Abstract
Urban development without adequate soil erosion control measures is becoming a major environmental concern in developing urban areas across Africa. These environmental disturbances encompass rampart Land Use and Land Cover changes (LULC) due to a high population growth rate and increased economic activities. To understand the influence of accelerated LULC changes and urban expansion as major drivers in landscape degradation in the Epworth district of the Harare Metropolitan Province, the RUSLE model was employed. This considers land use, soil, climate and topography as input parameters in the assessment of the extent and impact of these drivers on soil erosion. The Revised Universal Soil Loss Equation (RUSLE) was used to predict the potential erosion between 1984 and 2018 and soil erosion risk for the years 2000 and 2018. The mean rate of the predicted potential soil erosion was 13.2 t ha−1 yr−1 (1984–2018); areas especially vulnerable to erosion were predicted for foot slope areas with direct tributaries to the major streams and steep sloping zones. The average soil erosion risk was estimated at 1.31 t ha−1 yr−1 for the year 2000 and 1.12 t ha−1 yr−1 for 2018. While the overall potential soil loss decreased between 2000 and 2018, the potential soil loss was observed to increase tremendously in residential areas, which doubled in extent between 2000 and 2018. The findings reveal that about 40% of the Epworth district was threatened by unsustainable soil loss resulting from increased soil erosion risk within the built-up areas.
Highlights
Urbanization is a continuous process that has boldly accelerated with population increase, expansion and spread of built-up structures in a designated urban area [1]
The objectives of this paper are: (a) to model the spatial distribution of the soil erosion risk and potential erosion for Epworth district over different time slices: 2000 and 2018 in order to assess the dynamics of soil erosion over time in heterogenous urban landscapes; (b) to assess the influence of rampart land use and land cover changes on soil erosion risk in the Epworth district through the analysis of temporal soil erosion estimations between 2000 and 2018
The unrestricted Land Use and Land Cover (LULC) changes resulting from rampart informal settlements growth have accentuated soil erosion risk in the Epworth district
Summary
Urbanization is a continuous process that has boldly accelerated with population increase, expansion and spread of built-up structures in a designated urban area [1]. Urban development inevitably involves construction and sealing activities that alter natural landscapes [6] resulting in an increase in impervious surfaces, which replace natural vegetation and reduce the capacity for water infiltration. This in-turn results in surface runoff that substantially threatens soil loss in vulnerable landscapes through erosion processes [7]. Due to the unprecedented growing rates of urban-built up area in Harare Metropolitan Province [9,10,11], there is profound need for mapping potential erosion, and estimating potential soil erosion risk
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