The subject matter of the thesis is the identification of concentrated runoff waterways in the landscape and their consequent stabilization. The municipalities of Čejkovice and Mutěnice in the South Moravian region were analysed in order to reach this purpose. The thesis introduces theoretical bases for the definition of concentrated runoff waterways and their application in the calculation. The area was analysed on the basis of the digital elevation model in ArcGIS software environment. The CN curves method by means of the hydrological model DesQ – MAX Q was used for the calculation of concentrated runoff waterways.

Climate changes are predicted to increase precipitation intensities and occurrence of extreme rainfall events in the near future. Scandinavia has been identified as one of the most sensitive regions in Europe to such changes; therefore, an increase in the risk for flooding, landslides and soil erosion is to be expected also in Sweden. An increase in the occurrence of extreme weather events will impose greater strain on the built environment and major transport infrastructures such as roads and railways. This research aimed to identify the risk of flooding at the road-stream intersections, crucial locations where water and debris can accumulate and cause failures of the existing drainage facilities. Two regions in southwest of Sweden affected by an extreme rainfall event in August 2014, were used for calibrating and testing a statistical flood prediction model. A set of Physical Catchment Descriptors (PCDs) including road and catchment characteristics was identified for the modelling. Moreover, a GIS-based topographic Index of Sediment Connectivity (IC) was used as PCD. The novelty of this study relies on the adaptation of IC for describing sediment connectivity in lowland areas taking into account contribution of soil type, land use and different patterns of precipitation during the event. A weighting factor for IC was calculated by estimating runoff calculated with SCS Curve Number method, assuming a constant value of precipitation for a given time period, corresponding to the critical event. The Digital Elevation Model of the study site was reconditioned at the drainage facilities locations to consider the real flow path in the analysis. These modifications led to highlight the role of rainfall patterns and surface runoff for modelling sediment delivery in lowland areas. Moreover, it was observed that integrating IC into the statistic prediction model increased its accuracy and performance. The calibrated model was then validated in another area, located in the central part of Sweden, affected by severe rainfall event in August 2004, in order to verify its robustness even in ungauged catchments.

The consequences of recent flooding and extreme rain events have highlighted the importance of proper urban planning and preventative measures for storm water management. As cities become more urbanized the significance of permeable surfaces such as parks and other urban green spaces increases which infiltrate the water into the ground. Agricultural research has for many years emphasized the effect of compaction on soil parameters and how, not only the crop yield reduces but also how the infiltration decreases. This thesis aims to study how the infiltration rate, bulk density and soil resistance changes with compaction through field experiments where a vehicle is let to roll over an urban green area. The thesis will also simulate rainfall over five theoretical soils that can be found in urban environments exposed to compaction to determine what significance compaction has on surface runoff. The modelling software HYDRUS-1D will be used so simulate rain fall events on the different soils. The rain events simulated will be based on the five hyetographs that best represent Sweden’s rain events, based on historical data. A CDS rain will be simulated as well. They will be simulated for a 2, 10 and 100 year return period. A literature study will also be conducted to determine how relevant freeze-thaw cycles are to the soil parameters. It is since previously known that freeze-thaw cycles can improve aggregate stability, increase soil particle fragmentation which can lead to less soil penetration resistance and even partially return the soil conditions to those prior to compaction, but the process does not extend to layers beyond 40 cm. The field experiment results showed a clear decrease in infiltration rate with increasing number of vehicle passes. There was no clear correlation between bulk density and the number of vehicle passes. This result is attributed to the relatively light weight of the vehicle used as well as the heterogeneity of the soil. The cone penetration measurements showed an increasing resistance with increasing number of vehicle passes for only one of the three measured sites, with the most resistance being measured in a pathway on the green area. The insignificant results of one of the two other sites are attributed to wet weather conditions and unknown underlying material. The HYDRUS 1D simulations showed that a higher sand content mitigates the effects of soil compaction and leads to less runoff. The soil classified as sand (93% sand) had no runoff, the loamy sand (80% sand) had mild runoff. When comparing a sandy loam (60% sand) and a clay soil it is concluded that the sandy loam is more sensitive to soil compaction as more compaction leads to more runoff compared to the non-compacted scenario. The clay soil has little variation between the compaction scenarios but has generally more surface runoff in total. Soil texture therefor affects the surface runoff more than soil compaction. Most amount of runoff was generated by the two hyetographs which had a late peak intensity, most likely due to the soil already being saturated when the peak occurs. The runoff also increases with the return period of the rain event for both the hyetographs and the CDS rain.

