For the management of estuaries and the preservation of tidal flats it is crucial to understand the tidal flat shape and development. Previous work focused predominantly on the quasi-equilibrium shape of tidal flats along open coasts with a dominant cross-shore flow and wave exposure. This paper evaluates the shape of fringing tidal flats in engineered estuaries, where longshore velocities generally dominate. Using a long-term (20 years) topographic data set of an anthropogenically modified estuary in the Netherlands (the Western Scheldt estuary), we relate key profile shape parameters and changes over time to natural and anthropogenic processes. In an engineered estuary, the tidal flat shape depends on the estuary geometry, hydrodynamic forcings and human interventions. In contrast to open coast tidal flats, the presence of the channel and dominant longshore flow determines the available cross-shore length (accommodation space) of the tidal flat and the shape of the tidal flat. This accommodation space defines the maximum tidal flat height and opportunity for marsh development. We propose the use of the Index of Development, indicating to what extend tidal flats have space to develop. This index is not only influenced by longshore and cross-shore flow, but also (or even more) by hydraulic structures, dike realignments and channel migration. Especially the latter two strongly influence the accommodation space and thereby the maximum tidal flat height and the opportunity for marsh development. For large stretches of the Western Scheldt, the accommodation space is too small, and the majority of the tidal flats do not vertically extent to mean high water. The success of tidal flat and marsh restoration projects depends on the accommodation space.

中文翻译：

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工程河口边缘滩涂的形状

对于河口的管理和滩涂的保护，了解滩涂的形状和发展至关重要。以前的工作主要集中于开放海岸沿线潮滩的准平衡形状，其中跨岸流和波浪暴露占主导地位。本文评估了工程河口边缘潮滩的形状，其中沿岸速度通常占主导地位。使用荷兰人为改造河口（西斯海尔德河口）的长期（20 年）地形数据集，我们将关键剖面形状参数和随时间的变化与自然和人为过程联系起来。在工程河口中，潮滩形状取决于河口几何形状、水动力和人类干预。与开阔的海岸滩涂相比，河道和主要沿岸流的存在决定了滩涂的可用跨岸长度（容纳空间）和滩涂的形状。该住宿空间定义了最大滩涂高度和沼泽开发的机会。我们建议使用发展指数，表明滩涂有多大的发展空间。该指数不仅受到沿岸和跨岸水流的影响，而且（甚至更多）受到水工结构、堤坝调整和河道迁移的影响。特别是后两者强烈影响住宿空间，从而影响最大滩涂高度和沼泽开发的机会。对于西斯海尔德河的大片地区来说，住宿空间太小，而且大多数滩涂没有垂直延伸，这意味着高水位。滩涂和沼泽恢复工程的成功取决于住宿空间。