The lower Kennet Valley terraces reflect fluctuations in river regime through the Quaternary. Sediments and valley floor geomorphology provide a detailed record of Devensian and Flandrian fluvial behaviour and environmental change. Two major surfaces occur, the floodplain and the Beenham Grange Terrace (2 - 3m above the floodplain). Levelling showed that the terrace south of the river, underlain by deposits of two Early Devensian interstadials, was part of the Beenham Grange level, and not the Thatcham Terrace as previously proposed. The fluvial succession consisted of the subflood plain Midgham Peat Formation overlying the Woolhalllpton Gravel Formation The latter also rises to form the surface of the Beenham Grange Terrace adjacent to the floodplain. A subunit of the Woolhampton Formation, the Heales Lock Gravel Member, thickened over a large depression in the local Tertiary bedrock and was associated with syndepositional subsidence which aided excellent subfossil preservation in the sediments. A major channel fill within the member - the Wasing Sand Bed - contained Betula with a distinctive herb flora which, with 14C data, indicates a correlation with the Late Devensian Windermere Interstadial. Lithostratigraphy, biostratigraphy and 14C data from gravels resting unconformably on the Wasing Sand indicated a Loch Lomond Stadial age. The sedimentology of the Midgham Peat Formation reflected early Flandrian reductions in flow competence associated with silt, peat and tufa deposition. Regional woodland expansion was followed by alder can' closing of the floodplain during the Atlantic. A subsequent hiatus ended ,with Sub-boreal (?Bronze Age) flooding and deposition, perhaps anthropogenically induced. An upper silt reflects lower energy flooding in an agricultural landscape. To avoid taphonomic difficulties macrofossil interpretations utilised only well-preserved material. Pollen taphonomy was more problematic. A pilot study in subarctic Canada suggested that, while fluvial pollen assemblages were not exactly equivalent to regional pollen rain through local inputs and sorting, vegetation changes were identifiable.

The genesis, development, character, spatial variability and sedimentary composition of floodplains have been a much neglected study in the geomorphological literature. This is evidenced by the fact that the three most recent authoritative texts on fluvial geomorphology devote less than 2% of available space to this drainage basin component. As floodplains are one of the most extensive and widespread of fluvial landforms, this lack of analysis is important and surprising. It is the objective of this study partially to redress this previous neglect and to provide a better understanding of this important landform. Following a critical review of previous floodplain geomorphological and sedimentological studies, attention is focused on detailed case studies of floodplain development in the Oise and Cuckmere valleys, two small catchments in the southern Weald. Geornorphological maps have been constructed which are used to to describe floodplain form-process relationships. Subsurface investigations by hand-augering techniques at nineteen locations within the two valleys have enabled the form of the underlying sub-alluvial surfaces and the nature and thickness of the overlying litho-stratigraphic units to be described. A classification of the various types of valley rockhead encountered is outlined and form-lithology relationships investigated. Earlier interpretations of sub-alluvial surfaces are rejected for research has indicated that they are better explained as ccaplex, composite, polygenetic, diachronous response surfaces. The alluvial geometry of the fill sequences is discussed and analysed. The sedimentological and mineralogical characteristics of these deposits are analysed by a number of techniques including scanning electron microscopy, infrared spectrophotometry and X-ray diffraction. Results indicate that the fine-grained alluvial fill deposits comprising these floodplain tracts appear to consist largely of reworked aeolian (loe"ss) sediments with varying inclusions of locally derived materials. Further sampling and analyses of the alluvium found in floodplains throughout the Weald have indicated that deposits with characteristics similar to those in the Ouse and Cuckmere valleys are to be found, which provides an indication of the former widespread deposition of loess in this area. A working model of floodplain and valley development is derived for the Holocene period using palynological and radiocarbon evidence. This is then used to re-examine some of the previous concepts regarding the origins and evolution of floodplains, including a re-evaluation of Dury's meandering valley and underfit stream model as it relates to south-east England.

