Browsing by Author "Jayasinghe, SN"

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item: Conference-Full-text
Flood risk assessment in the vulnerable economic zones: a case study in the Kelani river basin
(Business Research Unit (BRU), 2023-12-04) Jayasinghe, SN; Madurasinghe, MAVN; Weerahannedige, DC; Weerakoon, DRYYB; Dassanayake, SM; Gunawardana, A; Dissanayake, DMPV; Prasanna, R
This research presents a comprehensive framework for managing flood risk in the Kelani River basin, employing the Analytic Hierarchy Process (AHP) and spatial analysis to enhance flood risk comprehension, support informed decision-making, and facilitate effective flood management. Initially, the framework identifies key parameters influencing flood risk, which are then used to create flood hazard and vulnerability indexes through AHP. The hazard index indicates the likelihood of a flood event, while the vulnerability index assesses potential impacts. These two indexes are combined to form an overall flood risk index. Subsequently, this index is utilized to develop a web-based spatial decision support system (SDSS), enabling businesses and stakeholders to visualize and analyze flood risk information, aiding them in making well-informed decisions regarding flood mitigation and adaptation measures. This research offers valuable insights for policymakers and authorities in the Kelani River basin, fostering resilience and sustainable development in the region. Though the study acknowledges limitations related to data availability and generalization to other regions, it serves as a valuable foundation for the development of more comprehensive and effective flood risk management frameworks in the Kelani River basin and beyond.
item: Conference-Full-text
Hydrological Modelling Approach for Flood and Water Pollution Control in an Ungauged Catchment - A Case Study in Erewwala Catchment in Bolgoda River Basin, Sri Lanka
Jayasinghe, SN; Rajapakse, LHL
The data scarcity is a widespread, global issue and unavailability of reliable hydro meteorological data is one of the major issues the hydrologists and researchers are facing in Sri Lanka when it comes to water resources planning and management. A significant increase in occurrence of flash flood incidents and water quality degradation in surface water bodies have been noted in the recent past. Hence, developing an approach to identify underlying causes and recommend mitigation or preventive measures for floods and water pollution is a timely requirement that planners, designers and researchers should attempt. The objective of this project is to formulate a hydrological modeling approach to recommend preventive or migratory measures for floods and water pollution in ungauged catchments based on the findings of a case study in Erewwala catchment in Bolgoda River Basin, Sri Lanka. The parameters of hydrological models for ungauged catchments can be estimated using regional information. For this case study, a rainfall-runoff model was developed in spreadsheet and graphical format where the monthly runoff coefficient and base flow were the model calibration parameters. The model was calibrated based on observed data for three years and validated for two years. Observed discharge data at Millakanda gauging station, basin rainfall obtained from Rakwana, Horagoda and Usk Valley rainfall stations and evaporation data from Colombo were used for the model developed for Kaluganga. The calibrated parameters of Kaluganga basin were used for the water resources assessment in Erewwala catchment (2.9 km2). The catchment was divided into three sub-catchments for water pollution control purpose and the incremental runoff at the each sub-catchment outlet node was estimated using the rainfall- runoff model. The types of water uses were identified for each sub-catchment unit and the discharges due to each water use in individual catchments were calculated, subsequently deriving the contribution of each catchment to its overall water pollution. These values were compared with the stipulated permissible pollutant level in surface water bodies. For flood control measures, the HEC-HMS (US-ACE) software was used to estimate the peak discharge with 10 year return period storm event and the peak discharge in each catchment node was obtained. The required flood controlling measures were identified and recommended for the critical catchments which contribute to the highest discharge leading to flashflood conditions in the downstream areas. Based on the peak flow and pollutant source analyses, the sub-catchment No. 1 was identified as the most polluted catchment as well as the one which contributes the most to the flash floods in Erewwala catchment.
item: Thesis-Abstract
Simplified design guidelines on upper floor slabs of two-storeyed houses
Jayasinghe, SN; Chandrdadkeerthy, SRDS
The two-storeyed house is very popular now and its usage has overflown from Colombo and suburbs, to most provincial towns and their suburbs. It has come to stay because of: (a) escalating land prices due to increased demand and scarcity of buildable land; (b) higher social status it bestows on its owners and occupants; (c) imposing dominance of the surrounding environment with attractive views; and (d) possibility of construction at a higher but affordable cost even in relatively poor soil conditions. However, structural designs of two-storeyed houses are rarely referred to structural engineers probably because: (i) Local Authorities do not ask for structural details when plans are approved; and (ii) Clients prefer to make a saving on professional charges of structural engineers. One way to overcome this is to develop simplified design methods so that design office time and hence the cost of a structural engineer can be reduced. It will also help the new initiative taken by the institution of Engineers, Sri Lanka to get structural engineers to Design or check two-storeyed house designs. This concept is gradually gaining ground in developed countries with the provision of simplified design codes such as BS 8103: Structural design of low rise buildings. Further, upper floor slab is a very costly element in a two-storeyed house. Hence an investigation on development of a simplified design method for upper floor concrete slabs of two-storeyed houses was considered beneficial and timely. The investigation consisted of a literature survey, a survey on frequency of occurrence of various slab configurations in typical two-storeyed houses, and a design study. The literature survey highlighted the importance of structural optimization in developing simplified design methods and the methodologies adopted by various researchers to formulate simplified design methods. The survey on typical two-storeyed houses popular in Sri Lanka covered 30 such houses focussing on dimensional variations as well as different end conditions, dealing with 217 distinctly different floor slabs. The design study consisted of over 3800 repetitive designs giving rise to 495 optimally designed reinforced concrete slabs, and 270 optimally designed slabs for. Studying sensitivity of optimal designs to variations in cost. To facilitate the conduct of repetitive designs, the structural design process was-computerized by developing an EXCEL computer programme. The investigation concluded that; (a) In all the designed solutions developed, the competition for the structurally 'optimized designs was always between 150mm and 125mm overall slab thicknesses; (b) The primary result of the structural optimization process was the overall slab thickness, as steel reinforcement areas get generated automatically independent of slab bending moments as governing design criterion is cracking; (c) The two design recommendations were developed for selection by the user called the "preferred method" and the "alternative method"; and (d) All slabs had nominal reinforcements corresponding to the effective depth derived from the respective overall slab thickness.
