Master of Science / Department of Biological & Agricultural Engineering / Aleksey Y. Sheshukov / Soil erosion is one of the main reasons for agricultural land degradation in the world. Losses of land because of high soil erosion rates and rapidly expanding population result in significant reduction of cultivated land area per capita, and shortage of food on the global scale. Soil erosion can be a major source of sediment in the aquatic systems leading to reduction of organism population and poor water quality. Many factors affect soil erodibility, such as, soil properties, rainfall, topographic features, land use, and management practices, among others. The impacts of soil moisture content, however, are not well understood and. therefore, the primary goal of this study was to quantify two soil erodibility parameters, the erodibility coefficient and critical shear stress, under different soil moisture conditions using the jet erosion test (JET). The JET test uses the apparatus (called mini-JET) that creates an impinging jet of water into the soil and records the resulting scour depth over time. The scour depth time series are then fitted into a non-linear soil erosion equation, yielding the sought values of erodibility parameters. For this study, more than 40 soil samples were collected from several sites in Kansas, processed, and prepared to conduct JET tests in the lab setting. The effects of tillage and soil moisture content were of interest to this study. The results showed varied effects of soil type and sample soil moisture condition on the scour depth development and parameters sensitivity. The critical shear stress decreased and the erodibility coefficient increased with the increase of initial moisture content for clay loam soil, while critical shear stress did not change for sandy loam soil. The study also revealed higher erosive properties of soil collected from the tilled field compared to the no-till field.

O estudo da erodibilidade ganha importância quando se tratam de solos localizados em regiões tropicais, caracterizadas por altas pluviosidades e evaporações que dificilmente permitem ao maciço atingir um estado de saturação em campo. A erodibilidade e as propriedades hidráulicas determinam as condições de infiltração e de escoamento superficial e podem acelerar as feições erosivas através das perdas de partículas. Neste trabalho, observou-se que o grau de saturação in situ estabelece um potencial de sucção matricial (Sm) capaz de orientar o fluxo, absorção e armazenamento da água nos poros do solo. Deste modo, foi possível correlacionar as propriedades de absorção de água com as sucções mátricas de três solos (arenoso, argiloso e areno-argiloso), com comportamento erosivo e não-erosivo, ensaiados a diferentes teores de umidade inicial. Após o controle da sucção e umidade, através da panela de pressão de Richards, os solos foram submetidos ao ensaio de erodibilidade proposto por Nogami & Villibor (1979). Os índices de absorção (Iabs), de perda de massa por imersão (P) e de erodibilidade (E) determinados neste ensaio, quando correlacionados com as curvas características dos solos, mostraram a influência da sucção matricial no início do processo erosivo. Verificou-se uma tendência de aumento da perda de massa por imersão, quanto menor era o teor de umidade inicial imposta (maior sucção). Provavelmente, quando do início do evento chuvoso, o solo tende a ser mais erodível quanto mais seco estiver. Além disso, as correlações obtidas mostraram-se coerentes com o comportamento dos solos em estudo, permitindo uma estimativa da sucção (Sm) de um solo a partir de grandezas facilmente mensuráveis como o Iabs, obtido em ensaio simples e de fácil execução. / The study of erodibility gains importance when dealing with soil located in tropical regions, characterized by high precipitation and evaporation that allow hardly the massive soil to reach a state of saturation in the field. The erodibility and hydraulic properties define the infiltration conditions and the superficial flow, and they can accelerate the erosive process due to the losses of particles. In this work, we observed that the degree of saturation in situ establishes the potencial for suction matrix (Sm) can guide the flow, absorption and storage of water in soil pores. Therefore, experimentally, it was possible to correlate the properties of water absorption with the matrix suctions of three soils, with different initial moisture contents and erosive and non-erosive behaviors. After controlling the suction and moisture through the pressure Richards pressure chamber the soils were subjected to the erodibility test proposed by Nogami & Villibor (1979). The indexes of absorption (Iabs), mass loss by immersion (P) and erodibility (E) determinated in this experiment, when correlated with the characteristic curves of soils, showed the influence of matrix suction at the beginning of the erosion process. There was a trend of increased weight loss by immersion, the lower was the initial moisture content imposed (greater suction). Furthermore, the correlations obtained were consistent with the behavior of soils under study, allowing to estimate of suction (Sm) of a soil from easily measurable values such as the Iabs.

