10 research outputs found
Lanka /
No full textCopyright © 2013, by IWMI. All rights reserved. IWMI encourages the use of its material provided that the organization is acknowledged and kept informed in all such instances. Photos: Cover photo by Prof. J. Katupotha showing fishermen engaged in fishing in the Negombo Lagoon. All photos in the text are by Prof. O. Amarasinghe. Please send inquiries and comments to
Palaeoclimate change during Glacial Periods: Evidence from Sri Lanka
No full textIn the Earth’s history, there were five major glaciations, namely, Huronian (2,300 Ma),Cryogenianor Sturtian-Varangian(850-635 Ma), Andean-Saharan (460-430 Ma, Karoo (360-260 Ma) andthe Quaternary (2.58 Ma to Present) that occurred between 2,300 Ma and 0.0114 Ma. It is revealed thatGondwanaland emerged between the Huronian glaciation (2300-2100 Ma) in the Paleoproterozoic Eraand the Andean-Saharan glaciation (460-420 Ma) in the Early Paleozoic Era. During this time, mostcontinental land masses were clustered in the southern hemisphere, and Sri Lanka was part of theGondwanaland landmass comprising present day Africa, Madagascar, India and Antarctica. Within theOrdovician (485.4-445.2Ma) to Permian Periods (299.0-254.2 Ma) there were signs of the breaking up ofGondwanaland resulting in the severing of India and Sri Lanka together and subsequently Sri Lanka fromIndia. By end of the Permian Period (260 Ma) Karoo Glaciation had ended and the present Mannar Basindeveloped within a deep canyon (about 4-7 km deep) on the Precambrian basement.Although the island of Sri Lanka presently lies in the Indian Ocean between 5º 52´N-9º 54´N and79º 30´E-81º 55´E, to the southwest of Bay of Bengal and southeast of Arabian Sea, it was positionedwithin 67ºS-65ºS and 34ºE-43ºE during the Lower and Middle Jurassic Era (201.3-166.1 Ma). Huge rockyblocks (erratic boulders) have been transported to different places by continental ice sheets due to climaticchanges in the Permian, Triassic and Jurassic Periods, but erratic pebbles (2 to 8 cm or more in size) andstreams fed deposits have been transported by glacifluvial processes. These glaciofluvial processesoccurred on four occasions during the Jurassic Period and Eocene, Miocene and Pliocene Epochs on SriLankan landmass, which fallowed the climatic changes and sea level fluctuations that broke up thesedimentary beds, initiating establishment of the present topography and structural configuration. As aresult, the earlier sedimentary deposits were obliterated from greater part of Sri Lanka. During theQuaternary Period the erosional rate increased and the resultant erratic boulders along withglaciofluvialdeposits can still be found on “Planated Surfaces”of Sri Lanka
Anthropogenic impacts on urban coastal lagoons in the Western and North-western coastal zones of Sri Lanka
No full textSix lagoons namely Negombo, Gembarandiya, Chilaw, Muthupantiya, Mundel and Puttalam along the Western and North Western coast of Sri Lanka are showing signs of some change due to urbanization related anthropological activities. Among the issues related to anthropogenic activities, the development of urban centres on both sides of the Negombo Lagoon, Chilaw and Mundal Lakes, and Puttalam Lagoon is prominent. The other impacts are their use as fishing anchorages and the presence of a high density of fishing craft (Negombo, Chilaw and Puttalam Lagoons); land reclamation for road construction, settlements, expansion of agriculture (all Lagoons); conversion of marginal lands of lagoons for shrimp farms (Gembarandidiya, Chilaw and Mundal Lakes, Puttalam Lagoon); salterns (Mundal and Puttalam Lagoon); use as municipal waste disposal sites (Negombo and Chilaw Lagoons); and inflows of inorganic fertilizer runoff and manure runoff from inland agricultural areas (Negombo, Mundal and Puttalam). Lagoon communities were consulted to understand their dependency on lagoons and to identify the issues associated with anthropogenic activities. Identified activities have direct implications o n morphological features of lagoons, elimination of wetlands (mangrove swamps and marshy lands) and pasture lands, land degradation due to encroachment for shrimp farms, shrinking of lagoons, production of higher nutrient and heavy metal loads, decline in bird and fish populations and degradation of the scenic beauty. As a result, the lagoon ecosystems have suffered to such a degree that numerous faunal and floral species have disappeared or have diminished considerably over the last few years. All these anthropogenic impacts were identified by the author during 1992, 2002, 2006 and 2011 as well as a study on “Lagoons in Sri Lanka” conducted by IWMI between 2011 and 2012.Keywords: Anthropogenic impacts, coastal lagoons, urban lagoons, land degradatio
GEOLOGICAL SIGNIFICANCE OF MARINE MOLLUSCAN BEDS : EVIDENCE FROM SOUTHERN COASTAL ZONE OF SRI LANKA
No full textUnderstanding the River Basin Classification of Sri Lanka
