Hydrolink 2010/1. Topic: Change Course JHR JRBM

Topic: Change Course JHR JRB

Identification and correction of water velocity measurement errors associated with ultrasonic Doppler flow monitoring

Ultrasonic Doppler flow monitoring (UDFM) is used to measure water flow in pipes and channels. However, a lack of scattering particles and signal noise can cause velocity errors, particularly for smaller discharges and surface water (‘clean’) flows. A post-processing methodology is presented that identifies and corrects these errors, maximising the value of existing data. Test criteria are used to identify errors. The error correction procedure defines depth-velocity relationships from cleaned ‘training data’ representing the range of flow conditions (including backed up) and uses these relationships to automatically replace erroneous velocities. UDFM velocity errors have been successfully identified and corrected in example applications. Routine use allows early identification of changes in instrument or site behaviour. The methodology is practical, consistent and updateable. This is a significant advancement on previous methods for correcting velocity errors, improving the applicability of UDFM

Parâmetros relevantes para caracterização de rios montanhosos : revisão

Mountain rivers are situated in a large portion of the terrestrial surface, especially in headwaters regions, and have been used for various purposes such as recreation, sporting activities, water resources and hydroelectric power generation. However, hydrogeomorphic characteristics of mountain rivers are not fully understood. In this context, the present paper aimed to identify relevant parameters for characterizing rivers in these environments based on bibliographical review. It was identified which parameters have been used and how they have been used to characterize mountain rivers in distinct classifications. The most cited parameters were channel gradient, relation between river width and depth, entrenchment ratio, discharge, sediment transport and grain-size distribution. Also, the current situation related to researches in fluvial geomorphology in mountain rivers in Brazil was evaluated, and the strong need of field survey as basis for the best understanding of mountain fluvial dynamics and characterization was verified.Rios montanhosos estão presentes em uma grande porção dos territórios do planeta, especialmente nas regiões de cabeceiras, e vêm sendo utilizados para diversos fins, tais como recreação e atividades desportivas, mananciais de água e geração de energia hidrelétrica. Entretanto, suas características hidrogeomorfológicas ainda não são plenamente conhecidas. Neste contexto, o presente trabalho abordou os parâmetros relevantes necessários para caracterização de rios nestes ambientes a partir de revisão bibliográfica, em que se buscou avaliar o modo como os rios estavam sendo caracterizados e quais parâmetros hidrogeomorfológicos estavam sendo analisados em diferentes classificações. Os parâmetros mais comumente utilizados na caracterização de rios montanhosos são a declividade do canal, a relação entre largura e profundidade do rio, o grau de entrincheiramento do canal, a vazão, a carga de sedimentos e a granulometria dos sedimentos. Ainda, avaliou-se o cenário brasileiro no que tange a pesquisa em hidrogeomorfologia fluvial em rios montanhosos, constatando-se a necessidade de realizar mais atividades em campo para melhor entendimento da dinâmica fluvial montanhosa e caracterização fluvial

Parâmetros relevantes para caracterização de rios montanhosos : revisão

Mountain rivers are situated in a large portion of the terrestrial surface, especially in headwaters regions, and have been used for various purposes such as recreation, sporting activities, water resources and hydroelectric power generation. However, hydrogeomorphic characteristics of mountain rivers are not fully understood. In this context, the present paper aimed to identify relevant parameters for characterizing rivers in these environments based on bibliographical review. It was identified which parameters have been used and how they have been used to characterize mountain rivers in distinct classifications. The most cited parameters were channel gradient, relation between river width and depth, entrenchment ratio, discharge, sediment transport and grain-size distribution. Also, the current situation related to researches in fluvial geomorphology in mountain rivers in Brazil was evaluated, and the strong need of field survey as basis for the best understanding of mountain fluvial dynamics and characterization was verified.Rios montanhosos estão presentes em uma grande porção dos territórios do planeta, especialmente nas regiões de cabeceiras, e vêm sendo utilizados para diversos fins, tais como recreação e atividades desportivas, mananciais de água e geração de energia hidrelétrica. Entretanto, suas características hidrogeomorfológicas ainda não são plenamente conhecidas. Neste contexto, o presente trabalho abordou os parâmetros relevantes necessários para caracterização de rios nestes ambientes a partir de revisão bibliográfica, em que se buscou avaliar o modo como os rios estavam sendo caracterizados e quais parâmetros hidrogeomorfológicos estavam sendo analisados em diferentes classificações. Os parâmetros mais comumente utilizados na caracterização de rios montanhosos são a declividade do canal, a relação entre largura e profundidade do rio, o grau de entrincheiramento do canal, a vazão, a carga de sedimentos e a granulometria dos sedimentos. Ainda, avaliou-se o cenário brasileiro no que tange a pesquisa em hidrogeomorfologia fluvial em rios montanhosos, constatando-se a necessidade de realizar mais atividades em campo para melhor entendimento da dinâmica fluvial montanhosa e caracterização fluvial

