Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A serra do Tepequém, área objeto de estudo encontra-se no extremo norte do estado de Roraima, no município do Amajarí. O topo da serra possui morfologia diferenciada, com altitudes variadas que atingem 1100m. Esta região foi palco de diversos estudos geológicos, geomorfológico e histórico, os quais registram fatos importantes na sua historia de evolução da paisagem, como a atividade garimpeira diamantífera. Esse estudo teve como objetivo entender os processos erosivos e suas influências no modelado da paisagem atual da serra do Tepequém. Para o entendimento da temática foi realizado levantamento bibliográfico e cartográfico de estudos anteriores, bem como aquisição de dados de campo como: medidas morfométricas quanto à profundidade, largura e comprimento de feições erosivas lineares; identificação e medidas de micro feições erosivas; descrição de perfis de solos em parede de voçorocas e coletas de solos em diferentes horizontes. Posteriormente, foram executadas análises granulométricas, pH, porosidade, densidade e mineralógicas dos solos. O modelado atual da serra do Tepequém é subordinado às estruturas geológicas de falhas e fraturas que condicionam as formas de relevo e drenagem presente no topo, além dos solos rasos e incoesos parcialmente recobertos por vegetação. Tais características aliadas a índices elevados de precipitação contribuem de forma significativa no processo erosivo e por consequência na formação de ravinas e voçorocas nas áreas de planícies e vertentes de colinas e morros. Foram identificadas micro feições erosivas no entorno, parede e talvegue das calhas erosivas, essas feições fragilizam os locais onde se estabelecem e auxiliam no avanço e crescimento das erosões. No geral, as voçorocas se desenvolvem em áreas de planícies, e em menor número nas vertentes de morros e colinas. As morfologias identificadas foram: linear, bifurcada e mista. Os solos são predominantemente arenosos, representado por areia fina a média, de morfologia angulosa a subangulosa. A densidade do solo variou para cada horizonte, assim como a porosidade e pH. As maiores concentrações de matéria orgânica foram identificadas no horizonte A. A composição mineralógica apresentou maior concentração de quartzo. O estaqueamento da voçoroca do Barata apontou maior evolução na porção montante parede direita, enquanto que a evolução da voçoroca da Encosta foi bem menor. Portanto, a Serra do Tepequém vem sendo esculpida por processos erosivos que promovem a evolução da paisagem atual. / The Tepequém saw area that is the object of study is located at the northern end of the Roraima state in the county of Amajarí. The top of the mountain ridge has a differentiated morphology, with varying altitudes reaching 1100m. This region was the scene of several geological, geomorphological and historical studies, which record important events in its history of evolution of the landscape, such as diamond mining activity. This study aimed to understand the erosive processes and their influences on the patterned of the current landscape of Tepequém saw. To understand the theme was conducted bibliographic and cartographic survey of previous studies as well as acquisition of field data as morphometric measurements on the depth, width and length of linear erosional features; identification and measures of micro erosional features; soil profile description in gullies wall and soil sampling at different horizons. Later, analyzes were performed granulometric, pH, porosity, density and mineralogical of the soils. The current modeled of the Tepequém saw is subject to the geologic structures of faults and fractures that affect the landforms and drainage present at the top, beyond the shallow soils and incoesos partially covered by vegetation. These features combined with high levels of rainfall contribute significantly to erosion and result in the formation of ravines and gullies in the areas of plains and slopes of hills and mountains. Were identified micro erosive features in the surrounding wall and thalweg of erosive chutes, these features undermine the places where they settle and assist in the advancement and growth of erosions. Overall, the gullies develop in areas of plains, and fewer on the slopes of hills and hills. The morphologies were identified: linear, forked and mixed. The soils are predominantly sandy, represented by fine to medium sand, of angular morphology subangular. The density of the soil varied for each horizon, as well as the porosity and pH. The highest concentrations of organic matter were identified on the horizon A. The mineralogical composition showed higher concentration of quartz. The staking of the gully pointed further evolution in the portion amount on the right wall, while the evolution of the gully Hill was much lower. Therefore, the Serra do Tepequém has been sculpted by erosion processes that promote the evolution of the present landscape.