No full textThe need has arisen to understand the rivers and river basins as a subject for achieving related policy making, development, conservation and management goals. The interpretation of the river basins concept was first attempted by Hunting Survey Corporation Limited, Toronto, Canada, and Surveyor-General of Ceylon (Sri Lanka) in 1962. Consequently, Arumugum in 1969 explained that the island could be divided into 103 components of natural river basins. Unfortunately, in the past six decades, misinterpretation of said river basins with rivers and misunderstanding of river drainage patterns have been identified many research articles and even in the Sri Lankan educational system. Most of the authors and scientists have misinterpreted the number of rivers in Sri Lanka as 103, and they flow radially from the Central Highlands to the sea. The present study is focused on providing clarifications of the river basin concept, rivers and understanding the drainage system of the island. Therefore, river basin maps and digital elevation models were developed to understand the river basins, river origin locations and flow patterns. These data coupled with previous field observations were then used to critically evaluate existing scientific literature. Accordingly, there are 29 rivers (15 perennial and 14 seasonal rivers) that flow directly to the sea. This could be further categorised as drowned river valley, bar-built perennials, bar-built seasonal, perennial delta estuaries, and seasonal delta estuaries. Considering the origin of these 29, only 8 rivers begin from the central highlands and its margins (over 1,200 m contour line), and most rivers/Oya emerge below the 1,200 m contour line. Another 64 rivers/Oya found out to be emptied into lagoons even though traditionally classified as flows directly to the sea. Mahsilawa, Katupila Ara, Pallakutti Ara and Rathmal Oya identified as rivers, but they connect to other rivers or salt marshes while, Bolgoda lake, Madu Ganga, Madampe lake, Telwatte Ganga, Rathgama lake and Koggola lake turned out to be back-barrier coastal lagoons mistakenly identified as rivers in the traditional classification. Also, all these originate from the coastal plain (below 100 m contour line). Hence, it is clear that there are some misreading of river basins and rivers in existing scientific studies. As this information is valuable in many ways to the country, misreading of these subjectmatters must be corrected immediately. Further studies on the river basins concept must be done analytically and the context of the Sri Lankan education system should be updated accordingly.Keywords: River basins, Misunderstanding, Radial drainage, Central highland, Sri Lanka
GRANITE QUARRYING PROJECTS AND THEIR IMPACT OF THE ENVIRONMENT
No full textSurface and subsurface charnockitic gneissic boulders of the Kolonna DivisionalSecretariat area have been separated-and detached using bores and compressor machines toproduce "blocks" for export. Four granite-quarrying projects were in operation at theLanka-Beriya Estate, Bulutota Kadamuduna, near the Circuit Bungalow at BulutotaKadamuduna and at Udahakanda village (Pitakanda). However quarrying in the above foursites has been abondoned stopped consequent to pressure brought by the public. Only oneproject is active at the Aigburth Estate in Suriyakanda to date.This study aims at identifying the existing problems of the quarrying projects, examineshow these quarrying projects can contribute to slope failure in the future; and makesrecommendations as mitigatory measures for better understanding of uses and themanagement of resources. Accordingly, following conclusions can be made regarding theexploitation activities in the sites:(a) local relief and other geographical parameters (physical and social) have not beengiven and concern prior to exploitation of the resources(b) damaged and destroyed boulders and fragments have been dispersed and havedumped in the sites(c) reservations made by Ordinances and Laws for natural streams (Poddana,Bulutota and Ittakanda GNDs), electrical transmission lines and cemeteries(Ittakanda GND) have been ignored during these exploration(d) after removal of boulders, pits burrows have not been filled properly withcompacted earth(e) trees and vegetative species have been destroyed and growth retarded due tooperations carried out (Bulutota Kadamuduna, Aigbirth Estate and Udahakandavillage(f) vibration during drilling and dynamiting (dynamiting is not presently used) havecreated surface cracks in the area immediately behind the boulders(g) dust from drilling operations ace removed by wind and create environmental andhealth hazards(h) development of gullies and surface erosion is caused by heavy rains after blocksare removed; and(i) closed pits as well as the open pits of the area are able to create gullies by surfaceerosion and can store an extensive volume of water increasing sub-surface erosionIt is evident from detailed field inspections and slope analysis around the sites that illegaland unmethodical quarrying of these boulders in whatever form contributes to slope failureand exerts a negative impact on the environment. The threats to human life and property aswell as the degradation of the environment has contributed to a strong opposition by thepublic to the operation of quarries