As part of the effort to satisfy the ever increasing demand for a greater understanding of fluvial, hydrological, chemical, sedimentological and geomorphological processes operating on the floodplain, mathematical simulation models have come to play a significant role in the understanding, prediction and management of the floodplain environment. Underlying the accurate numerical representation of hydraulically driven processes is the provision of a suitable floodplain hydrology model which accounts for the interaction between surface hydraulics and subsurface hydrology. Such a numerical representation is currently not available at the spatial and temporal resolution required. It is the aim of this thesis to develop a novel conceptual approach to modelling floodplain hydrology in which the fundamental need to consider the interaction between surface and subsurface flow is the floodplain environment is addressed. This is achieved through the interactive coupling of a one-dimensional finite difference infiltration model with the state-of-the-art two-dimensional physically based finite element hydraulic model, TELEMAC2D. The coupled model provides an unparalleled spatial and temporal representation of surface and subsurface flow processes within the floodplain environment. The utility of this integrated approach is explored through an application of the model to two areas of contemporary floodplain research. In the first of these the model is run to assess the impact of infiltration on flood flow prediction for an llkm reach of the River Culm, UK, over a range of flood and soil conditions. In the second the model is run to investigate the nitrate buffering potential of floodplain riparian soils during flooding. For this investigation a model accounting for nitrate transport and denitrification is developed within the existing integrated hydraulic-infiltration model structure. An evaluation of the results from both of these investigations supports the need for a new approach to modelling fluvially driven floodplain processes which accounts for the spatially interactive nature of floodplain hydrology.

The objective of this research was to investigate the sediment behaviour in a compound channel and, in particular, the transfer of sediment between a main channel and its flood plain. A review of the literature on compound channels showed that, whilst research on fixed boundaries had been carried out or was in hand, there was no evidence that the loose boundary situation had previously been studied.Experiments were conducted in a loose boundary, outdoor sand channel of symmetrical compound section. The channel was of straight alignment, 50 m long, with an overall width of 3 m. Pumping equipment was available for recirculation of the water and the sediment.Samples of suspended sediment were collected from the shallow and deep sections and analysed by Coulter Counter to obtain the particle size distributions. The distribution curves were found to be very similar for the main channel and the flood plains.Sand from the channel was labelled by fluorescent dye and inserted in the bed of the main channel so as to simulate a point release. Bed samples were collected at sections 5 m and 10 m downstream of the injection point and examined under UV light for their tracer proportions. It was found that the cross-sectional distribution of tracer concentration was approximately Gaussian indicating that there had been some sediment transfer to the flood plains.A two-dimensional diffusion model, which accounts for the movement in the longitudinal and lateral directions, has been applied to describe the transport and dispersion of the tracer particles. A best-fit overlay with the experimental results enabled the longitudinal and lateral dispersion coefficients to be established. The model results, for the distribution of tracer, are depicted in 2 and 3-dimensional form at a sequence of time intervals for up to 2 hours after tracer release.It was concluded that under steady state conditions there would be a constant transfer of sediment from the main channel to the flood plains; in fact, analysis showed that approximately 40% of a continuous tracer injection in the main channel would be transferred to the flood plains.

Previous studies of overbank hydraulics and sedimentation have adopted a variety of methods to investigate overbank processes, using either field based, physical or numerical modelling approaches. In this study a two-dimensional depth-averaged model of overbank hydraulics (Hydro2de) is tested and then used to develop a two-dimensional model of suspended sediment transport and deposition. A model grid was used with a higher resolution than those employed in most equivalent model applications in order to represent the topographic complexity of the natural floodplain in detail. The models were calibrated and rigorously tested using a varied and detailed set of spatially and temporally distributed field data. Models were applied to a short reach of the River Culm, Devon, UK. A wide range of field and laboratory data were used to enable model implementation, calibration and validation. Continuous monitoring of stage and sediment concentration were carried out at the site for the period of study and existing data were used from gauging stations located up- and downstream of the site. A large data set of spatially distributed sediment concentration, velocity and flow depth data were collected across the floodplain over a series of flood events. Inundation boundaries were identified using GPS surveys supplemented by field observations and both ground and aerial photography. The amount of overbank deposition was measured for individual floods using astroturf sedimentation traps. Medium-term sedimentation rates were estimated at selected locations using the Caesium-137 whole core technique. Both models were shown to yield good results which, when compared with field measurements were within the limits of uncertainty associated with these data. Simulation results allow a number of conclusions to be drawn about floodplain processes and their representation by numerical models. First, representation of complex, small-scale floodplain topography (features with dimensions <10 m) is of considerable importance when modelling flow and sedimentation on natural floodplains. Second, sediment transfer from the channel to the floodplain is dominated by advection rather than diffusion. Third, low magnitude events are more important than infrequent high magnitude events in terms of total conveyance losses, despite the lower sediment load of the former. Fourth, high resolution distributed models may be used to develop simple conceptual statistical models that capture the complexity of hydraulic conditions on natural floodplains. Finally, further work on floodplain modelling should concentrate on the development of a physically-based understanding of deposition processes in the presence of vegetation.