Today’s climate changes will probably give rise to precipitation in Sweden, which will cause more floods in Swedish rivers. Many of the Swedish rivers are regulated and have lots of hydro-electro power plants. Higher floods in the rivers will give greater water loads on the dams, which mean that a higher discharge through the sluice gates and in the spillway channels is needed. High discharge of water in a spillway channel can create scour of the material in the channel. Usually, for spillways in Swedish hydropower plants, this material is rock and the scour is in form of rock blocks. Scour downstream of dams can in the worst case endanger the dam construction. The purpose of this study was to identify the extent and the type of rock scour that may appear in spillway channels of Swedish hydro power plants. The scour in rock material in a spillway channel is usually caused by pressure fluctuations in the water, which can cause large differences in pressure on the top and bottom surfaces of blocks. This pressure difference can be high enough to lift whole blocks. The main factors that affect this kind of scour are the crack pattern of the rock mass, the geometry of the spillway, the discharge of water and the surface fluctuation in the water. In this study a numeric model analyse, a field study and a literature study has been made in order to examine the influence on scour of the orientation of cracks in a rock mass. A rock mass containing a group of cracks with small or no dip is more likely to scour when it is exposed to discharging water. The orientation of the cracks in a rock mass relative to the direction of the water flow has also an impact on the capacity of the rock mass to resist scour. In the field study the scour pattern in the spillway channels of the hydro power plants in Ligga, Harsprånget, Porjus, Satisjaure and Seitevare was examined. The scour of rock mass in the spillway channels in Ligga, Harsprånget and Porjus has been extensive. The rock mass in these channels has bedding cracks of small distances. This is probably the reason why these rock masses are sensitive for loads from discharging water. The rock mass in the spillway channel in Satisjaure has lots of cracks and is also very sensitive for loads from discharging water. This channel has been rebuilt during 2004. There are different methods to predict the ability of a rock mass to resist scour. The Erodibility Index Method is a semi-empirical method that is verified by field observations in the USA. In this work the ability to apply this method on Swedish channels has been examined with field observations from Porjus, Harsprånget and Seitevare. As the Erodibility Index Method seemed to work in the case of these three spillways, it was also applied on the spillways in Satisjaure and Ligga. Measures to reduce the energy in the discharging water in the spillways are very effective to reduce the risk of scouring in the rock mass. Blasted stairs in the rock mass in a channel or a stilling basin downstream the sluice gate is something that can reduce the energy in discharging water. Further documentary of spillway channels, like mapping and laser scanning, would contribute to a further verification of the Erodibility Index Method and to get a general survey of the risk of scour in Swedish spillways. / Dagens klimatsituation ser ut att ge ökad mängd nederbörd i Sverige, vilket innebär att de svenska älvarna kommer att utsättas för allt högre vattenflöden. De flesta av Sveriges älvar är reglerade, d v s längs älvarna finns en mängd större och mindre dammar. Ett högre flöde i älvarna innebär även rikligare tillrinning till dammarna vilket medför att avbördningen från dem måste bli större. Avbördningen från dammarna sker genom utskov och höga vattenflöden i utskovskanalerna kan orsaka erosion på det berg som kanalen vanligen består av. Erosionen är av typen ”blockerosion” där hela bergblock av större eller mindre storlek lösgörs från bergmassan. I värsta fall kan blockerosionen krypa uppströms och erodera dammkroppen bakifrån, vilket skulle kunna innebära att dammen brister. Syftet med detta arbete var att identifiera omfattning och typ av bergerosionsproblem som uppkommer i utskovskanaler. Blockerosion uppkommer i regel då forsande vatten skapar tryckskillnader mellan övre och undre ytan på block. Tryckskillnaden kan då skapa tillräckliga lyftkrafter för att block ska lossna. De huvudsakliga faktorerna som styr blockerosionen är bergmassans sprickighet och material, utskovskanalens geometri och vattnets flöde och ytfluktuation. Genom litteraturstudie, numerisk modellanalys samt fältstudie har inverkan på blockerosionen av sprickriktningar utretts. En bergmassa som innehåller sprickgrupper som har liten, nära