Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This investigation arose out of the pressing need for alternatives to ineffective existing methodologies for low flow measurement in boulder bed rivers, with particular focus on the mountain streams in the Western Cape. Both empirical and mathematical verification were regarded as important if progress was to be made towards identifying a suitable approach. Historically the inability to determine the frictional effect of the streambed on the flow rate has been a major obstacle limiting the accuracy of flow calculations. From literature, the most likely relationship appears to be a power function, utilising hydraulic variables derived from physical parameters characteristic of a section of stream. Local Western Cape data was thus collected from various typical mountain streams, so that relevant analysis could be done. Testing of existing equations from literature sources on this set of data revealed limited applicability. Subsequent empirical experimentation has shown that particle size is a dominant variable in determining boulder bed flow resistance under low flow conditions. A mathematical approach was sought to provide a more suitable base for a locally applicable formula. Sediment transport theory, based on simple power conservation laws, was successfully implemented, partially bridging the gap between the applications for sand bed and boulder bed flow conditions respectively. After a certain degree of empirical adjustment, an equation form was finalised that is believed to be the most suitable for Western Cape mountain streams, with definite potential for wider application, provided further research is done. / AFRIKAANSE OPSOMMING: Hierdie ondersoek spruit uit die dringende behoefte aan bruikbare alternatiewe vir bestaande laagvloei meetmetodes in riviere met bodems bestaande uit spoelklip, met spesifieke klem op die bergstrome van die Wes Kaap. Dit is as belangrik beskou om beide empiriese en wiskundige bevestiging te vind vir 'n verbeterde metode. Histories is die akkuraatheid van vloeitempo berekeninge hoofsaaklik beperk deur die onvoorspelbaarheid van die ruheidseffek van die rivierbodem op die vloei. Uit bestaande literatuur blyk dit dat die mees geskikte verwantskap waarskynlik 'n magsfunksie is, wat saamgestel is uit hidrouliese veranderlikes verkry vanaf fisiese parameters kenmerkend aan die spesifieke riviersnit. Plaaslike Wes-Kaapse data is dus versamelop verskeie tipiese bergstrome in die gebied sodat geskikte ontledings gedoen kon word. Verskeie bestaande formules is getoets teen hierdie stel data en ongeskik gevind vir direkte aanwending. Empiriese toetse het gevolg en getoon dat partikel grootte 'n dominante invloed het op die vloeiweerstand van spoelklip bodems onder laagvloei omstandighede. 'n Wiskundige benadering is daarna gevolg om 'n beter basis te verskaf waaruit 'n plaaslik bruikbare vergelyking kon volg. Sedimentvervoer beginsels, wat gebaseer is op basiese drywingsteorie, is suksesvol aangewend vir hierdie doel, en het in 'n mate die gaping tussen aanwending op sand en klip bodems oorbrug. Na afloop van empiriese verstelling is 'n formule gefinaliseer wat beskou word as die mees geskikte vir Wes-Kaapse bergstrome, maar wat ook die potensiaal besit vir wyer aanwending, mits verdere navorsing gedoen sou word.

