Estratégia Metodológica para Zoneamento pelo Potencial de Perda de Solo na Bacia Hidrográfica Cachoeira Cinco Veados, RS-Brasil

The aim of this study was to propose a methodological approach to determine the best land use based on USLE model parameters, using the watershed as planning unit. The model USLE parameters were spatialized using the software ArcGis 10.5, for the case study of the Cachoeira Cinco Veados watershed, RS-Brazil, and the erosive values were categorized according to the methodology of Ribeiro (2006). We reclassified the areas in “suitable” and “not suitable” to the tested use, according to two limit-criteria adopted as maximum acceptable soil losses (20 and 50 t ha-1 year-1). The methodology consists of constructing two strategies: the first is a construction of a thematic map, considering a priority order of uses in the watershed, where the most spendthrift use was analyzed first (Script of Hierarchical Analysis among Uses); and the second consists of the construction of maps that correspond to scenarios with watershed areas suitable to a given use, according to the classification criterion used, and their crossing with the current use map (Analysis Script by Use). The results show it is possible to classify the areas in “suitable” and “not suitable” for a given use, allowing with this organizational strategy to identify, quantify and spatialize the areas in accordance with the limit of potential soil loss and point out those that do not tolerate the tested use. This is a useful information for decision makers when studying regional planning.

Assessment of Soil Erosion Using the RUSLE Model for the Epworth District of the Harare Metropolitan Province, Zimbabwe

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.

Integration of remote sensing, RUSLE and GIS to model potential soil loss and sediment yield (SY)

Land use activities within a basin serve as one of the contributing factors which cause deterioration of river water quality through its potential effect on erosion. Sediment yield in the form of suspended solid in the river water body which is transported to the coastal area occurs as a sign of lowering of the water quality. Hence, the aim of this study was to determine potential soil loss using the Revised Universal Soil Loss Equation (RUSLE) model and the sediment yield, in the Geographical Information Systems (GIS) environment within selected sub-catchments of Pahang River Basin. RUSLE was used to estimate potential soil losses and sediment yield by utilizing information on rainfall erosivity (R) using interpolation of rainfall data, soil erodibility (K) using field measurement and soil map, vegetation cover (C) using satellite images, topography (LS) using DEM and conservation practices (P) using satellite images. The results indicated that the rate of potential soil loss in these sub-catchments ranged from very low to extremely high. The area covered by very low to low potential soil loss was about 99%, whereas moderate to extremely high soil loss potential covered only about 1% of the study area. Sediment yield represented only 1% of the potential soil loss. The sediment yield (SY) value in Pahang River turned out to be higher closer to the river mouth because of the topographic character, climate, vegetation type and density, and land use within the drainage basin.