As part of the effort to satisfy the ever increasing demand for a greater understanding of fluvial, hydrological, chemical, sedimentological and geomorphological processes operating on the floodplain, mathematical simulation models have come to play a significant role in the understanding, prediction and management of the floodplain environment. Underlying the accurate numerical representation of hydraulically driven processes is the provision of a suitable floodplain hydrology model which accounts for the interaction between surface hydraulics and subsurface hydrology. Such a numerical representation is currently not available at the spatial and temporal resolution required. It is the aim of this thesis to develop a novel conceptual approach to modelling floodplain hydrology in which the fundamental need to consider the interaction between surface and subsurface flow is the floodplain environment is addressed. This is achieved through the interactive coupling of a one-dimensional finite difference infiltration model with the state-of-the-art two-dimensional physically based finite element hydraulic model, TELEMAC2D. The coupled model provides an unparalleled spatial and temporal representation of surface and subsurface flow processes within the floodplain environment. The utility of this integrated approach is explored through an application of the model to two areas of contemporary floodplain research. In the first of these the model is run to assess the impact of infiltration on flood flow prediction for an llkm reach of the River Culm, UK, over a range of flood and soil conditions. In the second the model is run to investigate the nitrate buffering potential of floodplain riparian soils during flooding. For this investigation a model accounting for nitrate transport and denitrification is developed within the existing integrated hydraulic-infiltration model structure. An evaluation of the results from both of these investigations supports the need for a new approach to modelling fluvially driven floodplain processes which accounts for the spatially interactive nature of floodplain hydrology.

Η παρούσα μεταπτυχιακή διατριβή ειδίκευσης εκπονήθηκε στο Τμήμα Γεωλογίας του Πανεπιστήμιου Πατρών, στα πλαίσια του Προγράμματος Μεταπτυχιακών Σπουδών με γενικό θέμα «Γεωεπιστήμες και περιβάλλον». Σκοπός της εργασίας είναι η περιβαλλοντική και υδρογεωλογική μελέτη της λεκάνης του Θολοποτάμου ποταμού, Δήμου Αιγείρας, ενώ η ευρύτερη περιοχή έρευνας περιλαμβάνει επίσης τις υδρολογικές λεκάνες των ποταμών Κράθι και Κριού. Προκειμένου να εξαχθούν τα κατάλληλα αποτελέσματα, προηγήθηκε επεξεργασία και μελέτη των γεωλογικών, υδρογεωλογικών και μετεωρολογικών συνθηκών που επικρατούν στην περιοχή, ύστερα από την απαραίτητη συλλογή δεδομένων. Η ευρύτερη περιοχή χαρακτηρίζεται ως επί το πλείστον από πρόσφατους Πλειο-Πλειστοκαινικούς και Τεταρτογενείς σχηματισμούς στο πεδινό και ημιορεινό της τμήμα, ενώ στις πιο ορεινές τοποθεσίες οι σχηματισμοί είναι αλπικοί και συγκαταλέγονται κυρίως στη γεωτεκτονική ζώνη Ωλονού – Πίνδου. Πιο συγκεκριμένα, στην