Changes in Coastal Landforms from the Poonaryn Peninsula to the Malwathu Oya (Aruvi Aru) Estuary, Northwestern Coastal Zone (NWCZ) of Sri Lanka
No full textChanging coastal landforms are constantly occurring due to wind, waves, sea currents, tidal fluctuations, and human interference. This paper makes a special effort to ensure the correct usage, management and utilization of these landforms, which will benefit society through economic growth. A variety of peculiar coastal landforms have formed between the Poonaryn Peninsula (9°36'10.23"N, 80°03'16.74"E) and Malwathu Oya (Aruvi Aru) estuary (8°46'30.22"N and 79°56'12.85"E), which are approximately 120 km long coastal stretch. The Poonaryn Peninsula extends from Pallikuda Beach to Kalladi Yutha Kovil (9°35'53"N, 80°3'10"E). The peninsula stretches northwest to southeast, covering dunes with a maximum elevation of 17 meters. The selected study location is favourable for the coastal environment, and the coastal environment can be defined as the area lying at the interface between land and Mannar Bay, Palk Bay and a part of the Jaffna Lagoon. This area includes non-barrier delta estuaries with seasonal rivers and bar-built perennial delta estuaries. The zone of shallow water within which waves can move sediment and the area landward of this zone, including beaches, low coastal dunes and vegetation cover, are affected to some degree by the direct or indirect effects of waves, tides, winds and currents. The coastal environment itself may extend inland for many meters or kilometers. These processes make it possible to identify several coastal habitats, such as mangroves, salt marshes, covered and covered dunes, beaches, barrier beaches and spits. Lagoons, riverine estuaries, brackish water bodies, water holes, and marshes. When considering biodiversity, local and migratory avifauna, beach mangroves, seagrass beds, tidal creek system are very important for tourist attraction. Additionally, fishery harbours, boat landing sites, traditional fisheries (beach seines, koodo fishing), etc., and tourism were established in the northwestern coastal stretch owing to enticing coastal processes and landforms in the area for correct usage, management and utilization for enormous benefits of the fishing society, the environment and the economy.
DOI: http://doi.org/10.31357/fhss/vjhss.v09i02.0
Inselbergs in Vijayan complex of Sri Lanka
No full textThe distribution of inselbergs and their relationship to geomorphology, structure, and lithology controls in Southeastern Sri Lanka is a significant characteristic of regional geology. Inselbergs are isolated hills that stand above well-developed plains and appear as an islands rising from the sea. Inselbergs and associated there caves are considered animal kingdoms, monasteries, and geo-heritage sites that can be developed for geotourism. Geo-tourism is defined as tourism that sustains or enhances the distinctive geographical character of a place and its environment, heritage, aesthetics, culture, and the well-being of its residents. The preset study analyzed the inselbergs of the Vijayan Complex (VC) of Sri Lanka concerning their rock types using GIS Pro interpolations as the preliminary stage of a detailed field project. Geological maps (1:100 000) covering the whole VC were carefully interpolated with the contour map of the VC and all inselbergs with more than 100 m height for the background were considered. A total of 474 inselbergs were notified and 34% of them are rest on granite gneiss whereas 17% are rest on hornblend biotite migmatites. About 15% of inselbergs are on alkali feldspar granitic gneiss/migmatites and 11% are on biotite hornblend garnet gneiss. The geological composition itself suggested the high weathering resistance of the rocks might be the reason for the formation of such inselbergs. Particularly, these specific morphologies have stood out against the leveling process of nature largely because they are made of resistant granitic rocks containing large proportions of quartz, one of the indestructible rock-forming minerals. In addition, structural control is observed which developed the striking dome shape and piedmont. The castellated and Bernhardt appearance is significant in the VC inselbergs, which were recognized as rock monasteries such as Dimbulagala, Danigala, Rajagala, Buddangala, Piyangala, Westminster Abbey (Govinda Hela) etc. Though high scenic value and geo-heritage are prominent in some high elevated inselbergs, the deficit of proper management and route guide for geo-touristic purposes is identified which can be recommended for income development projects