item: Thesis-Abstract
Study on locations for future coal-fired power plants
(2014-08-12) Jayasinghe, SN; Perera, HYR
Evaluation of suitable sites for coal-fired thermal power plants is very important as there are several such plants to come up in the future. All generating plants except Upper Kotmale Hydro Power plant in "Long Term Generation Expansion Plan 2009-2022" published by the CEB are coal power plants. Two locations already have been identified for coal power plants at Norochcholei and Sampur for 900MW and 1000MW respectively. The study reveals that there is no provision to expand beyond the designed capacity at Norochcholei plant. There is no technical limitation to expand the designed capacity at Sampur plant. The aim of this study is to evaluate a further eight proposed sites analyzing following important factors which influence site suitability. These factors are; 1 Supply of coal and transportation facilities on land and at sea 2 Availability of sufficient cooling water and feed water 3 Proximity to the load centers / access to the national grid 4 Distance from populated area (Environmental aspects including impact on the population) 5 Depth of the sea near the coast 6 Availability of sufficient area for power plant, coal storage and ash disposal 7 Other factors 7.1 Access to the land 7.2 Topography/ geology 7.3 Meteorology 7.4 Hydrogeology 7.5 Natural hazards Of the eight sites to be evaluated the CEB has identified five tentative locations in its "Long Term Generation Expansion Plan 2009-2022" near Athuruwella, Mawella, Mirijjawela, Karagan Lewaya, and Mirissa along the southern coast. No detailed study has been done for these locations. Hence, initially, these five locations were taken into consideration for the study from among the eight proposed sites. Three additional locations are proposed by the author for consideration along the eastern coast. They are near Panama, Sangamankanda Point and Vakarei. Although CEB proposed Karagan Lewaya to be considered as a site it had to be abandoned subsequently because the GOSL has used this site for the recently commissioned Hambantota harbor. As a result of that the study is carried out based on the other seven proposed sites for detailed evaluation. Sri Lanka has no coal mines, thus coal needs to be imported to the sites from countries such as Indonesia, South Africa or Australia who have indigenous coal mines. Hence coal transporting has to be done by vessels to the site especially with Panamax size vessels and Cape size vessels to keep the cost at a minimum level. Another major factor is the supply sufficient water to the site in order to cool the process and process water. These two factors require that the site has to be close to the coast. It can be seen that the four sites Athuruwella, Mawella, Mirissa and Mirijjawela on the southern coast are close to the populated areas and the lands in the vicinity are ideal for agriculture as well as tourism. Some major resettlement plans are required with a suitable compensation scheme when acquiring the lands for the sites at these four locations in the southern province. In contrast, however, the population density at Panama, Sangamankanda Point and Vakarei in the eastern province is comparatively low but the infrastructure needs to be developed. The grid substations at Ambalangoda, Matara, Hambantota, Ampara and Valachchena are considered as gateways to the national grid from the proposed locations. These can access only the 132kV grid and needs to be augmented to handle 220kV at the substation andtransmission lines. Other major factor to be considered is the depth of the sea near the proposed site as this determines how far the vessels can approach the coast and hence estimates the distance of the coal unloading conveyor and the size of the jetty in the sea. Mirijjawela has the advantage of having use of the newly commissioned Hambantota harbor for this purpose as it is about 1 km away from the site. Acquiring of required land area for the proposed site needs to be carefully done. When it is needed to acquire the lands from the residents in the area a reasonable compensation scheme and resettlement plan has to be introduced. Therefore it is of great benefit and cost saving if government owned bare land is available in the proposed areas. Although access to the lands, topography/ geology, meteorology, hydrogeology, natural hazards are minor factors for site selection of a coal power plant, these should also be taken into consideration because the damages can be very high when natural hazards occur like the Tsunami in 2004, although this occurs rarely. The proposed locations should be selected away from any protected wildlife zones, sanctuaries and places with historical values in the country. Then proposed locations are analyzed based on the above factors and for comparison a site validation matrix is prepared with introducing a suitable marking scheme in order to select the best location for the next coal power generation plant.