horisontell, stupning är känslig för vattenbelastning. Stupningsriktningen i förhållande till flödesriktningen har också betydelse för blockerosionen. Stupningsriktning i flödesriktningen gör bergmassan mer känslig för belastning av forsande vatten och gynnar därmed erosionen. Utskovskanalerna i Ligga, Harsprånget, Porjus, Satisjaure samt Seitevare har undersökts med avseende på erosionsrisk. Erosionen i Ligga, Harsprånget och Porjus har varit omfattande och detta beror troligtvis på att dessa kanaler har subhorisontella bankningssprickor med litet sprickavstånd. I Satisjaure är bergmassan mycket sprickig, varför denna kanal är mycket känslig för vattnets belastning. Där har dock åtgärder vidtagits så att kanalen ska tåla sitt dimensionerande flöde. I Seitevare är erosionsrisken i kanalens övre del liten. Det finns olika metoder för att bedöma erosionsrisken i en bergmassa. Erosionsindexmetoden är en semiempirisk metod som är verifierad med platsobservationer i USA. Med hjälp av observationer från Porjus, Harsprånget och Seitevare har erosionsindexmetodens tillämplighet på svenska kanaler undersökts. För dessa tre observationer verkar metoden fungera bra och har därför även använts i kanalerna i Satisjaure och Ligga. Energidämpande åtgärder i kanalerna, såsom energiomvandlargropar och utsprängda trappor i kanalerna, har visats sig vara mycket effektivt för att minska erosionsrisken. En noga dokumentering av utskovskanaler, som t ex kartering och inmätningar, skulle bidra till att erosionsindexmetoden kunde verifieras ytterligare och att en översiktlig bedömning av erosionsrisken i utskovskanaler enkelt kan erhållas.

Dreissenid mussels alter particle transport dynamics in the near shore environment of the Great Lakes by intercepting, retaining and recycling suspended solids that might otherwise be exported to the offshore environment (Hecky et al., 2004). Particulate materials filtered from the water column by dreissenids are subsequently released as either feces or pseudofeces (Walz, 1978). This bio-transformation process alters the nature (grain size distribution, settling velocity and density) and transport properties (critical shear stress for erosion, erosion rates and bed stability) of particulate matter in surficial sediments. While knowledge of the transport characteristics of this material is required to refine particle transport dynamics and energy flow models in the Great Lakes, few studies have been specifically conducted to directly quantify these processes. An annular flume was used to determine the bed stability, rate of erosion and critical shear stress for erosion of dreissenid biodeposits. Materials studied in the flume consisted of 1) a combination of biodeposits and surface sediments collected from dreissenid beds and 2) biodeposits harvested in a weir box with dreissenids. The results show that erosion characteristics and sediment transport properties were strongly influenced by bed age; however particle sizes did not increase in the presence of mussels as originally speculated. Bed stability increased after 7 days, with a τcrit of 0.26 Pa compared to the 2 and 14 day consolidation periods (τcrit= 0.13 and 0.15 Pa respectively). In 2010, following a 2 day consolidation period, pure biodeposits harvested in the weir box had a critical shear stress for erosion of 0.052 Pa. The decrease in bed stability found in biodeposits from 2010 compared to the 2008 biodeposit mixture, may be a result of a more diffuse biofilm developing on the highly organic substrate. The mixture of biodeposits collected in 2008 were a combination organic and inorganic materials which may be creating a nutrient limited environment, where biofilm structure consists of more tightly organized biofilm cells and as a result enhance stability in the bed sediments. The decrease observed after 14 days is likely a result of the microbes depleting their resources and dying off. Due to the added roughness the mussels created in the flume, τcrit could not be measured and critical revolutions per minute (RPM) for erosion are reported for flume runs with mussels. During experiments conducted in 2009 with pure biodeposits and mussels the critical RPM was 5.83 while in 2010 in the presence of mussels a critical RPM was not observed. Settling experiments found biodeposits from both years (2008 and 2010) had decreased settling velocities when compared to different sediment types from lacustrine environments. I speculate that the added enrichment of the surficial sediments by mussel biodeposits is enhancing the process of biostabilization and increasing the bed stability and that the presence mussels themselves may additionally be enhancing bed stability by inhibiting flow from reaching the surface sediments/biodeposits.

