Browsing by Author "Wanniarachchi, SS"

Now showing 1 - 6 of 6

item: Thesis-Full-text
An Analysis of the influence of the field level hydraulic property approximations in storm water modelling
(2018) Wanniarachchi, SS; Wijesekera, NTS
This study analyses the effect of the catchment field approximations for accurate flood hydrograph prediction. Considering the availability of gauged data, the Karasnagala watershed of Attanagalu Oya, located in Gampaha district in the Western province of Sri Lanka was modelled with EPA SWMM 5. Following an event based approach, 3 days Minimum Inter event Time (MIT) and 0 mm/day Minimum inter Event Depth (MED) were used as the threshold. Fifty events were separated from the 1971 to 1982 period. Concave method and constant slope method were compared for baseflow separation in this study. Four major field approximation types were identified as stream geometrical parameters approximations, soil infiltration parameter approximations, approximation of watershed intermittent storages, and subcatchment delineation approximation. Quantitative representation of the catchment intermittent storages and qualitative representation of the connectivity of the catchment intermittent storages were identified as the objectives of the layout parameter optimization. Soil parameter approximations and the stream network geometry parameter approximations were verified by the field observations. Model calibration and verification revealed that EPA SWMM5 can be successfully used to develop regional Karasnagala watershed model with mean ratio of absolute error (MRAE) 0.289 for calibration, and 0.375 MRAE for verification. Incorporation of intermittent storages with optimized model layout obtained best fitting of hydrograph recession MRAE 0.167. Evaluation of available models and the modelling carried out with calibration & verification revealed that EPA SWMM 5 can be used to develop a rural watershed model. Field approximation for subcatchment lumping with a 16 sub basin configuration showed the marginal increment of modelling error when compared with distributed modelling. Stream parameter approximations revealed that the head water streams/lesser order streams parameters sensitivity is higher than the higher order streams. In soil parameter approximations, saturated hydraulic conductivity of the soil was the most influencing parameter.
item: Article-Full-text
Challenges in field approximations of regional scale hydrology
(Elsevier, 2020) Wanniarachchi, SS; Wijesekera, NTS
Study region: Considering the availability of gauged data, the Karasnagala watershed of Attanagalu Oya located in the Gampaha district in the Western province of Sri Lanka was modeled with EPA SWMM 5. Study focus: This study analyses the effect of the catchment field approximations for accurate flood hydrograph prediction. Following an event based approach, 3 days Minimum Inter event Time (MIT) and 0 mm/day Minimum inter Event Depth (MED) were used as the threshold. Fifty events were separated from 1971 to 1982 period. Four major field approximation types were identified: stream geometrical parameters approximations, soil infiltration parameter approximations, approximation of watershed intermittent storages, and subcatchment delineation approximation. Soil parameter approximations and the stream network geometry parameter approximations were verified by the field observations. New hydrological insights for the region: Model calibration and verification revealed that EPA SWMM5 can be successfully used to develop regional Karasnagala watershed model with mean ratio of absolute error (MRAE) 0.289 for calibration, and 0.375 MRAE for verification. Incorporation of intermittent storages with optimized model layout obtained the best fitting of hydrograph recession MRAE 0.167. Subcatchment lumping with a 16 sub basin configuration showed the marginal increment of modeling error when compared with distributed modeling. Stream parameter approximations revealed that the head water streams/lesser order streams parameters sensitivity is higher than that of the higher order streams. In soil parameter approximations, saturated hydraulic conductivity of the soil was the most influencing parameter.
item: Conference-Extended-Abstract
Demonstration of application potential of stormwater management model for flood plain management-case study at Kotuwegoda, Matara, Sri Lanka
(2010) Wijesekera, NTS; Wanniarachchi, SS
Stream hydrology is highly affected by the dynamic behavior of the urban terrain due to urbanization In a pre-developed setting, much of the rainfall is absorbed by the surrounding vegetation, soil and ground cover. In a developed setting, the water balance changes and a disproportionate amount of rainfall becomes surface runoff and causes flash floods. These excessive volumes are caused by both the total amount of impervious cover as well as the rate at which the runoff is delivered to the stream. Kotuwegoda ungauged urban catchment at Matara Municipal Council is frequently subjected to storm water induced flooding. In this research, storm water flow of the existing channel network was modeled using mathematical model EPASWMM5. Research comprises three basic steps as Identifying the catchment parameters through field observation and Modeling. Using Arc GIS tool converting model output to flood inundation area. Verify the results using field observations and making flood plain management proposals.
