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Low-lying coastal plains comprised of unconsolidated infill are internally complex hydrogeological settings, due to the high level of heterogeneity in the infill material. In order to resolve the hydrogeological processes active in these complex settings, an integrated multi-disciplinary, geoscientific approach is required. This research determines quantitatively, the effects of sedimentary aquifer heterogeneity on groundwater flowpaths and groundwater processes within a heavily laterised, coastal plain setting. The study site is the Bells Creek catchment in southeast Queensland, Australia. The methodology developed in this study provides a new approach to enable the determination of groundwater flowpaths and groundwater processes at macroscale resolution within other shallow alluvial and coastal plain aquifers. The multi-disciplinary approach utilises sedimentological, geophysical, chronological and hydrogeological techniques (including hydrochemistry and groundwater flow modelling) to develop a high-resolution aquifer framework, and to determine accurately, both groundwater flowpaths and relative flow rates. Sedimentary framework is confirmed to be the principal factor controlling the distribution of aquifer permeability pathways in any given setting, and is therefore, the dominant control over groundwater flow and processes. For the Bells Creek catchment, interpretation of stratigraphic and sedimentary data allowed the compilation of a detailed sedimentary framework. This interpretation demonstrated that weathering of the low-lying arkose sandstone bedrock has developed thick lateritic profiles. Within the weathering profiles, cemented, iron-rich horizons have resisted erosion and developed raised and elongated ridges in the modern landscape, while other clay-rich weathered layers have submitted to erosion and downgraded around those iron-rich ridges. Consequently, alluvial deposition throughout the Late Quaternary has been restricted to narrow, and relatively deep valleys containing sandrich channels, and thin floodplains at shallow depth. From a hydrogeological perspective, there is significant macroscopic aquifer heterogeneity between fine-grained lateritic mixed clay layers, floodplain clays, ironcemented ferricrete horizons, and permeable sand-rich alluvial aquifers. This variability of aquifer material has created a complex subsurface arrangement of permeability pathways. Application of Ground Penetrating Radar (GPR) in this setting enabled accurate definition of alluvial channel boundaries and the high degree of connectedness within the channels themselves. Interpretation of a comprehensive GPR dataset (that covered the entire catchment) allowed refinement of the sedimentary framework previously established to develop a detailed threedimensional aquifer framework. Finite-difference groundwater modelling and particle tracking analysis (using MODFLOW and MODPATH) has clearly demonstrated that the macroscopic heterogeneity within the various aquifer materials of the plain has marked impacts on groundwater pathways, and especially groundwater travel times. The variability between a maximum residence time of 18 months for groundwater within the alluvium, compared to hundreds of years for groundwater within the mixed clay layers of the laterite, clearly demonstrates the importance of accurately defining the spatial distribution of the various aquifer materials in a groundwater flow investigation. In this setting, the interconnection of the narrow alluvial channels feeding into a deeper alluvial delta has provided an effective conduit for shallow groundwater flow. The role of the alluvial delta in discharging the bulk of fresh groundwater from the central plain into the coastal and estuarine aquifers to the east, is certainly critical in preventing saline intrusion from encroaching further west. Hydrochemical and isotopic indicators have identified the dominant recharge processes and groundwater flowpaths within the plain, and indicated that the processes are strongly related to sub-surface permeability distributions determined in the aquifer framework (and groundwater modelling), as well as seasonal fluctuations in rainfall. In the northwest of the plain, sandstone hills provide a delayed and slightly mineralized component of groundwater recharge into adjacent highly permeable, unconfined alluvial aquifers; these aquifers also recharge directly via precipitation. Aluminosilicate weathering in the bedrock hills and eastern peripheries of the laterised bedrock are a source of excess Na, SiO2, and HCO3 to the alluvial groundwater. As this groundwater flows down-gradient to the east, however, its chemical composition evolves by sulfate reduction, silica equilibrium and ion exchange processes into a more mature Na-Cl type. Within the shallow coastal aquifers proximal to the eastern shoreline, sulfate enrichment is occurring (associated with increases in Ca, HCO3, Fe and Al) resulting in major deterioration in groundwater quality. The deterioration is produced by saline intrusion from the adjacent estuary coupled with oxidation of sulfide materials in shallow marine and estuarine clays. Reverses in salinity in those coastal aquifers have been correlated with surges in fresh recharge waters from unconfined coastal dunes and semi-confined landward alluvium, following significant rainfall events. The multi-disciplinary methodology developed, provides an effective approach for accurately defining the three-dimensional distribution of shallow aquifer material of varying permeability via detailed stratigraphic interpretation and GPR analysis. Utilising this aquifer framework, finite-difference groundwater modelling aided by hydrogeological data and hydrochemical analysis, allows accurate determination of groundwater flowpaths and groundwater processes. This research provides a new hydrogeological analogue for alluvial channel aquifers within a laterised coastal plain setting. Key Words: groundwater flow, aquifer heterogeneity, numerical modelling, hydrochemistry, recharge, ground penetrating radar, coastal plain aquifers, weathering, alluvial channels.

