Master of Philosophy (M.Phil.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/18722

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item: Thesis-Abstract
Development of a land use/cover monitoring system using satellite images
(2004) Jayakody, JAS; Puswewala, UGA
Remote Sensing and Geographical Information System are modem tools for ecosystem management. Remotely sensed data gives convenient and rapid solutions to problems in a variety of applications. Land is limited, and vital as it is the main provider of important natural resources. The fast growing human population has created many problems, due to the increasing demands for food, water, shelter and fuel. Thus such socio-economic factors often dictate how land is used regionally. Land use affects land cover and in turn, changes in land cover affect land use. Thus land plays a major role in any development process. In tropical countries, due to the impact of human beings, the rates of change in vegetation cover and land use are high. Hence frequent updating of land use maps is necessary to provide the information needed by planners and politicians. The main objective of this research is to investigate the possibility of using different remote sensing satellite images for developing a land use/cover monitoring system. This research is carried out in an area of approximately 400 square kilometres in the southern part of Sri Lanka. Imageries of SPOT, IRS and Landsat satellites are used. Different colour combinations are prepared and false colour composite images are used for image processing. Maximum likelihood method is used for image classification and the overall accuracy of the classifications is more than 90%. Using this classification, change detection matrices are developed to give changes for every land use class considered. A primary problem encountered in the study area is the mixed pixels. It is difficult to separate crop land from residential area, as some people reside in houses within the cultivated area. Filtering techniques can only partially remedy this problem. In order to monitor the land use/cover, image differencing method is applied and the extent of the detected changes in terms of pixels or hectares is calculated. A procedure is proposed as the land use/cover monitoring system using satellite images. Under this monitoring system, the extent of land use/cover changes can be computed by using different satellite images with varied spatial and spectral ranges.certainty.
item: Thesis-Abstract
Development of conceptual geological model for the formation of hot water springs in Sri Lanka
Premasiri, HMR; Wijesekara, DS; Weerawarnakula, S; Puswewala, UGA; Abeysinghe, AMKB
As natures wonderful gift, several hot water springs occur in Sri Lanka though it does not fall within very active tectonic zone in the earth. They are mostly confined to the eastern sector of the island. However, hot water springs at Mahapelassa off Embilipitiya, Kanniyai off Trincomalee and Mahaoya are well known to people. These thermal springs show their out flow temperature ranging between 34°C to 56°C. The hottest springs lie at Kapurella (56°C), followed by Mahaoya (55°C), Marangala-Wahawa close to Padiyatalawa (42-45 ° C ), Mahapelassa (44-46 DC) and Nelumwewa, which was known earlier as Madawewa and now under a lake, records 45° C in mud samples (Fonseka 1994). The present research was aimed out mainly to model the formation of hot water springs in Sri Lanka based on geological and tectonic settings using geological, geophysical and Remote Sensing techniques while evaluating the hot water springs for their potential as energy resources or development as places for eco-tourism. Geological, structural and tectonic setting of the areas have been studied using geological, geochemical and geophysical techniques. Both field and libratory studies were carried out in order to compile geological and geophysical profiles and to determine geochemical and physical parameters of hot water springs in Sri Lanka. According to the results of this study, the major boundary between Highland Complex and Vijayan Complex show multiple thrust planes and shear zones showing imbrecated lithological slices of both Highland Complex and Vijayan Complex. Other than the ductile structures, brittle fractures, joints and fault planes extend as mega lineament for several kilometers. These lineaments produce good secondary aquifer conditions with adequate porosity. The surface mapping and geophysical evidence of the lineaments show that they are very deep and are interconnected. Therefore, they offer better pathways for surface water to percolate deep levels and return upwards with adequate pressure to reach the surface after heating. These structurally controlled hot water springs in Sri Lanka are associated with deep geologically weak zones of fracture or fault systems within the tectonically active thrust boundary. According to geochemical parameters and field evidence, hot water springs in Sri Lanka can be divided into three groups, Groupl: Mahapelassa Group 2: Kapurella, Mahaoya, Padiyatalwa , Palanoya and other around the Mahiyangana, Ampara and Group 3: Kannyai, Rathkhiriya and Adampane areas.). According to the chemical and physical parameters of hot water it can be concluded that Group (1) and Grou (3) are more suitable for therapeutic uses and have a good potential for development for eco-tourism. The Group (2) has hot water with low contaminations of salt, and show fairly high potential for generation of geothermal energy
item: Thesis-Abstract
Durability of rocks under tropical conditions
Samaradivakara, GVI; Dharmaratne, PGR; Puswewala, UGA