Bridge scour is the term which describes the erosion of soil surrounding a bridge foundation due to water. Bridge scour can cause the reduction of the load carrying capacity of bridge foundations, excessive foundation settlements, and damage to bridge abutments. Bridges with foundations that are unstable for calculated and/or observed scour conditions are termed scour critical bridges. Approximately 25,000 bridges in the United States are classified as scour critical and about 600 of them are in Texas. This designation comes in part from the use of over-conservative methods that predict excessive scour depths in erosion resistant materials. Other methods have been developed to eliminate this over-conservatism but are uneconomical because they require site-specific erosion testing. The major contribution of this dissertation is a new method to assess a bridge for scour and erosion classification charts which categorizes the erodibility of geomaterials according to conventional engineering properties. The new method is a three level Bridge Scour Assessment (BSA) procedure which is relatively simple and economical. It does not require site-specific erosion testing and eliminates the over-conservatism in current methods. The first level, BSA 1, uses charts that extrapolate the maximum scour depth recorded during the life of the bridge to obtain the scour depth corresponding to a specified future flood event. The second level, BSA 2, determines the maximum scour depth and is carried out if BSA 1 does not conclude with a specific plan of action for the bridge. The third level, BSA 3, determines the time dependent scour depth and is carried out if BSA 2 does not conclude with a specific plan of action. The scour vulnerability depends on the comparison between the predicted and allowable scour depths. The 11 case histories used to validate the new method showed good agreement between predicted values and field measurements. BSA 1 was then applied to 16 bridges. In this process, 6 out of 10 bridges classified as scour critical by current methods were found to be stable. These results show that the new method allows for more realistic evaluation of bridges for scour while not requiring site-specific erosion testing.

Dreissenid mussels alter particle transport dynamics in the near shore environment of the Great Lakes by intercepting, retaining and recycling suspended solids that might otherwise be exported to the offshore environment (Hecky et al., 2004). Particulate materials filtered from the water column by dreissenids are subsequently released as either feces or pseudofeces (Walz, 1978). This bio-transformation process alters the nature (grain size distribution, settling velocity and density) and transport properties (critical shear stress for erosion, erosion rates and bed stability) of particulate matter in surficial sediments. While knowledge of the transport characteristics of this material is required to refine particle transport dynamics and energy flow models in the Great Lakes, few studies have been specifically conducted to directly quantify these processes. An annular flume was used to determine the bed stability, rate of erosion and critical shear stress for erosion of dreissenid biodeposits. Materials studied in the flume consisted of 1) a combination of biodeposits and surface sediments collected from dreissenid beds and 2) biodeposits harvested in a weir box with dreissenids. The results show that erosion characteristics and sediment transport properties were strongly influenced by bed age; however particle sizes did not increase in the presence of mussels as originally speculated. Bed stability increased after 7 days, with a τcrit of 0.26 Pa compared to the 2 and 14 day consolidation periods (τcrit= 0.13 and 0.15 Pa respectively). In 2010, following a 2 day consolidation period, pure biodeposits harvested in the weir box had a critical shear stress for erosion of 0.052 Pa. The decrease in bed stability found in biodeposits from 2010 compared to the 2008 biodeposit mixture, may be a result of a more diffuse biofilm developing on the highly organic substrate. The mixture of biodeposits collected in 2008 were a combination organic and inorganic materials which may be creating a nutrient limited environment, where biofilm structure consists of more tightly organized biofilm cells and as a result enhance stability in the bed sediments. The decrease observed after 14 days is likely a result of the microbes depleting their resources and dying off. Due to the added roughness the mussels created in the flume, τcrit could not be measured and critical revolutions per minute (RPM) for erosion are reported for flume runs with mussels. During experiments conducted in 2009 with pure biodeposits and mussels the critical RPM was 5.83 while in 2010 in the presence of mussels a critical RPM was not observed. Settling experiments found biodeposits from both years (2008 and 2010) had decreased settling velocities when compared to different sediment types from lacustrine environments. I speculate that the added enrichment of the surficial sediments by mussel biodeposits is enhancing the process of biostabilization and increasing the bed stability and that the presence mussels themselves may additionally be enhancing bed stability by inhibiting flow from reaching the surface sediments/biodeposits.

