An analysis of the effects of changes in land use and land cover on runoff in the Luvuvhu catchment, South Africa

Abstract

The aim of this study was to map and assess the impacts of land use and land cover (LULC) changes on runoff in the Luvuvhu catchment in Limpopo, South Africa. To achieve this, the study determined past spatial trends of LULC change, using Landsat images from 1990 to 2020 and Support Vector Machine (SVM). The study also predicted future LULC in 2025 and 2030 using artificial neural networks-cellular automata (ANN-CA) simulation model, as well as established the response of runoff to LULC changes, using Soil and Water Assessment Tool (SWAT) model. The results revealed significant LULC changes in the Luvuvhu catchment during the study period. Bare land had the largest increase of 15.2% whereas natural vegetation had the largest decrease of 18.9%. The LULC classification results showed high overall accuracies ranging from 93% to 98% and Kappa coefficients above 0.9. The predicted LULC for 2025 show that bare land will have the largest increase of 168 km2 whereas natural vegetation may lose the largest area of 356 km2 in 2025. The same trends observed in 2025 are expected to continue to the year 2030. Results further indicated that, on average, overall surface runoff increased by 7.3% from 169.14 mm to 181.49 mm between 1990 and 2020. The results showed that the surface runoff of the Luvuvhu catchment was altered due to the significant LULC changes in bare land and natural vegetation with 15.2% increase and 18.9% decrease, respectively. Therefore, these changes contributed significantly to the runoff response of the Luvuvhu catchment. Owing to the anticipated ongoing LULC alterations, the likelihood of increased surface runoff persists, posing potential catchment management challenges, including flooding and erosion of riverbanks or stream channels. Hence, prioritizing the development of effective catchment management strategies is crucial, serving as a pivotal measure to mitigate the impacts of LULC changes. This study provides baseline information on the impacts of LULC changes on surface runoff within the Luvuvhu catchment in Limpopo, South Africa.