πεδινή περιοχή, εμφανίζονται σε μεγάλη έκσταση μάργες, ψαμμίτες και κροκαλοπαγή, συνιστώντας έτσι το κύριο υδροφόρο στρώμα της περιοχής, ενώ στα μεγαλύτερα υψόμετρα διακρίνουμε ασβεστόλιθους της ζώνης Πίνδου αλλά και της ζώνης Τριπόλεως. Από τεκτονικής άποψης, η περιοχή είναι ιδιαίτερα ενεργή, γεγονός που έχει παίξει καθοριστικό ρόλο στην μεταλπική ιζηματογένεση, στη διαμόρφωση της γεωμορφολογίας αλλά και στην ανάπτυξη του υδρογραφικού δικτύου. Η εκφόρτιση του συστήματος της περιοχής πραγματοποιείται μέσω ενός πλήθους πηγών, σχηματίζοντας έτσι τις υπό μελέτη υδρολογικές λεκάνες. Όσον αφορά τον Θολοπόταμο, οι πηγές του βρίσκονται σε Πλειο-Πλειστοκαινικό γεωλογικό υπόβαθρο μαργαϊκής σύστασης, σε αντίθεση με τους ποταμούς Κράθι και Κριό, των οποίων οι πηγές εμφανίζονται στην επώθηση της ζώνης Πίνδου με την Τριπόλεως. Σύμφωνα με τις χημικές αναλύσεις που πραγματοποιήθηκαν, τα νερά της υπό έρευνα περιοχής ομαδοποιούνται σε τέσσερις κύριους υδροχημικούς τύπους: Τα νερά με χημικό τύπο Ca-Mg-HCO3 τα οποία αποτελούν το επικρατέστερο τύπο υδάτων της περιοχής, τα νερά με χημικό τύπο Ca-Mg-HCO3-SO4 που έχουν σχετικά μεγάλη εμφάνιση, τα νερά με τύπο Ca-HCO3 που εμφανίζονται ελάχιστα και τέλος αυτά με χημικό τύπο Ca-Na-HCO3-Cl-S που αποτελούν τμήμα της περιοχής και συναντήθηκαν μόνο σε μια τοποθεσία. Επιπλέον, οι τιμές των ιοντικών λόγων Na+/K+ και (Ca2++Mg2+)/(Na++K+) δείχνουν τη διαφοροποίηση μεταξύ των σημείων εμπλουτισμού του υδροφόρου και των σημείων στα κατάντη τμήματα του υδροφόρου, δηλαδή στις περιοχές εκφόρτισης του υδροφόρου. / The purpose of this Master Thesis is to deal with the environmental and hydrochemical conditions of the basin of the river Tholopotamos, in Aigeira, Achaia. The study area also includes the neighboring basins of the rivers Krios and Krathis. In order to export the final results, firstly the necessary data were gathered and then they were appropriately elaborated. The lower and plain regions of the study area consist of recent Pleio-Pleistocene and Quaternary formations, whereas the higher and mountainous regions are comprised of the alpine formations of the Olonos – Pindos geotectonic Zone. Specifically, the plain areas are covered by marls, conglomerates and sandstones which appear in a great scale, comprising the main aquifer bed of the basin of Tholopotamos. On the other hand, the alpine bedrock of the mountainous areas consists of limestone of the Olonos – Pindos or the Tripoli’s Zone. The aquifer discharges through numerous springs that are located on the marls formations, in contrast to the springs of Krathis and Krios basins, which occur on the overthrust of the Olonos zone over the Tripoli’s one. Αccording to the chemical analysis, the study areas’ waters can be classified in three categories: waters with hydrochemical type Ca-Mg-HCO3, which are the most common for the study area, waters with hydrochemical type Ca-Mg-HCO3-SO4 which appear in a rather great scale, waters with type Ca-HCO3 that appear in one area and lastly, those with chemical type Ca-Na-HCO3-Cl-S which were found only in one place.

