Browsing by Author "Welhena, T"

Now showing 1 - 3 of 3

item: Conference-Extended-Abstract
Damage mechanism of Hikkaduwa due to December 2004 Indian Ocean tsunami
(2007) Welhena, T; Samarawickrama, SP; Hettiarachchi, SSL
More than two thirds of the Sri Lankan coastline got affected from the December 2004 Indian Ocean Tsunami. Field surveys conducted clearly indicate that some of the cities in the western coast of Sri Lanka in the shadow of the incident tsunami experienced significantly high damage similar to that of the eastern coast which was directly facing the incident tsunami. Destruction caused by the tsunami in the western coast was patchy and the cities like Galle and Hikkaduwa could be identified as the worst affected. In the case of Galle, the Bay and Headland combination would have increased the height and speed of the Tsunami wave and the damages accordingly. Even without such prominent coastal features Hikkaduwa experienced a similar scale of damages. This led to the investigations in identifying the damage mechanisms of Hikkaduwa where inundation and wave heights were as much as 5-10 times of the surrounding areas of the south west coast. Such complex mechanism of damages can be interpreted via results of Numerical Modeling and analysis of the existing coastal features in Hikkaduwa.
item: Thesis-Abstract
Impact of marine oil spills to Sri Lanka and it's numerical modelling
Welhena, T; Hettiarachchi, SSL; Samarawickrama, SP
Over the last couple of decades there has been a growing concern regarding the marine pollution due to spill of oil from ship operations and accidents. This is because the oil spills have devastation and obnoxious effect on marine ecology, which may not be recovered. Hence, there is a need for analyzing or predicting the movement of spilled oil slicks. The occurrence of oil spills is fundamentally a matter of probability. There is no certainty regarding the amount of oil that would be transported, or the size or likelihood of a spill that would occur, during the period where the predication is carried out. Neither can the winds and ocean currents that transport oil spills be known for certain. A probabilistic event such as an oil-spill occurrence or oil-spill contact to an environmentally sensitive area cannot be predicted with certainty. Only an estimate of its likelihood (its probability) and the vulnerability of such sensitive resources can be quantified. Such estimations can easily be done with the help of advanced computer modelling techniques. Numerical models have various aspects and various modelling methods based on the level of the accuracy required by the purpose it is being used. In this study, impact of marine oil spills to South west coast of Sri Lanka has been investigated using available numerical modelling techniques combined with a set of available environmental data. The extensive amount of modelling work was carried out in areas where the overall sensitivity ofthe coastal zone is high. OILMAP _4, an oil spill probability and fate model developed by Advanced Science Associates of USA has been used for all the modelling work and in house model developed by Wijeratne (1997) was used for exploring the numerical modelling techniques. Having identified the areas most exposed to potential oil spills, the methodology was proposed to assess risk involved in each area by a method of risk score allocation. Such a scoring method directly reflects the lc:vel of attention need to pay regarding preventive measures and planning for response operations. Based on the results of modelling and risk assessment there is a strong and urgent demand for well prepared plan to meet those circumstances. Hence scope of the study is extended to identify the requirement of an oil spill contingency management plan and its development guidelines.
item: Conference-Extended-Abstract
Oil spills - risk analysis and modelling the potential impacts along the South- West coast of Sri Lanka
(2004) Samarawickrama, SP; Hettiarachchi, SSL; Welhena, T
Oil enters the marine environment by a number of different routes as a result of both human activities and natural processes. Tanker accidents account for about 12% of the total amount of oil entering the oceans, which is estimated as 400,000 tonnes per year. Despite the introduction of many millions of tonnes of oil into the world's oceans, there is little evidence of a build-up of oil residues in the sea. Accidental oil spills are usually of greatest concern since these often give rise to conspicuous acute pollution.