Recent morphological development of anabranches on the Elbe estuary, Germany

Anabranches in rivers and estuaries represent an important ecosystem service for different aspects, from protection against floods till improvement of fauna and flora quality. In estuaries, anthropogenic interferences have altered these systems for centuries while its relevance has increased. In this work, multibeam echosounding measurements covering three concessive years are used to describe the actual morphology and recent development of four anabranches on the Elbe estuary, a high anthropogeniclly influenced area. Results show that the four anabranches differ greatly in length, depth and presence of bed features. Their development during the three years period is also different. Two anabranches close to the city of Hamburg, deeper and richer in bed features, are mostly stable, with slight aggradation rates. On the other hand, two anabranches more downstream, both shallower and mostly flat, show a clear aggradation tendency. The high-resolution measurements also allowed the analysis of the development of sand dunes in the two anabranches closer to Hamburg, showing a propagation upstream accordingly with the tidal asymmetry in favor of the flood tide present in the Elbe estuary.

Subjects

Anabranch

Elbe

Estuary

Morphology

DDC Class

333.7: Natural Resources, Energy and Environment

620: Engineering

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Recent morphological development of anabranches on the Elbe estuary, Germany