Contemporary row-crop practices in the mid-southern, USA contribute to declining water tables and impairment of downstream waters, threatening the sustainability of irrigated agriculture and vital ecosystem services. This research was conducted to determine if various conservation practices and technologies can economically reduce negative environmental consequences of regional corn (Zea mays L.) production. The environmental, agronomic, and economic effects of implementing cover crops, manipulating traffic pattern, and integrating irrigation water management (IWM) technologies (computerized hole selection, surge irrigation, and soil moisture sensors) were investigated at either the small plot or field scale in the Delta region of Mississippi. Cover crop effects on runoff, water quality, corn grain yield, and net returns were primarily neutral or negative. Under furrow irrigation, cover crops did not affect runoff or nitrogen and phosphorus transport, but decreased erosion 16%. No cover crop decreased rainfall-induced runoff, erosion, or N and P transport. Over the four years of the experiment, cover crops maintained or decreased yield, net returns, and water use efficiency. Eliminating equipment traffic from furrows largely maintained or reduced runoff and subsequent contaminant transport. For both furrow irrigation and simulated rainfall, runoff and erosion were consistently less from nontraffic furrows than traffic furrows. Traffic effects on nutrient transport was more variable. Transport of some phosphorus constituents was decreased in the absence of furrow traffic; however, rainfall-induced nitrogen transport was greater from nontraffic furrows during the late-season event. Irrigation water management technologies improved corn grain yield, net returns, and irrigation water use efficiency across multiple locations in the mid-southern USA. Relative to standard production practices, implementing IWM technologies reduced total water applied 40% and increased corn grain yield 6.5 bu acre-1, which constituted a 51% increase in irrigation water use efficiency. The decrease in cost for irrigation water applied and increase in returns from yield gains exceeded the cost of the IWM technologies and resulted in an increase in net returns across a range of pumping depth and diesel price scenarios. Of the evaluated conservation strategies, reducing equipment traffic and implementing IWM technologies will most consistently improve the sustainability of irrigated agriculture and ecosystem services in the mid-southern USA.

Antibiotics and antibiotic resistance genes from animal manure applied to soil as fertilizer are now among the most concerned contaminants in soil. The widespread use of antibiotics in livestock might amplify the risk of developing antibiotic resistance, causing once treatable diseases to turn deadly. The World Health Organization declared antibiotic resistance as "one of the biggest threats to global health, food security, and development". The goal of this dissertation was to develop best manure management practices by understanding the behavior of manure-associated antibiotics in manure, water, and soil. In particular, my research focused on the effects of manure application methods, on-site manure treatment methods, manure application seasons, and manure-rainfall time gaps on antibiotic surface runoff losses, antibiotic distribution and movement in soil, antibiotic dissipation in soil, and development of antibiotic resistance. Rainfall simulation field-scale and soil incubation lab studies were combined to find the best manure management practices. My research has shown for the first time that using the manure soil subsurface injection method, especially during spring application season due to moist soil, applying manure at least 3 days before a subsequent rainfall, and using composted manure, can significantly reduce the quantity of antibiotic loss with runoff from manure-applied fields to the surrounding environment. The majority of applied antibiotics remained in soil. All antibiotics showed a similar dissipation pattern with fastest kinetics during the first 14 d before slowing down. The effect of two manure application methods on antibiotic dissipation kinetics varied with different antibiotics. Although the half-life of tested antibiotics in soil was short (<21 days), some remained detectable even at 6 months after a single manure application. Results also showed that compared to the surface application, the subsurface injection slits acted as a "hot zone" with a higher amount of antibiotics, manure microbes, and antibiotic resistance. The results provide information for policy makers, manure managers, and farmers to develop better manure management practices that can use manure as fertilizer while minimizing the spread of antibiotics to surrounding water, soil, and plants. / Doctor of Philosophy / There is growing concern about antibiotic resistance as a serious human health threat because a resistant infection may kill, can spread, and increases health costs. Every year in the United States, there are 2 million people infected with antibiotic resistant bacteria, 23,000 people die as a direct result of these infections, and $55 billion is lost due to increased hospital stay and lost work days. Although bacteria naturally develop the ability to resist antibiotics, the problem is the length between antibiotic introduction and resistance development is shortening because of the widespread and overuse of antibiotics, especially in the livestock industry. The goal of this study was to develop the best manure management practices balancing the benefits of antibiotics in livestock and animal manure and their impact on the environment. In particular, we monitored, using field-scale and laboratory studies, the effects of manure application methods, on-site manure treatment methods, manure application seasons, and manure-rainfall time gaps on antibiotic loss through surface runoff, antibiotic distribution and movement in soil, antibiotic dissipation in soil, and development of antibiotic resistance. In order to reduce the amount of antibiotic loss with surface runoff from manure-applied fields to the surrounding environment, farmers are recommended to 1) compost manure before application, 2) watch the forecast to apply manure at least 3 days before a subsequent rainfall, and 3) use the subsurface injection method, especially when the soil is wet (spring season). The majority of applied antibiotics remained in soil. All tested antibiotics showed a similar dissipation pattern with the fastest rate during the first two weeks after manure application, then slowing down. Although the half-life of tested antibiotics in soil was short (<21 days), some remained detectable even at 6 months after a single manure application. Besides, the subsurface injection slits acted as a hot zone with a concentrated amount of antibiotics, manure microbes, and antibiotic resistance. The results provide recommendations for policy makers, manure managers, and farmers to maximize benefits of manure as fertilizer while minimizing the spread of manure-associated antibiotics to surrounding water, soil, and plants.

