elbe River Landscape in Lower Saxony, ABRE
• BBodSchV (1998): Bundes-Bodenschutz- und Altlastenverordnung. Bundesministerium der Justiz, 17.03.1998.
• FutterMPAV, 2000: Futtermittel-, Probenahme- und Analysenverordnung vom 15.03.2000 (BGBl. I, S. 226), geändert durch Verordnung vom 27.04.2004 (BGBl. I, S. 852).
• LGN, 2006: Website of the Authority for Survey and Geo Data in Lower Saxony, LGN (Decembre 18th 2006): www.lgn.niedersachsen.de
• Simon, M., 1994: Hochwasserschutz im Einzugsgebiet der Elbe. Wasserwirtschaft Wassertechnik, 7/94, pp. 25-31.