Water erosion in the Czech Republic is the largest phenomenon that degrades and seriously damages agricultural areas throughout the country. It is influenced by many factors that have changed since the 1950s. Various methods are used to assess the intensity of erosion. In the Czech Republic, the USLE (Universal Soil Loss Equation) is the most widely used equation, which is the cornerstone of the model used in this work. I quantified and localized water erosion in the Odlezel lake basin for individual scenarios of land use change using the WaTEM / SEDEM model. The results show the seriousness of water erosion in relation to landscape management, as the modeled intensity of erosion in 2018 is almost the same as in the period of collectivization. The results of modeling are confronted with changes of individual input factors, with measured data of river sediment export in the Mladotický brook and up to date knowledge about clogging of the lake basin. Key words: water erosion, modeling erosion, WaTEM/SEDEM

This study investigates gully erosion on an east Tennessee hillslope in a humid subtropical climate. The study area is deeply gullied in Ultisols (Acrisol, according to the World Reference Base for Soil), with thirty years of undisturbed erosional history with no efforts to correct or halt the erosion. The objectives are (1) to examine how different gully morphologies (channel, sidewall, and interfluve) behave in response to precipitation-driven erosion, and (2) to identify an appropriate temporal scale at which precipitation-driven erosion can be measured to improve soil loss prediction. Precipitation parameters (total accumulation, duration, average intensity, maximum intensity) extracted from data collected at an on-site weather station were statistically correlated with erosion data. Erosion data were collected from erosion pins installed in four gully systems at 78 locations spanning three different morphological settings: interfluves, channels, and sidewalls. Kruskal-Wallis non-parametric tests and Mann-Whitney U-tests indicated that different morphological settings within the gully system responded differently to precipitation (p<0.00). For channels and sidewalls, regression models relating erosion and precipitation parameters retained antecedent precipitation and precipitation accumulation or duration (R2=0.50, p<0.00 for channels, R2=0.28, p<0.00 for sidewalls) but precipitation intensity variables were not retained in the models. For interfluves, less than 20% of variability in erosion data could be explained by precipitation parameters. Precipitation duration and accumulation (including antecedent precipitation accumulation) were more important than precipitation intensity in initiating and propagating erosion in this geomorphic and climatic setting, but other factors including mass wasting and eolian erosion are likely contributors to erosion. High correlation coefficients between aggregate precipitation parameters and erosion indicate that a suitable temporal scale to relate precipitation to soil erosion is the synoptic time-scale. This scale captures natural precipitation cycles and corresponding measurable soil erosion.

Federal, state and local governments are increasingly focused on the effects of development on water quality and quantity. With waterbodies being especially sensitive to certain pollutants, such as sediment and nutrients, regulations have been put in place to control the amount of pollutant that gets discharged. Sediment is a cause for concern as it originates during both rural and urban activities, and often carries other pollutants (metals, nutrients, etc.) with it. Existing erosion models focus primarily on estimating erosion from agricultural watersheds. Methods are needed to predict areas with high erosive potential (EP) in urban watersheds. Highlighting highly erosive areas in urbanized watersheds allows for the prioritization of maintenance and installation of Stormwater Control Measures (SCMs), and monitoring of sediment by municipal planners and engineers. This study utilizes commonly available geospatial layers in conjunction with a computational procedure to compute relative EP risk throughout a target urban watershed. A case study of the developed methodology was performed on a watershed in Blacksburg, VA, to generate EP risk maps. Results of the study indicate areas of erosive potential within the target watershed and provide a methodology for creating erosion potential risk maps for use by municipal planners and engineers / Master of Science

As more dams experience spillway flows from flood events, identification and analysis of erosion in auxiliary rock surface spillways has become a primary focus in maintaining dam integrity. The spillway erosion risk assessment developed for this research is based on parameters identified and discussed in previous research as the leading factors influencing spillway damage from erosion. Parameters applied in this analysis were channel geometry, stream hydrology, and geologic materials. Channel geometry is described by the length of spillway channel and slope of the spillway floor; stream hydrology is classified by the peak discharge and its duration; and geologic material is identified by its behavior in resisting erosion. The Sites Spillway Erosion Analysis (SSEA) was used to produce a risk assessment based on U.S. Army Corps of Engineers case histories. The risk assessment was used to classify and refine model uncertainties, an important advancement in evaluating spillway erosion.

