TY - JOUR
T1 - Salt Transport Regimes Caused by Tidal and Subtidal Processes in Narrow Estuaries
AU - Dijkstra, Yoeri M.
AU - Schuttelaars, Henk M.
AU - Kranenburg, Wouter M.
PY - 2022
Y1 - 2022
N2 - Tidally averaged transport of salt in estuaries is controlled by various subtidal and tidal processes. In this study, we show the relative importance of various subtidal and tidal transport processes in a width-averaged sense. This is done for a large range of forcing and geometric parameters, which describe well-mixed to salt wedge estuaries. To this end, we develop a width-averaged process-based model aimed at conducting and analyzing a large number of experiments (∼40,000). We find that the salt transport is dominated by one of seven salt transport balances, or regimes. Four of these regimes are dominated by subtidal processes, while the other three are dominated by tidal processes. Which regime occurs in a part of an estuary depends on four dimensionless parameters, representing local geometry, and forcing conditions. One of the regimes features salt import by correlations between the depth-averaged tidal velocity and salinity. While this mechanism was previously only associated with along-channel geometric variations, we find it can also be a dominant mechanism in a significant part of the parameter space due to river-induced tidal asymmetry, independent of river geometry. We apply our classification to a case study of part of the Dutch Rhine delta and compare to decomposition results of a fully realistic three-dimensional model. We find the estuary features two regimes, with import dominated by subtidal shear transport in the seaward part of the estuary and by depth-averaged tidal correlations in the landward part of the estuary.
AB - Tidally averaged transport of salt in estuaries is controlled by various subtidal and tidal processes. In this study, we show the relative importance of various subtidal and tidal transport processes in a width-averaged sense. This is done for a large range of forcing and geometric parameters, which describe well-mixed to salt wedge estuaries. To this end, we develop a width-averaged process-based model aimed at conducting and analyzing a large number of experiments (∼40,000). We find that the salt transport is dominated by one of seven salt transport balances, or regimes. Four of these regimes are dominated by subtidal processes, while the other three are dominated by tidal processes. Which regime occurs in a part of an estuary depends on four dimensionless parameters, representing local geometry, and forcing conditions. One of the regimes features salt import by correlations between the depth-averaged tidal velocity and salinity. While this mechanism was previously only associated with along-channel geometric variations, we find it can also be a dominant mechanism in a significant part of the parameter space due to river-induced tidal asymmetry, independent of river geometry. We apply our classification to a case study of part of the Dutch Rhine delta and compare to decomposition results of a fully realistic three-dimensional model. We find the estuary features two regimes, with import dominated by subtidal shear transport in the seaward part of the estuary and by depth-averaged tidal correlations in the landward part of the estuary.
KW - classification
KW - estuary
KW - Rotterdam Waterway
KW - salt intrusion
KW - salt transport
KW - tides
UR - http://www.scopus.com/inward/record.url?scp=85145098744&partnerID=8YFLogxK
U2 - 10.1029/2021JC018391
DO - 10.1029/2021JC018391
M3 - Article
AN - SCOPUS:85145098744
SN - 2169-9275
VL - 127
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
IS - 12
M1 - e2021JC018391
ER -