Modelling surface runoff can be beneficial to operations within many fields, such as agriculture planning, flood and drought risk assessment, and water resource management. In this study, we built a data-driven model that can reproduce monthly surface runoff at a 4-km grid network covering 13 watersheds in the Chesapeake Bay area. We used a random forest algorithm to build the model, where monthly precipitation, temperature, land cover, and topographic data were used as predictors, and monthly surface runoff generated by the SWAT hydrological model was used as the response. A sub-model was developed for each of 12 monthly surface runoff estimates, independent of one another. Accuracy statistics and variable importance measures from the random forest algorithm reveal that precipitation was the most important variable to the model, but including climatological data from multiple months as predictors significantly improves the model performance. Using 3-month climatological, land cover, and DEM derivatives from 40% of the 4-km grids as the training dataset, our model successfully predicted surface runoff for the remaining 60% of the grids (mean R2 (RMSE) for the 12 monthly models is 0.83 (6.60 mm)). The lowest R2 was associated with the model for August, when the surface runoff values are least in a year. In all studied watersheds, the highest predictive errors were found within the watershed with greatest topographic complexity, for which the model tended to underestimate surface runoff. For the other 12 watersheds studied, the data-driven model produced smaller and more spatially consistent predictive errors. / Master of Science / Surface runoff data can be valuable to many fields, such as agriculture planning, water resource management, and flood and drought risk assessment. The traditional approach to acquire the surface runoff data is by simulating hydrological models. However, running such models always requires advanced knowledge to watersheds and computation technologies. In this study, we build a statistical model that can reproduce monthly surface runoff at 4-km grid covering 13 watersheds in Chesapeake Bay area. This model uses publicly accessible climate, land cover, and topographic datasets as predictors, and monthly surface runoff from the SWAT model as the response. We develop 12 monthly models for each month, independent to each other. To test whether the model can be applied to generalize the surface runoff for the entire study area, we use 40% of grid data as the training sample and the remainder as validation. The accuracy statistics, the annual mean R2 and RMSE are 0.83 and 6.60 mm, show our model is capable to accurately reproduce monthly surface runoff of our study area. The statistics for August model are not as satisfying as other months’ models. The possible reason is the surface runoff in August is the lowest among the year, thus there is no enough variation for the algorithm to distinguish the minor difference of the response in model building process. When applying the model to watersheds in steep terrain conditions, we need to pay attention to the results in which the error may be relatively large.

