Browsing by Author "ATONYA STANLEY CHASIA"

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    ANALYSIS OF LAND-USE CHANGE IMPACT ON SOIL EROSION VULNERABILITY IN THE TRANSBOUNDARY SIO-MALABA-MALAKISI CATCHMENT OF KENYA AND UGANDA
    (TUK, 2024-08-27) ATONYA STANLEY CHASIA
    ABSTRACT Changes in land surface conditions affect hydrological processes which have important feedback on regional climate and local ecosystems. It is therefore essential to assess space-time alterations in land-surface conditions to support hydrological impact assessment and integrated environmental management. This study evaluated the impact, and extent of present and future land-use/cover (LULC) changes on soil erosion and sediment deposition, to develop a framework for managing soil erosion in the transboundary catchment of Sio-Malaba-Malakisi (SMM). This was achieved through four objectives: First, historical LULC conditions for SMM were analyzed, to understand historical trends in LULC state for the area. This was accomplished by analyzing archived Landsat satellite data for the period 1986 – 2017, using a hybrid image classification technique that clustered individual satellite images using the Iterative Self-Organizing Data Analysis Technique algorithm; the Maximum Likelihood Function was then used to assign image pixels into land-cover classes with the highest probability. Thereafter, transition matrices were applied to the classified maps to identify space-time alterations. An overall classification accuracy of between 84 % – 88 % was obtained for all the years, and kappa statistic values ranging between 0.80 – 0.86 were realized, indicating a strong correlation between classified results and the actual LULC map. It was also noted that approximately 12 % of mixed forest cover declined, while cropland area increased by 30% over the period 1995 – 2008. The second objective, modelled future LULC conditions using two conceptual scenarios plausible in the study area. This was important to understand how future land-use (LU) scenarios could affect soil erosion dynamics in the study region. The scenarios studied represented options for agricultural expansion (Scenario I), and land reclamation (Scenario II). To achieve this, the potential LULC driving factors, which were estimated from physical datasets in a Geographical Information System (GIS), were identified and analyzed. The datasets and concerned factors were thereafter applied within the Conversion of Land Use and its Effects at small regional extent (CLUE-s) modelling framework to simulate potential LULC change trajectories between the period 2017 and 2047, representing thirty years prioritized for catchment conservation by the local managers. The results of this objective indicated that Scenario I could lead to an increase in the cropland area by 24 %, covering approximately 62 % of the whole basin area by 2047. Scenario II indicated a 30 % increase in forest cover, indicating an improvement in forest recovery, and restoration of ecosystem area. The third objective of the study, analyze soil erosion and deposition patterns consequent to current and projected LU change scenarios in the basin. The Unit Stream Power-based Erosion Deposition (USPED) model, capable of accounting for potential impacts of present and future change-effects on erosion and deposition patterns across the basin was adopted and applied. Considering limitations about consistently harmonized land-cover datasets, a classified LU map for the year 2017 was used to simulate the baseline reference situation from where the effects of the two LU scenarios for the period 2027 to 2047 were compared. The results of this objective indicated that the study area recorded high erosion rates in the upper sub-catchments of Lwakhakha and Malakisi, while sediment deposition was mainly concentrated along stream banks and floodplain zones where Mpologoma and Malaba sub-catchments are located. When compared to the reference year (2017), the erosion rate for Scenario I increased by 16.3 %, while that of Scenario II decreased by 61.2 %. Further, a coefficient determination (𝑅2) value of 0.74 was recorded in the study, depicting a strong relationship between USPED-modelled results and total suspended sediments recorded for the basin. The fourth and final objective of the study evaluated soil erosion vulnerable areas by estimating the annual rate of soil erosion, and their zonal spatial distribution to propose targeted conservation strategies recommended for appropriate soil conservation practices in the affected areas. The annual soil loss for the SMM basin was thus estimated by analysing physical parameters driving soil erosion using the Revised Universal Soil Loss Equation (RUSLE). The study recorded a maximum soil loss rate of approximately 5,703 t ha-1 yr-1 for SMM. High erosion rates (>50 t ha-1 yr-1) were recorded in the sub-catchments of Lwakhakha and Malakisi, representing a high severity class for soil conservation prioritization. Overall, the findings of this study present important empirical baseline information which could support the development of appropriate land and water management programs in the region, as well as establishing a policy framework for governing the transboundary water resource.