The basin factor is a hydrologic parameter that represents the overall impedance to flow of a watershed in the PC-Hydro peak discharge model for small ( < 10 mi2) semi-arid watersheds in Pima County, Arizona. To improve peak discharge estimates and provide validation of the basin factor as a physically-based parameter, basin factor values were "back-calculated" for return period and observed events on six undeveloped rangeland watersheds and correlated with Manning's n roughness coefficients, rainfall intensities, and hydraulic radii. Observed basin factor values displayed a positive trend with observed peak discharge. The results suggest that the correlated variables can predict the basin factor on small undeveloped sub-basins in Pima County and the basin factor is measurable as a physical parameter. Empirical models for basin factor prediction are proposed. The study may also be useful for estimating hydraulic roughness in hydrologic methods such as the kinematic wave time of concentration equation.

Hydraulic losses in sewer pipes are caused by wall roughness, blockages and in-pipe sedimentation. Hydraulic resistance is a key parameter that is used to account for the hydraulic energy losses and predict the sewer system propensity to flood. Unfortunately, there are no objective methods to measure the hydraulic resistance in live sewers. A common method to estimate the hydraulic resistance of a sewer is to analyse collected CCTV images and then to compare them against a number of suggested hydraulic roughness values published in the Sewer Rehabilitation Manual. This thesis reports on the development of a novel, non-invasive acoustic method and instrumentation to measure the hydraulic roughness in partially filled pipes under various structural and operational conditions objectively. This research presents systematic laboratory and field studies of the hydraulic and surface water wave characteristics, of shallow water flows in a sewer pipes with the presence of local and distributed roughness, in order to relate them to some fundamental properties of the acoustic field measured in the vicinity of the flow surface. The results of this thesis indicate that for the local roughness the energy content of the reflected acoustic signal is an indicator of the pipe head loss and hydraulic roughness. In the case of the distributed roughness, the variation in the temporal and frequency characteristics of the propagated sound wave can be related empirically to the mean flow depth, mean velocity, wave standard deviation and hydraulic roughness.

Hydraulic losses in sewer pipes are caused by wall roughness, blockages and in-pipe sedimentation. Hydraulic resistance is a key parameter that is used to account for the hydraulic energy losses and predict the sewer system propensity to flood. Unfortunately, there are no objective methods to measure the hydraulic resistance in live sewers. A common method to estimate the hydraulic resistance of a sewer is to analyse collected CCTV images and then to compare them against a number of suggested hydraulic roughness values published in the Sewer Rehabilitation Manual. This thesis reports on the development of a novel, non-invasive acoustic method and instrumentation to measure the hydraulic roughness in partially filled pipes under various structural and operational conditions objectively. This research presents systematic laboratory and field studies of the hydraulic and surface water wave characteristics, of shallow water flows in a sewer pipes with the presence of local and distributed roughness, in order to relate them to some fundamental properties of the acoustic field measured in the vicinity of the flow surface. The results of this thesis indicate that for the local roughness the energy content of the reflected acoustic signal is an indicator of the pipe head loss and hydraulic roughness. In the case of the distributed roughness, the variation in the temporal and frequency characteristics of the propagated sound wave can be related empirically to the mean flow depth, mean velocity, wave standard deviation and hydraulic roughness.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / Stepped spillways constructed of roller compacted concrete (RCC) is a hydraulic and cost effective measure to dissipate energy of large water flows over the spillway of a dam. Stepped spillways, like other spillway types, have its limitations and a measure to improve the energy dissipation effectiveness is proposed. Two hydraulic models were constructed at the hydraulics laboratory of the Department of Water Affairs and Forestry (DWAF) in Pretoria, South Africa. The scales of the models were 1:20 and 1:30. The study proposes the use of triangular protrusions applied over the spillway surface. The protrusions have the same height as the steps, with the width of the protrusions varying. The triangular protrusions deflect the water sideways resulting in higher energy losses. The results indicate that the protrusions reduce scouring at the toe of the dam, thus increasing the roughness of the steps. It also indicate that aeration occur earlier than with normal stepped spillways. An optimal spacing, lateral and across the steps, are proposed. The construction of the protrusions is also discussed, as well as the cost implications. It is concluded that the protrusions are effective at a unit discharge up to 35 m3/s.m. This value is however dependent on the configuration of the apron downstream of the toe of the dam. It is proposed that protrusions be added on the downstream face of the dam on every second step, with one protrusion and then no protrusion alternating in the flow path. It is recommended that the protrusions be cast in situ.