O estudo da erodibilidade ganha importância quando se tratam de solos localizados em regiões tropicais, caracterizadas por altas pluviosidades e evaporações que dificilmente permitem ao maciço atingir um estado de saturação em campo. A erodibilidade e as propriedades hidráulicas determinam as condições de infiltração e de escoamento superficial e podem acelerar as feições erosivas através das perdas de partículas. Neste trabalho, observou-se que o grau de saturação in situ estabelece um potencial de sucção matricial (Sm) capaz de orientar o fluxo, absorção e armazenamento da água nos poros do solo. Deste modo, foi possível correlacionar as propriedades de absorção de água com as sucções mátricas de três solos (arenoso, argiloso e areno-argiloso), com comportamento erosivo e não-erosivo, ensaiados a diferentes teores de umidade inicial. Após o controle da sucção e umidade, através da panela de pressão de Richards, os solos foram submetidos ao ensaio de erodibilidade proposto por Nogami & Villibor (1979). Os índices de absorção (Iabs), de perda de massa por imersão (P) e de erodibilidade (E) determinados neste ensaio, quando correlacionados com as curvas características dos solos, mostraram a influência da sucção matricial no início do processo erosivo. Verificou-se uma tendência de aumento da perda de massa por imersão, quanto menor era o teor de umidade inicial imposta (maior sucção). Provavelmente, quando do início do evento chuvoso, o solo tende a ser mais erodível quanto mais seco estiver. Além disso, as correlações obtidas mostraram-se coerentes com o comportamento dos solos em estudo, permitindo uma estimativa da sucção (Sm) de um solo a partir de grandezas facilmente mensuráveis como o Iabs, obtido em ensaio simples e de fácil execução. / The study of erodibility gains importance when dealing with soil located in tropical regions, characterized by high precipitation and evaporation that allow hardly the massive soil to reach a state of saturation in the field. The erodibility and hydraulic properties define the infiltration conditions and the superficial flow, and they can accelerate the erosive process due to the losses of particles. In this work, we observed that the degree of saturation in situ establishes the potencial for suction matrix (Sm) can guide the flow, absorption and storage of water in soil pores. Therefore, experimentally, it was possible to correlate the properties of water absorption with the matrix suctions of three soils, with different initial moisture contents and erosive and non-erosive behaviors. After controlling the suction and moisture through the pressure Richards pressure chamber the soils were subjected to the erodibility test proposed by Nogami & Villibor (1979). The indexes of absorption (Iabs), mass loss by immersion (P) and erodibility (E) determinated in this experiment, when correlated with the characteristic curves of soils, showed the influence of matrix suction at the beginning of the erosion process. There was a trend of increased weight loss by immersion, the lower was the initial moisture content imposed (greater suction). Furthermore, the correlations obtained were consistent with the behavior of soils under study, allowing to estimate of suction (Sm) of a soil from easily measurable values such as the Iabs.

