The Nilwala river basin is prone to frequent flooding during the southwest monsoon and second int... more The Nilwala river basin is prone to frequent flooding during the southwest monsoon and second intermonsoon periods. Several studies have recommended coupling 1D and 2D models for flood modelling as they provide sufficient descriptive information of floodplains with greater computational efficiency. This study aims to couple a 1D hydrological model (HEC-HMS) with a 2D hydraulic model (iRIC) to simulate flooding in the Nilwala river basin. Hourly rainfall and streamflow data of three flood events were used for calibration and validation of HEC-HMS. The model performed exceptionally well considering the Nash–Sutcliffe coefficient, percent bias, and root mean square error. The flood event of May 2017 was simulated on iRIC using the streamflow hydrographs modelled by HEC-HMS. An overall accuracy of 81.5% was attained when the simulated extent was compared with the surveyed flood extent. The accuracy of the simulated flood depth was assessed using the observed water level at Tudawa gaugin...
Forecasting scenarios of future intra-urban land-use (intra-urban-LU) expansion can help to curb ... more Forecasting scenarios of future intra-urban land-use (intra-urban-LU) expansion can help to curb the historically unplanned urbanization in cities in sub-Saharan Africa (SSA) and promote urban sustainability. In this study, we applied the neural network–Markov model to simulate scenarios of future intra-urban-LU expansion in Lusaka city, Zambia. Data derived from remote sensing (RS) and geographic information system (GIS) techniques including urban-LU maps (from 2000, 2005, 2010, and 2015) and selected driver variables, were used to calibrate and validate the model. We then simulated urban-LU expansion for three scenarios (business as usual/status quo, environmental conservation and protection, and strategic urban planning) to explore alternatives for attaining urban sustainability by 2030. The results revealed that Lusaka had experienced rapid urban expansion dominated by informal settlements. Scenario analysis results suggest that a business-as-usual setup is perilous, as it signa...
Air pollution has been identified as one of the silent killers in the present world as pollutants... more Air pollution has been identified as one of the silent killers in the present world as pollutants are taking lives of people without making any noise. Unlike other disasters, air pollution destroys human life gradually. People can see and people can predict when disasters occur. However, people cannot understand or cannot see when air pollution is taking place until people are seriously affected. The road transport and traffic significantly contribute to degrade the quality of air in any region of the world. This study attempts to examine the spatial pattern of Sulfur dioxide and Nitrogen dioxide in the city of Colombo using the data collected by the National Building Research Organization (NBRO), Sri Lanka from January, 2003 to December, 2005. Some socioeconomic data which are used as explanatory variables for the spatial pattern of air pollutants were collected from different government organizations. GIS techniques such as spatial interpolation, spatial query and Geostatistical t...
Recent climatological studies by scholars from different disciplines and different parts of the w... more Recent climatological studies by scholars from different disciplines and different parts of the world have proven that the surface temperature of urban areas is generally higher than those of neigh bouring vegetated areas.
Groundwater is often a forgotten resource in Sri Lanka. Despite the fact that groundwater covers ... more Groundwater is often a forgotten resource in Sri Lanka. Despite the fact that groundwater covers over 90 % of Sri Lanka’s coastal freshwater consumption. Groundwater is very important and is the only source of fresh water in the northern coastal belt of Sri Lanka, especially in the sand stretches located between brackish water lagoons and the sea. It provides water for domestic use as well as for agriculture. Saltwater intrusion from both lagoon and sea can lead to lesser and lesser freshwater lens for the domestic purposes. Due to the saltwater intrusion, hundreds of acres of lands, hundreds of wells are in abandon stage at Jaffna Peninsula. Therefore this study was conducted to assess the extent of the saltwater intrusion at Vadamaradchi lagoon area.