Au sein des communautés végétales, les traits fonctionnels dirigent et influencent les processus sol-plantes. Le ruissellement et l'érosion concentrés, causes principales de la dégradation des sols, peuvent être contrôlés par des végétations herbacées qui créent une rugosité hydraulique induisant la réduction de la vitesse des flux de ruissellement et la rétention des sédiments. L'approche des traits, plutôt que taxonomique, permet de comprendre et caractériser les effets directs de la végétation sur le ruissellement et la rétention des sédiments. Ce projet de recherche vise à approfondir les connaissances vis-à-vis des effets (i) des traits fonctionnels (Chapitre 1), (ii) de la complémentarité des traits (Chapitre 2), et (iii) de la diversité fonctionnelle (Chapitre 3) sur les écoulements concentrés et la rétention des sédiments afin d'évaluer l'efficacité et le design de haies herbacées pour réduire les impacts de l'érosion des sols dans les bassins versants limoneux d'Europe. Parmi les combinaisons de traits principaux identifiées comme augmentant la rugosité hydraulique (densité et diamètre des tiges, et densité et surface foliaire), certains traits sont négativement corrélés. Un meilleur effet pourrait donc être atteint au sein d'assemblage d'espèces par un effet complémentaire des traits. Cependant, des effets non-additifs des diversités en espèces et fonctionnelle ont été trouvés, chacun généré par un effet dominant des traits dans les communautés testées. Ces effets des traits et de la diversité fonctionnelle sur la rugosité hydraulique et la rétention des sédiments constituent une nouvelle avancée dans la compréhension des effets de l'assemblage des traits sur les processus d'écoulement et d'érosion des sols ainsi qu'une base pour le design et la modélisation des haies herbacées pour le contrôle du ruissellement et de l'érosion. / Plant-soil processes are driven and influenced by plant functional traits in vegetation communities. Concentrated runoff and erosion constitute the main cause of soil degradation and can be managed by herbaceous vegetation creating hydraulic roughness that induces flow velocity reduction and sediment retention. Using plant trait-based approach, unlike taxonomical approach, allows to understand and characterise the direct effects of the vegetation on runoff and sediment retention. This research project aims to deepen the knowledge regarding the effects of (i) plant functional traits (chapter 1), (ii) traits' complementarity (chapter 2) and (iii) functional diversity (chapter 3) on concentrated runoff and sediment retention processes, in order to evaluate the efficiency and design of herbaceous hedges to reduce the impacts of soil erosion in loamy European agricultural catchments. The identification of the main efficient traits and traits' combinations towards hydraulic roughness increase (stem density, diameter, leaf area and density) highlighted negatively correlated traits, suggesting that a trade-off could be reached within a plant species assemblage through a complementarity effect of the traits. However, non-additive effects of plant species diversity and functional diversity were found, both driven by dominant traits in the community. The effects of traits and functional diversity on the hydraulic roughness and sediment retention constitute a new advance in the understanding of plant trait assemblage on runoff and soil erosion processes and a baseline for the design and modelling of herbaceous hedges for runoff and erosion control.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-07-11T14:45:22Z No. of bitstreams: 1 Flavio Adriano Marques.pdf: 3199315 bytes, checksum: a208fb8314e3ffa0d451678350503edb (MD5) / Made available in DSpace on 2016-07-11T14:45:22Z (GMT). No. of bitstreams: 1 Flavio Adriano Marques.pdf: 3199315 bytes, checksum: a208fb8314e3ffa0d451678350503edb (MD5) Previous issue date: 2013-02-21 / The Brazilian region known as Brejo Paraibano, in recent decades has been undergoing a process of replacing its native coverage by crops, mainly for pasture for extensive livestock farm, which has favored the occurrence of soil degradation in the form of water erosion. Given this context, this study aimed to quantify the rates of interrill erosion under simulated rainfall and evaluate the roughness parameters vegetable emerged to laminar flow in a pasture area hilly relief. The experiment was conducted in a completely randomized design with 4 treatments, 15%, 25%, 35% and 45% slope in a Ultisol under pasture, 5 replications, totaling 20 plots. The mean flow velocity and infiltration rates of pasture varied significantly with increasing slope contributing to increased erosion rates up to 35%. In the condition of 45% slope was not the greatest soil losses have occurred because of the removal of the horizon, in which the erosion process is acting on the argilic B horizon. The vegetation drag coefficient to pasture expressed elevation when there was a decrease of turbulent flow between plants. In the condition height flow increase, there was a greater energy flow between the mass of water and the plants structure of Brachiaria decumbens that resulted in decreasing on the force drag tension of plants. / A microrregião do Brejo Paraibano nas últimas décadas vem sofrendo um processo de substituição de sua cobertura nativa por culturas agrícolas, sobretudo por pastagens para exploração de pecuária extensiva, o que vem favorecendo a ocorrência de degradação do solo na forma de erosão hídrica. Diante desse contexto, este estudo teve como proposta quantificar as taxas de erosão em entressulcos sob chuva simulada e avaliar os parâmetros da rugosidade vegetal emersa ao escoamento em área de pastagem em relevo movimentado. O experimento foi conduzido em delineamento inteiramente casualizado nas condições de declive: 15%, 25%, 35% e 45%, em um Argissolo Vermelho-Amarelo sob pastagem, em 5 repetições, totalizando 20 parcelas experimentais. A velocidade média do escoamento e as taxas de infiltração na pastagem variaram significativamente com a elevação do declive contribuindo para elevação das taxas de erosão ate o declive de 35%. Na condição de 45% de declive não ocorreram as maiores perdas de solo em virtude de ter ocorrido a remoção do horizonte A, estando o processo erosivo atuando sobre o horizonte B textural. O coeficiente de arraste vegetal da pastagem expressou elevação quando ocorreu diminuição da turbulência do escoamento entre as plantas. Com o aumento da lâmina de escoamento, houve um maior fluxo de energia entre a massa de água e a estrutura vegetal da gramínea Brachiaria decumbens, que se refletiram na diminuição dos valores de tensão de arraste na planta.

