scholarly journals River discharge, storm surges and tidal interactions in the Meghna river mouth in Bangladesh

MAUSAM ◽  
2021 ◽  
Vol 48 (4) ◽  
pp. 531-540
Author(s):  
ANWAR ALI ◽  
HAFIZUR RAHMAN ◽  
SYED SAZZAD HAIDER CHOWDHURY

Interactions among river discharge, storm surges and tides in the Meghna river estuary in Bangladesh have been studied by using a two-dimensional vertically integrated numerical model of the northern Bay of Bengal. The study considers the interactions mostly in terms of flow across the river mouth under the three forcings, individually and in different combinations of them. River discharge and tidal flow across the river mouth act both positively and negatively depending on the tidal phase, positively during high tide and negatively during low tide. This is also true for the combination of all the three forces. On the other hand, in most of the cases, river discharge acts in opposition to the storm surges. Under certain conditions and on rare occasions they act positively. The interactions between river discharge and storm surges, however, depend on their relative magnitudes. In respect of total elevation in the estuarial region, river discharge tends to increase the surge height. However, away from the estuary, the effect of river discharge is hardly discernible.      

2005 ◽  
Vol 65 (1) ◽  
pp. 107-115 ◽  
Author(s):  
M. N Paranaguá ◽  
S Neumann-Leitão ◽  
J. D Nogueira-Paranhos ◽  
T. A. Silva ◽  
T. Matsumura-Tundisi

The study was conducted in the Capibaribe river estuary in Recife (Brazil) to assess the role played by cladocerans in a eutrophic environment. Samplings were carried out monthly at 4 fixed stations along the estuary from July 1987 to June 1988. Collections were made with a plankton net of 65 micrometers mesh size. Six cladocerans species were registered: Penilia avirostris, Diaphanosoma spinulosum, Chydorus barroisi, Ceriodaphnia rigaudi, Ilyocryptus spinifer, and Moina micrura. The most frequent species was Moina micrura with 49%. The only true marine species was Penilia avirostris, which was registered at station 1 (close to the river mouth), during high and low tide and in the dry season. The Cladocera average density decreased from 329 ind.m-3 (August 1987, high tide) to 2 ind.m-3 (March 1988, high tide) due to the high load of organic and chemical pollution received by the estuary. At all stations, D. spinulosum, M. micrura, and C. barroisi occurred with a wide distribution, mainly during the rainy season. C. rigaudi and I. spinifer were rare, occurring only during the rainy season. Cladocerans played an important role in the food webs of the plankton community of the Capibaribe tropical estuary and the dominance of a few small species indicated a hypereutrophic environment. A high level of disturbance was indicated by the decline in diversity of specialized species and the increase in abundance of opportunistic species like M. micrura.


2012 ◽  
Vol 170-173 ◽  
pp. 2248-2255
Author(s):  
Zhi Li Wang ◽  
Yan Fen Geng

A two dimensional semi-implicit finite volume free-surface ocean model(FVFOM2D) based on unstructured C-grid is built, in which the momentum equation is discretized on the faces of each cell, the continuity equation is discretized on the cell. The model is discretized by semi-implicit finite volume method, in that the free-surface is semi-implicit and the bottom friction is implicit, thereby removing stability limitations associated with the surface gravity wave and friction. The remaining terms in the momentum equations are discretized explicitly by integral finite volume method and second order Adams-Bashforth method. The performance of the present model to simulate tidal flow in a geometrically complex domain is examined by simulation of tidal currents in Pear River Estuary.


2008 ◽  
Vol 35 (12) ◽  
pp. 1476-1480 ◽  
Author(s):  
Fatemeh Zahed ◽  
Amir Etemad-Shahidi ◽  
Ebrahim Jabbari

Arvand River Estuary is the most important inland water body of Iran and its discharge has been reduced in the last decades due to construction of several dams. Hence, a two-dimensional laterally averaged time dependent hydrodynamic and water quality model called CE-QUAL-W2 was applied to this estuary to assess the impacts of river discharge reduction. The model was first implemented with three different closure schemes for parameterization of vertical transport of mass and momentum. It was found that the W2N scheme performs better than the other schemes in predicting the vertical salinity structure. The model was then used for prediction of salinity intrusion in different hydrological conditions and a simple equation was obtained for estimation of the intrusion length as a function of upstream freshwater discharge.