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Call number: LD2668 .T4 1959 L95

Electricity has been proved to be a crucial factor to achieve an economic and social development in emergent countries and is seen as a necessity to deplete the world’s poverty. As energy resources are getting scarce, a higher implementation of renewable electricity generation, such as hydropower, is a necessity. Hydrokinetic turbines, which use slow flowing water as a source of energy, are to be installed in the Amazonas River in Colombia. The Amazon River has high amount of sediment and flowing objects due to the large quantity of vegetation in the area. This leaves the turbine exposed to a higher degree of erosion on the blades and a higher risk of getting clogged. The efficiency will decrease and the turbine will have an impending risk of getting damaged. By adapting the hydrokinetic turbine for the conditions prevailing in the Amazon basin, the efficiency can be improved and a longer lifetime for the turbine is given. A field study was conducted to attain the velocity and amount of sediment in the Amazon River through measurements. The collected data was analyzed and used as input values during simulations of a turbine model by the Computational Fluid Dynamics program COMSOL. Areas on the turbine exposed to the water with a high velocity, and containing a high concentration of sediment, were examined and proposals for protection were given. Also the necessity and consequences of installing a protective grate in front of the turbine were investigated. The turbine will be exposed to almost a factor of 12 000 higher erosive wear in the Amazon River than in Swedish water as of the higher amount of sediment. The investigation states that areas on the tip of the blade’s rear side and the area close to the rotating center are most exposed to erosion and will be in need of protection in form of a harder surface. A grate will be necessary to provide a longer lifetime for the turbine, but will result in a decreased power output from the turbine by up to 46 %. / Elektricitet har bevisats vara en viktig komponent för en ekonomisk och social utveckling i utvecklingsländer och ses därför som en nödvändighet för att minska fattigdomen i världen. Energikällorna är dock hårt utnyttjade och en högre andel förnyelsebar elektrisk generering, genom bland annat vattenkraft, är en nödvändighet. Hydrokinetiska turbiner, vilka producerar el på långsamt flödande vatten, ska implementeras i Amazonfloden i Colombia. Amazonfloden har en hög andel sediment samt flytande objekt i floden på grund av den höga andel vegetation i området. Detta ger en ökad erosion på bladen samt risk för igentäppning av turbinen efter implementering. En lägre effektivitet samt hög risk för skada på turbinerna erhålls. Genom att adaptera den hydrokinetiska turbinen för förhållanden som råder i Amazonasfloden kan verkningsgraden förbättras och en längre livslängd på turbinen kan erhållas. En fältstudie utfördes där mätningar över vattenhastigheter, mängd sediment samt större objekt i floden genomfördes och analyserades. Data användes sedan som indata vid simuleringar över en uppbyggd modell av turbinen i Computational Fluid Dynamics-programmet COMSOL Multiphysics. Områden på turbinen utsatta för sedimentfullt vatten med en högre hastighet undersöktes och skyddsåtgärder föreslogs. Även behovet av ett skyddande galler framför turbinen granskades. Det visades att turbinen kommer utsättas för nästintill en faktor på 12 000 högre erosion i Amazonasfloden jämfört med i svenska vatten. Undersökningen visar att yttersta delarna av bladets baksida samt ett område nära det roterande centret är i behov av ett extra skydd i form av en hårdare yta. Ett galler kan bli nödvändigt för att uppnå en längre livstid för turbinen, men resulterar i en sänkt elproduktion med upp till 46 %.

published_or_final_version / Applied Geosciences / Master / Master of Science

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No description available.