Thesis (MEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study sets out to explore the possibilities and accuracy of flow measurement at natural controls, focussing specifically on Western Cape cobble-bed rivers. These rivers are regarded as being difficult in terms of flow measurement, mostly due to their large scale roughness and very turbulent and uneven flows. The aim is to determine a system through which various types of natural controls can be calibrated, by establishing a relationship between the discharge coefficient and the physical characteristics of each control type. This was achieved by conducting an extensive field investigation, focussing on the identification and gauging of both critical and uniform natural controls. Two types of critical controls were identified and investigated, namely step-pool controls and horizontal constriction controls as well as one type of uniform flow control, namely the plane bed control. Step-pool controls were found to be very robust controls which provided efficient critical controls for a wide range of flows. Horizontal constriction controls proved to be reasonably accurate measurement sites and, because of their physical characteristics, they are able to measure the full range of flows from low to flood flows. Uniform controls are widely used for flow measurements on deep rivers, but such measurements become highly unreliable when flow depths are small and bed roughness high as is the case with cobble-bed rivers. Under conditions of high roughness, generally speaking critical controls can be calibrated more accurately than uniform controls and are therefore to be preferred. The field study was followed by a series of laboratory tests, focussing on horizontal constriction controls. Calibration equations were derived by which the discharge coefficient value can be determined for a given constriction ratio and upstream energy head. Results from both the fieldwork and laboratory work were analysed and integrated to determine a calibration system applicable to natural controls in Western Cape cobbleand boulder-bed rivers. Reasonably accurate values of the discharge coefficients for different types of natural controls were established, which should be widely applicable. Additionally, guidelines were drawn up for the measurement of flow at natural controls, to be used by both engineers and non-engineers. Discharge measurement at natural controls in the Western Cape was found to be a viable and reasonably accurate way of determining river discharge. It proves to be an environmentally acceptable way of measurement, using the natural river characteristics rather than seriously interfering with them or damaging them. These advantages make discharge measurement at natural controls a promising means of determining river discharge in the future. / AFRIKAANSE OPSOMMING: Die beste posisie vir vloeirneting in riviere is waar die topografie van die rivier 'n unieke verhouding tussen die deurstroming en die water diepte bewerkstellig. Hierdie studie ondersoek die uitvoerbaarheid en akkuraatheid van vloeirneting by natuurlike kontroles met die fokus op Wes-Kaapse spoelklip riviere. Vloeirneting in spoelklip riviere word as baie ingewikkeld beskou weens die grootte van die bedpartikels relatieftot die vloeidiepte en gevolglike onewe, turbulente vloeie. Die doel van die studie was om 'n stelsel te ontwikkel waardeur verskillende tipes natuurlike kontroles gekalibreer kan word deur verwantskappe te bepaal tussen die deurstromings koëffisiënt en die stroom-op energie hoogte. Bogenoemde is bepaal met behulp van 'n uitgebreide veldstudie waarin die hoof tipes natuurlike kontroles, nl. die kritiese vloei kontrole en die uniforme vloei kontrole, geidentifiseer en gekalibreer is. Twee tipes kritiese vloei kontroles is ondersoek, naamlik die trap-poel ("step-pool") kontrole en die horisontale vernouing kontrole. Daar is bevind dat beide die trap-poel kontrole en die horisontale vernouing baie effektiewe kritiese kontroles is, waarmee 'n wye reeks van vloeie gemeet kan word. Uniforme vloei kontroles word algemeen vir vloeimeting in diep vloeiende riviere gebruik, maar sulke metings word hoogs onbetroubaar wanner die vloeidiepte klein is relatief tot die partikel grootte van die rivierbed, soos in die geval van spoelklip riviere. Onder hierdie omstandighede kan kritiese kontroles in die algemeen meer akkuraat gekalibreer word en word hul gevolglik bo uniforme vloei kontroles verkies. Die veldstudie is gevolg deur 'n reeks laboratorium toetse, wat fokus op die horisontale vernouing kontrole. Kalibrasie vergelykings is afgelei waarmee die deurstromings koëffisient vir 'n gegewe stroom-op energiehoogte en vernouings-verhouding bereken kan word. Resultate van beide die veldstudie en die laboratorium toetse is geanaliseer en geïntegreer om 'n kalibrasie stelsel te bepaal wat van toepassing is op natuurlike kontroles in Wes-Kaapse spoelklip riviere. Aanvaarbare waardes vir die deurstromings koëffisiente vir verskeie tipes natuurlike kontroles is bepaal, wat algemeen toepasbaar behoort te wees. Riglyne vir die meting van riviervloei by natuurlike kontroles is opgestel vir die gebruik deur beide ingenieurs en nie-ingenieurs. Vloeimeting deur middel van natuurlike kontroles is 'n lewensvatbare metingsmetode waarmee riviervloei redelik akkuraat bepaal kan word. Dit is 'n omgewingsaanvaarbare metings metode wat die natuurlike karakter van die rivier gebruik, eerder as om ernstig daarmee in te meng of dit te beskadig. Hierde positiewe eienskappe maak vloeimeting deur middel van natuurlike kontroles 'n belowende metingsmetode vir die toekoms.

