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Soil erosion is a global issue—with gully erosion recognized as one of the most important forms of land degradation. The purpose of this study is to compare and contrast the outcomes of four machine learning models, Classification and Regression (CART), eXtreme Gradient Boosting (XGBoost), Random Forest (RF), and Support Vector Machine (SVM), used for mapping susceptibility to soil gully erosion. The controlling factors of gully erosion in the Piraí Drainage Basin, Paraíba do Sul Middle Valley were analysed by image interpretation in Google Earth and gully erosion samples (n = 159) were used for modelling and spatial prediction. The XGBoost and RF models achieved identical results for the area under the receiver operating characteristic curve (AUROC = 88.50%), followed by the SVM and CART models, respectively (AUROC = 86.17%; AUROC = 85.11%). In all models analysed, the importance of the main controlling factors predominated among Lineaments, Land Use and Cover, Slope, Elevation and Rainfall, highlighting the need to understand the landscape. The XGBoost model, considering a smaller number of false negatives in spatial prediction, was considered the most appropriate, compared to the Random Forest model. It is noteworthy that the XGBoost model made it possible to validate the hypothesis of the study area, for susceptibility to gully erosion and identifying that 9.47% of the Piraí Drainage Basin is susceptible to gully erosion. Furthermore, replicable methodologies are evidenced by their rapid applicability at different scales.

Esse artigo aborda erosão por voçoroca, ao redor do mundo, chamando atenção das diversas formas de como recuperá-las. Em todas elas, técnicas de bioengenharia são apresentadas, assim como o sucesso e o baixo custo, quando aplicados. Além disso, esse artigo, destaca a necessidade de compreender como esse processo erosivo evolui nas encostas, as principais causas da formação das voçorocas e, consequentemente, o que fazer para mitigar esse processo geomorfológico. Finalmente, um exemplo de sucesso é apresentado, para São Luís, onde o monitoramento, usando técnicas tradicionais, e a recuperação da voçoroca, usando telas de buriti, que é uma palmeira local, provou que é possível, usando o conhecimento local, junto com o conhecimento acadêmico, recuperar uma voçoroca.

Soil can be considered an element of geodiversity with different values; however, its significance is often underestimated. In this perspective, this research aims to apply to the soils the geodiversity valuation system based on ecosystem support, provision, regulation, cultural and knowledge services, developed by Gray (2013). The research was conducted at the PROMATA Farm, in the river Escuro drainage basin, Ubatuba Municipality, São Paulo State. Results of physical and chemical analyzes refer to the good soil structure, soil density average less than 0.8 g/cm³, and the total porosity average over 70%, it is an important condition for the soil to perform its functions. Therefore, soils perform several ecosystem services, essential for the accomplishment of human activities and the balanced operation of the environmental systems.

This paper aims to present concepts, relations and the role of geodiversity,geologic heritage, geomorphological heritage, geotourism and geoconservation. The methodology is based on literature review from articles, books, PhD thesis and MSc dissertations, related to this issue. These concepts have been adopted within the geosciences, since geoconservation of the natural elements, composed by abiotic elements, constitutes a necessity to maintain life quality of the planet species, such as they may lead to the understanding of the planet origin and evolution. Geodiversity, represented by the abiotic elements (rock outcrop and landforms) has a group of geoforms, or geosites, which represent the heritage of a certain area. As a way of spreading these concepts, geotourism constitutes a tool, and also a challenge, seen by some authors, in publicizing the Earth Sciences.

Brazil covers 8,547,403 km2 and is divided into five regions (Northern, North Western, Central Western, South Eastern and Southern). The diversity of climate, geology, topography, biota and human activities have contributed to the considerable diversity of soil types and thus soil erosion problems. National soils can be classified into 12 classes. These are: Oxisols (38.7%), Alfisols (20.0%), Inceptisols (2.7%), Mollisols (0.5%), Spodosols (1.6%), Gleysols (3.7%), Aridisols (2.7%), Entisols (14.5%), Vertisols (2.0%), Ultisols (1.8%), Plinthosols (6%) and Alisols (4.3%). The erodibility of these Soil Orders is reviewed and is mainly related to soil texture. Sands and loamy sands are especially erodible. Soil erosion patterns are complex, being influenced by rainfall erosivity, soil erodibility, topography, land use and management characteristics. Urban areas have specific erosion problems and there are illustrated using a case study from São Luis (north-east Brazil). Soil erosion rates can be excessive, in some cases exceeding 100 tonnes per hectare per year. Particularly serious soil erosion is associated with six regions. These are north-western Paraná State; the Central Plateau, in the Centre Western Region; Western São Paulo State; the Paraíba do Sul middle drainage basin, in Rio de Janeiro State; Campanha Gaúcha in Rio Grande do Sul State and Triângulo Mineiro, in western Minas Gerais State. Examples of effective soil conservation are presented, using case studies from both Paraná and Santa Catarina States. Integrated management of drainage basins offers a promising way forward for effective soil conservation in Brazil.

Muitas pesquisas conferem maior peso na alta declividade do terreno como fator decisivo no processo hidro-erosivo. Porém, foi avaliado que baixas declividades (~4º) já são suficientes para se iniciar o escoamento superficial. A pesquisa teve como objetivo fazer uma caracterização físico-química de solo degradado, monitorar o seu potencial matricial e o processo de formação de escoamento em uma sub-bacia do rio Maranduba - Ubatuba/SP, em encosta com baixa declividade. O trabalho se baseou na instalação de parcelas de erosão em solo sem cobertura vegetal para analisar as perdas de solo e água, bem como as propriedades físicas e químicas do solo (Porosidade, textura, densidade, pH e matéria orgânica). As parcelas se localizam na parte intermediária de um morrote com encosta retilínea, esse sofreu alteração em sua morfologia original por meio de um corte de encosta (UTM: 0474211/7395934). O solo do local é um Latossolo que apresenta o horizonte B exposto. Cerca de 6,9 t/ha de solo foram perdidos durante o monitoramento (01 agosto 2013-20 dezembro 2014) e mais de 5.354,7 m3 de água foram escoados superficialmente. Salienta-se a fragilidade dos ambientes degradados de baixa declividade frente às altas taxas de perdas de solo e água, que, no período de 17 meses de monitoramento e com chuvas dentro da normalidade para o município, totalizaram 63 dias com ocorrências de escoamento, em solos que tendem à saturação por períodos prolongados. Portanto, o transporte das partículas de solo superficialmente está atrelado à baixa drenagem do terreno e à perda da resistência do solo, corroborando em períodos longos de umidade antecedente, sendo este um dos fatores decisivos para se iniciar o escoamento superficial.