[pt] A ocupação e uso dos solos têm claras implicações nos processos erosivos, porém devemos destacar também um dos atores principais para os processos erosivos, que é a evolução geomorfológica. A bacia do córrego das Palmeiras está inserida em um local com baixas amplitudes de relevo, mas que apresenta um alto potencial de vulnerabilidade a eventos de erosão e movimentos de massa. Destacamos obviamente o grande número de voçorocamentos que atingem determinadas áreas do médio vale do rio Paraíba do Sul, principalmente próximos ao seu eixo principal em um grande alinhamento de direção NE-SW a qual a bacia do córrego das Palmeiras está inserida. O presente estudo tem como objetivo principal descrever a origem e a distribuição dos processos erosivos na bacia do córrego das Palmeiras, na cidade de Barra do Piraí, Rio de Janeiro. Para que o principal objetivo desse trabalho seja alcançado, se torna necessário o cumprimento dos objetivos específicos, os quais são: Descrever a relação da orientação das voçorocas com as estruturas do substrato geológico; Descrever a relação entre processos erosivos e os níveis de base locais e; Descrever a relação entre processos erosivos e uso do solo. Para a realização deste trabalho foram utilizadas técnicas de análise e embasamentos teóricos da ciência geográfica e mais especificamente da área da geomorfologia. Podemos destacar como os principais resultados alcançados as análises referentes à relação entre os condicionantes geológicos/geomorfológicos e a ocorrência e comportamento de processos erosivos, permitindo afirmar que existe uma relação estreita entre a compartimentação geológica, orientação das estruturas, processos de rebaixamento de níveis de base, histórico de uso e ocupação do solo e a presença de processos erosivos. / [en] Land use has clear implications in the erosive processes and their relation with the geomorphological evolution can be seen notoriously. The Palmeiras stream basin is inserted in a place with low amplitudes of relief, but that presents a high potential of vulnerability to events of erosion and mass movements. We highlight obviously the large number of gully erosions that reach certain areas of the middle valley of the Paraíba do Sul river, mainly near its main axis in a great alignment of direction NE-SW to which the basin of the stream of Palmeiras is inserted. This study has as main objective the description of the origin and spatial distribution of the erosive processes in the Córrego dos Palmares basin. In order for the main objective of this work to be achieved, it is necessary to fulfill the specific objectives, which are: Analyze the spatial distribution of erosive processes; analyze the relation of the orientation of the gullies with the lithological structures of the geological substrate; Analyze the relationship between erosive processes and local base levels and; analyze the relationship between erosive processes and land use. For the accomplishment of this work, techniques of analysis and theoretical bases of the geographic science and more specifically of the area of geomorphology were used. We can highlight as the main results of the description the relationship between the geological / geomorphological conditions and the occurrence and behavior of erosive processes, allowing to affirm that there is a close relationship between the geological compartmentation, orientation of the structures. History of land use and occupation and the presence of erosive processes.