In recent years there has been a growing interest in the contemporary floodplain environment which has come from a number of fields including civil engineering, hydrology, geomorphology and ecology. A major advance in civil engineering has been the development of two-dimensional hydraulic models capable of a high degree of spatial representation. These models were originally developed for engineering applications although recent developments, such as their application to longer reach lengths, mean that these models are very powerful predictive tools with potential for application in many different fields. Two-dimensional floodplain hydraulic models can be viewed as a platform for further development through the incorporation of additional components to represent specific processes. For the case of the application of these models in hydrology, whilst the models provide a good representation of floodplain processes in a hydraulic context, catchment hydrology is essentially treated as a black box. The only input to the system is the upstream input hydrograph (occasionally rainfall over the floodplain surface and tributary inflows are included) and output only occurs at the downstream boundary. The floodplain is assumed to be impermeable and any input from the hillslopes bordering the reach is ignored. This investigation examines the significance of contributions to the floodplain from the hillslopes bordering the reach. In order to do this, the zero flux boundary condition at the hillslope-floodplain interface is relaxed. A two-dimensional floodplain inundation model, RMA-2, is set up for a 14 km reach of the River Culm in Devon. A distributed hillslope hydrology model, VSAS3 is set up for a section of the hillslopes bordering the reach. This model is coupled to RMA-2 using a simple external coupling mechanism whereby water produced by VSAS3 is applied to elements along the edge of the RMA- 2 finite element mesh. A sensitivity analysis is carried out using this coupled scheme to identify some of the range of hillslope environments which may contribute a significant volume of lateral inflow to the floodplain. Five key hillslope parameters are selected and altered over a range of values. It has been shown that hillslope inflows can have a significant effect on the predictions made by RMA-2, both in terms of changes to the predicted output hydrograph and localised changes in depth and inundation extent. It has also been shown that the timing of the hillslope inflow peak relative to the arrival of the floodwave from upstream is of great importance. The addition of inflows has also been found to affect the calibration of the floodplain inundation model.

This thesis examines landscape diversity within alluvial valley floors using the case study of a Scottish wandering gravel-bed river. The thesis aims are two-fold; firstly to investigate the spatial and temporal patterns of valley floor landscape diversity within semi-natural environments, and secondly to develop a methodology for quantifying alluvial valley floor landscape diversity in space and time. The diversity analysis involves quantifying the spatial patterns of geo-, pedo- and biodiversity (flora) within floodplain zones which have been exposed to approximately 100 years of recovery since flood embankment abandonment along the most active reaches of the river. In addition historical records including aerial photographs, maps and narrative accounts were used to assess the temporal patterns of the diversity of landscape patches and how they have changed through time using a series of landscape indices. The analysis thus accounts for the role of river channel change in producing a complex mosaic of land cover types within alluvial valley floors. The spatial analysis revealed that landscape diversity tends to be greater in the perpendicular orientation to the main channel, i.e. along an aquatic-to-terrestrial environmental gradient. The temporal analysis results revealed that the landscape over the last 50 years has changed from being dominated by few relatively large isodiametric patches to a landscape dominated by small irregular shaped patches. Thus although landscape patch richness has increased along with an increase in land cover types through time, the landscape patches have also become more fragmented. The major outcomes of the research are the deriving of quantitative results of the spatial and temporal patterns of floodplain landscape diversity, an evaluation of the role of channel dynamics in creating the diverse mosaic of land cover types, the identification of the environmental controls and supporting floodplain habitats of a number of rare species and a proposed methodology for assessing landscape diversity to be validated on other river systems.