The cross-sectional form of semi-alluvial bedrock channels was investigated. Channel geometry data were collected from a variety of streams in Ontario and Québec, Canada to develop empirical downstream scaling relationships. The relationships revealed that bedrock, mixed, and alluvial channels scale at similar rates with respect to discharge. The widest channels were formed in low-relief sedimentary bedrock with minimal alluvial cover. Channels influenced by resistant igneous/metamorphic bedrock produced a strong scaling relationship, whereas channels influenced by weak sedimentary bedrock produced a weak scaling relationship. Alluvial cover appeared to exhibit more control on channel width in low-relief settings in comparison to high-relief settings, with increased alluvial cover promoting channel narrowing. Channels influenced by igneous/metamorphic bedrock produced identifiable thalwegs, presumably due to well-defined bedload transport pathways. Channels influenced by sedimentary bedrock tended to have planar beds. Additionally, fish habitat was investigated at one semi-alluvial bedrock stream in Ontario, Canada. Fish sampling was conducted at proximate bedrock and alluvial sections followed by a survey of physical habitat parameters to evaluate habitat preferences. Adult logperch (Percina caprodes), juvenile white sucker (Catostomus commersonii), adult round goby (Neogobius melanostomus), and adult longnose dace (Rhinichthys cataractae) demonstrated preference toward alluvial substrate, whereas juvenile logperch and adult banded killifish (Fundulus diaphanus) demonstrated preference toward bedrock. Juvenile silver shiner (Notropis photogenis) and juvenile yellow perch (Perca flavescens) were indifferent to substrate type. Empirical depth and flow velocity habitat suitability indices (HSIs) were developed for each fish species. This study presents the first fish habitat suitability criteria developed from a small semi-alluvial bedrock stream and may provide valuable information for fisheries management endeavours in such environments.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-05T18:25:04Z No. of bitstreams: 1 HUGO MORAIS DE ALCÂNTARA - DISSERTAÇÃO PPGECA 2007..pdf: 2937576 bytes, checksum: 4120665ff013d35f135ab12cfe7ca9a5 (MD5) / Made available in DSpace on 2018-09-05T18:25:04Z (GMT). No. of bitstreams: 1 HUGO MORAIS DE ALCÂNTARA - DISSERTAÇÃO PPGECA 2007..pdf: 2937576 bytes, checksum: 4120665ff013d35f135ab12cfe7ca9a5 (MD5) Previous issue date: 2007-03-29 / O presente trabalho tem o objetivo de avaliar a natureza da variação da resistência total em canais aluviais e propor uma função de resistência total. A partir da equação fundamental da resistência da superfície, é definida uma função cuja variação pode ser associada aos efeitos da forma do leito e da distribuição granulométrica de sedimentos. A forma desta função, obtida através de análise dimensional utilizando a técnica de regressão linear múltipla, é apresentada para sedimentos unimodais e bimodais associada a cada tipo de canal e mistura de sedimentos. Foi utilizada uma grande massa de dados experimentais de laboratório e de campo coletados por diversos pesquisadores em vários estudos. Com base nos diversos estudos encontrados na bibliografia e considerando as incertezas envolvidas na separação da resistência total em, a resistência devido aos grãos na superfície e das formas do leito, decidiu-se propor uma função de resistência separadamente para cada forma do leito para o parâmetro de resistência B. A grande vantagem da metodologia proposta é que esta avalia a resistência total do leito sem a necessidade de separação dos efeitos dos grãos e das formas do leito. Os resultados mostram que uma excelente relação funcional pode ser estabelecida para cada forma do leito e mistura de sedimentos utilizando três e dois parâmetros adimensionais. O efeito da distribuição granulométrica dos sedimentos ficou evidenciado no caso do leito plano e com sedimentos bimodais, indicando que nos casos em que a distribuição natural – log-normal – de sedimentos não seja aplicável, o efeito da distribuição granulométrica é significativo na resistência total do canal aluvial. / The present work has the objective of evaluating the variation of the hydraulic resistance in alluvial channels and