A systems approach, utilizing a deterministic hydrologic simulation model and an optimization model, was developed to evaluate and optimize cropland Best Management Practices (BMPs). The approach consisted of using the Finite Element Storm Hydrograph Model (FESHM) to simulate runoff and sediment yield from a series of design storms with known return periods. The design storm simulations were the basis for sediment distributions representing unique cropland areas and management practices. The distributions were evaluated to obtain average annual sediment yields which were used as activity coefficients in a linear programming (LP) optimization model. The LP model selected the set of cropland management practices that minimized total sediment yield while meeting economic and agricultural production constraints. A postoptimality analysis was performed on the optimal solution to examine the effects of variations in: (1) income levels representing subsidy, and (2) sediment coefficients. The optimal solution was found to be insensitive to reductions in income levels (representing subsidy) and extremely sensitive to changes in the sediment coefficients. Limitations of the systems procedure models were discussed along with suggestions for improving the sediment coefficients and their practical usage. / Master of Science

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], v, 101 p. : ill. Includes bibliographical references (p. 63-64).

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A study of the state of reservoir sedimentation in South Africa based on reservoir sediment deposit data, has shown that a considerable number of reservoirs have serious sedimentation problems. The analysis of the reservoir sediment deposit data showed that almost 25% of the total number of reservoirs have lost between 10 to 30% of their original storage capacity. The average storage loss due to sedimentation in South African reservoirs is approximately 0.3% per year while the average annual storage loss for all the reservoirs in the world is 0.8%. The aim of this research was to develop sediment yield prediction methods based on analytical approaches and mathematical modelling. The sediment yield prediction methods can be used in planning and management of water resources particularly in reservoir sedimentation control. The catchment erosion and sediment yield modelling methods can be applied in temporal and spatial analysis of sediment yields which results are essential for detailed design of water resources, particularly in the identification of critical erosion areas, sediment sources and formulation of catchment management strategies. Current analytical methods for the prediction of sediment yield have been reviewed. Nine sediment yield regions have been demarcated based on the observed sediment yields and catchment characteristics. Empirical and probabilistic approaches were investigated. The probabilistic approach is based on analysis of the observed sediment yields that were calculated from reservoir sediment deposit, river suspended sediment sampling data and soil erodibility data. The empirical equations have been derived from regression analysis of the variables that were envisaged to have a significant effect on erosion and sediment yields in South Africa. Empirical equations have been developed and shown to have accurate and reliable predictive capability in six of the nine regions. The probabilistic approach has been recommended for the prediction of sediment yields in the remaining three regions where reliable regression equations could not be derived. The predictive accuracy of both the probabilistic and empirical approaches was checked and verified using the discrepancy ratio and graphs of the observed and calculated data. While the analytical methods are needed to predict the sediment yield for the whole catchment, mathematical modelling to predict sediment yields is applied for more detailed analysis of sediment yield within the catchment. An evaluation of available catchment sediment yield mathematical modelling systems was carried out. The main criteria for the choice of a numerical model to be adopted for detailed evaluation was based on the following considerations: the model’s capabilities, user requirements and its application. The SHETRAN model (Ewen et al., 2000) was therefore specifically chosen because of its ability to simulate relatively larger catchment areas (it can handle catchment scales from less than 1km2 to 2500km2), its ability to simulate erosion in channels, gullies and landslides, its applicability to a wide range of land-use types and ability to simulate land use changes. Another model, ACRU (Smithers et al., 2002) was also reviewed. The aim of the model evaluation was to provide a conceptual understanding of catchment sediment yield modelling processes comprising model set up, calibration, validation and simulation. The detailed evaluation of the SHETRAN model was done through a case