The purpose of this work is to increase our understanding of the long-term morphological consequences of major human interventions in the coastal area. This will enable better predictions of the consequences of large-scale future interventions in tidal basins and estuaries.This study focuses on the effects of the closure of a tidal inlet in the southwestern part of The Netherlands: the Eastern Scheldt, during 1972-1986. An analysis of morphological and hydrodynamic parameters have been carried out to see if the Eastern Scheldt system has reached morphological stability after the closure works.For this the development of the following morphological and hydrodynamic parameters has been evaluated and compared:
cross-sectional area of the inlet
volume of the outer tidal delta
Discharge data and bathymetric soundings between 1960 and 1996 have been used for a reconstruction of the evolution of the parameters. Equilibrium relationships between tidal prism and inlet cross-sectional area, and tidal prism and sand volume of the outer tidal delta present the final situation of the parameters.The comparison of the parameters shows that the basin volume does not change, but redistribution of the sediment in the basin results in sedimentation in the channels and erosion in the inter-tidal area, until equilibrium velocities are reached. It will take more than 11 years before the outer tidal delta of theEastern Scheldt reaches equilibrium.The equilibrium relationship between tidal prism and cross-sectional area shows that the tidal volume and tidal prism should decrease with 77 %. This means that the final equilibrium situation in the inlet at the storm surge barrier location will only be reached after a very long period. The equilibrium relationship for the sand volume of the outer tidal delta cannot be used, due to a large difference in sand volumes caused by the different calculation methods of the sand volumes.Without human interference (decreasing the basin area by building dams) the system will never reach equilibrium, because the inlet will never reach an equilibrium situation. The other parameters already have reached an equilibrium or will reach an equilibrium within 20 years or more.Future studies with more digital bathymetric data of the basin can give more insight and enable predictions on the equilibrium situation of the basin.
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