Application of remote sensing and GIS techniques for exploring construction material from inaccessible terrains; case study in Eastern Province of Sri Lanka

Demand for construction materials in the North and Eastern provinces of Sri Lanka has risen significantly due to accelerated construction work in progress to restore the destroyed infrastructures during the civil war. Ground surveying methods to locate quarries within this area are not applicable due to security reasons and the larger area to be covered. Thus a Remote Sensing method is suitable for this task. This study introduces a methodology to locate suitable quarries and sand mines for constructions in the Eastern province. LANDSAT ETM+ images were used for classification. Feasible rocks and sand deposits for quarry operations were located using Multicriteria Analysis (AHP).The highly suitable rock quarries and sand deposits were considered in closest facility analysis. The results showed that the integration of Remote Sensing (RS) and Geographic Information System (GIS) can serve as an effective tool in demarcating suitable sites for construction material and this methodology can also be applied for projects of similar nature

Development of conceptual geological model for the formation of hot water springs in Sri Lanka

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 energ

Assessment of Geothermal Gradient in Bogala Area, Sri Lanka

Geothermal gradient gives important assessment to geothermal potential in an area. This study aimed to study geothermal potential in Sri Lankan crust using measurement from available deep mines. Bogala Graphite mines is one of accessible deep mine available and located 124 km away from the well demarcated tectonic boundary in Sri Lanka. In this research, 476 m deep Bogala Graphite mines was selected to study the geothermal gradient in Sri Lankan crust. Drill holes made in the bed rock horizontally, temperature sensors placed approximately in the same direction and kept continuously around 72 hours period. All the places selected to install sensors were far ends of long run abandoned tunnels/ adits in the mine. The average values of temperatures in those levels were computed, and then geothermal gradient was calculated as 28.046 0C/km. This method gave some reliable information about, how temperature gradient varies at different levels of Sri Lankan crust

Modeling water quality changes o f urban canalsin Colombo cit y against rainfall an d land use patterns

Modeling the relationships between surface water quality with rainfall and land-use patterns is of prime importance in exploring effective method s for mitigating the water pollution in areas like Colombo city. These models are important for land-use planning and resource management to plan for best environmental management practices and it is possible to compile detailed inventories and to monitor water quality in surface water bodies. This study focuses on modeling the surface water quality change s of urban canals in Colombo from 2003 to 2009 in relation to rainfall of different climatic seasons, land use types, and population density using a G IS based approach together with statistical modeling. The data on land use, monthly rainfall, population density and water quality from 200 3 to 200 9 was collected from the Department of Survey, Department of Meteorology, Department of Census & Statistics and Sri Lanka Land Reclamation & Development Company respectively. Results revealed that there is a strong significant difference within the mea n values of Conductivity, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD) and Salinity percentage according to the climatic seasons. The water quality attributes; Conductivity, Phosphate , BO D and Salinity percentage were significantly correlated to land-use types (Built-up/Homesteads, Barren, Marsh/Paddy, Park/Playground, Plantation, Scrub and Water bodies). A significant regression model could be drawn to predict the surface water quality in Colombo city using one water quality indicator (BOD) which ma y suggest that point-sources contribute more pollutants than non-point sources. Recommendation s were mad e to consider more important water quality parameters such as biological parameters within an extended study area for future studies because they will be providing complex models of water quality with other factors

Development of a methodology to map railway lines and surrounding land use using UAVs

High accurate railway maps and terrain information (Digital Elevation Models) is a major concern for future railway constructions and railway lines development.The mapping of railway line using ground based surveying techniques istime consuming and problematic.Unmanned Aerial Vehicles (UAV) technology has revolutionized the aerial photogrammetric mapping due to its low cost and high spatial resolution. It enables mapping the land use with greater accuracy in both 2D and 3D. The “DJI Phantom 4“ drone was selected as the UAV platform to acquire image data. In this study, we have developed a fully automated and highly accurate engineering approach for detecting land use and railway line, which is based on textural information from orthophoto and elevation information (Digital Surface Models)obtained from the drone.The Pix4D software was used to develop the orthophoto and a Digital Surface Model (DSM) and the DSM was validated by using the ground control points.The rule sets knowledge-based classification method in object oriented classification was used to classify the land use and railway with the use of “eCognition“ software. Finally, the results were compared with digitize land use layer to validate the results, and obtained overall accuracy of 90.15%

Geo-environmental assessment along Southern and Western coastal belt of Sri Lanka after Indian Ocean mega Tsunami.

Geo-environmental assessment after the recent mega tsunami, along the southern and western coastal belt indicates varying effects to the beach profile, mineral deposits, surface and ground water, and soil. The most significant effect was due to the beach erosion which had changed the beach profile creating deep water near the shore allowing waves to break much further inland than usual triggering further coastal erosion with the south western monsoon. Destruction of live corals, salinization of drinking water and agricultural soils, water logging in abandoned inland coral pits severely causing epidemic threats, are some of the other major geo-environmental issues along this coastal region. Considerable amount of heavy minerals (from Beruwela to Hambanthota) which are potential placer deposits of ilmanite, rutile, monazite, zircon, and garnet has been removed from the coast line and deposited further inland in a wide scatted area, thus, degrading this potential placer deposit. Immediate actions have to be undertaken to rectify most of these environmental issues

Effect of trenching on bast-Induced ground vibration in Sri Lankan metal quarries

