Riparian buffers are a commonly utilized best management practice (BMP) for mitigating non-point source pollution from agricultural fields. This practice is most effective when runoff enters the buffer as sheet flow. However runoff from becomes concentrated and forms concentrated flow paths (CFPs) breaking through the buffer in critical erosional areas. These critical areas can be determined prior to the implementation of a BMP such as a riparian buffer through incorporation of the Revised Universal Soil Loss Equation (RUSLE) with Geographic Information Systems (GIS). This approach utilizes field characteristics with hydrological processes in order to determine the erosion risk areas from observed field data throughout an entire watershed. In order to re-establish a riparian buffer in critical areas managers need a method that can prevent erosion and the loss of top soil. This study evaluates an innovative method, "Buffer in a Bag", used to restore riparian buffer benefits and to prevent further erosion in CFPs. There were three different treatments initiated for this study the first two treatments the "Buffer in a Bag", and Hand-Planted were implemented prior to the broadcasting of switchgrass seed. The final treatment was the Control, which required no planting within the treatment plot. The "Buffer in a Bag" treatment utilized the placement of giant cane rhizomes within burlap bags along the channel of concentrated flow. The hand planted treatment utilized the placement of giant cane rhizomes planted in the agricultural field adjacent to the path of concentrated flow. The presence of these CFPs breaking through riparian buffers has been noted, but the actual significant soil erosion occurring within the CFP and in the adjacent field has yet to be quantified. Through the use of topographical surveys and geostatistical analysis to produce digital elevation models (DEM) of in-field elevation changes the hydrological processes and volumetric difference for CFPs can be determined. The goal was to define the variability and the spatial pattern from the data as a means of providing comparisons between subsequent survey periods over time and space to estimate the difference and movement of sediment within CFPs. The volumetric differences found when comparing the DEMs between survey periods provide a quantifiable method for evaluating the implementation of a treatment, such as the "Buffer in a Bag". Using geostatistical analysis of volumetric difference between the treatment plots determined that that there was no significant difference between the CFP's over the study period. The mean percentage volumetric difference within the treatment plots between "Buffer in a Bag", Hand-Planted, and Control treatments were -2.49%, -3.72%, and -2.37%, respectively. There was overall net erosion across all treatments with the erosion and accumulation being significantly different across the survey periods for all the treatment CFPs. The mean percentage volume loss across treatments and survey periods varied from positive 10% accumulation to negative 15% erosion for overall loss when looking at each individual survey and CFP. The displayed loss of valuable topsoil and continued expansion of these concentrated flow paths emphasis the need for research in further management applications. There needs to be an effective method developed to address the volumetric difference within CFPs forming in these high risk erosion areas. Using a GIS/RUSLE approach to indicate these high risk erosion areas will hopefully facilitate the prevention of the formation of concentrated flow paths prior to the implementation of a BMP, such as riparian buffers.

