Analytical and numerical analysis of tides and salinities in estuaries; part II: salinity distributions in prismatic and convergent tidal channels |
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| Authors: | Kees Kuijper Leo C Van Rijn |
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| Institution: | (1) Deltares, Delft, The Netherlands;(2) University of Utrecht, Utrecht, The Netherlands |
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| Abstract: | Estuaries, commonly, are densely populated areas serving the needs of the inhabitants in multiple ways. Often the interests
are conflicting and decisions need to be made by the local managers. Intake of fresh water for consumption, agricultural purposes
or use by industries may take place within a region not far landward of the limit of salt intrusion. Human interventions (e.g.
deepening of the navigation channels) or climate changes (sea level rise, reduction of the river discharge) can bring these
intake locations within the reach of saline or brackish water and consequently endanger their function. To support policy
and managerial decisions, a profound knowledge of processes associated with the salinity structure in estuaries is required.
Although nowadays advanced numerical three-dimensional models are available that are able to cope with the complexity of the
physics there is still a need for relatively simple tools for quick-scan actions in a pre-phase of a project or for instructive
purposes. The analytical model described in this paper may serve these needs. It computes the maximum salinity distribution
using the dispersion coefficient in the mouth as the only model parameter. The model has been calibrated using observational
data in a large number of estuaries and experimental data in a tidal flume. The dispersion coefficient was successfully related
to geometric and hydrodynamic parameters resulting in an expression that can be used for convergent estuaries as well as prismatic
channels, see Eqs. 25a and 25b. Application of the model in a predictive mode showed its promising capabilities. Comparison with three-dimensional numerical
models indicates that the channel geometry in the estuary mouth largely influences dispersive processes. The analytical model
for salt intrusion may be used in combination with the analytical model for tidal propagation in convergent estuaries and
tidal channels by Van Rijn (part I). In this way, input is obtained on the tidal velocity amplitude and the Chézy roughness
following calibration of this model on tidal amplitudes along the estuary. |
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