The Palmiet wetlands located along the Kromrivier in the Eastern Cape province of South Africa have experienced severe degradation through gully erosion during the past decennia which has been threatening the water quality and water security of large towns in the Nelson Mandela Metropolitan hub. Water scarcity is a growing problem in this region as a result of land degradation and growing erratic rainfall patterns. The main causes of wetland degradation are argued to be land use and land cover change. With the aim of protecting the wetlands along the Kromrivier a total of eleven large gabion and concrete erosion-control structures were constructed between the 2002 and 2013 by the government initiate Working for Wetlands. This study aims to map the groundwater table in order to derive how erosion-control structures and gully erosion affect groundwater dynamics along the Kromrivier. This was achieved by several steps. Firstly, water table elevations were measured along several transects by installing a series of piezometers which allowed do investigate how the structures affected the water table. This also allowed for a comparison in groundwater dynamics between eroded and non-eroded reaches so that effects of gully erosion could be identified and potential causes discussed. Secondly, the analysis of aerial images allowed for the development of the aerial extent of the Palmiet wetland and gullies to be seen over a ten year period and longitudinal profiles provided specific characteristics of the wetland and gullies. Lastly, particle size distribution and organic matter content were analyzed as groundwater flow and gully erosion can vary greatly depending on soil characteristics. The hydraulic gradient was highest in proximity to the structures as a result of the created potential induced by the drop in surface water elevation. The radius of influence to where the structures were affected the water table was estimated to be approximately 40 m from the channel. Further away from the channel, the gradual slope of the water table indicated that the porous gabion side walls of the structures did not affect the water table. The groundwater flow is determined by Darcy's Law and the relatively flat water table along the non-eroded reaches of site A displayed local drainage points, thereby indicating variations in the local flow direction. In May the water table along the non-eroded reaches was sloping away from the channel resulting in an area of groundwater discharge with respect to the channel. Not only was the water table generally higher during August, the regime had also changed, indicating a potentially large seasonal variability. Along the eroded reaches downstream from the structures the water table was above the gully bottom during both months resulting in an area of groundwater recharge with respect to the channel. Also here the regime had changed from an approximately constant hydraulic gradient sloping towards the channel during May to a water table with a divide in flow direction. Since their implementation in 2003, the structures have been effective with respect to preventing the headcut in the main channel from migrating further upstream. However, the gullies downstream of the structures had significantly increased in width between 2003 and 2013 and the Palmiet wetland had also slightly decreased in size during the same period. However, it was unclear whether this decrease was part of the longer term ongoing trend or part of a shorter term cycle and/or seasonal fluctuation. For a gully bank to collapse, the shear strength of the slip surface needs to be exceeded and this often occurs because of an increase in pore water pressurewhich causes a reduction in shear strength. A large gully height of up to 4 m with nearly vertical slopes, a water table above the gully bottom and an increase in moisture content between May and August indicated that it is not unlikely that a high pore water pressure. played a significant role in the slumping of the gully walls. The two structures together were responsible for an surface water elevation difference of 7.76 m. Through damming this resulted in an elevated water table in the upstream Palmiet wetland, thereby increasing the saturation and promoting diffuse flow across the wetland. However, the structures also trap most of the sediment in upstream direction which appears to have resulted in the de-stabilization of the downstream streambed at site A as these eroded reaches now receive a significantly lower sediment load. By increasing the retention volume in the wetland, the structures also facilitated in ensuring flood retention as the wetland could now hold more water during high flows, thereby cutting off the peak flow. As gully erosion is known to occur during periods of high flow it is not unreasonable to argue that slumping of the gully walls would have been more severe without the structures in place. In this sense the structures increase the water quality and decrease the flux of sediment where the latter leads to a decrease in the sedimentation rate of the downstream Churchill Dam. Consequently, this contributes to securing the fresh water supply to towns in the Nelson Mandela Metropolitan hub. The discovery of Palmiet rests up to 2.6 m below the surface indicated that cycles of gully erosion followed by the re-establishment of Palmiet have been occurring in this valley for thousands of years. However, it seemed that land use and land cover changes had accelerated gully erosion during the past decades resulting in a loss of Palmiet wetland at a rate which was beyond 'natural'. Even though the structures could be seen as disruptions of long term natural cycles, they are in favor of the well-being of mankind as they protect the wetlands to a certain extent. The main results of this study provided a basic understanding of how the water table behaves in response to the structures and along eroded and non-eroded reaches of the Kromrivier. Furthermore, this study discussed the larger scale affects of the structures and showed how the gullies and the aerial extent of the Palmiet wetland have evolved since the implementation of the structures in 2003. In order to manage these Palmiet wetlands more effectively in the future, it is highly important that groundwater dynamics, gully erosion and the size and health of the wetland are annually monitored in order to get a more accurate idea of how effective these structures are. This new obtained knowledge could also assist in managing other peat lands in South Africa more effectively.