Sediment and nutrient loss from agricultural landscapes contributes to water quality impairment and has the potential to impact crop yield. Best management practices (BMPs) such as riparian buffers have been designed to combat these issues; however, concentrated flow paths (CFPs) reduce their effectiveness and are often overlooked in agricultural fields. Conventional management of CFPs is to fill and grade them, however this provides only a short term solution leading to their reformation and increased sediment loss. The objectives of this project were: i) to determine if the filling of CFPs influence crop growth (yield and biomass), ii) determine a distance at which crop growth is no longer influenced by CFPs, iii) assess the impact that topography and CFPs have on crop growth, iv) analyze water quality in surface runoff leaving crop fields via CFPs, and v) develop an economic analysis for CFP’s influence on crop returns. Six small agricultural catchments, CFPs, and topographic positions (i.e., depositional, backslope, and shoulder) were delineated using ArcGIS and LiDAR data. In each catchment, six 4 m2 plots were established along CFPs where crop biomass and crop yield were measured. Additionally, six plots with no influence from CFPs were established as reference plots. Surface water quality was assessed by taking edge-of-field grab samples at the CFP outlet during significant rain events (i.e., precipitation exceeding 2.5 cm). Water samples were analyzed for total suspended solids (TSS), total phosphorus (TP), dissolved reactive phosphorus (DRP), ammonium-nitrogen (NH4+-N), and nitrate-N (NO3- -N). Through this study it was shown that CFPs served as a conduit for transporting nutrient and sediment laden runoff to receiving waters, that increasing/decreasing distance from CFPs had an impact on crop yields, and that there was no crop yield advantage from the filling of CFPs vs. leaving them unfilled. Median values for NO3-N (1.85 mg L-1) and TSS (140 mg L-1) in the Fill catchments were higher than the No-Fill catchments (0.77 mg L-1 and 35.5 mg L-1, respectively), while DRP and TP concentrations were higher in the No-Fill catchments (1.31 mg L-1 and 2.37 mg L-1, respectively) compared to the Fill catchments (0.91 mg L-1 and 1.83 mg L-1, respectively) over the growing season. Crop biomass and yield results between the depositional and backslope positions were similar regardless of treatment, but were lower than the reference plots and shoulder position. Results from the economic analysis on the cost of farming in/near CFPs indicated that the economic return was greatly dependent on precipitation. CFPs are generally concave positions on the landscapes and have been eroded to a clayey subsoil, both resulting in greater water accumulation and retention than elsewhere in the field. During wetter years, an economic loss was incurred nearest to the CFP and during drier years, sites nearest to CFPs saw positive returns. Farmers and land managers may consider implementing stabilization measures, such as grassed waterways, in CFPs since crop yields are typically lower in wetter years, there’s increased cost to maintain these areas, and accelerated sediment loss can exacerbate the crop yield losses and impact on water quality.

Riparian buffers in agricultural landscapes are designed to trap pollutants in overland flow by slowing, filtering, and infiltrating surface runoff entering the buffer via sheet flow. However, observational evidence suggests that concentrated flow is prevalent from agricultural fields. Also, over time sediment can accumulate in riparian buffers forming berms that restrict sheet flow from moving into the buffers; these berms ultimately back up surface runoff, resulting in an eventual breakthrough which concentrates runoff. Breakthrough by concentrated flow can lead to gully formation that may reduce the filtering capacities of buffer systems by providing direct conduits to stream channels. This study explores the frequency of concentrated flow paths in riparian buffers at both the field and watershed scale. At the field scale, intensive topographic surveys were conducted at 10 field sites in southern Illinois to characterize concentrated flow paths, accumulated berm sediments, and field area drained by concentrated flow. Detailed digital elevation models (DEMs) were created for each site and riparian buffer and agriculture field characteristics were analyzed to assess the development and occurrence of concentrated flow paths. At each site, soil samples were analyzed to characterize sediment deposition patterns within the buffer. To assess the prevalence of concentrated flow paths at the watershed scale, three watersheds in southern Illinois were selected for walking stream surveys. Five stream segments, approximately 1000 m long, were randomly selected within each watershed and surveyed for the occurrence and size of concentrated flow paths. These data were analyzed with respect to riparian buffer vegetation, buffer width, and surrounding land cover data. Concentrated flow paths were identified in all topographic surveys and all walking stream surveys indicating a common occurrence in agricultural watersheds of southern Illinois. Among field scale sites, concentrated flow accounted for 82.5-100% of the drainage areas contributing to riparian buffers. Results from the watershed scale analysis suggest that concentrated flow paths are significantly more abundant in agricultural land cover, than forested land. Current riparian buffer design principles are based on the assumption that sheet flow is the primary form of surface runoff entering buffers. Furthermore, buffers are installed and not maintained which can lead to berm accumulation and buffer failure. Results from this study indicate that concentrated flow was the prevalent form of runoff at field scale sites. Managers need to consider the occurrence of concentrated flow paths when designing riparian buffers to protect stream water quality.