propose a function of total resistance. Starting from the fundamental concept of the resistance of the surface, a function is defined in which the variation of resistance can be associated with the characteristics of the bed form and the grain size distribution of the mixture of the sediments in the bed. The form of this function, obtained through dimensional analysis using the technique of multiple linear regression, is presented for unimodal and bimodal sediments associated with each channel type and mixture of sediments. Utilizing the data collected by various researchers in laboratory canals and rivers, the functional relationships for the resistance factor, here in identified as a dimensionless factor “B”, has been established utilizing three, or in a simple form, two, dimensionless parameters as independent variables. The great advantage of the resistance function proposed here is that it eliminates the need to separate the total resistance into two components. The results show that an excellent functional relationship can be established for each bed form and mixture of sediments using three parameters. The influence of the grain size distribution of the sediments was evidenced in the case of all the bed forms and especially bimodal sediments. In the cases of natural distribution (log-normal) of sediments in the sand range, the effect on the individual grain size distributions became hardly noticeable.

Common behavioral trends and characteristics of alluvial channels including rivers are extensively discussed in the literature. However, little is known about the hydrodynamic effects of seepage on alluvial channels. Factors like sand bed resistance, stream power of the channel, incipient motion of bed particles, and geometry of the channel cross section are significantly affected by seepage. This thesis presents the experimental investigations that are aimed to find out the quantitative effect of seepage, through a sand bed in downward (suction) direction, on the above mentioned factors. The problem in the sediment transport analysis is that the knowledge of complex interaction of several parameters with seepage cannot be fully obtained. In order to generalize the results, experiments are conducted in four rectangular smooth walled sand bed flumes under steady and fairly uniform flow conditions. Among the four, one is the Large Tilting Flume (LTF), which is 25 m long, 1.80 m wide and 1.00 m deep and with a seepage length of up to 20 m. This LTF is specially built at hydraulic laboratory, Indian Institute of Science exclusively for the present research work especially on alluvial channel regime. The experimental channels are designed to apply controlled amounts of uniform seepage flow in either direction in one flume (Flume-2), and only in downward direction to other three flumes (Flumes 1, 3 and 4). The application of seepage is perpendicular to the sand bed thickness over a sufficient length of the main channel. Appropriate instruments are used to accurately measure the basic experimental variables such as discharge in the main channel, seepage discharge, flow depth, water surface and bed slope, seepage gradients and cross sectional profiles. Experiments are carried out at different conditions (plane beds and curved shape channels) as explained below: Plane sediment beds Series – 1: Experiments to determine incipient motion of bed particles under no-seepage condition. Series – 2: Experiments on the non-transporting condition of the bed particles under both no-seepage and seepage condition. Series – 3: Experiments on the transporting condition of the bed particles under both no-seepage and seepage condition. Curved shape channels Series – A: Experiments to verify Lane’s (1953) geometric profile against higher discharge than prescribed by Lane (1953). Series – B: Experiments to verify the Lane’s (1953) geometric profile by allowing the discharge prescribed by Lane (1953). Series – C: Experiments to predict the final geometric profile by applying suction to Series – B experiments. A wide range of sediment particles are tested. Five different sized uniform sands (d50 = 1 mm, 0.56 mm, 0.65 mm, 1.00 mm and 1.77 mm) and gravel of size d50 = 8.00 mm are used for experimentation. Among the six sizes, three sizes (d50 = 0.56 mm, 0.65 mm, 2 mm) are