item: Conference-Abstract
The evaluation of factors influencing cycle trips in a heritage city. a case study on cycling tourist in Anuradhapura sacred city
(Department of Civil Engineering, University of Moratuwa., 2019-09) Wanniarachchi, SS; De Silva, GLDI; Pasindu, HR
As the world endures an energy dilemma, most developing communities advance toward energy efficient modes and non-motorised transport modes such as walking, roller skate, skateboard and cycling. Cycling is an environmentally friendly mode that enables the commuter to experience the surroundings. Other than commuting, cycling-tourism is about a long to medium distance cycling trip for pleasure, experience, and liberty rather than exercise or sports. Being one of the major tourist attraction zones in Asian region, Sri Lanka experiences over two million tourists’ arrivals every year to visit South and East Coast, Ancient Cities, Hill Country and Northern Region. Anuradhapura is one of the well-known ancient cities with many historical monuments connected with roadway links. This study identifies the design and influencing factors of local and foreign tourists to encourage cycling within the Anuradhapura ancient sacred city rather than using 3-wheeler taxi or other motorised travel methods. As phase 1 of the research, an initial survey was carried out inside the Anuradhapura sacred city with a sample of twenty-one respondents out of the target population of local and foreign tourists. Data has collected through a questionnaire survey and discussions. The factorial extraction has been run to determine the factors influencing cycling tourism, and descriptive statistics have used to present the socio-demographical features of the study sample. The secondary aim of the research is to review the variations in soft mobility choices by local and foreign tourists based on the design and the extracted manipulating factors. The analysis of data has generated factors with very strong loadings to represent the variables used in the survey. The descriptive analysis shows that the majority of the tourist visit Anuradhapura for pleasure, religious and business. Most of the tourist respondents had arrived from East Asia and Europe. The study explains that majority of them has used motorised transport to arrive at Anuradhapura and after arriving has used cycling within the sacred city. The analysis has highlighted that greater number of tourists prefer to use cycling for a short distance journey. The respondents have commented that safety and security issues have been a major tragedy in riding cycles inside the sacred city. It had mentioned that potholes in the road and the areas where the road has been damaged and unpaved had caused notable accidents to the cycling tourists. The risk of theft and the awful surroundings in some areas of the sacred city has discouraged cyclists from riding through the area. The further discussions with cycling renters and cyclists have highlighted that the cycling tourist, both local and foreign have been relying on verbal instructions of landmarks and road, as the Anuradhapura tourist city map provided by the Ministry of Tourism - North Central Province and the google maps has not been providing the accurate information on the routes and pathways inside the sacred city. The effort of the research is to help town planners prioritise services and improvements designated to the location to promote cycling tourism. Sri Lanka’s tourism is one of the revenue generations industries through cycling tourism in the early stages of development. This study has taken a general view concerning the influencing factors of Anuradhapura scared city cycling tourism to develop the cycling within the sacred city and to develop the soft mobility within the Anuradhapura district ensuring more eco-friendly urban surrounding.
item: Conference-Abstract
Seasonality patterns in dry bulk cargo handling at the port of Galle, Sri Lanka
(Transportation Engineering Group, Department of Civil Engineering, University of Moratuwa, 2023-12-08) Pinsara, GGP; Atapattu, AMCP; Wanniarachchi, SS; Jayantha, WRAN
The dry bulk cargo trade plays an important role in international trade by assisting the delivery of the dry bulk cargo demanded by different nations. Dry bulk cargoes cover a wide variety of produce/ raw materials and are transported using a wide range of ships from Mini Bulkers to Very Large Bulk Carriers (VLBC). Regarding both econometric and economic purposes, it is important to understand the differences between various seasonality patterns in the main dry bulk cargo types that arrive at the port in order to conduct operations more effectively and profitably. The study aims to analyse trends in dry bulk cargo unloading, mainly Clinker and Gypsum, under different months of the year to understand port congestion patterns at the Galle port, which operates primarily as a bulk cargo port, with a focus on dry bulk cargo unloading process. This study has used a longitudinal research approach with a quantitative design. This data includes the name of the vessel, capacity, the amount of cargo unloaded, the type of cargo, and the achievement rate over the previous ten (10) years employed for the time series analysis. The descriptive analysis of data shows that the number of vessels arriving increased from sixteen (16) to ninety (90), and the annual handling tonnage has sharply increased by 88.2%. In order to determine the nature of the phenomena represented by the sequence of data to predict the pattern of vessel arrival and handling tonnage, time series analysis has been applied. Data for Clinker and Gypsum were initially examined for stationary behaviour and analysis proved that Clinker and Gypsum are time-invariant and the model will not become spurious. The linear model test in Clinker and Gypsum displayed that Clinker has a volatility clustering and Gypsum does not. Further analysis using ARCH and GARCH models provided that there is no volatility effect on the Gypsum market, but the Clinker market has the volatility effect. The Dummy variables’ regression model shows the months of January have the highest Clinker unloads, while April has the lowest and the Gypsum unloads are high in October and August and minimum unloads are observed in the month of May. This analysis reveals clearly that the Gypsum unloading at the port of Galle can be forecasted with a pattern but the Clinker unloading pattern is associated with uncertainty. The limitations of the study face challenges due to random sample formation and assessing the single event impact due to multiple events occurring simultaneously at the port, making it difficult to determine the most intractable problem. The study is mainly focusing on the unloading quantity of the dry bulk and other factors may have an impact on data that are not being addressed in this study. Ship owners and charterers may find it useful when making choices about shipping operations to consider the kind and size of fluctuations in bulk cargo markets. Additionally, the study's findings will be contributed to use by local businesses involved in dry bulk cargo unloading operations at the Port of Galle to comprehend patterns and put into place the necessary adjustments to determine safety standards, demurrage, and the efficiency of unloading operations.
item: Article-Abstract
Using SWMM as a tool for floodplain management in ungauged urban watershed
Wanniarachchi, SS; Wijesekera, NTS
Mathematical modelling is a powerful tool for arriving at best water resources management. But it is necessary to possess gauged data for model calibration and verification. However most of the urban watersheds are not gauged and does not have high resolution terrain data when designing drainage infrastructure. There are many tools for urban stormwater modelling, but out of limited free tools, EPA SWMM5 has a good record of applicability in many locations elsewhere. The present work shows the applicability of SWMM5 for an urban land extent in the Matara Municipal Council area which is ungauged. This study used literature reported values and data collected during field visits to runoff modeling to obtain order of magnitude values with easy comparison of engineering alternatives for stormwater management. It is thought that possibility of using a systematic and extensive data collection program for parameter identification using simple field measurements and engineering judgment together with stakeholder information for historical record verification provides opportunity to initiate structured and solution oriented data collection programs and modelling. Kotuwegoda area with land extent of 0.475 km2 and 22 sub catchments draining via 8 outlets was modeled for a single event. It was identified that the most sensitive parameter is channel roughness and that engineering options by means of changing channel roughness and incorporating detention storage, could reduce the peak flow by approximately 30%