Ce travail de thèse s'intéresse à l'effet d'une variation longitudinale de l'occupation du sol de la plaine d'inondation sur l'écoulement d'une rivière en débordement. Nous traitons le cas d'une transition entre une zone de prairie et une zone de forêt, et vice versa. Cette variation d'occupation du sol est associée à une transition de rugosité hydraulique entre une rugosité de fond (prairie fortement immergée) et des macro-rugosités émergées (arbres), modélisées respectivement par une moquette plastifiée et par un champ de cylindres. Ces écoulements sont étudiés en laboratoire dans un canal de dimension 18 m x 3 m. Dans un premier temps, nous considérons l'écoulement à travers un champ de cylindres émergents en lit simple, en étudiant l'effet du fond sur le sillage des cylindres et le phénomène de seiche (fortes oscillations de la surface libre). Dans un deuxième temps, nous nous penchons sur le développement vers l'uniformité d'un écoulement en lit composé de rugosité uniforme. La croissance asymétrique de la couche de mélange du lit composé, la propriété d'autosimilarité ainsi que l'organisation tridimensionnelle des structures turbulentes cohérentes associées à la couche de mélange sont analysées. Le troisième temps fait l'objet de la transition longitudinale de rugosité en lit composé, dont l'effet sur la couche de mélange et sur les structures cohérentes est discuté. Nous évaluons également les différentes contributions au transfert latéral de quantité de mouvement entre lit mineur et plaine d'inondation par diffusion turbulente, par échange de masse et par les courants secondaires / This PhD thesis investigates the effect of a longitudinal change in floodplain land use on an overflooding river flow. We consider a transition between a meadow and a woodland and vice versa. This change in land use is associated with a change in hydraulic roughness, between a bed roughness (highly submerged meadow) and emergent macro-roughnesses (trees), respectively modelled by a plastic artificial grass and an array of emergent cylinders. The flows are experimentally investigated in an 18 m x 3 m laboratory flume. In a first step, we investigate the flow through a cylinder array in a single channel, focusing on the effect of bed roughness on the cylinder wakes and on the seiche phenomenon (strong free surface oscillations). In a second step, we study the development towards flow uniformity of compound channel flows with a uniform hydraulic roughness on the floodplains. The asymmetrical growth of the compound channel mixing layer, the self-similarity property and the three-dimensional organisation of the turbulent coherent structures associated with the mixing layer are analysed. In a third step, we investigate the longitudinal change in roughness in compound channel configuration, which effects on mixing layer and on coherent structures are discussed. We also assess the contributions to lateral transfers of momentum between main channel and floodplain by turbulent diffusion, by mass exchange and by secondary currents

This master thesis is divided into two parts: theoretical and practical one. In the theoretical part there is described hydraulic roughness, velocity distribution in the case of hydraulically rough surface and the process of grain sorting in surface layer. The practical part of the thesis resolves the influence of surface layer on hydraulic roughness of bed, expressed by Nikuradse sand grain size ks. The results are formulas explaining dependence of ks on characteristic grain size dx from grain-size distribution curve and comparison with coefficient ks according to different authors.

No description available.