used for seepage experimentation. The experimental data from the present experiments along with the available data from other sources on more sizes of sand are analyzed, thus covering a wide range of sand sizes. The following important results are obtained from the analysis. A new resistance equation has been developed for plane sediment beds (with little or no-transport) such that the average velocity in the channel depends on the shear velocity Reynolds number. A careful study has been done on incipient motion and concluded that incipient motion is better explained by critical stream power criterion for plane sediment beds. With the help of critical stream power criterion, a straightforward design procedure using design tables/design curves and analytical methods are presented to solve six possible design problems. For plane and non-transporting beds, in general, the stream power in the channel increases with suction and decreases with injection. The increase and decrease depend on the seepage power intensity parameter (NP), initial value of stream power (Ωbo), and critical stream power of the particles under no-seepage condition (Ωco). An expression relating all the influencing parameters is established to quantitatively estimate the stream power (Ωbs) variation with both the types of seepages, i.e., with suction and injection. It is found that the seepage has a significant influence in changing critical stream power for incipient motion of the bed material and the value is significantly different from the no-seepage critical value. An expression is established to quantitatively estimate the critical stream power with seepage (upward and downward) for a given critical stream power (Ωco) of the bed material under no-seepage conditions and initial stream power (Ωbo). It has been established that critical stream power curve used to define incipient motion is valid only for no-seepage condition of the bed and it cannot be used for sand beds under seepage condition, as seepage effects significantly alters the stream power. From the wide range of experimental data (including the observations from LTF) it is found that suction (downward seepage through the sand bed) enhances the transport or aids the incipient motion of bed particles which are initially at rest. Thus, suction reduces the stability and increases the erosion of bed particles when compared to no-seepage conditions. However, it is found that injection (upward seepage) affects in an opposite way, i.e., it can reduce the transport rate or even inhibit the incipient motion. Thus, injection increases the stability and reduces the erosion of bed particles when compared to no-seepage conditions. Therefore, it is concluded that suction increases the mobility of sand particles where as injection decreases their mobility. An expression to find the incipient motion with seepage (both suction and injection) is established in terms of stream power’s (Ωco, Ωbo and Ωbs) based on the present experimental data along with others' data. With the help of these expressions design procedure is developed for ten types of possible problems. A numerical model for spatially varied flow has been developed with the help of the seepage governing equations, developed in this thesis, to compute flow profiles along the channel length. A methodology of predicting the location of incipient motion section in sand bed channels affected by seepage is also presented. Channel geometry affected by seepage (suction) is established in the form of regression relationships for perimeter, flow depth and slope of the channel. Different combinations (bi-variate and tri-variate) of dimensional and non-dimensional regression relationships are developed. An approach to channel design has been developed based on the application of functional analysis of the salient variables that control the channel behavior. And also, it has been established that, Lane’s (1953) profile almost matches with experimental profile for no-seepage condition. The present investigation clearly shows the significance of seepage in altering the hydraulic and sediment transport behavior of sand bed channels. From the practicing engineer’s point of view it is hoped that present design procedures will be helpful in safe guarding the seepage affected channels.