Made available in DSpace on 2014-06-11T19:23:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-01-19Bitstream added on 2014-06-13T20:50:14Z : No. of bitstreams: 1 miqueloni_dp_me_jabo.pdf: 977047 bytes, checksum: 4aaa69273226d26e905b5fb3013aed3f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Devido sua importância, a perda de solo das microbacias de cabeceira do Córrego do Tijuco-SP foi estimada por meio da EUPS, e a variabilidade espacial dos fatores do processo erosivo foi investigada pelas análises multivariada e geoestatística. A perda de solo média estimada foi considerada alta, 118,50 Mg ha-1 ano-1, e a correlação de Pearson confirmou o fator erodibilidade do solo como o fator mais importante no processo erosivo. A erodibilidade local é condicionada pela distribuição das frações granulométricas e matéria orgânica, sendo o solo basicamente de textura média/arenosa de baixa coesão. Próxima a zona urbana, a interação do fator erosividade da chuva e do fator práticas conservacionistas se mostrou proeminente evidenciando alta perda de solo devido à concentração de água oriunda da camada impermeabilizada urbana e da falta de controle da velocidade do escoamento superficial da água. Em contraste, o fator cobertura vegetal mostrou maior atuação nas áreas de vegetação permanente, localizadas principalmente nas nascentes e canais de escoamento. Nas áreas mais convexas do terreno, localizadas nos divisores de águas, a atuação do fator erodibilidade foi proeminente, em contraste com o fator topográfico, este em áreas côncavas de maior declividade. Foram observadas ainda áreas com atuação conjunta dos fatores topográfico e erodibilidade, refletindo locais de inclinação mais suave, porém com alto potencial natural de erosão. Os resultados das análises multivariadas e geoestatística permitiram uma estratificação da área estudada identificando locais com propriedades específicas quanto à perda de solo o que contribui na compreensão do processo erosivo para a aplicação das práticas conservacionistas / Because of the importance of headwater watersheds of the Córrego do Tijuco-SP its soil loss was estimated by the USLE and the spatial variability of the erosion process factors was investigated by multivariate analysis and geostatistics. The estimated average soil loss was considered high, 118.50 Mg ha-1ano-1, and Pearson correlation confirmed the soil erodibility factor as the most important factor in the erosion process. Erodibility is conditioned by the local distribution of soil particle-size fractions and organic matter, and soil texture mostly medium/sandy of low cohesion. Near urban areas, the interaction of rainfall erosivity factor and conservation practices factor showed prominent high soil loss due to concentration of water coming from urban soil impermeabilization and the lack of speed control of runoff water. In contrast, the vegetation cover factor showed great performance in the areas of permanent vegetation, mainly located in the headwaters and drainage channels. In areas of more convex topography close to the watershed dividers, the action of erodibility factor was prominent, in contrast to concave areas of greater slope where the topographic factor was more prominent. We also observed areas with joint action of topographic factors and soil erodibility factor, with smoother topography, but with high natural potential of erosion. Results of multivariate and geostatistics analysis enabled to stratify the study area by identifying sites with specific properties of soil loss which helps in understanding the erosion process for the implementation of conservation practices

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2015-03-27T12:48:50Z No. of bitstreams: 2 Dissertação - Glacielle Fernandes Medeiros - 2014.pdf: 10386927 bytes, checksum: eb9905784a9f404ceeaedc20b5066184 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-03-27T15:31:56Z (GMT) No. of bitstreams: 2 Dissertação - Glacielle Fernandes Medeiros - 2014.pdf: 10386927 bytes, checksum: eb9905784a9f404ceeaedc20b5066184 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-03-27T15:31:56Z (GMT). No. of bitstreams: 2 Dissertação - Glacielle Fernandes Medeiros - 2014.pdf: 10386927 bytes, checksum: eb9905784a9f404ceeaedc20b5066184 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-08-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present research inserts in the Project “Mapping and Geological and Geotechnical Characterization Applied in Assessing the Erodibility of Unconsolidated Material Along the Stretch of Duct OSBRA from Petrobras”. Sand river watershed is crossed by this stretch of ducts highlights, relatively, for the occurrence of accelerated erosive focuses. Soil water erosion is composed by a natural process, which occurs regards weather factors, geological, geomorphological and pedological. However, water erosion may by intensified by anthropic modification in one of this factors, becoming an accelerated process. Runoff may be considered part of water erosion process, which has its main origin in precipitations, over specific unconsolidated material, with specific disaggregation resistance and transportation (erodibility), located in specific form of terrain. In this context, this research aims the investigation of the terrains of the upper