Journal Articles
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Item Managing a blackout : the consequences of an oil spill at sea /(Taylor & Francis, 2022-09-08) Shankar, Malini S.; Sivakholundu, K. M.The Ennore Oil Spill of 2017 triggered by a collision between two oil cargo vessels resulted in an environmental incident. This study is an attempt to cull the details from public domain and analyse the efficacy of the Government system to cope up with response. The information on events leading to the mishap indicates the suboptimal working conditions of seafarers prevailing on-board. The response activity drew negative publicity as the official communications were inconsistent. Besides declaring an under estimated quantum of oil spill, the perceived delay and inadequate resources seems to have aggravated the public sentiment. The episode of coastal spill clean-up came to close in two weeks with contributions from 30+ agencies of Government and industry along with 2000+ volunteers. The shoreline environment and fisheries activities returned to normalcy in three months’ time. Compensation to affected public was settled in a years’ time. However there is little information or unbiased evaluation of the episode available. An evaluation of such incidents will aid in addressing issues in future.Item Use of swath data in realtime navigation by pattern recognition(Marine Geodesy, 1989) Prabaharan, N.; Sivakholundu, K. M.A new method is proposed with the aim of reducing dead reckoning error (DRE) during multibeam echosounding survey in deep ocean. Bathymetric data is used in this method to estimate DRE in position fixing. This method can be activated at any desired interval to check the DRE accumulation in addition to available external navigation systems. A pattern recognition algorithm is developed to quantify the shift in position of a selected bathymetric feature that has been observed already once. This difference is used to correct the position fixing and navigation dataItem Stability analysis and design of offshore submerged breakwater constructed using sand filled geosynthetic tubes(Procedia Engineering, 2015) Kiran, A. S.; Ravichandran, V.; Sivakholundu, K. M.Kadalur Periyakuppam (KPK) is a fishing village located 70 km south of Chennai in Tamil Nadu. The coastline of KPK was subjected to severe erosion due to high energy waves during Thane (2011), Nilam (2012) and Madi (2013) cyclones. The Tamil Nadu Fisheries department facilities located near the coast is subjected to damage as the coastline has receded by 45 m in the last few years following the severe erosion caused by cyclones. Since most of the erosion occurred after the storm waves hit the shoreline, sustainable option for shoreline protection would be to shift wave breaking to deeper depths. Based on numerical model studies and assessment of shoreline behaviour over two years, it is proposed to construct a submerged segmented breakwater. The submerged breakwater is proposed to be constructed at 4 m water depth up to a height of 3.5 m using sand filled geosynthetic tubes. Geosynthetic tubes shall be placed in a stacked manner with 2 tubes of 1.5 m high each at the bottom and a tube of 2.5 m height at the top accounting for height loss due to settlement. Design and stability checks are carried out by using available literature as no standard methods or design codes are available for design or stability checks for the geosynthetic tubes. The breakwater structure is checked for stability against sliding, overturning and bearing capacity. The geosynthetic tube material specifications such as tensile strength, ultra violet ray resistance, apparent opening size and fabric material are calculated using suitable design methods. The scouring, in front and behind the breakwater structure under prevailing wave conditions, is estimated for designing scour protection.Item Estuarine channel stability assessment through tidal asymmetry parameters(Journal of Coastal Research, 2009-03) Sivakholundu, K. M.; Mani J. S.; Idichandy V. G.; Kathiroli S.In an estuarine channel the tidal asymmetry, sediment transport, and morphology are interconnected. To maintain a stable channel, we need to take tidal asymmetry into account. A relationship connecting tidal asymmetry and sediment transport rate has been used to evaluate the relative merits of channel modification through numerical simulations. Two criteria have been identified for ensuring the channel stability: (a) maintaining ebb dominance and (b) minimizing the spatial gradient in the net sediment transport function ⟨q⟩. Using these criteria for a test case, we have evaluated Hooghly estuary (east coast, India), where heavy sedimentation is experienced and a permanent solution is needed. The approach provides better insight into the sedimentation pattern in a semidiurnal tidal process in a shallow estuary with braided channels. Among the factors affecting tidal asymmetry, the relative phase