2003 ◽  
Vol 46 (1) ◽  
pp. 73-82 ◽  
Author(s):  
Maria Luise Koening ◽  
Enide Eskinazi Leça ◽  
Sigrid Neumann-Leitão ◽  
Silvio José de Macêdo

In order to address the impact on phytoplankton, sampling was conducted monthly at 4 fixed stations, from April/86 to March/87 at diurnal low and high tide using a plankton net (65 mum mesh size) and a 1 L Van Dorn bottle. Among the 133 taxa identified, marine littoral euryhaline species were most common, outranking Gyrosigma balticum (Ehrenberg) Rabenhorst, Nitzschia sigma (Kützing) Wm. Smith, Licmophora abbreviata Agardh, Climacosphenia moniligera Ehrenberg, Surirella febigerii Lewis, Terpsinoe musica Ehrenberg and Cylindrotheca closterium (Ehrenberg) Reiman and Lewis. The port construction caused significant changes to the phytoplankton community with a strong influence of marine species (mainly dinoflagellate) because of the opening of the reef near the river mouth in 1983. The shallow depth and hydrodynamic brought many littoral species to the water columm. The community was composed by marine euryhaline and limnetic organisms, influenced by the salinity, rain and tide. Species diversity was high (> 3 bits.cel-1) owing to the high environmental heterogeneity (marine, freshwater and benthic interactions). After the port implantation, a strong decrease occurred in phytoplankton density owing to high loads of suspended matter. Lowest values (121,00 cells.l-1) were registered during rainy season. During dry season, when light intensity was higher, phytoplankton presented highest density ( 1,789,000 cells.l-1).


2012 ◽  
Vol 12 (12) ◽  
pp. 3799-3809 ◽  
Author(s):  
W.-B. Chen ◽  
W.-C. Liu ◽  
M.-H. Hsu

Abstract. Precise predictions of storm surges during typhoon events have the necessity for disaster prevention in coastal seas. This paper explores an artificial neural network (ANN) model, including the back propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS) algorithms used to correct poor calculations with a two-dimensional hydrodynamic model in predicting storm surge height during typhoon events. The two-dimensional model has a fine horizontal resolution and considers the interaction between storm surges and astronomical tides, which can be applied for describing the complicated physical properties of storm surges along the east coast of Taiwan. The model is driven by the tidal elevation at the open boundaries using a global ocean tidal model and is forced by the meteorological conditions using a cyclone model. The simulated results of the hydrodynamic model indicate that this model fails to predict storm surge height during the model calibration and verification phases as typhoons approached the east coast of Taiwan. The BPNN model can reproduce the astronomical tide level but fails to modify the prediction of the storm surge tide level. The ANFIS model satisfactorily predicts both the astronomical tide level and the storm surge height during the training and verification phases and exhibits the lowest values of mean absolute error and root-mean-square error compared to the simulated results at the different stations using the hydrodynamic model and the BPNN model. Comparison results showed that the ANFIS techniques could be successfully applied in predicting water levels along the east coastal of Taiwan during typhoon events.


2008 ◽  
Vol 30 (2) ◽  
pp. 130-135
Author(s):  
Hoa Mạnh Hùng ◽  
Nguyễn Quang Thành ◽  
Phan Thị Thanh Hằng
Keyword(s):  

Evaluating the dynamics of the Hau River estuary (Dinh An - Tranh De river mouth)


1991 ◽  
Vol 24 (6) ◽  
pp. 171-177 ◽  
Author(s):  
Zeng Fantang ◽  
Xu Zhencheng ◽  
Chen Xiancheng

A real-time mathematical model for three-dimensional tidal flow and water quality is presented in this paper. A control-volume-based difference method and a “power interpolation distribution” advocated by Patankar (1984) have been employed, and a concept of “separating the top-layer water” has been developed to solve the movable boundary problem. The model is unconditionally stable and convergent. Practical application of the model is illustrated by an example for the Pearl River Estuary.


