Exploring coastal morphodynamics of Ameland (the Netherlands) with remote sensing monitoring techniques and dynamic modelling in GIS

The Wadden islands are partly protected by ebb-tidal deltas. The spatial pattern of channels and shoals on these deltas is important for the coastal morphological development of the extremes of these islands. An extensive beachplain with a large swashbar occurs at the head of Ameland. Recent changes of Ameland's northwestern beachplain are cause for concern for management. Yearly elevation data for the past 11 years (1985-1996) were interpolated to create elevation maps. Two spatio-temporal GISs have been used to describe the long-term development of this beachplain: a fieldbased GIS and an object-oriented GIS. The description resulted in the differentiation of three phases in the morphological development of the beachplain. The beachplain shows a regular development within these three phases, although it is irregularly cyclic in the long-run. Prediction based on long-term historical trends is therefore difficult. However, in the last phase a decrease in activity was noted, because of a lack of erodible sand; in the past, Ameland's west coast has been stabilized with groynes. This state of inactivity might come to an end when a new phase begins, e.g. by the amalgamation of a shoal to the beachplain. A sequence of storm floods could change the stable situation for the swashbar; causing the landward migration of the swashbar and the filling of the lagoon. Submitted in an adapted form. M.A. Eleveld. The evolution of a beachplain related to the migration of channels and shoals on the ebb-tidal delta. Journal of Coastal Research.