Landslide hazard is one of the most common global hazards. In Sri Lanka, landslides are considere... more Landslide hazard is one of the most common global hazards. In Sri Lanka, landslides are considered as a disaster, and thus, scientific communities have paid attention to monitoring and prediction of landslide hazards. Landslide hazard zonation (LHZ) is a vital factor for preparedness and mitigation phases in a disaster management cycle. In the Sri Lankan contest, LHZ becomes more significant since 20% of the total lands are vulnerable. Spatial distribution of landslides of Sri Lanka is mainly influenced by geospatial criteria, rainfall distribution, geology, hydrology, geomorphology, land-use, and drainage network. However, the above factors do not equally contribute to determining the landslide susceptibility. This study attempted to map the landslide hazard zones in one of the tropical hilly region: Kegalle District and weighting causative factors rationally using statistical method in GIS environment. In this study, causative factors were weighted and modelled to define hazardous...
Cities play an important role in climate change mitigation and adaptation and enhancingclimate re... more Cities play an important role in climate change mitigation and adaptation and enhancingclimate resilience of their slum and vulnerable residents. Climate change adds to existingchallenges faced by cities. Climate change, together with a decrease in absorption capacity ofgreenhouse gasses due reduction in the amount of green cover, parks, trees and agriculturalsurfaces in urban areas, poses serious threats to urban infrastructure, access to basic servicesand quality of life in cities and negatively affect the urban economy. At the same time, rapidurban growth, growing urban poverty and increasing food prices raise concerns about urbanfood security, especially for the poor. Cities are highly vulnerable to disruption in critical(food) supplies and climate change exacerbates this vulnerability. The main objective of this study is to examine the spatial pattern of surface temperature in theKesbewa Urban Council Area and temperature variation with the different UPAF (UrbanPeri-urban and A...
The scarcity of surface water resources in the dry season in the Kilinochchi district increases t... more The scarcity of surface water resources in the dry season in the Kilinochchi district increases the demand for freshwater. Therefore, the existing groundwater resources should be managed to overcome the situation. Several authors worldwide have published studies on the delineation of potential groundwater zone. However, only a few studies addressed the delineation of potential groundwater zones in the Kilinochchi district. This study aims to delineate potential groundwater zones in Kilinochchi, Sri Lanka using integrated Remote Sensing, Geographic Information Systems, and Analytic Hierarchy Process techniques. Groundwater potential zones are demarcated for the Kilinochchi district by overlaying thematic layers: geology, geomorphology, land use/land cover, soil types, drainage density, slope, lineament, and rainfall. Saaty's scale was applied to the assigned weights of the chosen thematic layers and their features. The thematic layers were integrated into a Geographic Information...
This quantitative study investigated the determinants of students’ satisfaction with their online... more This quantitative study investigated the determinants of students’ satisfaction with their online learning experience at Sri Lankan universities during the COVID-19 pandemic. The data was collected from 1376 undergraduates enrolled in various courses in humanities and social sciences at three state-owned universities in the country. The results of the Structural Equation Modeling (SEM) revealed that the independent variables of the model, namely perceived learner motivation, perceived challenges of e-learning, and interaction significantly affected students’ satisfaction with their new online learning experience. Out of the three variables, learner motivation exerted the strongest effect on students’ satisfaction, implying the crucial role self-regulated learning—characterized by motivation—plays in online learning environments. The study has several implications for both creating and ensuring the long-term sustainability of productive and student-friendly online learning spaces in ...
The international statistics show that the global urban population will increase by up to 68% by ... more The international statistics show that the global urban population will increase by up to 68% by 2050 [...]
Although urbanization has contributed to improving living conditions, it has had negative impacts... more Although urbanization has contributed to improving living conditions, it has had negative impacts on the natural environment in urbanized areas. Urbanization has changed the urban landscape and resulted in increasing land surface temperature (LST). Thus, studies related to LST in various urban environments have become popular. However, there are few LST studies focusing on mountain landscapes (i.e., hill stations). Therefore, this study investigated the changes in the landscape and their impacts on LST intensity (LSTI) in the tropical mountain city of Nuwara Eliya, Sri Lanka. The study utilized annual median temperatures extracted from Landsat data collected from 1996 to 2017 based on the Google Earth Engine (GEE) interface. The fractions of built-up (BL), forested (FL) and agricultural (AL) land, were calculated using land use and cover maps based on urban–rural zone (URZ) analysis. The urban–rural margin was demarcated based on the fractions of BL (<10%), and LSTI that were mea...