Σκοπός της παρούσας εργασίας, είναι η διερεύνηση των υδροχημικών παραμέτρων των κοκκωδών υδροφόρων της λεκάνης του Σπερχειού, καθώς και η πιθανή τροφοδοσία τους από τα ανθρακικά πετρώματα. Για το σκοπό αυτό πραγματοποιήθηκαν μετρήσεις στάθμης, καθώς και υδροχημικές αναλύσεις κύριων στοιχείων, ιχνοστοιχείων και σπάνιων γαιών. Γεωλογικά η περιοχή, στο βορειοανατολικό και νοτιοανατολικό τμήμα της ,δομείται από τους σχηματισμούς της Υποπελαγονικής ζώνης, στο νότιο από τους σχηματισμούς της ζώνης Παρνασσού-Γκιώνας και στο δυτικό από τους σχηματισμούς της ζώνης της Πίνδου. Οι Ολοκαινικές και Πλειο-πλειστοκαινικές αποθέσεις, δομούν το πεδινό τμήμα της λεκάνης και φιλοξενούν τον κύριο υδροφόρο ορίζοντα της περιοχής. Ο ελεύθερος αυτός υδροφόρος μεταπίπτει σε υπό πίεση, εξαιτίας της παρουσίας αργιλικών σχηματισμών, στα ανατολικά της περιοχής. Στα ορεινά τμήματα της λεκάνης, εντός των ανθρακικών σχηματισμών, αναπτύσσονται σημαντικοί υδροφόροι ορίζοντες. Με βάση τον πιεζομετρικό χάρτη της περιοχής προκύπτει ότι η διεύθυνση της ροής του υπόγειου νερού, είναι κυρίως ΒΑ-ΝΑ και o προσχωματικός υδροφόρος, τροφοδοτείται πλευρικά, από τους ανθρακικούς σχηματισμούς, που βρίσκονται νότια και βορειοανατολικά του πεδινού τμήματος. Τα υπόγεια νερά της περιοχής, ομαδοποιούνται σε τρεις κύριους υδροχημικούς τύπους: Ca-HCO3, Ca-Mg-HCO3 και (Ca)-Νa-Cl-(HCO3). Ο πρώτος υδροχημικός τύπος χαρακτηρίζει τα φρέσκα νερά της περιοχής, ο δεύτερος τα νερά που παρέμειναν για μεγαλύτερο χρονικό διάστημα στον υδροφόρο και εμπλουτίστηκαν σε Μg+2, και ο τρίτος τα νερά που δέχονται την επίδραση είτε της θάλασσας, είτε των θερμών νερών από μεγαλύτερα βάθη. Από τα αποτελέσματα των υδροχημικών αναλύσεων προέκυψε ότι στην πλειοψηφία τους τα δείγματα είναι κορεσμένα σε ασβεστίτη και δολομίτη. Eπίσης σε μία ομάδα δειγμάτων, διαπιστώθηκε απεμπλουτισμός σε Na, γεγονός που αποδόθηκε σε διαδικασίες ιοντοανταλαγής. Οι αυξημένες συγκεντρώσεις Fe, Mn, αποδόθηκαν στη διάλυση των ορυκτών του φλύσχη της Πίνδου, ενώ ο Zn και τα NΟ3 σε ανθρωπογενείς παρεμβάσεις (βιομηχανικά απόβλητα και λιπάσματα). Το As το Li και το Β συνδέονται με την παρουσία θερμών πηγών. Τέλος η μεθοδολογία των σπάνιων γαιών, επαλήθευσε τα αποτελέσματα της πιεζομετρίας αλλά και τα υδροχημικών αναλύσεων, ότι δηλαδή ο προσχωματικός υδροφόρος της περιοχής, τροφοδοτείται πλευρικά από τα ανθρακικά πετρώματα της περιοχής και συγκεκριμένα από τους ασβεστόλιθους της Υποπελαγονικής ζώνης και της ζώνης Παρνασσού-Γκιώνας. / In the frames of this study the hydrochemical parameters of porous aquifers at Sperchios basin, were investigated. Moreover their possible recharge by carbonate rocks was examined. Therefore, a series of water level measurements and a sampling campaign were carried out. The samples were analysed for main, trace and rare earth elements. Regarding the area’s geological setting, its northeastern and southeastern part is comprised of formations of the Subpelagonic Zone, its southern edge of Parnassos-Giona Zone and its western part of Pindos Zone. At the lowlands these formations are overlain by Holocene and Pleistocene deposits which host the most important aquifer of the region. It is an unconfined aquifer, which at the eastern part turns into a confined one, due to the presence of clay formations. Many important aquifers have been also developed in the basin’s carbonate formations. The region’s piezometric map at the southern area indicates that the main water flow direction is NE-SE. Moreover it points out that the carbonate formations recharge the porous aquifer. According to their hydrochemical characteristics groundwater can be divided into three main types: Ca-HCO3, Ca-Mg-HCO3 and (Ca)-Na-Cl-(HCO3). The first one is typical of the region’s fresh water, the second one indicates longer residence time of the water that was enriched in Mg+2 and the third one of water that was either influenced by sea water or hot springs. The elaboration of the hydrochemical data also showed that the majority of water samples are saturated in calcite and dolomite. There is also a depletion of certain samples in Na+ which was attributed to ion exchange processes. High Fe and Mn concentrations originate from the dissolution of Pindos Flysch minerals, As, Li and B to the presence of hot springs, while Zn and NO3 were related to human impact (industrial waste and fertilizers). The rare earth elements confirmed the original hypothesis, which was based on piezometric data and hydrochemical data analysis, that the region’s porous aquifer is laterally recharged by the carbonate rock formations of Subpelagonic and Parnassos-Giona Zone limestones.