ABSTRACT
Formation of a tidal inlet due to natural events or human activities often leads to long-term and large-scale coastline changes as tidal inlets interrupt the existing alongshore sediment transport pattern. The nearshore wave climate which provides energy to mobilise sediment is in turn altered as a result of the evolving beach-inlet system. These processes might finally lead to significant impacts on the coastline adjacent to inlets resulting in socioeconomic and environmental hazards. Thus, inlet effects on adjacent coastlines are important in the context of sustainable coastal management planning. Sediment bypassing at tidal inlets is one main process that governs coastline morphology. FitzGerald et al (1978) described three main categories of sediment bypassing viz. migrating inlets, breaching ebb-tidal delta channels and stable inlets. Coastline changes associated with deep inlet gorges occur due to wave generated sediment transport (FitzGerald, 1988). The degree of inlet effects depends on the tidal range, resulting in specific morphological features (i.e. micro-tidal environment: long and relatively narrow barrier islands (Texas, eastern Florida), meso-tidal environment: short and stubby islands (Georgia, Wadden Sea)). The Ameland inlet which is the focus of this study, is located in a meso-tidal environment and consists of a deep inlet gorge (see section 2.4). Thus, sediment bypassing can be expected due to breaching of the ebb-tidal delta channels in combination with wave effects. Empirical formulas (i.e. based on littoral drift and inlet hydrodynamics) are used to classify tidal inlets and in turn imply the coastline effects (Brunn and Gerritsen, 1960; Hubbard, 1976; FitzGerald et al., 1978; FitzGerald, 1988; Oertel, 1988; Bruun, 1986). These studies suggested that the inlet effect on the downdrift coastline would be greater at mixed-energy tidal inlets. Work and Dean (1990) used an analytical even/odd method to evaluate the inlet effect on the adjacent coastlines of the Florida Coast. A similar approach can be found in Fenster and Dolan (1996) who analysed the existing inlet effects on the US mid-Atlantic Coast. Castelle et al (2007) applied a numerical model and used aerial photographs to investigate the inlet effect at the Gold Coast, Australia from 1973 to 2005. Galgano (2009a,b) analysed the spatial and temporal evolution of the downdrift coastline of
stabilised tidal inlets based on long-term coastline change data of the US Coast (e.g. Long Island, South Carolina, Delaware, Florida). To date, however, the inlet effects on barrier islands of the Dutch Wadden Sea have not been fully investigated. Hence, the present analysis was undertaken with the aim of gaining qualitative insights into the inlet effects and related physical processes of the Ameland inlet. The study adopts the realistic analogue modeling philosophy in which the long term morphological evolution of a schematised inlet that closely resembles the study site is examined in detail.