Field scale research shows concentrated flow paths (CFPs) are prevalent in agricultural watersheds. They are an important source of soil erosion in cropland and significantly contribute to the transport and delivery of agricultural pollutants such as sediment and nutrients to nearby water resources. High resolution LiDAR data have enabled the investigation of the prevalence of concentrated flow at a large geographic extent. This study focused on identifying CFPs in 389 agricultural fields in Jackson County in southern Illinois and estimating the contribution of the CFPs to drainage of the fields. Addressing the lack of literature on factors influencing CFP characteristics, this study also investigates various topographical and soil factors that influence CFP development. LiDAR derived DEMs with a cell resolution of 3 meters were used to identify areas of flow concentration and delineate a drainage basin of each CFP using the Hydrology tools in the Spatial Analyst toolbox in ArcMap 10.3.1. Information on the topographical and soil characteristics were obtained from the DEMs and SSURGO database using the Soil Data Viewer 6.2 extension for ArcMap. Multiple regression analysis in SAS v. 9.4 was used to identify factors influencing CFP characteristics, while CART analysis in R v. 3.3.1 was conducted to detect linear dependencies among predictor variables. An average of 5 CFPs per agricultural field were observed in the study area with a minimum of 0 and maximum of 17 CFPs, but only two fields had no CFPs indicating a high prevalence of CFPs throughout the study area. The mean percent of field area drained by CFPs was estimated to be 81 percent with minimum of 36 percent and ii maximum of 100 percent. The majority of the fields, 85 percent, had more than 70 percent of their area drained by CFPs. Statistically significant regression equations were found for all CFP characteristics with slope, LS factor, K factor and organic matter as the factors influencing CFP characteristics. However, the factors only explained 2 to 22 percent of variation observed. Both multiple regression and CART analysis indicated slope as the most important influencing factor. Variation in CFP characteristics followed regional trends with higher values in the floodplain region and lower values in the rough hills region suggesting residual variation could be explained by other environmental factors along with topographical and climatological factors which were not included in the study. Results from this study highlight the prevalence of CFPs at a regional scale and their substantial contribution to field drainage identifying a need for research in quantifying the impacts of CFP on soil loss and water quality. This study also reports a need of future research to identify important factors controlling CFP formation and development that could help build empirical and physical models to accurately predict CFP locations and morphology. Such information could be useful in designing and targeting conservation practices that protect both soil health and water quality.

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.

No description available.

[pt] Apresenta-se neste trabalho uma ferramenta numérica programada que permite a simulação bidimensional de corridas de detritos usando o Método de Elementos Discretos (DEM) desenvolvido por Cundall em 1979, cuja metodologia resolve as equações do movimento simultaneamente de cada elemento mediante a técnica numérica de Relaxação Dinâmica (MRD) por se tratar de um problema transiente. Esta metologia parte da existência do programa SAND desenvolvido na PUC (2002) para uma simulação da produção de areia em poços de petróleo sob fluxo bifásico. Dois aspectos novos incorporados neste tipo de análise são a representação gráfica de anteparos mediante segmentação de curvas spline cúbicas e o uso da metodologia de Munjiza na detecção de contatos com os propósitos de implementar o uso de paramentos irregulares próximos à curva real do terreno e diminuir o tempo de execusão do programa, respectivamente. Com diversos exemplos de paramentos e variando os parâmetros de entrada do modelo numérico é avaliada a idoneidade da ferramenta criada para simular os principais mecanismos físicos característicos do movimento deste tipo de fenômeno. Além disso, são descritas em detalhe as principais feições e terminologias usadas na classificação e identificação das corridas de detritos e fenômenos similares, pois estas são usualmente confundidas nas literaturas existentes e entre os profissionais das áreas da Geologia, Geografia e Geotecnia. / [en] A programed numerical tool that allows two-dimensional simulation of debris flows is presented in this dissertation. Cundall´s Distinct Element Method (DEM) is used to this purpose, which was developed in 1979. Following this methodology, motion equations are simultaneilly solved by the numerical method of Dynamic Relaxation (MRD) for each distinct particle. This method is used in order to the transient behavior of this particular problem. The numerical modeling is based on the SAND program, developed at PUC (2002) for a numerical application on sand production for petroleum extraction process considering biphasic flow motion. Two new features incorporated in this kind of analyses are the graphical representation of walls with cubic spline curves segmentation and the implementation of the Munjiza´s method for contact detection. They attemp to implement irregular curves that are closely to represent real sliding surface and to decrease the total program executation time respectively. The idoneousness of the programed numerical tool for the representation of the most caracteristic phisical mechanisms of these kind of flows is tested using several curves configurations as variation on the inicial parametrics values of the numerical model. Moreover, main features and associated terminologies for identification and classification of debris flows and similar events are largely described here because of the usual confusion in the use of them within scientific literatures and professional communications between technician of Geology, Geography and Geotechnical Engineering. / [es] En este trabajo se disponibiliza una herramienta numérica para la simulación bidimensional de flujos de detritos usando el Método de Elementos Discretos (DEM) creado por Cundall en 1979, donde las ecuaciones del movimiento para cada elemento son resueltas simultáneamente con la técnica numérica de Relajación Dinámica (MRD) debido al comportamiento transiente del fenómeno. La herramienta se basa en el programa SAND desarrollado en la PUC (2002) para la simulación de producción de arena en la extracción de petróleo en pozos considerando condiciones de flujo bifásico. Dos nuevos aspectos se introducen en este tipo de análises: la representación gráfica de paredes mediante la segmentación de curvas splina cúbicas y el uso de la metodologia de Munjiza en la detección de contactos. Ambos son implementados con la intención de hacer uso de paredes irregulares próximas a la forma real de la curva del terreno y de disminuir el tiempo de ejecución del programa respectivamente. Mediante varios ejemplos con diferentes superficies y con variación en los valores de los parámetros de entrada del modelo numérico fue posible evaluar la idoneidad de la herramienta aquí creada para simular los principales mecanismos físicos característicos del movimiento de este tipo de fenómenos. Además, se describen detalladamente las principales características e terminologías utilizadas en la identificación y clasificación de los flujos de detritos y fenómenos similares, pues estos son motivos de confusión en la literatura existente y entre los profesionales de las ramas de Geología, Geografía y Geotecnia.