Increased stormwater runoff due to urban development in the northern Shenandoah Valley (NSV) region of Virginia has prompted local officials and representatives to consider Low Impact Development (LID) as a stormwater management technique. LID is based on infiltrating stormwater runoff at the source through practices such as bioretention, rain gardens, and grass swales. The karst terrain that underlies the Shenandoah Valley presents a major barrier to the use of LID. Infiltration of surface runoff in karst landscapes may threaten groundwater quality and the stability of the bedrock. In 2004 the Center for Geospatial Information Technology (CGIT) at Virginia Tech developed an LID site suitability model for the NSV region incorporating karst as a key component in distinguishing unsuitable from suitable conditions for LID. But, due to the difficulty of mapping karst, the karst layer used in the site suitability model is very coarse in resolution, based primarily on carbonate versus non-carbonate rock. This study uses a 1:24,000 scale sinkhole map derived from sinkhole boundaries identified by geologist David Hubbard (1984) of the Virginia Department of Mines and Minerals (DMME) to develop a more detailed karst map for a sub-watershed of the NSV region. The analysis uses geospatial techniques to determine the relationship between sinkhole distribution and four major landscape factors: bedrock type, soil depth to bedrock, proximity to geologic faults, and proximity to surface streams. The analysis identified three major trends in sinkhole occurrence: (1) sinkholes are more abundant in relatively pure carbonate rocks of Ordivician age; (2) sinkhole occurrence increases with proximity to fault lines; and (3) sinkholes are sparse near streams, most abundant 600 to 1400 feet away from surface streams. Based on these findings a sinkhole susceptibility index was produced using weighted overlay analysis in ArcGIS. The sinkhole susceptibility index provides a more detailed karst layer for the LID site suitability maps and can be used by the NSV region as a predictive tool for future sinkhole occurrence. / Master of Science

No description available.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Factors influencing surface run-off of bitumen emulsions were studied in order to understand binders for use in the construction of surfacing seals. Run-off of the binder from the road surface causes an inconsistent film thickness leading to ravelling (Johannes, Hanz & Bahia n.d.) and bleeding at the upstream and downstream regions, respectively. There is currently no accepted specification for surface run-off viscosity. Practice mainly relies on empirical tests and experience. As the establishment of such a specification encompasses performance of the binder in various environments or field conditions, this study was undertaken to determine performance of the selected binder. Viscosity was kept constant by spraying the emulsion at a constant temperature and also holding the pavement temperature constant. In order to study the run-off behaviour of the binder, run-off tests were conducted at various gradients, texture depths and spray rates. Surfacing seals of various texture depths were constructed in the laboratory. Using a spray bar, the emulsion was sprayed at various spray rates. The sample surfaces were tilted to various gradients. Results portrayed the effects of the three factors (spray rate, gradient and texture depth) on the amount of runoff. An increase in the magnitude of the factors resulted in a variation in the runoff (increase or decrease). One notable finding was that the runoff from the 9.5 mm seal was less than that from the 13.2 mm seal. The other significant finding was that spray rate had the largest effect on runoff, followed by texture depth, and gradient. / AFRIKAANSE OPSOMMING: Sekere eienskappe wat oppervlakdreinering van bitumen emulsies op paaie beinvloed, is bestudeer om sodoende binders wat gebruik word in die konstruksie van die seëls beter te verstaan. Afloop van die binder vanaf die padoppervlak kan lei tot die vorming van ‘n laag met ongelyke dikte wat moontlike rafeling (Johannes, Hanz & Bahia nd) en bloeing vanuit die onderkant van die pad tot gevolg kan hê. Daar is tans geen aanvaarde spesifikasies wat hierdie verskynsels inperk nie. Konstruksie praktyk berus hoofsaaklik op empiriese toetse en ondervinding. Hierdie studie is dus onderneem om prestasie van die geselekteerde binder vas te stel. Viskositeit was konstant gehou deur die aangewende emulsie en padtemperatuur konstant te hou. Ten einde die afloopgedrag van die binder te bestudeer, is toetse uitgevoer op verskeie hellings, tekstuurdieptes en aanwendingskoerse. Seëls van die verskillende tekstuurdieptes is gebou in die laboratorium, en emulsies op hierdie oppervlaktes aangewend. Die toetsoppervlakte is gekantel om die vereiste helling te kry. Resultate vir die drie faktore wys die invloed op afloop. ‘n Toename in die grootte van die faktore het gelei tot 'n variasie in die afloop (toename of afname). Een noemenswaardige bevinding was dat die afloop van die seël van 9,5 mm minder was as dié van die seël van 13,2 mm. Belangrike bevindinge sluit ook in dat die spuitkoers die grootste invloed het op afloop, gevolg deur die tekstuur diepte en die gradiënt.