Although urbanization has contributed to improving living conditions, it has had negative impacts... more Although urbanization has contributed to improving living conditions, it has had negative impacts on the natural environment in the urbanized areas. Urbanization has changed the urban landscape and resulted in increasing land surface temperature (LST). Thus, studies related to LST in various urban environments have become a popular research topic. However, few LST studies focusing on the mountain landscapes (i.e. hill stations) have been carried out. The primary objective of this study is to investigate changes in the landscape and their impacts on LST intensity (LSTI) in the tropical mountain city of Nuwara Eliya, Sri Lanka. The study utilized annual median temperatures extracted from Landsat data collected from 1996 to 2017 based on the Google Earth Engine (GEE) interface. The fractions of built-up (BL), forest (FL), and agricultural (AL) land were calculated using land use and cover maps based on the urban-rural zone (URZ) analysis. The urban-rural margin was demarcated based on ...
Africa’s unprecedented, uncontrolled and unplanned urbanization has put many African cities under... more Africa’s unprecedented, uncontrolled and unplanned urbanization has put many African cities under constant ecological and environmental threat. One of the critical ecological impacts of urbanization likely to adversely affect Africa’s urban dwellers is the urban heat island (UHI) effect. However, UHI studies in African cities remain uncommon. Therefore, this study attempts to examine the relationship between land surface temperature (LST) and the spatial patterns, composition and configuration of impervious surfaces/green spaces in four African cities, Lagos (Nigeria), Nairobi (Kenya), Addis Ababa (Ethiopia) and Lusaka (Zambia). Landsat OLI/TIRS data and various geospatial approaches, including urban–rural gradient, urban heat island intensity, statistics and urban landscape metrics-based techniques, were used to facilitate the analysis. The results show significantly strong correlation between mean LST and the density of impervious surface (positive) and green space (negative) alon...
Urbanization has bloomed across Asia and Africa of late, while two centuries ago, it was confined... more Urbanization has bloomed across Asia and Africa of late, while two centuries ago, it was confined to developed regions in the largest urban agglomerations. The changing urban landscape can cause irretrievable changes to the biophysical environment, including changes in the spatiotemporal pattern of the land surface temperature (LST). Understanding these variations in the LST will help us introduce appropriate mitigation techniques to overcome negative impacts. The research objective was to assess the impact of landscape structure on the variation in LST in the African region as a geospatial approach in Addis Ababa, Ethiopia from 1986–2016 with fifteen-year intervals. Land use and land cover (LULC) mapping and LST were derived by using pre-processed Landsat data (Level 2). Gradient analysis was computed for the pattern of the LST from the city center to the rural area, while intensity calculation was facilitated to analyze the magnitude of LST. Directional variation of the LST was no...
The Nilwala river basin is prone to frequent flooding during the southwest monsoon and second int... more The Nilwala river basin is prone to frequent flooding during the southwest monsoon and second intermonsoon periods. Several studies have recommended coupling 1D and 2D models for flood modelling as they provide sufficient descriptive information of floodplains with greater computational efficiency. This study aims to couple a 1D hydrological model (HEC-HMS) with a 2D hydraulic model (iRIC) to simulate flooding in the Nilwala river basin. Hourly rainfall and streamflow data of three flood events were used for calibration and validation of HEC-HMS. The model performed exceptionally well considering the Nash–Sutcliffe coefficient, percent bias, and root mean square error. The flood event of May 2017 was simulated on iRIC using the streamflow hydrographs modelled by HEC-HMS. An overall accuracy of 81.5% was attained when the simulated extent was compared with the surveyed flood extent. The accuracy of the simulated flood depth was assessed using the observed water level at Tudawa gaugin...
