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Abstract: A 2D Hydrodynamic–Particle Analysis model was applied to the Gulf of Kachchh (GoK) to estimate the residence time of pollutants. The tidal currents in the Gulf have a strong E–W component, which prevents the material in the north being transported towards south. In the regions situated very close to the open boundary, where the GoK waters exchange freely with the northern Arabian Sea, dilution takes place rapidly with the incoming waters and hence, the residence time is on the order of 1day. Influence of eddies and a dynamic barrier across the Sikka–Mundra section on the residence time is apparent. Eastern GoK shows a relatively large residence time, on the order of 2–4days, warranting caution while releasing industrial wastes in the northeastern Gulf. The region around location-5 behaves like a bay; the dissolved matter gets trapped in this bay and the residence time increases by 3–4days. [Copyright &y& Elsevier]

Abstract: The Jatadharmohan creek lies between Mahanadi and Devi Rivers along the Orissa coast and it is separated from the sea by an elongated sand spit. It was proposed to mine a volume of 15×106 m3 of sand from the creek for land filling, but maintaining the spit intact. For this, the stability of sand spit is studied with different criteria. The results confirm that the creek mouth is a near permanent zone of deposition. The model results obtained for various depth scenarios show that the magnitude of currents would increase considerably when depth is increased by 7.0m and marginally for further increase in depth by 10.0m. Accordingly, a dredging scheme has to be designed without affecting the spit stability. Considering the existing hydrodynamics in the creek system, it is recommended that a bed slope of 1:6 (9.5°) be maintained during dredging, which is much less than 13.75°—the evaluated critical slope at the site when seepage flow is parallel to the bed slope. It is observed during monitoring that the creek is very productive, and the sand spit is totally intact. [Copyright &y& Elsevier]