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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-76
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
21 Mar 2017
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Spatiotemporal Variation of Van der Burgh's coefficient in a salt plug estuary
Dinesh Chandra Shaha1,2, Yang-Ki Cho2, Bong Guk Kim2, Md. Rafi Afruz Sony1, Sampa Rani Kundu3, and Md. Faruqul Islam4 1Department of Fisheries Management, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh
2School of Earth and Environmental Science/Research Institute of Oceanography, Seoul National University, Seoul, Korea
3Deparment of Oceanography, Chonnam National University, Gwangju, Korea
4Hydrography Division, Mongla Port Authority, Bagherhat, Bangladesh
Abstract. Saltwater intrusion in estuaries is expected to become a more serious issue around the world due to climate change. Van der Burgh's coefficient, K, is a good proxy for describing the relative contribution of the tide-driven and gravitational components of salt transport in estuaries. However, debate continues over the use of K value for an estuary where K should be constant or spatially varying or a time-independent factor for different river discharge conditions. In addition, whether K functions in an inverse salinity gradient area of a salt plug estuary has not been examined thus far. In this study, we determined K during spring and neap tides in the dry (<30 m−3 s−1) and wet (>750 m−3 s−1) seasons in a salt plug estuary with an exponentially varying width and depth to examine the relative contributions of tidal versus density-driven salt transport mechanisms. High-resolution salinity data were used to determine K. Gravitational circulation (K~0.8) was entirely dominant over tidal dispersion during spring and neap tides in the wet season such that salt transport upstream was effectively reduced, resulting in the estuary remaining in a relatively fresh state. In contrast, during the dry season, K increases gradually seaward and landward (K~0.74) from the salt plug area (K~0.65), similar to an inverse and positive estuary, respectively. As a result, density-induced inverse gravitational circulation between the salt plug and the sea facilitates inverse estuarine circulation. On the other hand, positive estuarine circulation between the salt plug and the river area arose due to density-induced positive gravitational circulation induced by the tide during the dry season, causing the intrusion of high-salinity bottom water upstream. Our results explicitly show that K varies spatially and depends on the river discharge. This result provides a better understanding of the distribution of hydrographic properties as well as the distributions of pollutants, nutrients and biota within large estuaries.

Citation: Shaha, D. C., Cho, Y.-K., Kim, B. G., Sony, Md. R. A., Kundu, S. R., and Islam, Md. F.: Spatiotemporal Variation of Van der Burgh's coefficient in a salt plug estuary, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-76, in review, 2017.
Dinesh Chandra Shaha et al.
Dinesh Chandra Shaha et al.
Dinesh Chandra Shaha et al.

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Short summary
In this work, Van der Burgh's coefficient, K, is determined in the dry and wet seasons in a salt plug estuary to examine the contributions of tidal versus density-driven salt transport mechanisms. Gravitational circulation was entirely dominant over tidal dispersion in the wet season whereas density-induced inverse and positive gravitational circulation facilitated an inverse and a positive estuarine circulation seaward and landward from the salt plug area during the dry season, respectively.
In this work, Van der Burgh's coefficient, K, is determined in the dry and wet seasons in a salt...
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