This dissertation is an analysis of the Quaternary fluvial history of central Northamptonshire. It uses new freshwater ostracod data which are interpreted using information on Quaternary and present day habitats and examines in detail associated patterns of environmental change in coarse sediments from which the ostracods were extracted. Stratigraphic, lithological and sedimentological data, supported by a study of geological maps, borehole logs and papers, are employed to produce a new hypothesis to explain the Quatemary development of the Milton River and the River Nene. The alignment of the Milton Formation Valley is established to have proceeded to the east of, but parallel with, the Nene Valley between Northampton and Higham Ferrers, where it turned to the south-east. It comprises locally derived deposits which are shown to be pre-Anglian Glaciation and, at the time of the deposition of the ostracods studied here, an interglacial environment prevailed. However, during a ‘cooling phase”, Milton Formation sediments were incised and the channel became partially infilled with fossiliferous boreal sediments. Further sedimentation continued to produce a non-fossiliferous, periglacial sand, which is typical of the Milton Formation. It is argued that this period of deposition was followed by two glacial episodes, the latter relating to the Lowestoft Formation. Stratigraphic, sedimentological and lithological evidence from the Nene valley shows vestigial terrace gravels exist between Northampton and Wellingborough. The oldest gravels of these features pre-date the Anglian age, sub-glacial tunnel valley” at Northampton, implying the Nene Valley existed prior to glaciation. Before glaciation it is suggested that the Milton River became confluent with the Nene at Northampton and, concurrently, diverted to the north-east at Higham Ferrers. This is believed to be associated with the simultaneous abandonment of the Milton Valley to the south-east of Higham Ferrers and the upstream stretch at Northampton. Evidence presented of downcutting, lateral migration, gravel reworking and changes in the ostracod assemblages in the Nene Valley confirm a history of several climatic oscillations which took place in the pre-Devensian, Devensian and Holocene. These oscillations are tentatively correlated with stages of deposition in the Nene established downstream at Peterborough. This revised fluvial history elaborates the course and age of the Milton River and establishes a pre-Devensian age for much of the Nene Valley sediment. The significance of this new understanding of the upper Nene Valley has been compared with that of the lower Nene Valley at Peterborough, Cambridgeshire. The combined evidence is used to produce a pattern of river development within the Quaternary which may be used as a model when reconstructing the palaeogeography of other rivers and their floodplains by means of their sedimentary structures and related fossils. This idea is explored to a small extent in the thesis, but is more applicable to future work. The new ostracod data throws new light on previous studies from other sites in England. Ostracod species new to the Pleistocene record are to be added to a worldwide data base

To comply with the European Union Water Framework Directive (2000), National Governments are required to achieve good chemical and ecological status of freshwater bodies. Fine sediment has been shown to be a major cause of the degradation of lakes and rivers, and as a result research in geomorphology has been directed towards the understanding of fine sediment dynamics. It was identified by a review of published literature that at present a paucity of information on sediment dynamics existed for the East Midlands, UK. The use of tracers within a sediment fingerprinting framework has recently become a heavily used technique to investigate the sources of fine sediment pressures. However, uncertainties associated with tracer behaviour have been cited as major potential limitations to sediment fingerprinting methodologies. At present few studies have quantified the uncertainties associated with tracer use, or the exact reasons why different tracers are producing different sediment provenance results. This thesis had two aims based on these gaps in published literature. First, to assess the impact of sediment sampling methodology, tracer selection, particle size corrections and organic enrichment corrections on a fine sediment fingerprinting study. Secondly, to develop a partial sediment budget for the Upper Nene river basin and its major tributaries. The results of this thesis were presented in two parts. The first part investigated Aim 1 when fingerprinting; historically deposited sediment, suspended sediment and recently deposited sediment. The second part investigated Aim 2 by constructing a fine sediment budget for the Nene river basin, consisting of; sediment yield, sediment provenance, floodplain sediment accumulation and channel bed sediment storage. A mean difference of 24.1% between the predicted contributions of sediment originating from channel banks was found when using nine different tracer groups to fingerprint the river sediment samples. When fingerprinting contributions from urban street dusts mean differences between tracer group predictions were lower, at between 8% and 11%. There was little indication that organic matter content and / or particle size caused differences between tracer group predictions. Within-source variability in tracer concentrations, and small contrasts between the tracer concentrations of the sediment source groups, were identified as probable causes of inherent uncertainty present in the fingerprinting analysis. It was determined that the ratio of the percentage difference between median tracer concentrations in the source groups and the average within-source tracer concentration coefficient of variation could indicate the likely uncertainty in model predictions prior to tracer use. When fingerprinting historically deposited sediment, a reservoir core was fingerprinted with the least uncertainty, with tracer group provenance predictions ~28% apart and with consistent down-core trends. When fingerprinting an on-line lake core and four floodplain cores, differences between tracer group predictions were as large as 100%; the down-core trends in changing sediment provenance were also different. The differences between tracer group predictions could be attributed to the organic matter content and particle size of the sediment. There was also evidence of the in-growth of bacterially derived magnetite and chemical dissolution affecting the preservation of tracer signatures. Despite the prior indications that organic matter and particle size were causing tracer non-conservatism in historical sediment cores, data corrections were found to often be ineffective at reducing the differences between tracer group predictions. The corrections were found to either have no effect on, or increase the mean differences between, tracer group predictions when fingerprinting river sediment. The sediment budget identified that the annual sediment yield of 13 - 19 t km-2 yr-1 for the Nene is low in comparison to other UK catchments. Channel banks were found to be the dominant sediment source in the Nene, typically contributing between 60% and 100% of the sediment. Rates of sediment accumulation on the Nene’s floodplain was found to be highly variable (920– 7,200 t km-2 yr-1); the presence of flood defences were likely to be a cause of this variability, and have caused a reduction in the accumulation rate since 1963. It was found that large quantities of sediment accumulated on channel beds during periods of low flows (~ 28% of the annual sediment yield), which was flushed from the bed by a series of flood events (leaving <1% of the annual sediment yield in temporary storage). An original contribution to research was made by quantifying the uncertainties associated with tracer use in a fine sediment fingerprinting investigation, as well as identifying the probable causes of the observed uncertainty. The fine sediment dynamics of the Nene basin were also investigated for the first time, and it was identified that the high contributions from channel banks in the Nene were highly a-typical for UK catchments.