Forecasting scenarios of future intra-urban land-use (intra-urban-LU) expansion can help to curb ... more Forecasting scenarios of future intra-urban land-use (intra-urban-LU) expansion can help to curb the historically unplanned urbanization in cities in sub-Saharan Africa (SSA) and promote urban sustainability. In this study, we applied the neural network–Markov model to simulate scenarios of future intra-urban-LU expansion in Lusaka city, Zambia. Data derived from remote sensing (RS) and geographic information system (GIS) techniques including urban-LU maps (from 2000, 2005, 2010, and 2015) and selected driver variables, were used to calibrate and validate the model. We then simulated urban-LU expansion for three scenarios (business as usual/status quo, environmental conservation and protection, and strategic urban planning) to explore alternatives for attaining urban sustainability by 2030. The results revealed that Lusaka had experienced rapid urban expansion dominated by informal settlements. Scenario analysis results suggest that a business-as-usual setup is perilous, as it signa...
Air pollution has been identified as one of the silent killers in the present world as pollutants... more Air pollution has been identified as one of the silent killers in the present world as pollutants are taking lives of people without making any noise. Unlike other disasters, air pollution destroys human life gradually. People can see and people can predict when disasters occur. However, people cannot understand or cannot see when air pollution is taking place until people are seriously affected. The road transport and traffic significantly contribute to degrade the quality of air in any region of the world. This study attempts to examine the spatial pattern of Sulfur dioxide and Nitrogen dioxide in the city of Colombo using the data collected by the National Building Research Organization (NBRO), Sri Lanka from January, 2003 to December, 2005. Some socioeconomic data which are used as explanatory variables for the spatial pattern of air pollutants were collected from different government organizations. GIS techniques such as spatial interpolation, spatial query and Geostatistical t...
Recent climatological studies by scholars from different disciplines and different parts of the w... more Recent climatological studies by scholars from different disciplines and different parts of the world have proven that the surface temperature of urban areas is generally higher than those of neigh bouring vegetated areas.
Groundwater is often a forgotten resource in Sri Lanka. Despite the fact that groundwater covers ... more Groundwater is often a forgotten resource in Sri Lanka. Despite the fact that groundwater covers over 90 % of Sri Lanka’s coastal freshwater consumption. Groundwater is very important and is the only source of fresh water in the northern coastal belt of Sri Lanka, especially in the sand stretches located between brackish water lagoons and the sea. It provides water for domestic use as well as for agriculture. Saltwater intrusion from both lagoon and sea can lead to lesser and lesser freshwater lens for the domestic purposes. Due to the saltwater intrusion, hundreds of acres of lands, hundreds of wells are in abandon stage at Jaffna Peninsula. Therefore this study was conducted to assess the extent of the saltwater intrusion at Vadamaradchi lagoon area.
Landslide hazard is one of the most common global hazards. In Sri Lanka, landslides are considere... more Landslide hazard is one of the most common global hazards. In Sri Lanka, landslides are considered as a disaster, and thus, scientific communities have paid attention to monitoring and prediction of landslide hazards. Landslide hazard zonation (LHZ) is a vital factor for preparedness and mitigation phases in a disaster management cycle. In the Sri Lankan contest, LHZ becomes more significant since 20% of the total lands are vulnerable. Spatial distribution of landslides of Sri Lanka is mainly influenced by geospatial criteria, rainfall distribution, geology, hydrology, geomorphology, land-use, and drainage network. However, the above factors do not equally contribute to determining the landslide susceptibility. This study attempted to map the landslide hazard zones in one of the tropical hilly region: Kegalle District and weighting causative factors rationally using statistical method in GIS environment. In this study, causative factors were weighted and modelled to define hazardous...