study of Glenmaggie Dam in Australia. The flow was calibrated and validated using data from 1975 to 1984, and 1996 to 2006 respectively. The results for both the calibration and validation were reasonable and reliable. The sediment load was validated against turbidity derived sediment load data from 1996 to 2006. The model was used to identify sources of sediment and areas of higher sediment yield. The land use of a selected sub-catchment was altered to analyse the impact of land use and vegetative cover on the sediment yield. Based on the results, the SHETRAN model was confirmed to be a reliable model for catchment sediment yield modelling including simulation of different land uses. / AFRIKAANSE OPSOMMING: ‘n Studie van die stand van damtoeslikking in Suid-Afrika toon dat daar ernstige toeslikkingsprobleme by baie reservoirs bestaan. ’n Ontleding van die toeslikkingsyfers gegrond op damkomopmetings toon dat omtrent 25% van die totale getal reservoirs tussen 10 en 30% van hulle oorspronklike opgaarvermoë verloor het. Die gemiddelde tempo van damtoeslikking in Suid-Afrika is 0.3%/jaar, wat laer is as die wêreld gemiddeld van 0.8%/jaar. Die oogmerk met hierdie navorsing was om sedimentlewering voorspellingsmetodes te ontwikkel deur gebruik te maak van analitiese metodes en wiskundige modellering. Die sedimentlewering voorspellingsmetodes kan gebruik word vir die beplanning en bestuur van waterbronne en veral vir damtoeslikking beheer. Die opvangsgebied erosie en die sedimentlewering modelleringsmetodes kan toegepas word in tydveranderlike en ruimtelike ontleding van sedimentlewering. Hierdie inligting word benodig vir die detail ontwerp van waterhulpbronne en veral vir die identifisering van kritiese erosiegebiede, bronne van sediment en die formulering van opvangsgebied-bestuur strategië. ‘n Literatuuroorsig oor die huidige metodes vir die voorspelling van erosie en sedimentlewering is gedoen. Nege sedimentasie streke is afgebaken in Suid-Afrika, gegrond op waargenome damtoeslikkingsdata en opvangsgebied-eienskappe. Proefondervindelike en waarskynlikheidsbenaderinge is ondersoek. Die waarskynlikheidsbenadering is gegrond op die ontleding van waargenome damtoeslikking wat bereken is uit reservoir opmeting data en rivier gesuspendeerde sediment data, asook data oor gronderosie. Die proefondervindelike metode se vergelykings is afgelei vanuit regressie ontleding van die veranderlikes wat ‘n belangrike invloed het op die erosie en sedimentlewering in Suid-Afrika. Daar is bevestig dat die ontwikkelde proefondervindelike (empiriese) vergelykings ‘n akkurate en betroubare voorspellingsvermoë in ses van die nege streke het. Die waarskynlikheidsbenadering is aanbeveel vir die voorspelling van sedimentlewering in die ander drie streke, waar betroubare regressie vergelykings nie afgelei kon word nie. Die voorspellingsakkuraatheid van albei metodes is nagegaan en bevestig deur gebruik te maak van die teenstrydigheidsverhouding en grafieke van die waargenome en berekende data. Analitiese metodes van sedimentleweringsvoorspelling is nodig vir ‘n volle opvangsgebied, terwyl wiskundige modellering om sedimentlewerings te voorspel gebruik kan word om ‘n meer in diepte ontleding van die sedimentlewering binne ‘n opvanggebied te doen. ‘n Evaluasie van beskikbare wiskundige modelle wat opvangsgebied sedimentlewering kan voorspel, is gedoen. Die hoofkriteria vir die keuse van ‘n model vir gebruik by gedetailleerde ontleding is gegrond op die volgende: die vermoëns van die model, wat verbruikers benodig en die aanwending van die model. Die SHETRAN model (Ewen et al., 2000) is spesifiek gekies weens sy vermoë om relatief groter opvangsgebiede te simuleer (dit kan opvangsgebiede van 1km2 tot 2500km2 wees) asook om erosie in kanale, dongas en grondverskuiwing simuleer. Dit kan toegepas word op ‘n wye reeks grondtipes en kan ook die gevolge simuleer as die gebruik van die grond verander. ‘n Ander model, ACRU (Smithers et al., 2002) is ook ondersoek. Die doel van die modelevaluering was om ‘n konseptuele begrip te kry van sedimentlewering modelleringsprosesse wat die opstelling, kalibrasie, toetsing en simulasies insluit. Die volledige evaluasie van SHETRAN is gedoen deur middel van ‘n gevalle-studie van die Glenmaggiedam in Australia. Die riviervloei is gekalibreer en getoets deur gebruik te maak van data wat strek van 1975 tot 1984, en van 1996 tot 2006 onderskeidelik. Die resultate van beide die kalibrasie en die toetswas redelik en betroubaar. Die sedimentlading is gekalibreer teen velddata van 1996 tot 2006. Die model is gebruik om bronne van sediment te identifiseer, asook gebiede met ‘n hoër sedimentlewering. Die gebruik van die grond op ‘n gekose sub-opvangsgebied is verander om die impak van grondgebruik en plantbedekking op sedimentlewering te ontleed. Die resultate bewys dat die SHETRAN model ‘n betroubare model is vir groot opvangsgebied sedimentlewering modellering, asook vir die simulasie van verskillende grondgebruike.

