Abstract:
The Nalwekomba catchment on the Eastern shoreline of Victoria Nile basin is a high valued ecosystem because of the numerous human-related activities it supports in Namasagali, Kamuli district in Eastern Uganda. The catchment has undergone tremendous human-induced land use/cover changes, which have not been quantified. This study aimed at quantifying the land use/cover changes as well as the rate at which these changes occurred over the last two decades in the catchment. This was achieved using remote sensing techniques and Geographic Information System (GIS) to analyze and contextualize the changes. To that effect, images of Landsat satellites TM, ETM+ and OLI with a resolution of 30metres were obtained and interpreted using supervised image classification technique to determine the land use/land cover changes from 2000 to 2020.
The Catchment area was classified into seven major LU/LC classes i.e. Built up areas, croplands, water bodies, forestlands, grassland, fallow/bare-land and wetlands. Change detection analysis was performed to compare the quantities of land cover class conversions between time intervals. The results revealed both increase and decrease of the different LULC classes from 2000 through to 2020. Significant shifts from some classes to others was also observed. Drivers of the observed changes ranged from Climatic factors such as rainfall and drought to socio-economic factors like poverty, population pressure. The obtained results also indicated that the catchment has undergone huge land use and land cover transformations over the last two decades attributable to rapid population growth, industrialization and urbanization. The prevailing changes in footprint between 2000 and 2020 were expansions and increment of built–up area (0.76% in 2000 to 18.49% in 2020) and cropland (8.42% in 2000 to 53.76% in 2020), and decreases in the following sectors: forestlands (from 29.19% in 2000 to 6.14% in 2020), grassland (from 31.18% in 2000 to 12.24% in 2020), fallow-land (from 19% in 2000 to 0.38% in 2020), open waterbody (from 0.25% in 2000 to 0.21% in 2020) and wetlands (from 11.20% in 2000 to 8.78% in 2020). The changes pose a threat to the environment and water quality of the Nalwekomba catchment and consequently increases socio-costs like flooding and access to safe water.
Therefore, there is the need to take critical and practical measures to regulate and police land use, water use rights and conserve the environment especially wetlands. Consistent LULC mapping should be carried out in order to quantify and characterize LULC changes. This will help establish trends and enable resource managers to project realistic change scenarios helpful for natural resource management.
Keywords: land cover, land use, change detection, supervised classification, Nalwekomba Catchment