Cities play an important role in climate change mitigation and adaptation and enhancingclimate re... more Cities play an important role in climate change mitigation and adaptation and enhancingclimate resilience of their slum and vulnerable residents. Climate change adds to existingchallenges faced by cities. Climate change, together with a decrease in absorption capacity ofgreenhouse gasses due reduction in the amount of green cover, parks, trees and agriculturalsurfaces in urban areas, poses serious threats to urban infrastructure, access to basic servicesand quality of life in cities and negatively affect the urban economy. At the same time, rapidurban growth, growing urban poverty and increasing food prices raise concerns about urbanfood security, especially for the poor. Cities are highly vulnerable to disruption in critical(food) supplies and climate change exacerbates this vulnerability. The main objective of this study is to examine the spatial pattern of surface temperature in theKesbewa Urban Council Area and temperature variation with the different UPAF (UrbanPeri-urban and A...
The scarcity of surface water resources in the dry season in the Kilinochchi district increases t... more The scarcity of surface water resources in the dry season in the Kilinochchi district increases the demand for freshwater. Therefore, the existing groundwater resources should be managed to overcome the situation. Several authors worldwide have published studies on the delineation of potential groundwater zone. However, only a few studies addressed the delineation of potential groundwater zones in the Kilinochchi district. This study aims to delineate potential groundwater zones in Kilinochchi, Sri Lanka using integrated Remote Sensing, Geographic Information Systems, and Analytic Hierarchy Process techniques. Groundwater potential zones are demarcated for the Kilinochchi district by overlaying thematic layers: geology, geomorphology, land use/land cover, soil types, drainage density, slope, lineament, and rainfall. Saaty's scale was applied to the assigned weights of the chosen thematic layers and their features. The thematic layers were integrated into a Geographic Information...
This quantitative study investigated the determinants of students’ satisfaction with their online... more This quantitative study investigated the determinants of students’ satisfaction with their online learning experience at Sri Lankan universities during the COVID-19 pandemic. The data was collected from 1376 undergraduates enrolled in various courses in humanities and social sciences at three state-owned universities in the country. The results of the Structural Equation Modeling (SEM) revealed that the independent variables of the model, namely perceived learner motivation, perceived challenges of e-learning, and interaction significantly affected students’ satisfaction with their new online learning experience. Out of the three variables, learner motivation exerted the strongest effect on students’ satisfaction, implying the crucial role self-regulated learning—characterized by motivation—plays in online learning environments. The study has several implications for both creating and ensuring the long-term sustainability of productive and student-friendly online learning spaces in ...
The international statistics show that the global urban population will increase by up to 68% by ... more The international statistics show that the global urban population will increase by up to 68% by 2050 [...]
Although urbanization has contributed to improving living conditions, it has had negative impacts... more Although urbanization has contributed to improving living conditions, it has had negative impacts on the natural environment in urbanized areas. Urbanization has changed the urban landscape and resulted in increasing land surface temperature (LST). Thus, studies related to LST in various urban environments have become popular. However, there are few LST studies focusing on mountain landscapes (i.e., hill stations). Therefore, this study investigated the changes in the landscape and their impacts on LST intensity (LSTI) in the tropical mountain city of Nuwara Eliya, Sri Lanka. The study utilized annual median temperatures extracted from Landsat data collected from 1996 to 2017 based on the Google Earth Engine (GEE) interface. The fractions of built-up (BL), forested (FL) and agricultural (AL) land, were calculated using land use and cover maps based on urban–rural zone (URZ) analysis. The urban–rural margin was demarcated based on the fractions of BL (<10%), and LSTI that were mea...
Although urbanization has contributed to improving living conditions, it has had negative impacts... more Although urbanization has contributed to improving living conditions, it has had negative impacts on the natural environment in the urbanized areas. Urbanization has changed the urban landscape and resulted in increasing land surface temperature (LST). Thus, studies related to LST in various urban environments have become a popular research topic. However, few LST studies focusing on the mountain landscapes (i.e. hill stations) have been carried out. The primary objective of this study is to investigate changes in the landscape and their impacts on LST intensity (LSTI) in the tropical mountain city of Nuwara Eliya, Sri Lanka. The study utilized annual median temperatures extracted from Landsat data collected from 1996 to 2017 based on the Google Earth Engine (GEE) interface. The fractions of built-up (BL), forest (FL), and agricultural (AL) land were calculated using land use and cover maps based on the urban-rural zone (URZ) analysis. The urban-rural margin was demarcated based on ...
