Modelling tide-driven currents and residual eddies in the Gulf of Kachchh and their seasonal variability: A marine environmental planning perspective
ABSTRACT Tide-driven currents in the Gulf of Kachchh (GoK) have been studied using MIKE21 hydrodynamic model. The results are validated with measured currents for three different periods characterized by different wind fields. Comparison of model results showed very good agreement with the measured currents. The study suggests that though the currents of GoK are predominantly tide-driven, they respond significantly to the seasonally changing wind system. Strong southwesterly winds enhance the flood tidal currents by about 20% but reduce the ebb tidal currents by about 20% during June–July. The currents intensify during NE monsoon period as well as SW monsoon period when the winds become stronger. However, the currents are comparatively weak during pre-monsoon transition. Irregular topography of the western gulf slows down the tidal wave propagation and induces a phase shift. Tidal residual currents computed from the model results exhibit the presence of three eddies in the western gulf. The tide–topography interaction could be responsible for generating eddies in the residual flow field. It is possible that these eddies could effectively decrease the flushing rate of materials discharged in the upstream gulf, and subsequently increase their residence time. The hydrodynamic modelling setup forms a base for future ecological modelling endeavours planned for the gulf in order to reduce stress on the ecosystem especially in the sensitive areas such as the Marine National Park and Marine Sanctuary.
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ABSTRACT: The objective of the present study is to understand the sediment transport along the central Kerala coast. The data used in the study include winds, tides, bathymetry and the satellite derived suspended sediment concentrations (SSCs). A sediment transport model - MIKE 21 Mud Transport (MT) - for combinedcurrents, and SSCs is used to quantify and to find out the movement of fine sediments along the coast. MIKE MT is interrelated with the other modules of MIKE 21 Hydrodynamics (HD) module. The HD module simulate the water level variations and flows in response to a variety of forcing functions in coastal areas. Suspended sediment transport in the coastal waters of central Kerala is simulated utilizing the SSC data derived from Oceansat-2 Ocean Colour Monitor (OCM) satellite imagery, using the MIKE-21 MT model for the period 18thto 24thJanuary 2011. The SSCs of 18thJanuary 2011 are considered as the initial condition in MIKE 21 MT model and the model is simulated for the period from 18th to 24th January 2011. The simulated SSCs are compared with satellite derived SSCs. The results exhibit good coefficient of determination among these variables. Sediment dispersion patterns are explained in relation to simulated tidal currents, dominated by the southward flowing coastal currents, which are more consistent in its direction and magnitude along the coast. It is observed that tides, winds and currents arethe important physical factors that control the dispersal patterns. The results suggest that sediment transport is from north to south during the study period i.e., in January 2011.12/2015; 4. DOI:10.1016/j.aqpro.2015.02.016
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ABSTRACT: Two-dimensional hydrodynamic and advection-dispersion simulations were carried out to identify the appropriate locations of inlet and outlet for cool seawater discharges from the proposed Liquefied Natural Gas (LNG) terminal using MIKE-21 suites of software. The model simulations were validated by comparing the observed and simulated hydrodynamics in terms of water depths, current speeds and directions. The model is satisfactorily correlated with coefficients 0.98, 0.86 and 0.91 for water depth, current speed and direction, respectively. The validated model was extended to predict the advection-dispersion phenomena for the two scenarios based on positions of inlet and outlet and their discharges. The predicted results of cool water discharges were compared to the existing Environmental Health and Safety, World Bank guidelines for LNG discharge facilities. It was observed that a trade-off is required before taking engineering decisions for selecting an environmentally acceptable and energy efficient option for such cool water discharges from an LNG facility.International Journal of Environmental Research 10/2014; 8(4):953-960. · 1.82 Impact Factor
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ABSTRACT: The present study is an attempt towards understanding the sediment routing system in the semi-arid margin of the Gulf of Kachchh, which is one of the largest macrotidal regimes in the northern Arabian Sea. Investigations based on heavy minerals, clay minerals, mineral magnetic properties and sediment geo-chemistry indicated that there are three major sources of sediments contributing to the Gulf of Kachchh basin: (1) Indus River, (2) Kachchh mainland coastal rivers and (3) the Saurashtra peninsular coastal rivers. The flanks of northern and southern coast of western Gulf of Kachchh show dominant signatures of Kachchh mainland/Saurashtra peninsular provenance. In contrast, the eastern Gulf of Kachchh coast bearing fine grained sediments shows dominant Indus River Provenance. Although ephemeral in nature, the small coastal rivers of Saurashtra and Kachchh contribute significant amount of sediments to the Gulf of Kachchh coastline because of their 'dryland' nature and thus they control the coarse grained sedimentation processes.