ABSTRACT Water erosion is a natural geological process that is common in tropical regions. It is important to monitor it to contain its physical, environmental, and socio-economic impacts. In the Espírito Santo state, Brazil, much of the land is used for agriculture and studies related to water erosion are scarce. The spatial modeling of water erosion is useful for proposing mitigating measures because combining it with data from geographic information systems can identify the areas most prone to soil loss. The Revised Universal Soil Loss Equation - RUSLE, is a model that requires little input data and is easy to use, providing results useful of helping to mitigate water erosion and promote sustainable land use planning. This study estimates the water erosion rates in the Espírito Santo state by RUSLE and compares them with the soil loss tolerance (T) limits. The parameters used in the model are the land use and management, the soil attributes, the relief and the climate factors. Approximately 38.65% of the state’s area shows soil loss above the T limit (7.79 - 14.14 Mg ha-1 year-1). The areas with steeper slopes and low vegetation cover have most of the highest erosion rates. The mean annual soil loss of the entire state is 33.55 Mg ha-1 year-1. RUSLE provided a diagnosis useful of directing erosion mitigation measures to the most susceptible areas, enabling sustainable planning to support the state's socio-economic development.

ABSTRACT Water erosion is one of the main problems faced by the Furnas Lake Surrounding Watershed, located in southeast Brazil. The erosive process is intensified by inadequate land occupation of the lake margins where should be riparian forests, or permanent preservation areas (APP), in order to protect water resources. In this context, our work aimed to estimate the soil losses of this watershed using the Revised Universal Soil Loss Equation (RUSLE) in two different scenarios: I - considering the actual occupation of the area, and II - building an alternative scenario where permanent preservation areas were present. Therefore, we considered physical, edaphoclimatic, and land use and management factors. To simulate the presence of preservation areas, we based it on the Brazilian Forest Code (Bill no. 12.651/2012). In the real scenario (I), the total soil loss estimated was 31,580,907.47 Mg.year-1 (32% over the Soil Loss Tolerance) with an average loss of 19.00 Mg.ha-1.year-1, while in the conservationist scenario (II), there was 10% decrease, which means the mitigation of the erosion process as well as of the negative environmental impacts that can be generated by soil degradation.

RESUMO Dentre os parâmetros considerados pela Equação Universal de Perda de Solo Revisada (RUSLE) a cobertura e manejo do solo (C) é o principal fator de influência humana na estimativa da erosão hídrica, e um dos mais sensíveis a variações espaço - temporais. Consequentemente, este estudo tem como objetivo comparar a eficiência das estimativas do fator C obtidas na literatura para cada classe de uso da terra (Clit) e por cálculo com base no Índice de Vegetação por Diferença Normalizada (CNDVI). Testamos a hipótese de que as estimativas de perda de solo com base na abordagem CNDVI são mais precisas do que aquelas baseadas no Clit. A erosão hídrica foi estimada com base nas propriedades morfológicas, físicas e químicas do solo, além de clima, relevo, práticas de manejo e uso e cobertura da terra. As etapas da modelagem foram realizadas com a ajuda do Sistema de Informações Geográficas. Os resultados foram validados utilizando os dados do sedimento total transportado com descarga de água e escoamento diário. RUSLE subestimou as perdas do solo em 0,64 Mg ha-1 ano-1 usando Clit e 0,45 Mg ha-1 ano-1 com CNDVI, o que corresponde aos respectivos erros de 21,05% e 14,80%. Portanto, os resultados do fator CNDVI são mais precisos. Ambas as metodologias identificaram áreas com altas taxas de erosão, onde a adoção de medidas mitigadoras deve ser priorizada.

ABSTRACT Among the parameters considered by the Revised Universal Soil Loss Equation (RUSLE), the soil cover and management factor (C) is the main human influenced factor affecting the estimation of water erosion, and one of the most sensitive to spatiotemporal variations. Consequently, this study aims to compare the efficiency of C factor estimates obtained from the literature for each land-use class (Clit) and by calculation based on the Normalized Difference Vegetation Index (CNDVI). We test the hypothesis that soil loss estimates based on CNDVI approach are more accurate than those based on Clit. Water erosion was estimated based on soil morphological, physical, and chemical properties in addition to climate, relief, management practices, and land use and cover. The modeling steps were realized with the help of the Geographic Information System. The results were validated using the data of total sediment transported with water discharge and daily runoff. RUSLE underestimated soil losses by 0.64 Mg ha-1 year-1 using Clit and 0.45 Mg ha-1 year-1 with CNDVI, which corresponds to errors of 21.05% and 14.80%, respectively. Therefore, the CNDVI factor results are more accurate. Both methodologies identified areas with high erosion rates where the adoption of mitigation measures should be prioritized.