Africa’s unprecedented, uncontrolled and unplanned urbanization has put many African cities under... more Africa’s unprecedented, uncontrolled and unplanned urbanization has put many African cities under constant ecological and environmental threat. One of the critical ecological impacts of urbanization likely to adversely affect Africa’s urban dwellers is the urban heat island (UHI) effect. However, UHI studies in African cities remain uncommon. Therefore, this study attempts to examine the relationship between land surface temperature (LST) and the spatial patterns, composition and configuration of impervious surfaces/green spaces in four African cities, Lagos (Nigeria), Nairobi (Kenya), Addis Ababa (Ethiopia) and Lusaka (Zambia). Landsat OLI/TIRS data and various geospatial approaches, including urban–rural gradient, urban heat island intensity, statistics and urban landscape metrics-based techniques, were used to facilitate the analysis. The results show significantly strong correlation between mean LST and the density of impervious surface (positive) and green space (negative) alon...
Urbanization has bloomed across Asia and Africa of late, while two centuries ago, it was confined... more Urbanization has bloomed across Asia and Africa of late, while two centuries ago, it was confined to developed regions in the largest urban agglomerations. The changing urban landscape can cause irretrievable changes to the biophysical environment, including changes in the spatiotemporal pattern of the land surface temperature (LST). Understanding these variations in the LST will help us introduce appropriate mitigation techniques to overcome negative impacts. The research objective was to assess the impact of landscape structure on the variation in LST in the African region as a geospatial approach in Addis Ababa, Ethiopia from 1986–2016 with fifteen-year intervals. Land use and land cover (LULC) mapping and LST were derived by using pre-processed Landsat data (Level 2). Gradient analysis was computed for the pattern of the LST from the city center to the rural area, while intensity calculation was facilitated to analyze the magnitude of LST. Directional variation of the LST was no...
The book contains an analysis of the cancer distribution of Sri Lanka by comparing the distributi... more The book contains an analysis of the cancer distribution of Sri Lanka by comparing the distribution of cancer cases against geographical risk factors implicated in the etiology of cancer. This book is an attempt to examine the possible causes of cancer and to determine whether the location where patients were living could have a direct influence on the incidence of cancer. To achieve this, maps of Cancer distribution were prepared using cancer patient data published by the National Cancer Control Unit in Sri Lanka and these maps were compared against thematic maps created for geographical risk factors implicated in the etiology of cancer. Once these two maps were visually compared and there seems to be a relationship, statistics were used to determine if a relationship could exist between them. Conclusions and recommendation were given based on these results.
The book contains the impact of tsunami in the Weligama area in Sri Lanka which happened on 26 De... more The book contains the impact of tsunami in the Weligama area in Sri Lanka which happened on 26 December 2004 due to the generation of the earthquake off the west coast of Sumetra. This book is an attempt to reduce this natural phenomenon through the understanding of the area at risk incorporating with the land use details. The numerical simulation of tsunami inundation was carried out using ComMIT model with the major input parameters of earthquake source parameters, topography and bathymetry data. The December 2004 Sumatra Earthquake source parameters were used for generation, propagation, and coastal amplification of the tsunami waves and finally the inundation extent and water level was obtained to prepare large scale action maps on tsunami inundation to protect the coastal communities. The GIS tool has been used to incorporate the tsunami inundation depth to identify the hazard and the reliability of model results was compared with the field data and a high resolution QuickBird images. The analysis allows determining the level of vulnerably associated with the coastal belt. This book also discourses for disaster management activities.
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Papers by Manjula Ranagalage