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Cohesive sediments
Published in Arved J. Raudkivi, Loose Boundary Hydraulics, 2020
An estuary is a semi-enclosed body of water with fresh water inflow and connection to the sea. There are numerous classifications of estuaries, such as highly stratified with a salt water wedge, fjords, partially mixed and homogeneous estuaries. For details reference is made to literature, e.g. Dyer (1986), Donkers & van Leusen (1988), Weilershaus (1981), a.o. The fresh water-salt water interaction leads to circulation and mixing processes which are affected by topography, river flow and tidal range. For shorter periods wind may also be a significant factor. Apart from salinity distribution the suspended sediment distribution in estuaries varies substantially along its length. The processes of sedimentation, erosion and distribution of sediment in estuaries are not only complex, but also of substantial ecologic and economic importance.
Coastal Environments
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.[9] Estuaries are protected from the full force of the ocean by mudflats, sandpits, and barrier islands. Estuaries are sometimes called bays, lagoons, harbors, or sounds. All these examples are estuaries if fresh water mixes with salt water.
Reclamation and Water Management of Tidal Lowlands in Indonesia
Published in Fransiscus Xaverius Suryadi, Soil and Water Management Strategies for Tidal Lowlands in Indonesia, 2020
A rise of the mean sea level results in an increase of salinity intrusion because of the increase in water level and in the tidal volume (referred to Estuary number). This effect can be compared with the effect due to the extra fresh water storage areas in delta area created by the drainage system (large scale lowland development) where as the result the salinity intrusion length may moves upstream in the river (see Figure 3.13).
Two-dimensional modeling of the vertical circulation of salt intrusion in the Sebou estuary under different hydrological conditions
Published in ISH Journal of Hydraulic Engineering, 2019
Soufiane Haddout, Abdellatif Maslouhi, Imad Baimik, Mohammed Igouzal, Hamid Marah
An estuary is a body of water that has inflow of river water at the landward boundary and an open connection to the sea (Leuven et al., 2016). Many definitions and classifications have been proposed for estuaries, which mostly depend on their application (Dalrymple et al., 1992; Davidson and Council, 1991; Hume and Herdendorf, 1988; Perillo, 1995; Pritchard, 1967; Savenije, 2006; Townend et al., 2000; Townend, 2005). In most cases, estuaries were defined based on the relative influence of tides, waves, rivers, sediment types, sediment supply, vegetation, geology, or time (Savenije, 2006, 2005). Additionally, estuaries play an essential role in the human–earth system, affecting freshwater resources, the mixing between ocean and river water, and the health of aquatic ecosystems (Savenije, 2015; Wei et al., 2017). This makes the functioning of estuarine systems an important field of research. A crucial element of estuarine dynamics is the interaction between saline and freshwater. The river discharges freshwater into estuaries, flushing out the salt, while saline water penetrates landward as a result of density gradients (Figure 1). The temporal and spatial variation of salinity in an estuary is determined by the competition between freshwater flushing and penetration of saline water by gravity (Zhang and Savenije, 2017). In short, estuaries are important water bodies where many dynamic factors interact and unfold (Xu et al., 2015). For decades, explosive increases in industrial and agricultural productivity, as well as the growing population in estuary regions, have led to numerous environmental concerns (Mai et al., 2002).
Impacts of climate change on the water quality of the Elbe Estuary (Germany)
Published in Journal of Applied Water Engineering and Research, 2018
Birte Hein, Carsten Viergutz, Jens Wyrwa, Volker Kirchesch, Andreas Schöl
Several studies examine potential climate change impacts on the oxygen concentration and phytoplankton production in rivers and estuaries. Decrease in oxygen concentrations due to lower oxygen solubility and a higher phytoplankton production leading to an increase in degradable organic carbon in the system are discussed as the main impacts of warming (Whitehead et al. 2009; Najjar et al. 2010, Quiel et al. 2010). Additionally, potential toxic algal blooms might be enhanced by lower flows and higher water residence times (Whitehead et al. 2009). Additional to the atmospheric and hydrological changes, the sea level rise in the Elbe Estuary is also a consequence of climate change (Hein, Mai, et al. 2014). However, the effect of sea level rise on water quality is not a purpose of this study.
Estuarine hydrodynamics and morphodynamics: a perspective
Published in Coastal Engineering Journal, 2018
Hitoshi Tanaka, Hubert Chanson
An estuary is a water system in which the tide meets a freshwater system with some mixing between freshwater and seawater. Estuaries may be classified as a function of their geomorphology, salinity distribution, and density stratification (Ippen 1966; Fischer et al. 1979; Dyer 1997; Savenije 2005). A salt wedge may develop when the freshwater flows into the sea with low tidal range. The fresher river waters flow at the surface over a dense bottom layer, i.e. the salt wedge. The strong density gradient at the wedge interface inhibits vertical mixing between surface freshwater and bottom saltwater. Shear stresses acting on the interface induced, however, some saltwater entrainment into the freshwater flow. With a moderate tidal range, some vertical mixing is induced by the tidal flow and the estuarine system becomes partially mixed. For larger tidal ranges, the estuary becomes well-mixed vertically. There is very little vertical variation in salinity and the residual flow is seaward at all elevations. Such a classification does not express the unique feature of each estuary, any seasonal change nor for differences between neap and spring tides (Figure 1). Figure 1 presents examples of estuarine zones across our Planet, illustrating the diversity between systems. Recent advancement of field measurement techniques, as well as progress in numerical simulation and physical modeling methods, have enabled to make more detailed and comprehensive investigations on estuarine hydrodynamics and morphodynamics from various viewpoints, with a range of practical applications including flood control, navigation channel maintenance and environmental issues.