Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 168 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 148-167).

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Traditional culvert designs, in many cases, have become habitat barriers to aquatic animal species. In response, environmentally sensitive culvert designs have been developed to function as ecological bridges. Bottomless and buried invert culverts are examples of such designs and are commonly used for fish passage. Additional design guidance specific to streambed stability in buried-invert or bottomless culverts under high flow events is needed. This study investigated incipient motion conditions for four substrate materials in a 2-ft (0.61-m) diameter circular bottomless arch culvert and in a 1-ft (0.30-m) wide rectangular flume in a laboratory setting. General scour of the streambed within the bottomless arch culvert was also investigated under partially pressurized and non-pressurized flow conditions. This thesis discusses the experimental methods used to determine incipient motion conditions and analyses of incipient motion prediction methods. This thesis also presents the experimental results obtained from both test facilities with the results of other published incipient motion studies on gravel streambeds. Finally, the prediction efficiency of eight stone sizing methods (open channel and culvert application) applied to the experimental results was analyzed, which may be useful for determining stable stone diameters to be used as riprap in simulated streambeds through bottomless culverts.

This thesis investigates the shore processes of Lake Pukaki to assess the suitability and performance of existing and potential future options for management of shore hazards. Following two successive raisings of the water level in the past sixty years, Lake Pukaki’s shoreline has undergone extensive erosion. Since mid 1987 until early 1988, shoreline erosion control structures (i.e. rock revetments, gabion baskets and groynes) were constructed and maintained to protect sections of road and other assets from further encroachment of the lake shoreline. The use of the RBR XR-620 pressure sensor in this study marks the first occasion when wave statistics were measured via instrumentation at Lake Pukaki. The mean significant wave height (Hs) identified for this study was 0.53 m, while the maximum recorded wave height was 1.84 m. Similar to other alpine lakes, Lake Pukaki has characteristics of steep plunging waves. The LAKEWAVE wave hindcasting model is used to describe the wave environment about the Lake Pukaki shoreline in terms of its optimum energy potential. The maximum wave height and wave period values estimated by LAKEWAVE have been found to compare well with measured wave statistics. Under the current wave climate, experienced during this study period (July 2010 – February 2011), the majority of the assessed rock revetments seem to be performing well. The Hudson and Van der Meer formula seemed to predict respectable stability thresholds that agree with what was observed in the field. The revetment at Site 3 is the biggest concern in terms of performance based on field observations. The short-period high-magnitude storm events, eventuating from a strong north/northwest wind flow, that coincide with high lake levels tend to cause the most significant erosion along the shoreline at Lake Pukaki and have a major influence of riprap stability. Other environmental factors including the steep nearshore profile, the glacial till backshore, groundwater and precipitation were identified as controlling factors leading to the success or failure of the shore protection structures.

Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Riprap is commonly used as an erosion protection measure around the world. In some cases, for example when constructing bed arrestors, riprap has to be designed to be stable on steep slopes. The literature shows that the problem of incipient motion is reasonably well understood, but existing hydraulic design methods are found to be largely unreliable. The main objective of this study is to improve the understanding of the different factors affecting incipient motion in order to furnish the prospective design engineer with a reliable method for sizing riprap on steep slopes adequately. Eight existing theories dealing with the threshold of incipient motion are reviewed, of which Liu’s work (1957) seems most promising. Naturally, the required median rock diameter of the riprap is reasonably large (due to the steep slopes), with high particle Reynolds numbers. However, little data is available for these flow conditions. Data collected from 12 large scale laboratory tests carried out for this research indicate that the dimensionless Movability Number is in fact constant for large particle Reynolds numbers. For design purposes, the recommended Movability Number which emerged from this study is 0.18, provided that the steep bed slope is taken into account, and that the theoretical settling velocity is calculated using an accurate drag coefficient and the d90 sieve size. A comparison of the laboratory data with design equations showed that a large variety of results are obtained, which supports the need for this study. Finally, it was shown that a calibrated one dimensional hydrodynamic model can be used by the practicing engineer to extract the hydraulic properties needed for applying Liu’s theory. It was found that the ratio ks/d90 = 0.81 may be applied to estimate the bed roughness for the grading used in this study. / AFRIKAANSE OPSOMMING: Stortklip is ‘n metode wat wêreldwyd gebruik word om erosie te voorkom. In sommige gevalle, byvoorbeeld vir die konstruksie van erosietrappe, moet stortklip teen steil hellings spesifiek ontwerp word om stabiliteit te verseker. Die literatuur beskryf die probleem van aanvanklike beweging redelik goed, maar dit is bevind dat die bestaande ontwerpmetodes grotendeels onbetroubaar is. Die hoofdoelwit van hierdie ondersoek was om die faktore wat beweging van stortklip veroorsaak, beter te verstaan en ‘n betroubare metode te ontwikkel wat ’n ingenieur kan aanwend om stortklipbeskerming wat op steil hellings geplaas word te ontwerp. Agt verskillende metodes wat die begin van beweging beskryf is bestudeer, en dit wil voorkom asof die Liu teorie van 1957 die grootste potensiaal het. As gevolg van die steil hellings wat ondersoek word, is die benodigde klipgroote redelik groot wat weereens die oorsaak is vir ‘n hoë deeltjie Reynolds getal is. In die literatuur kon geen data gevind word vir so ‘n vloeitoestand nie. Daarom is 12 laboratoriumtoetse gedoen en daar is gevind dat die Mobiliteitsgetal redelik konstant is vir groot deeltjie Reynoldsgetalle. Vir onwerpdoeleindes word ‘n Mobiliteitsgetal van 0.18 aanbeveel, met die voorwaarde dat die bodemhelling in ag geneem word, en dat die teoretiese valsnelheid bereken word met die d90 klipgroote en ‘n akkurate sleurkoëffisiënt. Verder is gevind dat die labaratorium data die voorspellings van die bestaande ontwerpvergelykings nie bevredigend pas nie. Dit ondersteun die behoefte vir hierdie studie. Om die bogenoemde bevindings vir praktiese probleme bruikbaar te maak, is daar gewys dat ‘n gekalibreerde een dimensionale hydrodinamiese rekenaarmodel gebruik kan word om die nodige hidrouliese eienskappe te verkry om die Liu teorie toe te pas. Dit is bevind dat die verhouding ks/d90 = 0.81 ‘n goeie benadering vir die hidrouliese ruheid kan voorsien.