1993 ◽  
Vol 27 (7-8) ◽  
pp. 381-385 ◽  
Author(s):  
Y. Oziransky ◽  
B. Shteinman

Data of high spatial and temporal resolution, and a special sampling program are essential for successful application of mathematical models designed to reproduce observed seasonal patterns of temperature, dissolved oxygen, nutrients, pH, and algal biomass for both vertical and longitudinal gradients in a water body. Lake Kinneret suspended solids are of great potential value for estimating transport, exposure to water body elements, and fate of many toxic substances. Therefore the distribution of admixtures in two longitudinal and five vertical segmentation schemes were examined with the two-dimensional water body quality box model “BETTER” (Bender et al, 1990). The transects were taken in the north-western part of Lake Kinneret close to the Jordan River mouth and the National Water Carrier (NWC) head pumping station. The outflow volumes were given according to regular sampling of natural speed of water outflow from different lake layers under calm conditions. Temporal distribution of mixing concentrations as well as turbulent diffusion horizontal coefficients due to the spatial distribution of turbulent scale were obtained during the model's run with the December 1991 data.


2020 ◽  
Vol 12 (24) ◽  
pp. 10677
Author(s):  
Ronghui Ye ◽  
Jun Kong ◽  
Chengji Shen ◽  
Jinming Zhang ◽  
Weisheng Zhang

Accurate salinity prediction can support the decision-making of water resources management to mitigate the threat of insufficient freshwater supply in densely populated estuaries. Statistical methods are low-cost and less time-consuming compared with numerical models and physical models for predicting estuarine salinity variations. This study proposes an alternative statistical model that can more accurately predict the salinity series in estuaries. The model incorporates an autoregressive model to characterize the memory effect of salinity and includes the changes in salinity driven by river discharge and tides. Furthermore, the Gamma distribution function was introduced to correct the hysteresis effects of river discharge, tides and salinity. Based on fixed corrections of long-term effects, dynamic corrections of short-term effects were added to weaken the hysteresis effects. Real-world model application to the Pearl River Estuary obtained satisfactory agreement between predicted and measured salinity peaks, indicating the accuracy of salinity forecasting. Cross-validation and weekly salinity prediction under small, medium and large river discharges were also conducted to further test the reliability of the model. The statistical model provides a good reference for predicting salinity variations in estuaries.


Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 106
Author(s):  
Yuhan Yan ◽  
Dehai Song ◽  
Xianwen Bao ◽  
Nan Wang

The Ou River, a medium-sized river in the southeastern China, is examined to study the estuarine turbidity maximum (ETM) response to rapidly varied river discharge, i.e., peak river discharge (PRD). This study analyzes the difference in ETM and sediment transport mechanisms between low-discharge and PRD during neap and spring tides by using the Finite-Volume Community Ocean Model. The three-dimensional model is validated by in-situ measurements from 23 April to 22 May 2007. In the Ou River Estuary (ORE), ETM is generally induced by the convergence between river runoff and density-driven flow. The position of ETM for neap and spring tides is similar, but the suspended sediment concentration during spring tide is stronger than that during neap tide. The sediment source of ETM is mainly derived from the resuspension of the seabed. PRD, compared with low-discharge, can dilute the ETM, but cause more sediment to be resuspended from the seabed. The ETM is more seaward during PRD. After PRD, the larger the peak discharge, the longer the recovery time will be. Moreover, the river sediment supply helps shorten ETM recovery time. Mechanisms for this ETM during a PRD can contribute to studies of morphological evolution and pollutant flushing.


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