Continuous measurements of discharge from a horizontal acoustic Doppler current profiler in a tidal river

Acoustic Doppler current profilers (ADCPs) can be mounted horizontally at a river bank, yielding single-depth horizontal array observations of velocity across the river. This paper presents a semideterministic, semistochastic method to obtain continuous measurements of discharge from horizontal ADCP (HADCP) data in a tidal river. In the deterministic part, single-depth velocity data are converted to specific discharge by applying the law of the wall, which requires knowledge of local values of the bed roughness length (z0). A new filtration technique was developed to infer cross-river profiles of z0 from moving boat ADCP measurements. Width-averaged values of z0 were shown to be predominantly constant in time but differed between ebb and flood. In the stochastic part of the method, specific discharge was converted to total discharge on the basis of a model that accounts for the time lag between flow variation in the central part of the river and flow variation near the banks. Model coefficients were derived using moving boat ADCP data. The consistency of mutually independent discharge estimates from HADCP measurements was investigated to validate the method, analyzing river discharge and tidal discharge separately. Inaccuracy of the method is attributed primarily to mechanisms controlling transverse exchange of momentum, which produce temporal variation in the discharge distribution over the cross section. Specifically, development of river dunes may influence the portion of the discharge concentrated within the range of the HADC

Flow discharge measurement by a linear width contraction device

In this paper, the outflow process of a linear width contraction device for a free-flow condition is modeled using the dimensional analysis and the incomplete self-similarity condition. The proposed theoretical stage-discharge relationship is tested using measurements available in the literature. The proposed power stage-discharge equation is characterized by a value of the exponent close to 2 and a coefficient depending on the angle of the device sides with the channel bank. The proposed flume is characterized by simple construction, easy installation, low cost, and a good accuracy of the measured discharge (errors in the estimate ranging from - 3.84 to 1.9%). The deduced stage-discharge equation is characterized by errors in the estimate of discharge lower than or equal to & PLUSMN; 3% for 93.7% of the investigated cases. The main result of this paper is a stage-discharge relationship giving an accurate estimate of discharge but, at the same time, having the advantage of working regardless of the discharge coefficient estimate

Hydrogeomorphological characterization of a canyon river in southern Brazil : a specific type of a mountain river