Sedimentation (erosion, transport, and deposition) is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to environmental, engineering, and agricultural sedimentation problems. The field experiments for this research includ physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. This research project has proposed, developed, and tested a new method for evaluation of sediment size from theoretical acoustic attenuation; evaluated and further developed recently introduced empirical methods for estimating acoustic attenuation by sediment; found and quantified data mischaracterization issues for laser-diffraction metrics; defined deterministic causes for observed hysteresis and variance in suspended sediment to surrogate relations; compared the accuracy of sediment concentration models and loads for each tested surrogate; and compared sediment surrogate technologies on the basis of reliability and operational considerations.

Hazelmere Dam situated on the Mdloti River in KwaZulu-Natal has, since its completion in 1977, lost 25 % of its original design capacity through sedimentation. This storage loss has brought about an environmental concern as well as a socio -economic threat to the region. The aim of this research was to investigate the effect of land use change on the sedimentation rate in the catchment. This was undertaken to obtain a better understanding of the processes and leads towards an integrated catchment management strategy. Geographical information systems afforded the opportunity to determine land use change from a number of sequential land use maps and to run statistical analyses and overlays. It was determined that a large change in land use had taken place between subsistence cultivation/small-scale agriculture and subsistence grazing. The rainfall, soil and slope conditions cause the catchment to have a naturally high erosion potential. As a result of the interrelated nature of all these factors in the catchment the most effective manner in which to deal with the sedimentation problem is through a multidisciplinary approach such as is afforded by integrated catchment management strategies. In terms of controlling the sedimentation problem in the Hazelmere Dam recommendations concerning conservation practices necessary in minimising the impact of the land use practices and changes are made for inclusion in such a management approach. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.

Contaminants introduced in solution to coastal waters eventually accumulate in sediment. Pollution by these contaminants is only evident when biological effects occur. Geochemical procedures lack the ability to identify biological effects of pollution. Biological methods (i.e. community structure analyses and/or bioassays) are currently the best available techniques for pollution assessment. Standardised and locally relevant protocols for pollution assessment are lacking in many developing countries, including South Africa. This study aims to develop a sediment toxicity testing protocol using an amphipod species endemic to South Africa, Grandidierella lignorum. Initial research focussed on establishing ranges of physico-chemical parameters (i.e. salinity, temperature, sediment grain size and organic matter content) within which sediment toxicity tests should be performed. The sensitivity of the amphipod was then determined by exposing the amphipod to cadmium, copper and zinc at various salinities. Lastly, the amphipod was exposed to effluents (to test the amphipod’s sensitivity in water only tests) and whole sediment (to tests the amphipod’s sensitivity to solid phase material). G. lignorum tolerates salinities between 0 and 56, but prefers salinities between 7 and 42. Preferred salinity range is modified by temperature, with salinity of 42 becoming less tolerable. Salinities between 7 and 35 are most preferred at 10-25°C. G. lignorum prefers fine- (27.48±12.13%), medium- (25.11±12.99%) and coarse-grained sand (21.45±8.02%). Sediment with low (≤2%) organic matter content is most preferable, regardless of sediment grain size or type of organic matter (protein-rich vs. carbohydrate-rich). Cadmium toxicity decreased with increasing salinity (LC₅₀: 0.34 ± 0.17 mg l⁻¹ (salinity of 7), 0.73 ± 0.05 mg l⁻¹ (salinity of 21) and 1.08 ± 0.49 mg l⁻¹ (salinity of 35)). Zinc toxicity increased with decreasing salinity (1.56 ± 0.33 mg l⁻¹ at a salinity of 21 to 0.99 ± 0.13 mg l⁻¹ at a salinity of 7) and with increasing salinity (from salinity of 21 to 0.82 ± 0.19 mg l⁻¹ at a salinity of 35). Copper toxicity did not differ significantly with salinity and ranged between 0.72 ± 0.18 mg l⁻¹ (salinity of 35) and 0.89 ± 0.24 mg l⁻¹ (salinity of 21). Toxicity testing using Grandidierella lignorum should be performed in coarse- to fine-grained sediment at salinities of 7 - 35, at 10 – 25°C. Amphipods do not need to be fed during toxicity testing. A control chart using cadmium as a reference toxicant was established to determine the acceptability of toxicity results. Toxicity test results should be accepted when cadmium toxicity falls between 0.49 and 4.02 mg l⁻¹. The amphipod responded consistently to effluents and was able to discriminate polluted and unpolluted sediment in Durban Bay. Recommendations for refining the effluent and sediment toxicity test are suggested. / Ph.D. University of KwaZulu-Natal, Durban 2013.

