NISCAIR Online Periodicals Repository Community: IJMS Vol.39 [2010]

Role of oceanography in naval defence

Sun, 28 Nov 2010 22:58:59 GMT

Title: Role of oceanography in naval defence

Authors: Swain, J; Umesh, P A; Harikrishnan, M

Abstract: The study of oceans is an essential aspect from strategic, economic and ocean engineering points of view. Recent advancements in SONAR (Sound Navigation and Ranging) technology for under water applications including naval defence demand a clear understanding of the sound propagation in the ocean which is vital for detection of a target. As compared to deep waters, the detection in coastal waters is relatively a challenging task. Detection becomes still complex in the littoral waters. To ensure success in these highly complex oceanic regions, high resolution descriptions/predictions of past, current and future conditions (hindcast, nowcast and forecast) as well the analysis of open ocean, coastal, and nearshore/littoral zones around the Indian continent is an essential pre-requisite. At any given situation, the detection and discrimination of an underwater target is highly dependant on the propagation characteristics of the medium, the surface and bottom boundaries, leaving apart the efficiency of the SONAR system and the type of the target. It can be either a SONAR performance model or an operational model for tactical warfare; one has to have the predicted sound speed for the 3-dimensional ocean environment concerned since it is not always feasible to depend only on measurements. There are on-going programs of collecting and analyzing ocean and atmospheric data and a wide range of research and development activities, some of which are reviewed/presented in this paper with typical examples. In addition to in-situ measurements, significant progress has been achieved in India by demonstrating the utility of satellite based remote sensing data for oceanographic research and applications. By utilizing the existing and on-going experimental data from the regions of interest, it has become feasible for implementation of an integrated “Naval Operational Ocean Prediction System” consisting of wave, tide, circulation and internal wave models. The ocean environmental information predicted by these ocean models shall provide necessary inputs to the SONAR range prediction models for routine operational use, tactical operations and simulating warfare scenarios.

Page(s): 631-645

Geomorphology for Integrated Coastal Zone Management: A theoretical approach with examples from Kerala, India

Sun, 28 Nov 2010 22:58:59 GMT

Title: Geomorphology for Integrated Coastal Zone Management: A theoretical approach with examples from Kerala, India

Authors: Chattopadhyay, Srikumar

Abstract: Coastal zone, triple interface of land, ocean and air, is a geographic entity of intense human activities. This area experiences several problems due to competing and multiple usability of coastal resource, which is a matter of global concern. Concept of Integrated Coastal Zone Management (ICZM) is advanced as a tool to tackle these problems and to devise sustainable development plans. Drawing examples from Kerala at macro and micro scales this paper demonstrates that in depth study of geomorphic processes and geomorphic assets is necessary as part of ICZM plan. Identification of morpho-dynamic units following the scheme of landscape classification at the ground level helps devising appropriate management action plans. While dealing with the geomorphologic processes a larger approach/perspective should be maintained by identifying system boundaries and the degree of activity and the relationships among the processes involved. This also includes human induced processes that, in aggregation, trigger large scale environmental change.

Page(s): 623-630

Modelling of coastal ocean environment for underwater surveillance

Sun, 28 Nov 2010 22:58:59 GMT

Title: Modelling of coastal ocean environment for underwater surveillance

Authors: Prasada Rao, C V K

Abstract: Significance of ocean environment for underwater surveillance, namely for sonar systems, has been discussed in this paper. The passive as well as active sonar equations and the various parameters which are important for assessing sonar performance from environment point of view are highlighted. Some important published results which are available in the literature on the modelling of thermohaline structure of our coastal waters have been reviewed in this paper. Among 1-D mixed layer ocean models the model by Niiler and Kraus¹ shows lesser deviations on Mixed Layer Depth (MLD) and Mixed Layer Temperature (MLT) when compared to the observations. The model given by Price et al ² simulates the Sea Surface Temperature (SST) and the vertical profile of temperature. The comparison of simulated values with observations revealed that the diurnal variability of SST is well represented through this model but deviations are noticed in the thermocline zone. The 1-D ocean models are simple and easy to implement for operational purposes because they are computationally less intensive. However, it was found that these models accumulate more error for long-term simulation due to non-inclusion of advection processes which are important in coastal as well as open ocean conditions. The observed and predicted results of a 3-D model proposed by Blumberg and Mellor³, also known as Princeton Ocean Model (POM), showed a reasonable good comparison and this model could simulate successfully the Arabian Sea mini warm pool which is an important phenomenon that occurs in the south-eastern Arabian Sea before the onset of summer monsoon.

Page(s): 616-622

Reliability based design method for coastal structures in shallow seas

Sun, 28 Nov 2010 22:58:59 GMT

Title: Reliability based design method for coastal structures in shallow seas

Authors: Prasad Kumar, B

Abstract: Reliability based approach is considered an important component in risk assessment of coastal related projects. Such an approach is mandatory during the initial planning stage of coastal projects thereby providing information on the failure of structures. The damage to a structure can result from various environmental forcing and moreover depends on where the structure is located. As a case study, an existing coastal jetty at Andaman Sea was chosen which was subjected to extreme waves during a cyclonic episode prevalent in the Bay of Bengal. Wave information encompassing this coastal jetty was investigated using a very high resolution state-of-art SWAN wave model run in non-stationary mode. Wave forces are estimated using Sainflou and Miche-Rundgren methods along structural length of this jetty. In addition, wave run-up and wave overtopping were estimated using SWAN model generated wave information. A Level-II reliability analysis was carried out for this coastal jetty, subjected to various levels of assumed uncertainty. Further, lifetime and encounter probability under various degrees of uncertainty in load and resistance for this coastal jetty has been investigated and analyzed. Based on analysis, it is believed the significance of this work can lead vital information for assessment studies in integrated coastal zone management.

Page(s): 605-615