Mountain rivers are presented on all continents, representing an important portion of the territories. During the last decades, their utilization has been increasing by many objectives, such as tourism, recreation, water supply, and land use. However, mountain rivers are less studied than alluvial rivers, even though extreme hydrological events used to reach these areas and cause damages in the mountain environments. Furthermore, when considering rivers carved on canyons, the studies are even more scarce. For this reason, the present dissertation aims to identify relevant parameters for characterizing mountain rivers. In addition, it seeks to perform a hydrogeomorphological characterization of a canyon river located in Southern Brazil, which is part of the most extensive canyon chain in South America, inserted in the Aparados da Serra National Park. It was performed an extensive literature review on mountain rivers. Also, field surveys, computational modeling, and statistical analysis were conducted to realize the characterization. The field surveys include measurements on topography, bathymetry, discharge, grain size distribution, and geomorphic units in three reaches of the Boi River. Furthermore, distinct conditions of flow resistance in the three considered reaches along the Boi River were evaluated. The results indicate that canyon rivers are those rivers under the direct influence of canyon environments concerning sediment supply processes, sediment transport, grain size distribution, geomorphic patterns, and hydraulic conditions. In addition, canyon, transition, and floodplain landscapes present different behaviors in terms of river morphometry. Thus, canyon rivers are not restricted to those rivers presented in the canyon landscape but also those in the transition to alluvial rivers. The canyon influence decreases from upstream (close to the gorge) to downstream (towards the floodplain). Also, the canyon landscapes present higher resistance to flow than floodplain landscapes. As the differences are remarkable, it evidences the hydrogeomorphological differences among reaches in the same river.Rios montanhosos estão presentes em todos os continentes, representando uma boa porção dos territórios. Ao longo das últimas décadas, sua utilização vem aumentando com diversas finalidades, tais como turismo, recreação, manancial de água e ocupação territorial. No entanto, rios montanhosos são menos estudados que rios de planície, embora eventos hidrológicos extremos possam apresentar maior potencial de dano no ambiente montanhoso. Quando considerado rios montanhosos escavados em cânions, esses estudos são ainda mais escassos. Por essa razão, a presente tese buscou identificar parâmetros necessários para caracterizar um rio montanhoso, além de realizar a caracterização hidrogeomorfológica de um rio de cânion localizado no sul do Brasil, o qual faz parte da maior cadeia de cânions da América do Sul e que está inserido na área do Parque Nacional de Aparados da Serra. Para tal, foi realizada uma extensiva revisão bibliográfica, trabalhos de campo, modelagem computacional e análises estatísticas para realizar tal caracterização. Os trabalhos de campo envolveram medições topográficas, batimétricas, vazão, distribuição do tamanho de sedimentos e de unidades geomorfológicas de pequena escala em três trechos do rio do Boi, compreendido. Também foram avaliadas as diferentes condições de resistência ao fluxo nos três trechos. Os resultados indicam que rios de cânion são aqueles sob influência direta do ambiente de cânion em relação aos processos de suprimento de sedimentos, transporte de sedimentos, distribuição do tamanho de sedimentos, padrões geomórficos e hidráulicos. Além disso, cânion, transição e planície apresentam diferentes comportamentos em termos de morfometria dos rios. Desse modo, rios de cânion não são restringidos a rios presentes na paisagem de cânion, mas também aqueles na transição para rios aluviais. A influência do cânion decresce de montante (próximo às paredes do cânion) para jusante (em direção à planície). Além disso, os locais identificados como cânion apresentam maior resistência ao fluxo do que aqueles locais identificados como planície. Como as diferenças são consideráveis, fica evidenciado as diferenças hidrogeomorfológicas em diferentes trechos de um mesmo rio

Environmental Impact of Undular Tidal Bores in Tropical Rivers

A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment motion beneath tidal bores. In the absence of detailed systematic field measurements, a quasi-steady flow analogy was applied to investigate undular tidal bores with inflow Froude numbers between 1.25 and 1.6. Experimental results indicated that rapid flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of undular tidal bores. The effects of periodic loading on river sediments, scour of river bed and flow mixing behind the bore are discussed. A better understanding of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx and Daly rivers in tropical Australia

Quantifying the Impact of Water Abstraction for Low Head ‘Run of the River’ Hydropower on Localized River Channel Hydraulics and Benthic Macroinvertebrates

‘Run of the river’ (ROR) hydropower schemes have undergone a recent resurgence in Europe, and with legislation requiring the protection and enhancement of the physical and ecological condition of European rivers, there is a need to understand the impacts of these schemes. This paper presents an assessment of the eco-hydraulic impact of a ROR hydropower scheme in the Peak District National Park, UK. Due to the ponded nature of the depleted stretch at the study site, this paper focuses on the characterization of the hydraulic impact of water abstraction for a ROR scheme at the hydropower outlet and samples microhabitats of benthic macroinvertebrates within the hydraulically affected zones. Measurement of hydraulic transects shows that the scheme's operation notably alters river channel hydraulics at 60% of water depth, whilst impacts are much less distinct in close proximity to the river bed. We identify eco-hydraulic relationships between benthic macroinvertebrate communities and localized near-bed velocity and turbulence conditions, thus indicating the potential for water abstraction by ROR schemes to impact lower trophic levels of riverine ecosystems. However, spatial patch-scale (10–100 m2) meso-habitat comparisons of invertebrate communities around the hydropower outlet showed only subtle differences, suggesting that in this case benthic communities are only minimally impacted by the ROR scheme