Five research topics were handled within the hydro-geomorphology study: (1) tidal damping/amplification, (2) relation between habitats and the tide, (3) suspended sediments, (4) residence times, and (5) tidal marshes. For each topic a number of specific research questions were listed (see §2). To be able to answer these questions several main parameters (i.e. Directly measured in the estuary) were collected (topo-bathymetry data, tide, salinity, SPM, freshwater discharges and tidal marsh data). Furthermore some additional parameters were derived (e.g., flow velocities, tidal energy, tidal damping scale) using some specific techniques (e.g., cubage technique, Dalrymple energy concept).
We found that tidal damping in an estuary becomes important once the estuary depth (i.e. Cross-section averaged depth at low water) becomes lower than 4.2 – 7.7 m, depending on the estuary-convergence. Similar results were found for the habitat analysis: once the area of the deep subtidal habitat (> 5 m below low water) becomes smaller than 20 %, and the area of the shallow subtidal habitat (< 5 m below low water) becomes larger than 35 %, tidal damping in an estuary prevails. Concerning SPM, turbidity maxima are associated with maxima in tidal energy. We further found that these high SPM values force tidal marshes to faster attain a high climax vegetation state with less plant diversity.