PGIHS-RC 2024

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/4847

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Browsing PGIHS-RC 2024 by Author "Bandara, T.W.M.T.W."

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    Analysing changes of wetland components using geospatial techniques: A case of Sri Jayewardenepura Kotte wetland complex, Sri Lanka
    (Postgraduate Institute of Humanities and Social Sciences (PGIHS), University of Peradeniya, Sri Lanka, 2024-12-19) Thushani, J.; Bandara, T.W.M.T.W.; Subasinghe, S.
    The Sri Jayewardenepura Kotte Wetlands Complex is a distinct urban wetland in the Colombo region. Due to rapid development and population growth in the region, wetlands are losing their components and becoming a terrestrial landscape. GIS and RS technologies provide an excellent platform for investigating changes in the above features. Since there are not many studies on this subject, the study uses NDVI, NDWI, and NDMI to examine how wetland vegetation, moisture, and water content changed between 1997 and 2023. The research used primary data, including field observations and interviews with village officials, and secondary data sources, including previous studies, satellite imagery, books, and articles. The satellite imagery study used Landsat 5 images from 1997, 2005, and 2008, as well as Landsat 8 images from 2017 and 2023. To better understand the variability of the data, the indicators were reclassified using the mean and standard deviation into three groups: low (mean-standard deviation), moderate (between low and high), or high (mean + standard deviation). The image difference technique was used to detect pixel-wise changes in wetland components in reclassified images. Based on the results, the NDVI value range was -0.384 to 0.735 in the study area in 1997, which changed from - 0.001 to 0.437 in 2023. Similarly, the NDWI value ranged from -0.366 to 0.740 in 1997, which varied between -0.379 and 0.049 in 2023. The NDMI value range was -0.428 to 0.5 in 1997, which reduced to -0.101 to 0.315 in 2023. The study area's low category saw the highest percentage of NDVI, NDWI, and NDMI due to land encroachment for urban expansion. According to the change detection analysis, the total change from the high to low conversion category was shown by the NDVI at 2.31 Km2 (6.46%), the total change from the NDWI at 1.20 Km2 (3.36%), and the total change from the NDMI at 3.05 Km2 (8.52%). The study underscores the concerned parties taking additional steps to strengthen conservation of wetlands.
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    Geomorphological mapping and landforms classification in Attanagalu Oya River Basin
    (Postgraduate Institute of Humanities and Social Sciences (PGIHS), University of Peradeniya, Sri Lanka., 2024-12-19) Kaushalya, G.N.; Bandara, T.W.M.T.W.; Wijeratne, V.P.I.S.
    Geomorphological mapping and landform classification are essential for understanding the processes shaping the Earth's surface, managing natural resources, planning land use, and assessing natural hazards. Previous research studies stated that the Attanagalu Oya River basin is a vulnerable area for geomorphological changes. This work aims to present a geomorphological mapping and landform classification of an area in the Attanagalu Oya River Basin, based on morphometric analysis of Digital Elevation Models (DEMs), and terrain analysis while classical methods focus on photo interpretation. Further, the study focused on identifying the geomorphologically changing hotspots in the river basin and exploring the factors contributing to the changes in geomorphology using spatial analysis. All the analysis and digitized maps for the years 1981, 2001 and 2021 were generated using ArcGIS 10.8 and Google Earth Pro software. The secondary data used in this study were obtained from global open-source databases and institutions. Maps, data tables and analytical diagrams were used to interpret the findings. Total area of the Attanagalu Oya River basin is 839 KmĀ². Based on the analysis, five primary types of geomorphological landforms by their origin were identified in the Attanagalu Oya River Basin area. They are structural origin landforms, denudational origin landforms, fluvial origin landforms, coastal origin landforms and anthropogenic origin landforms. Geomorphological classification was developed based on these main types of origins. Fluvial origin landforms and anthropogenic origin landforms are the main dynamic types of geomorphological landforms in this area. The hotspot areas of geomorphological changes were located in the middle and lower Attanagalu Oya sub basin along with coastal areas. Rainfall, slope, disaster impact and land use and land cover changes were identified as physical factors that contribute to the changes in geomorphology in this area. The contribution of those factors are higher in the middle and lower Attanagalu Oya sub basin along with the coastal area when compared to other areas. Moreover, human factors such as population growth, urbanization, infrastructure development, and disaster management practices were identified as factors that contribute to the changes in anthropogenic geomorphology in the Attanagalu Oya River basin. This kind of study enables us to explore the landscape dynamics to effective watershed environmental management for sustainable development practices.