abstract: Vegetative filter strips (VFS) are an effective methodology used for storm water management particularly for large urban parking lots. An optimization model for the design of vegetative filter strips that minimizes the amount of land required for stormwater management using the VFS is developed in this study. The resulting optimization model is based upon the kinematic wave equation for overland sheet flow along with equations defining the cumulative infiltration and infiltration rate. In addition to the stormwater management function, Vegetative filter strips (VFS) are effective mechanisms for control of sediment flow and soil erosion from agricultural and urban lands. Erosion is a major problem associated with areas subjected to high runoffs or steep slopes across the globe. In order to effect economy in the design of grass filter strips as a mechanism for sediment control & stormwater management, an optimization model is required that minimizes the land requirements for the VFS. The optimization model presented in this study includes an intricate system of equations including the equations defining the sheet flow on the paved and grassed area combined with the equations defining the sediment transport over the vegetative filter strip using a non-linear programming optimization model. In this study, the optimization model has been applied using a sensitivity analysis of parameters such as different soil types, rainfall characteristics etc., performed to validate the model / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2015

M.Sc. (Aquatic Health) / Sediments can contain a variety of organic and inorganic contaminants. These contaminants accumulate, resulting in extremely high concentrations even once the overlying water concentrations are at or below acceptable water quality guidelines. Any changes in the physical parameters of the overlying water can cause these pollutants to be released back into solution. Accumulated contaminants can be released at even higher concentrations than previously detected. In recent years, sediment contamination has highlighted the need to monitor these previously overlooked pollutant sources that have accumulated in aquatic ecosystems. South Africa does not currently have standardised methods to assess sediment toxicity. Although international methods exist, they are largely untested in South Africa and the organisms needed to conduct these tests are not readily available. Over the years numerous culture methods have been develop globally for culturing organism to be used for water and sediment toxicity tests. In South Africa, the focus has mainly been on culturing organisms for water toxicity testing. Sediment toxicity testing with indigenous organism however, was not developed. Established international culture methods from the United States Environmental Protection Agency, the Organisation for Economic Cooperation and Development, and Environment Canada were taken into consideration when developing the laboratory culture method for two(2) of the selected organisms (Chironomus spp. & Hydra sp.) from this study. A preliminary culture method was also developed for the third selected organism, Melanoides tuberculata (gastropod). The organisms cultured in this study were selected based on their extent of contact with the substrate, ease of handling, availability, culture maintenance as well as their reproductive cycle. The Hydra, Chironomids and M. tuberculata cultures were successfully breeding under laboratory conditions and remained stable. The Chironomus sp. and M. tuberculata maintain contact with the sediment making them suitable as ecologically relevant organisms for use in whole sediment toxicity testing in South Africa.

Silt fence is one of the most widely used perimeter control devices and is considered an industry standard for use in the control of sediment transport from construction sites. Numerous research studies have been conducted on the use of silt fence as a perimeter control, including a number of studies involving controlled laboratory flume tests and outdoor tests performed in the field on construction sites with actual monitored storm events. In field tests, due to the random and uncontrollable nature of real storm events and field conditions, studies have shown difficulty in evaluating silt fence performance. These field studies have shown the need for performance testing of silt fence in a more controlled environment, which can also simulate the actual use and performance in the field. This research, which is a continuation of ongoing research on silt fence fabrics at UCF Stormwater and Management Academy, was conducted in order to evaluate silt fence performance under simulated field conditions. Presented in this thesis are evaluation of two silt fence fabrics, a woven (ASR 1400) fabric and nonwoven (BSRF) fabric. Both fabrics were installed separately on a tilted test bed filled with a silty-sand soil and subjected to simulated rainfall. Previous field studies on the performance of silt fence fabrics have evaluated the turbidity and sediment removal efficiencies only after the rain event, with the assumption that the efficiency values represent the true overall performance of silt fence. The results of this study revealed that the turbidity and suspended sediment performance efficiencies of silt fence were significantly affected by the time of sampling. The performance efficiencies during rainfall remained less than 55 percent, however, after the rainfall event ended, the performance efficiencies increased over time, reaching performance efficiency upwards of 90 percent. The increase in efficiency after rainfall was due to the constant or decreasing ponding depth behind the silt fence, increased filtration due to fabric clogging, and sedimentation of suspended particles. The nonwoven fabric was found to achieve higher removal efficiencies and flow-through rates both during and after the rain event when compared with the woven fabric. However, over the entire test duration (during and after rainfall combined), the projected overall efficiencies of both fabrics were similar. The projected overall average turbidity performance efficiencies of the woven and nonwoven silt fence fabrics was 80 and 78 percent, respectively. Both fabric types also achieved comparable overall average suspended sediment concentration efficiencies of 79 percent. This result leads to the conclusion that silt fence performance in the field is dependent on three main processes: filtration efficiency occurring during the rain event, filtration and sedimentation efficiency occurring after the rainfall event, and flow-through rate of the silt fence fabrics. Decreases in the flow-through rate lead to increases in the overall efficiency. This thesis quantifies the different mechanisms by which these processes contribute to the overall efficiency of the silt fence system and shows how these processes are affected by different conditions such as the degree of embankment slope and rainfall intensity.

