Browsing by Author "Gallage, C. V."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    GIS based multicriteria analysis for flood hazard assessment: A case study from Walawe River basin, Sri Lanka
    (Faculty of Science, University of Kelaniya Sri Lanka, 2023) Gallage, C. V.; Wijesundera, A. A. S. G.; Kodithuwakku, K. C.; Wickramasingha, W. S. B.; Weerasinghe, V. P. A.
    Flood hazard mapping has been recognized as a crucial task supporting disaster management efforts. For the study, the lower reach of the Walawe River, which drains the suburbs of the island's southern region, was selected due to its regular flooding. This study used ArcGIS and remote sensing data, and the river basin extent was extracted from satellite images available for the Walawe River, Sri Lanka. Multi-criteria decision analysis (MCDA) was used in this process. The main criteria evaluated are land use, rainfall data, drainage density, elevation, slope, and soil type around the river basin. These criteria are reclassified into five categories depending on the highest to lowest risk of vulnerability to flood. The Analytical Hierarchical Process (AHP) was used to give the weights for the mentioned criteria, and as the outcome, the weighted overlay map (flood hazard map) was obtained and classified under five categories. According to the results, the flood hazard assessment map shows that 25.74% (646.09 km2 ) and 1.92% (48.13km2 ) of the study area was under high or very high hazard levels, respectively, with more populated regions, water bodies, and agricultural land, as well as low-lying flat terrain with lower elevations. The Walawe River basin's lower watershed has high and very high flood-prone areas, while the upper catchment has low and very low flood-prone areas, according to the geographical distribution of the flood hazard map. Low and very low flood hazard zones comprised 18.63% of the total area, whereas moderate flood hazard areas comprised most of the basin. According to the current study, this aims to identify areas within the Walawe River basin that are at risk of flooding, to assess the potential impact of floods on people, property and the environment which support the development of flood risk reduction measures and to provide public awareness.
  • Thumbnail Image
    Item
    Influence of vegetation attributes on bird functional traits in a Pinus mixed forest at Yagirala forest reserve, Sri Lanka
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gallage, C. V.; Perera, W. W. A. M. R.; Subasinghe, K.
    Although many studies have examined changes to overall species composition and diversity of birds following the conversion of natural forests into forest plantations, only a few have examined changes to functional trait compositions. The present study investigated the functional trait responses to the conversion of natural forests to forest plantations by comparing the richness and abundance of functional categories of three traits: i) feeding guild (categories: carnivores, insectivores, frugivores, nectarivores, omnivores and granivores), ii) nesting habit (categories: non-cavity tree dependence nesting, tree cavity nesting, ground nesting and parasitic nesting), and iii) foraging stratum (categories: ground foraging, mid-high foraging, and canopy foraging) of a bird community in pinus mixed forest and adjacent natural forest at Yagirala Forest Reserve located in the Southern part of Kalutara district, Sri Lanka. Further, the study examined the relationships between the functional categories and vegetation attributes to explore the factors that drive functional trait responses to conversions. The richness and abundance of functional categories were estimated using the data of point count surveys conducted at pinus mixed forest, which encompasses areas undergoing natural regeneration and enrichment planting, and in the natural forest. At each point count station within the pinus mixed forest, vegetation surveys were conducted to determine the number of standing dead trees, native tree species density, number of woody debris, percentage of canopy cover, percentage of herbaceous cover and the heterogeneity of tree height and tree dbh. The functional categories in pinus mixed forest areas and the natural forest were compared using One-way ANOVA followed by Tukey’s pairwise comparison. The relationships between bird functional categories and vegetation attributes were analyzed using linear mixed models (LMMs). According to the findings of this study, the abundance of six functional categories and the richness of three functional categories per point count station were significantly differed between the pinus mixed forest areas and natural forest (p < 0.05; one-way ANOVA, Tukey’s post hoc test). The findings further revealed significant relationships between the richness and abundance of functional categories including tree cavity dependents, frugivores, insectivores and canopy foragers with vegetation attributes such as number of standing dead trees, native tree species density, number of woody debris and percentage of canopy cover (p < 0.05; LMMs). This study emphasizes the potential of exotic forest plantations to support local bird communities by managing vegetation composition and structure effectively.