Sri Lanka has a basement rock formation of metamorphic origin that the majority is gneissic type, which is intensively used in many of the civil engineering constructions. In addition, foundations of most of the important civil engineering structures are extended up to or into the fresh gneissic rock strata. Sri Lanka has a tropical climate. Therefore the study on durability of gneissic rocks under tropical conditions would be immensely beneficial to the construction industry of the country. The simulation of exact natural weathering conditions is quite complicated. This study concentrates mainly on how heat stress affects deterioration of index properties of gneissic rocks. When the rock mass gets heated, and cooled rapidly due to sudden rainfall, there is a possibility of propagating micro-fractures in the rock mass which will initiate weakening the strength properties of the rock mass. Most of the bridge abutments and dam constructions are associated with basement rock. In such locations rocks mass is alternately subjected to wetting and drying processes. Therefore the deterioration of rock resulting in its breakup, which is termed as "slaking" is also studied in this research. One hundred and sixty rock samples of gneissic rock of diameter 54mm (NX size) are tested in this research. Out of these 132 samples are fresh competent rocks and 28 are weathered to different degrees. These samples are selected from biotite gneiss and quartzo-feldspathic gneiss; the major two gneissic rock formations found in Sri Lanka. Fresh gneissic rock samples were subjected to heating and the weakening of their strength properties were studied upon cooling. Naturally weathered gneissic rock samples belonging to different weathering grades were also tested for their index properties. These were compared with the index properties of artificially weathered fresh gneissic rock samples and some correlations are established. The rate of deterioration of index properties of quartzo-feldspathic gneiss is seen to be more than that of biotite gneiss. Therefore more attention should be paid in the designing of foundations of important civil engineering structures in quartzo-feldspathic gneiss as far as the 'durability, is concerned, based on the project location..
item: Thesis-Abstract
Site suitability analysis for water harvesting structures in Suriyawewa, Hambantota district using GIS techniques
Senanayake, IP; Puswewala, UGA; Dissanayake, DMDOK
Sri Lanka receives an average annual rainfall varying from 900mm to 6000mm. However, the rainfall is not distributed equally over the island. Hence, traditionally, the country is divided into three main climatic zones as wet zone, dry zone and intermediate zone. Two thirds of the island is occupied by the dry zone, which receives less than 1750mm of average annual rainfall. The dry zone periodically has faced water stress conditions from the past, and Hambantota District appears to be a severely affected area, on the basis of surface water availability. With the ongoing development projects, the demand for water in the district will increase in the next few years. Therefore, implementation of a proper water management system as well as preservation of existing surface and groundwater resources is essential to overcome this problem. A methodology is developed to find the most suitable locations for water harvesting structures in Hambantota District by using Geographic Information System (GIS) techniques. Suriyawewa Divisional Secretariat area is selected as the research area considering its average climatic conditions and location within Hambantota District. This methodology can be generalized to the whole District in the first instance. The research area is hydrologically analyzed to discretize the area into catchments and the preferred catchments to harvest the runoff based on surface area, slope and rainfall are found by using GIS techniques. The selected catchments are then analyzed with geological data and drainage characteristics to find the most suitable catchments to construct reservoirs to store rainwater. The analysis yields four such locations, which were subsequently field verified for spatial accuracy. However detailed local investigations are necessary before proceeding to actual construction of the reservoirs. Groundwater recharging also plays an important role in water management, as groundwater represents 30.1% of the world’s fresh water resources. GIS techniques are employed to integrate data on land use, climate, soil, stream pattern and ground slopes, and consequently to find potential areas for groundwater recharging. Here also, detailed local investigation must precede any construction work in the selected areas. Also, potential areas to implement roof water harvesting projects in Suriyawewa are found by analyzing the rainfall and building cover by using GIS techniques. These areas are recommended to be used as project areas when implementing efficient roof water harvesting methods. The methodology adopted here for Hambantota District can be used for water management in other Districts of the Dry Zone of Sri Lanka such as Monaragala, Puttalam, Ampara, Badulla and Kurunegala, as a solution for water stress conditions in those areas. An increment in water harvesting can significantly increase the crop yields in these areas and improve the economy as most of the Districts in the Dry Zone are agriculture-based. Also, a proper water management system is a must for the industrial development of the area under focus, while it gives a solution to the problems regarding drinking water. Proper water supply plays a major role in infrastructure development of these areas and would form the foundation for the overall development of the country.

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Browsing Master of Philosophy (M.Phil.) by Author "Puswewala, UGA"