ALMEIDA, Cícero Lima de. Impacto da recuperação de área degradada sobre as respostas hidrológicas e sedimentológicas em ambiente semiárido. 2011. 132 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola, Fortaleza-CE, 2011. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-06-17T13:36:15Z No. of bitstreams: 1 2011_dis_clalmeida.pdf: 3766101 bytes, checksum: 4476b1021ccb20f6b1f9c8caaabe3473 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-06-17T13:39:51Z (GMT) No. of bitstreams: 1 2011_dis_clalmeida.pdf: 3766101 bytes, checksum: 4476b1021ccb20f6b1f9c8caaabe3473 (MD5) / Made available in DSpace on 2016-06-17T13:39:51Z (GMT). No. of bitstreams: 1 2011_dis_clalmeida.pdf: 3766101 bytes, checksum: 4476b1021ccb20f6b1f9c8caaabe3473 (MD5) Previous issue date: 2011 / As regiões semiáridas compreendem áreas muito sensíveis às alterações do seu ambiente natural. O semiárido brasileiro, por ser um dos mais populosos do mundo, está mais susceptível às atividades antrópicas, como o desmatamento para atividades agrosilvopastoris. Esta pesquisa foi desenvolvida no âmbito do projeto “Estudos dos processos de degradação/desertificação e suas relações com o uso da terra em sistemas de produção no semiárido cearense: o caso da microrregião de Sobral – Ceará”. A área experimental localiza-se no município de Irauçuba, inserida em um dos núcleos de desertificação do semiárido brasileiro. O clima da região é do tipo quente e semiárido com chuvas de verão (média anual de 530 mm) e índice de aridez 0,34. O solo é do tipo Planossolo Nátrico Órtico típico, A fraco; e a vegetação nativa é do tipo Caatinga arbustiva aberta. A principal atividade econômica da região é a pecuária extensiva (bovino e ovino) em sobrepastejo, sem uso de práticas conservacionistas. O presente trabalho tem como objetivo comparar os processos hidrossedimentológicos de duas encostas em ambiente semiárido: uma (370 m²) está submetida à prática de pousio desde 2000; enquanto que a outra (468 m²) se encontra degradada, sendo usada como área de pastagem há mais de vinte anos. As duas encostas possuem as mesmas condições de solo, clima e relevo, diferenciando-se somente quanto ao uso e à cobertura do solo. São comparadas analiticamente variáveis hidrológicas e sedimentológicas. Os experimentos foram realizados entre 01 de janeiro de 2010 e 15 de abril de 2011. Para promover essa comparação foram coletados dados de precipitação (lâmina e intensidade), escoamento superficial e perda de solo. A precipitação foi de 264 mm em 2010 e de 445 mm até 15 de abril de 2011, tendo sido registrados 55 eventos nos 16 meses. As chuvas de Irauçuba demonstraram alta variabilidade espacial: há diferença estatística (nível de significância de 5%) entre os dois pluviômetros usados na pesquisa, embora estejam a uma distância de apenas 200 m. O padrão hidrológico das chuvas na região é de intermediário a atrasado (70% dos eventos), o que causa maior potencial erosivo. Conclui-se, a partir da análise comparativa, que os dez anos de pousio reduziram em 60% o escoamento superficial em relação à encosta degradada. A menor precipitação capaz de gerar escoamento superficial foi 7,2 mm na encosta degradada, enquanto que esse valor foi de 8,6 mm para a encosta em pousio. Isso demonstra o incremento de abstração inicial da encosta preservada, ou seja, sua maior capacidade de retenção de umidade. O incremento da capacidade de retenção se dá através da interceptação vegetal, da serrapilheira e da camada superficial do solo. No entanto, observou-se que a maior precipitação incapaz de gerar escoamento superficial foi idêntica (17 mm) nas duas encostas. A explicação para tal resultado é que o parâmetro dominante nesse processo é a estrutura do solo: embora haja diferenças na superfície dos solos, os dez anos de pousio ainda não foram capazes de alterar sua estrutura, conforme avaliou Sousa em pesquisa independente. Observou-se que a taxa de decaimento da vazão foi sensivelmente afetada pela prática de pousio: a taxa, de 0,107 min-1 na encosta degrada, decresceu para 0,045 min-1 na encosta preservada. A menor taxa de decaimento de vazão na encosta em pousio indica o início da recuperação de seu escoamento de base, o que favorece maior permanência da água no corpo hídrico. Os dez anos de pousio também foram capazes de reduzir a perda de solo. Essa redução, de 83% em relação à encosta degradada, induz à melhoria das condições físicas, químicas e biológicas do solo, responsáveis pelo incremento da produção vegetal. Conclui-se, com base nos experimentos aqui realizados, que os dez anos de pousio melhoraram, de modo mensurável, as condições hidrológicas e sedimentológicas na encosta semiárida. A prática de pousio, portanto, pode ser adotada para fins de recuperação de áreas de Caatinga degradada. Sugere-se que sejam realizadas novas investigações, que avaliem a associação dessa prática a outras, a fim de intensificar o processo de recuperação de áreas degradadas no semiárido