watershed of Barreiro creek, affluent located in the medium course of Areias river, in the county of Alexânia – GO, about erosion susceptibility, with emphasis in runoff in relation to erodibility of existing unconsolidated material. To achieve such goals, equipment like high precision GPS were used, for tracking, from the fast static method of the sample points and the stop and go method on the back road which gave access to the watershed limits and its interior, besides digital modeling of morphometric variables which interferes in runoff. In the same way, samples were collected and points observed, for non-alleatory characterization of the study area, from the rational method, as suggested by Zuquette and Gandolfi (2004). This research aimed to analyze soils resistance toward disaggregation and material transportation, related to runoff, with specific geotechnical tests, associated to basic cartographic documentation. Those consisted in Inderbitzen tests and disaggregation, in collected samples on chosen points according to different slopes, associated with erosive focuses occurrence. As results, were compiled and developed cartographic products such as: unconsolidated material maps, documentation, slope, curvatures, hipsometrics, soil use and occupation, susceptibility and potential to laminar and linear erosive process. During the test Inderbitzen was observed that the behavior of materials in relation to the slope of the standard ramp (10 °) and similar to the field slope better reflected the susceptibility of materials in the second case, showing greater loss of material at higher inclinations . As for the disaggregation test, the sample lateritic proved more resistant to flooding processes than saprolítica sample, both processes by total immersion, as the processes by partial immersion. During the disintegration test and the result Inderbitzen occur as expected, ie lateritic samples showed to be more resistant, especially because of cohesive forces existing in these types of soil. / A presente pesquisa insere-se no projeto “Mapeamento e Caracterização Geológico-Geotécnica Aplicados na Avaliação da Erodibilidade dos Materiais Inconsolidados ao Longo da Faixa do Duto OSBRA da PETROBRAS”. A bacia do rio Areias é atravessada por essa faixa de dutos e destaca-se, relativamente, quanto à ocorrência de focos erosivos acelerados. A erosão hídrica nos solos constitui-se em um processo natural, que ocorre em função de fatores climáticos, geológicos, geomorfológicos e pedológicos. Contudo, o processo erosivo hídrico pode ser intensificado por modificação antrópica em um desses fatores, tornando-se um processo acelerado. O escoamento superficial pode ser considerado parte do processo erosivo hídrico que tem origem principal nas precipitações, sobre determinado tipo de material inconsolidado, com determinada resistência à desagregação e ao transporte (erodibilidade), localizado em determinada forma de terreno. Neste contexto, esta pesquisa tem por objetivo a investigação dos terrenos da alta bacia do ribeirão Barreiro, afluente localizado no médio curso do rio Areias no município de Alexânia-GO, quanto à susceptibilidade à erosão com ênfase no escoamento superficial em relação à erodibilidade dos materiais inconsolidados existentes. Para atingir tais objetivos, foram utilizados equipamentos do tipo GPS de alta precisão, para o rastreamento, pelo método estático rápido dos pontos amostrados e pelo método stop and go das estradas vicinais que deram acesso aos limites e ao interior da bacia em questão, além da modelagem digital das variáveis morfométricas que interferem no escoamento superficial. Do mesmo modo, foram coletadas amostras e observados pontos, para caracterização da área de estudo de maneira não aleatória, pelo método racional, conforme sugerido por Zuquette e Gandolfi (2004). Com a realização de ensaios geotécnicos específicos, associados à documentação cartográfica básica, nesta pesquisa buscou-se analisar a resistência dos solos à desagregação e transporte dos materiais, em relação ao escoamento superficial. Estes consistiram nos ensaios de Inderbitzen e de desagregação, em amostras coletadas em pontos escolhidos segundo diferentes declividades do terreno, associadas às ocorrências de focos erosivos. Como resultados, foram compilados e/ou elaborados produtos cartográficos tais como: mapas de materiais inconsolidados, de documentação, de declividades, de curvaturas, hipsométricos, de uso e ocupação do solo, de susceptibilidade e de potencialidade aos processos erosivos laminares e lineares. Durante o ensaio de Inderbitzen foi possível observar que o comportamento dos materiais em relação à inclinação da rampa padrão (10°) e à inclinação semelhante à do campo, refletiram melhor a suscetibilidade dos materiais no segundo caso, apresentando maior perda de material em inclinações maiores. Quanto ao ensaio de desagregação, a amostra laterítica mostrou-se mais resistente aos processos de inundação do que a amostra saprolítica, tanto nos processos por imersão total, quanto nos processos por imersão parcial. Durante o ensaio de desagregação e Inderbitzen os resultado ocorram conforme o esperado, ou seja, as amostras laterítica apresentaram-se mais resistente, devido principalmente às forças de coesão existentes nestes tipos de solo.