Problems due to ground vibration are a matter of serious concern for the users of explosives, as it is not possible to eliminate vibration totally or to contain them at the source. Efforts need to be made in controlling the vibration to fall within the safe level, without affecting the production schedules and economic viability of the project. If ground vibrations predicted or monitored exceed the statutory limit, control measures are taken by modifying the blast design parameters. In the research, digging a trench between the vibration source and the point of observation has been studied as a technique to reduce the transmission of the Rayleigh waves. The extent to which ground vibration could be reduced has been examined by field experiments carried out at an open cast quarry situated at Arankele, Sri Lanka. Blast vibration measurements have been carried out for active isolation, where the trench is excavated closer to the blasting point. An average of ten single shot hole blasts carried out correspondingly for four different depths of shot holes namely 1 m, 1.5 m, 2 m and 2.5 m with varying depths of trench shows ground vibration reduction percentages of 6.3%, 1.2%, 7.0% and 18.3% at a point immediately after the trench keeping the depth of the trench greater than that of the shot hole in each blast, and reduction percentages at a point closer to the observation point under the same conditions for the four shot hole depths were 72.2%, 54.4%, 55.1% and 45.1% respectively. The corresponding values after digging the trench show ground vibration reduction percentages as 57.8%, 53.9%, 40.5% and 36.7% at the point immediately after the trench location and vibration reduction percentages of 55.5%, 64.7%, 56.8% and 42.3% at the point closer to the point of observation for the corresponding four shot hole depths. Results indicate that after digging the trench, ground vibration reduction levels recorded were much higher, compared to those obtained before digging the trench. However, results obtained closer to the point of observation do not indicate a reduction for each shot hole depth. This leads to the conclusion that active isolation results in a considerable reduction in ground vibration level under given geological conditions

Nearshore sediment dynamics in Sri Lanka

Coastal environment is a unique morphodynamic system for diverse changes. The present study estimated coastal morphodynamic changes and sediment transportation directions at locations of Uswetakeiyawa beach nourishment and Colombo harbour expansion project areas. In addition, heavy mineral occurrences were studied in beach sediments altogether parameters of mineralogical and geochemical compositions to identify depositional environments. Moreover, time series satellite images were used to identify seasonal coastal sediment accretion and depositional trends. Uswetakeiyawa beach nourishment project area indicates complex sand accretion or erosion, and a net reduction of overall beach widths with reference to the initial field visit. This site records bi-directional sediment transportations by longshore currents during the monsoon periods. Similarly, Colombo harbour expansion project area shows that the cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). The cumulative and site-specific sand accretion and erosion patterns show clear influence with the monsoon seasonality. Beaches were wider during the stormy south-western monsoon, whereas beaches were narrower during fair weather of north-east monsoon. In contrast, ilmenite, zircon, garnet, monazite and rutile were identified as main heavy minerals in beach sediments. The heavy mineral potential of the north-eastern coast was high (average about 45-50% in the Verugal and 70-85% in the Pulmoddai deposits and 3.5-5.0% in the offshore samples from Nilaveli to Kokkilai), compared to the south-western sediments (average about 10% in onshore and 2% in offshore Gin River mouth). Observed high concentrated heavy minerals in beach and low concentrated offshore sediments suggest the panning system in the surf zone to form enriched placer deposits. The whole rock major and trace compositions of beach sediments were marked enrichment of TiO2, Fe2O3, Ce, Cr, Nb, Th and V compared to the average upper continental crust values. The analysis of prominent coastal longshore transport patterns shows that clockwise flows in the eastern and north-western coasts. In the south-western coast, transport directions were divided into two branches of anti-clockwise and clockwise. Therefore, the schematic representation of monsoon-derived longshore currents suggests that the sources of heavy minerals in the Pulmoddai and Verugal deposits may have probably influenced by clastic sediment supply in eastern India and Sri Lanka (the Mahaweli River), respectively. Heavy minerals in the western coast can probably derive from Precambrian metamorphic rocks, and supplied to coast through river systems in Sri Lanka

Ground penetration radar obseravtions at Kahagolla Landslide and evaluation of potential failure mechanism

The term landslide is used to describe a wide variety of processes that result in the perceptible downward and outward movement of soil, rock and vegetation under gravitational influence. The material may move by falling, sliding, spreading, or flowing. Landslide disaster is caused to produce a significant impact to the economy of the country and caused to create number of social and enviromentalimpacts. This research was forced on studying the methods that can be used for evaluating the potential mechanism of Kahagolla landslide by applying geotechnical and geophysical techniques. The study was based on slow moving landslide located near the Kahagolla Estate. It belongs to Haputhale District Secretariate divisionin Badulla district.This study involves the use of Ground Penetrating Radar (GPR) and existing borehole information.GPR, technique used for defining underground structure, providing a time effective survey that yield high resolution data making it suitable for shallow and deep subsurface analyzing. The results were validated using the available borehole information. The GPR survey information revealed a close relationship with the borehole data. Hence, an optimum combination of GPR survey and borehole drilling can be proposed for cost controlling in landslide monitoring and instrumentation programme. After interpretation of GPR observations, could identify some of active slip surfaces and their depths from the ground surface

Interference of natural coastal sediment dynamics due to the Colombo harbour expansion project

Man-made coastal structures directly affect sediment balance in the surrounding beaches. Ongoing South Colombo harbour expansion project has created 5 km long breakwater affecting the sediment dynamics of the Colombo beaches. Present study is focussed on quantitatively and qualitatively analyse the effect of Colombo harbour expansion project on economically important beaches in an around Colombo city area and to forecast possible consequences to the Colombo harbour itself. We have taken monthly variations of beach width, beach profile and the mean grain size of the sediments at mean sea level from selected 8 beaches. Data was processed and analysed to establish sitespecific erosion vulnerability. Results shows cumulative beach erosion has high affinity to erosion causing drastic reduction of beach width after the construction of the breakwater. This study highlights necessity of proper mitigation plan to protect the beaches affected by the construction of southern Colombo harbour expansion project