This thesis develops methodologies for continuous estimation of hydrological variables which infill missing daily rainfall data and the forecast of weekly streamflows from a watershed. Several mathematical programming formulations were developed and used to estimate missing historical rainfall data. Functional relationships were created between radar precipitation and known rain gauge data then are used to estimate the missing data. Streamflow predictions models require highly non-linear mathematical models to capture the complex physical characteristics of a watershed. An artificial neural network model was developed for streamflow prediction. There are no set methods of creating a neural network and the selection of architecture and inputs to a neural network affects the performance. This thesis addresses this issue with automated input and network architecture selection through optimization. MATLABª scripts are developed and used to test many combinations and select a model through optimization. / by Ricardo Eric Brown. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Comprehensive evaluation of changes in streamflow extremes and characteristics due to climate change and variability is the main focus of this study. Available streamflow data at several gaging stations in least anthropologically affected watersheds of the Southeastern Gulf-Atlantic Region, were used for this analysis. To evaluate influences due to climate change, nonparametric trend tests were applied to annual and monthly extremes, while considering seasonality, along with changes in streamflow characteristics. To understand climate variability influences, streamflow data is partitioned in to cool and warm phases of four oceanic and atmospheric oscillations known to have an effect on hydroloclimatology of the region: El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO); Atlantic Multi-decadal Oscillation (AMO); and North Atlantic Oscillation (NAO). Generally, results showed decreasing trends in overall streamflow extremes, as well as spatially varying, temporally non-uniform influences of climate variability on streamflow extremes and characteristics. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Qin, Jie. / "November 2010." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 162-173). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

An archival-stratigraphic investigation of the middle Gila River provides insights into late-Holocene channel behavior and flood-plain formation. Historical records detail changes in channel patterns that correlate with changing frequency of large floods, but channel sensitivity is also affected by factors such as flood seasonality, changes in sediment load, human disturbances, and internal thresholds. Because the frequency of large floods is the dominant factor in channel changes, radiocarbon-dated flood deposits in late-Holocene alluvial terraces allow for a reconstruction of prehistoric channel behavior. A period of reduced large flood frequency and channel stability 4,000-1,000 years BP separates periods of increased large flood frequency and channel instability 5,000-4,000 and 1,000-0 years BP. Transformations between braided and single channel morphologies affect the conveyance of floods and change the spatial characteristics of flood hazards. These channel dynamics are also important in analyzing changes in Hohokam-Pima irrigation technology and settlement patterns.

Project Completion Report, OWRT Project No. A-040-ARIZ / Agreement No. 14-31-0001-4003 / Project Dates: July, 1972 - June, 1974 / Acknowledgement - The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Research and Technology, as authorized under the Water Resources Research Act of 1964. / Hydraulic and physicochemical measurements were made on treated sewage effluent releases at established locations within the channel of an ephemeral stream, the Santa Cruz River of Southern Arizona. Water quality samples were taken in sequence so that incremental flows at different hydrograph stages could be traced as the effluent moved downstream. Hydrographs obtained from two H -L flumes were used to calibrate a modified kinematic wave model. Hydraulic parameters from the kinematic model and physicochemical measurements from water quality samples were combined together into a statistical-empirical kinetic model of nitrogen transformations which may occur in sewage effluent releases. There was fair agreement between the measured data and the nitrogen species values calculated with the model. Measured nitrogen species values indicated that the rate of nitrification in sewage effluent releases is related to flow distance and physical characteristics of the stream.

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