The study of which this Master s Thesis results was developed in a gully along State Highway RS 377, in the city of São Francisco de Assis, RS. Themain objective of this study was theerodibilityof the superficial soils(horizons A,BandC) and of the rock substrate(layers 1Aand2C) of atypical profile from the gully area. Themethodology used consisted in review ofliterature, field investigation, characterization testings, chemical testings, direct shear resistance testings, testingsforindirect valuation (degradation and infiltration testings and loss by immersion) and indirect valuation (Inderbitzen) of erodibility and the comparison with the proposal from Bastos (1999) of an estimate of erodibility of unsaturated soils in Porto Alegre region. The results obtained from the erodibility indirect testing through the erodibility factor estimate (KUSLE), from soil disaggregation potential valuation and from criterion based on MCT methodology were as follows: for horizons A, B and C and layers 2C and 1A, the values were between 0,10 and 0,21, and it was verified that these materials cannot be separated regarding erodibility. The MCT methodology presented good relation and correspondence between the testing results and the soils/rocks behavior on the studied location, proving its applicability to these materials. The direct valuation, achieved through the Inderbitzen testings, whose main purpose is to quantify the erodibility of the studied soils and rocks, through the erodibility rate, K and the hydraulic critical shearing stress (thcrít), confirmed that the loss of soil is as higher as higher is the ramp and the testing flow. According to this assessment, for sandstones samples (layers 2C and 1A), it was verified some tendency for higher values of erodibility in air-dried condition. It was also verified higher erodibility values from the horizon C and sandstone layers compared to the layer A. Regarding to the horizon B, the values were situated in an intermediate level. The horizon A presented a value for K=0,0095 g/cm²/min/Pa, lower than the result from horizon B (K=0,17 g/cm²/min/Pa). The values of K for the horizon C and the layers of sandstone were between 0,33 and 0,42 g/cm²/min/Pa. It was not possible to determine the critical hydraulic stress for the horizon A, but for the horizon B these values were between 1 and 1,3 Pa. For the horizon C and the sandstones, these values were between 0,5 and 1 Pa. The horizon C and the sandstones from the layers 2C and 1A were the more potentially erodible materials. Due to the little amount of fine portion, the little organic matter and the low plasticity, these horizons/layers are more erodible than the soils studied by Bastos (199) e Fernandes (2011). The criterion that presented a better correlation with the geothecnic purpose from Bastos (1999) were the erodibility coefficient obtained through the Inderbitzen testing and the erodibility criteria from the MCT methodology. / A pesquisa, da qual resulta esta dissertação de mestrado, foi desenvolvida em uma voçoroca localizada as margens da RS 377, no município de São Francisco de Assis, RS. O objetivo principal foi o estudo da erodibilidade dos solos superficiais (horizontes A, B e C) e do substrato rochoso (camadas 2C e 1A) de um perfil típico da área da voçoroca. A metodologia aplicada consistiu no levantamento bibliográfico; investigação de campo, ensaios de caracterização, ensaios químicos, ensaios de resistência ao cisalhamento direto, ensaios para avaliação indireta (ensaios de desagregação, infiltrabilidade e perda por imersão) e direta (Inderbitzen) da erodibilidade e comparação com a proposta de Bastos (1999) para a estimativa da erodibilidade de solos não saturados na região de Porto Alegre. Os resultados obtidos na avaliação indireta da erodibilidade através da estimativa do fator erodibilidade (KUSLE), da avaliação do potencial de desagregação dos solos e dos critérios baseados na metodologia MCT foram os seguintes: para os solos dos horizontes A, B e C e camadas 2C e 1A, situou-se entre 0,10 e 0,21, verificando que não se consegue separar estes materiais quanto à erodibilidade. A metodologia MCT apresentou uma boa relação e correspondência entre os resultados dos ensaios e o comportamento dos solos/rochas nos locais estudados, comprovando sua aplicabilidade a estes materiais. A avaliação direta, feita através dos ensaios de Inderbitzen, os quais tem por objetivo quantificar a erodibilidade dos solos e rochas estudadOs, através da taxa de erodibilidade, K e a tensão cisalhante hidráulica crítica (thcrít), confirmou que a perda de solo é tanto maior quanto maior for à inclinação da rampa e a vazão de ensaio. Segundo esta avaliação, para as amostras de arenito (camadas 2C e 1A) verificou-se certa tendência de valores mais elevados de erodibilidade na condição seca ao ar. Também se verificou valores mais elevados de erodibilidade do horizonte C e camadas de arenito em relação ao horizonte A. No horizonte B os valores situaram-se em um patamar intermediário. O horizonte A apresentou um valor de K = 0,0095 g/cm2/min/Pa, bem inferior ao horizonte B (K = 0,17 g/cm2/min/Pa). Os valores de K para o horizonte C e camadas de arenito situaram-se entre 0,33 e 0,42 g/cm2/min/Pa. Não se conseguiu determinar as tensões hidráulicas críticas para o horizonte A, mas para o horizonte B estas se situaram entre 1 e 1,3 Pa. Para o horizonte C e os arenitos estes valores situaram-se entre 0,5 e 1Pa. O horizonte C e os arenitos das Camadas 2C e 1A foram os materiais mais potencialmente erodíveis. Devido a fração fina ser pequena, pouca matéria orgânica e baixa plasticidade, estes horizontes/camadas são mais erodíveis que os solos estudados por Bastos (1999) e Fernandes (2011). Os critérios que obtiveram melhor correlação com a proposta geotécnica de Bastos (1999) foram o coeficiente de erodibilidade obtido no ensaio Inderbitzen e o critério de erodibilidade da metodologia MCT.

