Analyses of spatio–temporal dynamics of wetland cover in Kampala

Abstract

Globally, wetland cover is declining due to the fragile nature of these ecosystems and unplanned land consumption practices. Kampala has undergone tremendous transformation in its landuse/landcover due to rapid urbanization. It has therefore become important for environmental planners to extract, detect, monitor and predict wetland cover changes. The objective of this research was to evaluate the spatio-temporal dynamics of wetlands in Kampala using GIS, RS techniques and Land change modeler between the years 1986 to 2016 so as to forward and encourage development interventions. To estimate the land cover change in Kampala, Landsat ETM ETM+ for 1986,1996,2006 and 2016 respectively were analyzed using ArcGIS10.0 and IDRISI Selva. After processing the imagery/land use/land cover, (LULC) images were classified, analyzed and used to predict the future wetland cover of 2040 using Land Change Modeller (LCM) of TerrSet software. The data for road network, and population data for Kampala, were used as ancillary data to run the modeller. The study adapted the Kappa index for assessing accuracy of the landuse/cover maps generated from the analysis to improve the accuracy of results. An accuracy level of 89.2% was achieved. The results reveal an overall significant increase in built-up area and other landuses at the expense of wetlands from 30.6% in 1986 to 6.1% in 2016. Wetlands lost 3,535 ha to built and woodlots 1,200 ha and a minor proportion to open water. Woodlots and built-up constituted more than half of the total area of Kampala with 4,523.3 ha (23.3%) and 12,117.1 ha (62.3%) respectively. The remaining portion of the area is covered by open water with 1,621.7 ha (8.3%). The study projects a further decline of wetland cover by 428 ha (or by 2.2%), built up covering 15,643.7 ha ( 80.4%) and woodlots with 1,759 ha (9.0%) in 2040 if steps are not instituted to control the rate of decline. These results provide new insights for predicting future changes of wetland vegetation influenced by the on-going threats from climate change and human activities, and form a foundation for sustainable wetland management in Kampala. The study further recommends more research on wetland valuation (including indirect and non-use values) in Kampala should be conducted. This may assist in assessing trade-offs between maintenance of intact wetland against its conversion into other uses.