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The construction of big electrical power dams on the São Francisco river channel have led to changes in its hydrological system and altered its discharge and sediment s transport behaviour, and then generating some environmental impacts and potencialized others. The accelerated bank erosion is considered one of the most harmful ones leading to application of various of alternatives in order to control it and consequently the channel sedimentation. This research was developed in order to monitor bank erosion process in the right margin of the Low San Francisco River, during January 2004 until February 2005, in four different sites located from Propriá to the river estuary, studying the possible causes and also the riprap efficiency in order to control the river bank erosion. The pegs methods was used to measure erosion rate and to describe it the profiling method was used in four different sites (A, B, C and D). Water Level Indicators in three of the studied sections was installed in order to study the subterranean waters flux on the river banks. The annual rates of bank erosion was 2,06 meter to site A, 4,06 meter to site B, 4,35 meter to site C and 10,03 meter to site D. They are lower numbers then was recorded in previous years, explained by the redesign of the bank morphology promoted by the occurenc of January 2004 flood, which promotes an apparent stabilization of the erosion process. The variation of erosion among the sites was related to the localization, soil texture, the bank height climate and hydrological features, also wind speed, monthly amplitude waves near the edge and the hydraulic flux from soil to the river. The behavior of riprap constructed in order to control the erosion is efficient in the most of locals they were implanted, although they could collapse in the future because of lack of studies related to the river morphological changes near them. These data can subsidy public decisions in order to minimize the environment negative impacts caused by unsustainable natural resources uses in the San Francisco River Basin. / A implantação de grandes projetos hidrelétricos na Bacia do Rio São Francisco tem provocado modificações no regime hídrico e alterado o comportamento de descarga e transporte da carga sólida do rio, e, assim, gerado impactos ambientais ou potencializado outros. A acelerada erosão marginal é considerada uma das mais graves alterações ambientais nesta bacia hidrográfica e tem levado à implementação de várias alternativas para o seu controle e do conseqüente assoreamento. Este estudo teve como objetivos monitorar as taxas de recuo da margem direita do rio São Francisco, no período de janeiro de 2004 a fevereiro de 2005, em quatro seções localizadas no trecho entre o município de Propriá e a foz do rio, estudar as causas do processo e verificar a eficiência dos enrocamentos implantados no controle da erosão no trecho em estudo. Para quantificação das taxas de erosão foi utilizado o Método das Estacas e para descrição do processo erosivo atuante na margem o Método das Perfilagens Sucessivas em quatro diferentes seções (A, B, C e D). As seções foram instrumentadas com Indicadores de Nível D água INAs, para o estudo da interação das águas superficiais e subterrâneas na interface dos taludes marginais. O recuo do topo do talude, nas seções estudadas foram de 2,06 m na seção A, 4,06 m na seção B, 4,35 m na seção C e 10,03 m na seção D. São números bem inferiores em relação aos anos anteriores, explicados pelo retaludamento promovido pelas cheias de janeiro de 2004, que temporariamente promoveram uma desaceleração do processo. A variação das taxas de erosão aconteceu em função da localização das seções, da composição granulométrica do material que compõe a face dos taludes, da altura dos barrancos, da pequena variação mensal da cota do nível d água, da ação dos ventos e conseqüente formação de ondas, da velocidade do fluxo próximo à margem e devido ao sentido do fluxo hidráulico nos taludes, do solo para o rio. Os enrocamentos têm evitado o avanço do processo erosivo na maioria dos pontos em que foram implantados. Porém, poderá haver um futuro colapso da estrutura, em conseqüência do solapamento de sua base devido ao impacto das ondas. Os dados obtidos servirão para subsidiar decisões voltadas para o planejamento e gestão ambiental da região que busquem minimizar os impactos ambientais negativos resultantes das políticas públicas de utilização dos recursos hídricos da Bacia do Rio São Francisco.