MORPHODYNAMIC PROCESSES IN ESTUARIES - COMPARISON OF MARINE AND LIMNIC TIDAL FLATS

Tidal flat areas in estuaries are affected by strong morphodynamics. Changes of sedimentation and erosion occur on different temporal and spatial scales. These changes challenge the responsible authorities due to the high importance of sufficient navigation channel depths and the ecological importance of those unique zones. In cooperation with the Hamburg Port Authority the Hamburg University of Technology runs broad field measurements on tidal flat areas in the Elbe estuary. The results provide a fundamental data set to improve the knowledge about morphodynamic processes. For more than 3 years water levels, waves, current parameters and suspended sediment concentrations are being recorded continuously and in a high resolution at different positions on a marine investigation area. Therefore, ADCP's, optical backscatter sensors (OBS) and pressure transducers (PT) are used. To observe the consequences of the morphodynamic processes, the bathymetry of the investigation areas is determined with a multi-beam echo sounder (MBES) in frequent intervals as well as after extreme events like storm surges. Derived from the field data certain patterns of erosion, sediment transport and sedimentation could be observed depending on tidal currents, waves and large scale weather conditions. Seasonal effects are analyzed as well as the influence of extreme events. The observed processes are compared with data from a limnic investigation area, where a second, shorter field study was carried out.