Coastal inlets and tidal basins

lecture note: Tidal inlets and their associated basins (lagoons) are a common feature of lowland coasts all around the world. A significant part ofthe world's coastlines is formed by barrier island coasts, and most other tidal coasts are interrupted by estuaries and lagoon inlets. These tidal systems play a crucial role in the sediment budget ofthe coastal zone and thus influence the long-term coastal evolution. From a morphological point of view, tidal inlets form highly dynamical systems, which are interlinked with the adjacent coast and the tidal basin or backbarrier area to which they give access. Often, the natural morphodynamic behaviour interferes with unnatural constraints (e.g. coastal defence works) and with the effects of human utilisation (e.g. sand mining). Estuaries and tidal lagoons attract a variety of human activities, such as navigation, recreation, fishing and aquaculture, economical activity in the border zone, sand mining, land reclamation and in some cases hydrocarbon mining. On the other hand, many estuaries and lagoons form the basis of highly valuable and sometimes unique ecosystems. They function as nursery grounds for many species and as resting and feeding grounds for many others. Hence human activities which affect the properties of such a system, or put the environmental functions otherwise at risk, may have important environmental implications. For the proper management of these systems, it is therefore most important to be able to predict the impacts of such activities. At a larger scale, a deficit of sediment in the backbarrier area, due to sea level rise, for instance, can have major effects on the sediment budget of the coastal zone. The outer deltas of the inlets seem to act as sediment buffers, but the ultimate source of the sediment which goes to the backbarrier area is the coast. Since long-term coastal zone management should include sediment management, the capability to predict the large-scale exchange of sediment is of great importance to ICZM (Integrated Coastal Zone Management). The inlets and their outer deltas play a key role in this exchange. These lectures intend to develop an insight into the physical functioning of coastal inlets and tidal basins, such that possible engineering inten/entions are executed from a sustainable, holistic and integrated management perspective. The emphasis will be on inlet and basin systems which are subject to a mixed tidal and wave forcing, with negligible fresh water runoff, typical examples being the Wadden Sea and the Zeeland inlets and basins. Foreign examples are typically barrier-inlet coasts, such as found abundantly along the east-coast of the USA. This implies that fresh and salt water dynamics are not of strong relevance, and that the morphodynamics of these systems are largely determined by the interaction between the coarser sediment (fine to medium sands) and the tide and wave induced water motions.Hydraulic EngineeringCivil Engineering and Geoscience