The microbasin of the Sarandi little stream, that it crosses the cities of Saint Maria and Dilermando de Aguiar, situated in the State of Rio Grande do Sul, south region of Brazil, presents innumerable erosions; the most significant soil erosion on that region is well known as Buraco Fundo gully, which is also our case of study. The general goal of this dissertation was to delimitate and to characterize the geological and geotechnical materials of that soil erosion, in order to understand the parameters that influence that erosive process. As specific goals tries to evaluate the erosive marks and the pseudo-karstic relief, as well as the degree of erodibility of that materials, in order to minimize its advance. Nevertheless, this writing involved theoretical research, fieldwork and laboratory, where the assays of geotechnical characterization and direct and indirect evaluation of erodibility had been executed. The soil erosion of the Buraco Fundo gully occurs in sedimentary rocks according to direction N20º-35ºE. It results of rotational slippings and pseudo-dolines that evaluates to ridges and ravines. It was assayed the superficial horizon (A/B) and the sandstone layer located in the amphitheater of that soil erosion. The horizon A/B presents an arenaceous and argillaceous texture, plastic behavior and the biggest quotient of emptiness, while the sandstone did not present plasticity. The coefficient of sorption(s) was bigger in the sandstone than in the superficial horizon. Therefore, it can be foreseen that the saturation in rainy events is faster in the sandstone than in the superficial horizon. The sandstone makes the material, after the saturation, establish the superficial draining. It occurs, as consequence, the carry of fine materials. It was verified a direct relationship between the results of the slaking test and the assays of infiltrability. The sandstone showed high desagregation and high coefficient of infiltrability. The values of Pi/s had been superior to 50, for both samples; they were classified as erodible according to Nogami and Villibor (1979). The coefficient of erodibility (k) was 10 times bigger in the sandstone, which can be related to the loss of resistance due to suction and the apparent fragility of the cementing agent. The soil revealed to be very resistant cause presents organic matter , roots and fines. The results indicate the necessity of protection of this area since the initial period of erosion, in order to avoid that process of erosion reaches the rock. / A microbacia do Arroio Sarandi, nos municípios de Santa Maria e Dilermando de Aguiar/RS apresenta inúmeras erosões sendo a mais significativa uma voçoroca conhecida na região como Buraco Fundo escolhida para estudo de caso. O objetivo geral desta dissertação foi a caracterização geológico-geotécnica dos materiais da voçoroca, procurando compreender os parâmetros que influenciam no processo erosivo. Como objetivos específicos procurou-se avaliar as feições erosivas e as formas de relevo pseudo-cársticos bem como a erodibilidade dos materiais sugerindo ações para minimizar o seu avanço. Este trabalho envolveu etapa de escritório; de campo e de laboratório, onde foram executados os ensaios de caracterização geotécnica e avaliação direta e indireta da erodibilidade. A voçoroca do Buraco Fundo ocorre em rochas sedimentares segundo a direção N20º-35ºE. A evolução se dá por escorregamentos rotacionais e pseudo-dolinas que evoluem para sulcos e ravinas. Foram ensaiados o horizonte superficial (A/B) e a camada de arenito localizados no anfiteatro da voçoroca. O horizonte A/B apresenta uma textura areno-argilosa, comportamento plástico e maior índice de vazios, enquanto o arenito não apresentou plasticidade. O coeficiente de sorção (s) foi maior no arenito do que no horizonte superficial e, portanto, pode-se prever que a saturação em eventos chuvosos, seja mais rápida no arenito, fazendo com que neste material, após a saturação, se estabeleça o escoamento superficial e ocorra, como consequência, o carreamento de materiais finos. Verificou-se uma relação direta entre os resultados do ensaio de desagregação e os de infiltrabilidade, onde o arenito mostrou alta desagregação e elevado coeficiente de infiltrabilidade. Os valores de Pi/s foram superiores a 50 para ambas as amostras, classificadas como erodíveis segundo Nogami e Villibor (1979). O coeficiente de erodibilidade (K) foi 10 vezes maior no arenito o que pode estar relacionado à perda da resistência devido à sucção e a aparente fragilidade do agente cimentante. O solo, por apresentar matéria orgânica, raízes e finos mostrou-se mais resistente. Os resultados apontam para a proteção das áreas em estágio erosivo inicial evitando que o processo atinja a rocha.