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.

This study focuses on quantifying explicitly the sediment budget of deeply incised ravines in the lower Le Sueur River watershed, in southern Minnesota. High-rate-gully-erosion equations along with the Universal Soil Loss Equation (USLE) were implemented in a numerical modeling approach that is based on a time-integration of the sediment balance equations. The model estimates the rates of ravine width and depth change and the amount of sediment periodically flushing from the ravines. Components of the sediment budget of the ravines were simulated with the model and results suggest that the ravine walls are the major sediment source in the ravines. A sensitivity analysis revealed that the erodibility coefficients of the gully bed and wall, the local slope angle and the Manning’s coefficient are the key parameters controlling the rate of sediment production. Recommendations to guide further monitoring efforts in the watershed and increased detail modeling approaches are highlighted as a result of this modeling effort.

The diploma thesis is focused on the topic of pre-treatment of rainwater before entering the infiltration tank. The theoretical part deals with the issue of rainwater, their division and pollution, as well as technical solutions for rainwater management. In the practical part, testing of selected street drains of various construction systems in the laboratory of VHO (municipal water management) was performed and subsequently these drains were evaluated according to various criteria - the amount of captured material, drain cleaning system and filter construction.

The thesis deals with analysis of factors contributing to the development of ephemeral gully erosion on area of the Czech Republic. Method used to direct measurements of ephemeral gully erosion was developed. The statistical sample of gullies was measured to describe the characteristics of ephemeral gullies. Statistical methods were used to compute simple and multiple linear regression models. The models describe relationships between ephemeral gully parameters or factors contributing to development of ephemeral gully. The thesis is concentrated with the development of methodology for prediction the occurrence and prediction of parameters of ephemeral gullies. The methodology can be used to design the optimal erosion control measures in the conditions of the Czech Republic.

Gullies are significant contributors of sediment to streams in the southeastern USA. This study investigated gully erosion in the clay-rich soils of east Tennessee under a humid subtropical climate. The aims of this study were to (1) estimate long-term erosion rates for different gully geomorphic settings, (2) compare patterns of erosion for the different settings, and (3) model the response of gully erosion to freeze-thaw events. Erosion was measured weekly from June 2012 to August 2018 using 105 erosion pins distributed in gully channels, interfluves, and sidewalls. Erosion rates were estimated from average slopes of lines of best fit of pin lengths versus time. Maximum and minimum temperature was calculated daily using an on-site weather station and freeze-thaw events were identified. Gully erosion was modeled using antecedent freeze-thaw activity for the three geomorphic settings. Long-term erosion rates in channels, interfluves, and sidewalls were 2.5 mm/year, 20 mm/year, and 21 mm/year, respectively; however, week-by-week erosion was statistically different between the three settings, indicating different erosive drivers. Models of erosion with lagged freeze-thaw variables explained up to 34.8% of the variability in erosion variables; sidewall erosion was most highly related to freeze-thaw activity. Freeze-thaw in prior weeks was an important variable in all erosion models.

Gully erosion is a global problem that degrades land and reduces its utility for agriculture, development, and water quality. Quantification of sediment yield and control of sediment sources is essential for environmental protection. Five methods to evaluate erosion rates and sediment yield on an east Tennessee, USA, hillslope were compared: (1) physical measurement by removal of accumulated sediment using 10 L buckets; (2) repeated measurement of erosion pins in gully (erosional) and delta (depositional) areas; (3) geometric model using a combination trapezoidal prism-cylinder segment; (4) geometric model using a series of trapezoidal pyramids; and (5) 3D solid computer modeling. The 3D solid model created in SolidWorks was selected as the reference model and all other methods overestimated sediment yield to varying degrees. Erosion pin methods overestimated sediment yield by 368% in deltas and 123% in gullies. Volumetric measurement of sediment using buckets overestimated sediment yield by 160% due to void space in the buckets. The trapezoidal prism-cylinder segment model overestimated sediment yield by 66% and the trapezoidal pyramids method overestimated sediment yield by 5.7%. For estimation of sediment trapped behind an elliptical or circular silt fence dam, use of the trapezoidal pyramid method provides a good approximation comparable to 3D solid computer modeling.