Geotextildukar används idag som tillfällig kontroll av sedimentgrumling vid vattenarbeten. Syftet med examensarbetet är att ge ökad kunskap kring olika geotextildukars genomsläpplighet med avseende på suspenderat material, PAH (Polycykliska aromatiska kolväten) och kvicksilver vid suspension av sediment från Karlbergskanalen. Detta har gjorts genom en laboration. Resultaten visar att det inom några minuter bildas en filterkaka på de tre undersökta dukarna. Dukarna blir täta då de utsätts för finpartikulärt suspenderat sediment med koncentrationen 57 g/l hämtat från Karlbergskanalen. Under de 2,5 timmar långa försöken har dukarnas permeabilitet kraftigt reducerats. Under laborationen var PAHtot och mängden PAH i den filtrerade fraktionen störst vid turbiditetsmaximum. Den filtrerade fraktionen PAH följde turbiditeten och reducerades med 21 % samtidigt som turbiditeten reducerades med 24 % under försöket. Även den totala kvicksilvermängden var störst vid turbiditetsmaximum, resultaten är dock inte statistiskt säkerställda. Under laborationen gav en högre halt suspenderat material en lägre andel PAH i den filtrerade fraktionen, troligtvis beroende på re-adsorption. För att utvärdera hur stor andel av PAH, kvicksilver, kadmium och koppar som befinner sig i den filtrerade fasen har det genomförts försök där sediment och vatten skakats 3x10 timmar. Av den totala PAH koncentrationen var 0,07 % i den lösta fasen. Endast en låg andel av koppar, kadmium och kvicksilver återfanns i den lösta fasen (< 1 %). Trots den låga andelen i den filtrerade fraktionen skulle motsvarande haltökningar i Karlbergskanalen innebära halter långt över aktuella gränsvärden[1]i dukbassängen. Innan filterkakan bildats sker ingen reduktion av turbiditeten för två av de tre undersökta dukarna. Geotextilskärmarna förhindrar således ingen spridning av miljögifter utan bildningen av en filterkaka. Om filterkakan bildas och består i fält går inte att fastställa utifrån laborationen. [1]MKN MAC för löst Hg och Cd, Naturvårdsverkets föreslagna GV för löst Cu MKN MAC för den totala PAH koncentrationen / Geotextiles are used as temporary sediment controls in water during construction work. The aim of this project is to give background information to a cost effective control program and to increase the knowledge about geotextiles and their permeability for suspended sediment, PAH and Hg for a site specific sediment. Laboratory studies have been conducted in order to evaluate three geotextiles with regard to their ability to separate suspended sediment, PAH and Hg. The results show that a filter cake is formed. The textiles became clogged within a time period of 15 minutes and no sediment passed the textiles after this. A sediment concentration of 57 g/l was used. The separation of suspended particulate matter is 28-78 % and the textile with the greatest reduction capacity was the thinnest one. The separation of PAHtot was 79 %, meanwhile the average separation of suspended sediments was 78 %. The geotextile did not reduce the dissolved fraction of PAH. This fraction was larger on the outside suggesting that the concentration of suspended material was too low to re-adsorb the dissolved PAH. The turbidity decreased with 24 % during the experiment due to sedimentation, the dissolved fraction of PAH was reduced with 21 % during the same time period. The amount of Hgtot was largest at turbidity maximum. Laboratory experiments where sediment was shaken 3x10 hours with distilled water have also been conducted in order to evaluate the amounts of PAH, Hg, Cu and Cd that partition in the dissolved phase. 0, 07 % of the total amount of PAH was found in the filtered phase and only small fractions of Cu, Cd and Hg (< 1 %). Despite the small percentage in the filtered fractions the corresponding increase in Karlbergskanalen would result in concentrations well above maximum allowed concentrations[1]in the geotextile encircled area. There is no reduction of the turbidity before the filter cake is formed. It is not possible to draw any conclusions about the formation of a filter cake in field and if a formed filter cake would be broken by hydraulic forces or not. [1]MKN MAC for dissolved Hg and Cd, Swedish Environmental Protection Agency’s suggested limit value for dissolved Cu, MKN MAC for the total PAH concentration