difference (β) between M2 and M4 current constituents has a major influence and is thus responsible for the sedimentation pattern. Through numerical study it was found that a combination of deepened, uniform channel with enhanced ebb flow led to a favorable β, indicating less deposition.Item A program to compute the area of an irregular polygon on a spheroidal surface(Computers and Geosciences, 1998) Sivakholundu, K. M.; Prabaharan, N.Item A new archaeological find in the Gulf of Cambay, Gujarat(Journal of the Geological Society of India, 2002) Kathiroli, S.; Badrinarayanan, S.; Venkata Rao, D.; Rajaguru, S.; Sivakholundu, K. M.; Sasisekaran, B.Detailed underwater surveys carried out in the Gulf of Cambay, about 20 km west of Hazira, deploying side scan sonar and sub bottom profiler brought to light, the presence of a submerged palaeochannel traceable to a length of 9 km. Associated with this on either side are basement like features found in a grid pattern at water depths of 20-40 m. Sub-surface sampling carried out with dredge and grab sampler revealed stone artefacts, potsherds, hearth pieces, animal bones and human teeth embedded in fluvial sands and silts. In the upper part of the deposit, a carbonised wooden log was found and dated to around 9500 years BP by 14C method. Marine magnetic survey carried-out does not indicate the presence of any major metallic debrislobjects. This appears to be one of the early records of prehistoric human activity of early Holocene age in the marine environment of India.Item Seasonal and interannual changes of significant wave height in shelf seas around India during 1998–2012 based on wave hindcast(Ocean Engineering, 2018) Sanil Kumar, V.; Dubhashi, K. K.; Amrutha, M. M.; Joseph, Jossia; Jena, B.K.; Sivakholundu, K. M.Present study examines the interannual changes of significant wave height (Hs) in shelf seas around Indian mainland based on the 15-year (1998–2012) wave hindcast data obtained from numerical model. Validation of the hindcast data with buoy-measured data shows that hindcast Hs is reasonably in good agreement with the observation (Pearson correlation coefficient values of 0.92–0.97). Annual average Hs varied from 0.9 to 1.4 m and the wave heights are higher (∼20%) in western shelf seas compared to eastern shelf seas. The analysis reveals seasonal fluctuations of wave climate, with a strong influence of Asian summer monsoon in the western shelf seas compared to the eastern shelf seas of India. Maximum Hs varied from 3.65 to 7.36 m and these maximum values were during the tropical cyclones. During 1998 to 2012, a statistically significant positive trend of 0.8–1.4 cm yr−1 in annual mean Hs is observed and the increasing trend is higher (∼0.7–2.5 cm yr−1) during the Asian summer monsoon period (June–September). The average trend of annual mean wind speed is also positive and is higher (∼1.67 cm s−1 yr−1) for the western shelf seas than that for eastern shelf seas (∼0.93 cm s−1 yr−1).Item A description of tidal propagation in Hooghly estuary using numerical and analytical solutions(Ocean Engineering, 2018) Jena, B. K.; Sivakholundu, K. M.; Rajkumar, J.A tidal propagation characteristic of Hooghly estuary is presented using numerical (ADCIRC) and analytical models (Friedrichs and Aubrey, 1994) along with observations. The analytical model is based on Friedrichs and Aubrey (1994) that simplifies the governing hydrodynamic equations greatly by retaining only those terms that are significant without losing the overall understanding of the propagation process. The analytical model is compared with corresponding 2-D depth averaged numerical (ADCIRC) model that retains all non-linear terms. The assumptions for simplification are found to be reasonable in the light of close agreement among analytical, numerical models and observations. A plan-form geometrical characteristic as well as hydrodynamic variable of the Hooghly has been compared with that of Delaware estuary for corroborating similar tidal propagation process. The Hooghly estuary has flood dominant asymmetric tidal propagation and a positive amplitude growth factor (μ). The observed tidal celerity (phase speed) on an average is slightly more than frictionless celerity. Using the conventions of Toffolon et al. (2006), Hooghly can be classified into ‘strongly convergent – strongly dissipative’ estuary. From the results it can be construed that the estuary is yet to stabilise and reach its equilibrium morphology. It can be close to its equilibrium as very little amplification (0.1 m) is noticed in the predominant semi-diurnal constituent M2 over 78 km (barely 7%) in the estuary. The parameters of width variation (γ) and the ratio between friction and inertia (χ) have been used to define the marginal condition for amplification. The relative position of Hooghly in terms of marginal condition is consistent with similar set of estuaries elsewhere that have been grouped using the above parameters.