El presente trabajo se basa en un modelamiento hidrológico e hidráulico de la quebrada del Diablo que se ubica en el distrito de Alto de la Alianza de la ciudad de Tacna. Cuyo fin es plantear un mapa de amenaza para reducir el impacto de los flujos hiperconcentrados y mejorar la planificación urbana de dicho distrito. Para el modelamiento hidrológico, se procedió con la caracterización de la zona de estudio a través de informes e imágenes satelitales, asimismo, se realizó un análisis de las precipitaciones en la zona de la cabecera de la quebrada. Generando así, una base de datos de entrada para el HEC-HMS para obtener los caudales máximos para periodos de retorno de 50, 100, 200, 250 y 500 años. El modelamiento hidráulico de los flujos se realizó con el software FLO-2D, teniendo en cuenta las diversas metodologías existentes en los artículos para definir los parámetros reológicos como son el esfuerzo de cedencia y la viscosidad propios de la zona de estudio. Posteriormente, se obtuvo los tirantes y velocidades máximas de las diversas simulaciones para los diferentes periodos previamente mencionados. Por último, se realizó un análisis del nivel de amenaza en la zona urbana a través de mapas generados por el software FLO-2D Mapper para los diferentes escenarios planteados. Además, se evaluó el efecto de colocar estructuras de mitigación a lo largo del cauce de la quebrada del diablo y contrastar los valores de profundidades, velocidades y nivel de amenaza en la zona urbana. / This work is based on hydrological and hydraulic modeling of the Diablo creek located in the Alto de la Alianza district of the city of Tacna. The purpose of this is to create a hazard map to reduce the impact of hyper-concentrated flows and improve the urban planning of said district. For the hydrological modeling, we proceeded with the characterization of the study area through reports and satellite images, also, an analysis of the rainfall in the area of ​​the head of the stream was carried out. Thus, generating an input database for the HEC-HMS to obtain the maximum flows for return periods of 50, 100, 200, 250, and 500 years. The hydraulic modeling of the flows was carried out with the FLO-2D software, taking into account the various existing methodologies in the articles to define the rheological parameters such as the yield stress and the viscosity of the study area. Subsequently, the maximum tie rods and speeds were obtained from the various simulations for the different periods previously installed. Finally, an analysis of the level of threat in the urban area was carried out through maps generated by the FLO-2D Mapper software for the different scenarios proposed. In addition, the effect of placing mitigation structures along the creek of the devil was evaluated and contrasting the values ​​of depths, speeds, and levels of threat in the urban area. / Tesis