Σκοπός της πτυχιακής αυτής εργασίας είναι η προσέγγιση και η μελέτη των υδρογεωλογικών, υδροχημικών και περιβαλλοντικών συνθηκών της υδρολογικής λεκάνης των Τρικάλων. Η περιοχή έρευνας βρίσκεται στη Δ. Θεσσαλία. Γεωλογικά ανήκει στην Πελαγονική Γεωτεκτονική Ζώνη. Έγινε δειγματοληψία επιφανειακών υδάτων για 9 σημεία, καλύπτοντας ένα μεγάλο εύρος της περιοχής μελέτης. Ύστερα από επί τόπου μετρήσεις και αναλύσεις στο εργαστήριο και επεξεργασία τους, προέκυψε ότι τα νερά χαρακτηρίζονται ως κανονικά, γαιοαλκαλικά οξυανθρακικά νερά με βασικό χημικό τύπο Ca-HCO3-. Σε ότι αφορά τις φυσικοχημικές παραμέτρους, οι τιμές της θερμοκρασίας κυμαίνονται από 11 έως 15 οC, και οι τιμές του pH ~8, παρουσιάζοντας ένα βασικό αλκαλικό περιβάλλον, χαρακτηριστικό των επιφανειακών υδάτων. Το σφάλμα ισοζυγίου για το σύνολο των μετρήσεων ήταν εντός των ορίων αξιοπιστίας, παρουσιάζοντας για τα βασικά κατιόντα τις εξής μέσες τιμές: Ca-60mg/l, Mg-18mg/l, Na-6,4 mg/l και K-1,01 mg/l. Για τα ανιόντα, οι αντίστοιχες μέσες τιμές είναι: HCO3 - 243mg/l, SO4- 28,9 mg/l και για το χλώριο 8 mg/l. / --

The saltmarshes within the Solent area have retreated significantly over the past 120 years. The expansion of tidal creek systems contributes considerably to the net loss of these saltmarshes. The development of a tidal creek system at Exbury Marsh was studied, as being representative of the tidal creeks within the Beaulieu Estuary, with emphasis placed upon the evolution of the crosssectional profiles. The present geomorphology of the studied tidal creek system was investigated, together with the measurements on the bank sediment stability, the parameters of the root systems (Sea Purslane and Sea Rush) and the hydrodynamics. This study aims to understand the influences of various factors, e.g., root systems and bank sediment stability, on the geomorphological evolution of a natural tidal creek system, within a low energy environment. The results reveal that within this low energy saltmarsh, the erosion takes place at a low rate (1-2 cm a-1) on bank faces, greater than the vertical accretion rate of marsh surface (2.5 mm a-1). The geomorphology of the tidal creek system is mainly characterised by the presence of cantilevers. The bases of the cantilevers are found to be located at certain levels, related to submergence/emergence cycles. The cantilever stability analyses suggest that lateral expansion rate of the channel is approx. 2.9 cm a-1, caused by the periodic bank failure. The root systems are central in increasing bank sediment stability, contributing a maximum of 6 Pa to the erosion threshold and a maximum of 7 kPa to the shear strength of the bank sediments. The Sea Purslane root system is more effective than the Sea Rush root system, in retarding the bank erosion. The flow-induced bed shear stress (<0.1 Pa) is lower than the erosion threshold of the bank sediments (>0.5 Pa), under normal weather conditions. The water level frequency analysis suggests that the erosion below the cantilever bases can be achieved by submergence/emergence cycles, aided by low tidal currents, over a long-term period. The evolution of the cross-sectional profiles is controlled mainly by the transformation from mudflat to saltmarsh, the presence of a gravel base, the stabilisation by root systems on bank sediments and the erosion caused by submergence/emergence cycles (together with low tidal currents), over a long-term period. The main contributions of this study to practical application are: (1) root systems (e.g., Sea Purslane) with high resistance to fluid-induced erosion are more efficient than those (e.g., Sea Rush) with high resistance to gravity-induced mass failure, in stabilising tidal creeks. (2) The retreat of the banks, in low energy environments, is associated with long-term processes, e.g., submergence/emergence cycles (together with low tidal currents).

This thesis presents a novel technique for the quantitative characterisation of bathymetric data sets. The technique integrates three main geomorphometric methods: morphometric attributes and their statistical analyses, feature-based quantitative representation, and automated topographic classification. These methods allow useful morphological information to be extracted from bathymetric data and can significantly enhance submarine geomorphological investigations. The methods are applied to bathymetric data from the Storegga Slide, one of the largest known submarine landslides, to investigate three aspects of submarine mass movements: spreading, fractal statistics and morphology and slide development. The morphological signature of spreading, in the form of a repetitive pattern of ridges and troughs, covers at least 25% of the Storegga Slide scar. Two modes of failure can be identified for submarine spreading. The first involves retrogressive slide development via the unloading of the headwall. The second entails the extension of a thin coherent slab of semi-consolidated material downslope by gravity. Both modes of failure involve the break up of surface sediment units into coherent blocks and their displacement along planar slip surfaces. The block movement pattern entails an exponential increase of displacement, and thinning of the failing sediment, with distance downslope. Loss of support and seismic loading are the main potential triggering mechanisms of submarine spreading. Analysis of headwall morphologies within the Storegga Slide reveals the occurrence of spatial scale invariance. One explanation for this scale invariance is that the Storegga Slide is a geomorphological system that may exhibit self-organised criticality. Spatial scale invariance may also be linked to the retrogressive nature of the Storegga Slide. The shape and fractal dimension of headwalls, on the other hand, can be used as a proxy for the type and number of the formative mass movements. A detailed reconstruction of the development of the north-eastern Storegga Slide shows that after the initial evacuation of the surface sediment as turbidity currents, the area failed as an extensive spread. The spreading blocks subsequently underwent higher displacement and remoulding, and were partly removed by debris flows and turbidity currents. The renewed instability within the spreading areas may have been related to gas hydrate dissociation and pore pressure increases due in response to the changing overburden, and the distribution of contourite drift deposits within underlying palaeoslide scars.

This project conducts an analysis of bank erosion processes on a large, monsoonaffected river, the Lower Mekong River in Laos. The methodological approach taken was to build integrated models of bank erosion processes at three study sites on the Lower Mekong River in Laos (Friendship Bridge, Ang Nyay and Pakse) to simulate processes of (i) groundwater seepage and pore water pressure evolution, (ii) the effect of this on mass-wasting (using the Geo-slope model) and, (iii) fluvial erosion (using a model adapted from Kean and Smith, 2006ab). In all cases the models were parameterised using measured bank geotechnical properties. Across the study sites, a total of 42 simulations were undertaken to represent a wide range of observed flow events. Specifically, 14 selected flow hydrographs (comprising three types: single peak, multiple peak and rapid fall) were evaluated at each of the study sites, such that the influence on bank erosion of the hydrological properties of different monsoon floods could be evaluated. The main findings indicate that although the Mekong is a big river, its dominant bank erosion process is one of slow, gradual, fluvial erosion. This research forms a partial contribution to understanding bank erosion processes operating in the Mekong. It was found that bank stability on the Mekong responses to variations in flood magnitude in ways that are similar to other rivers located within humid temperate areas. However, the Mekong has had the greater stability than these rivers due to its greater bank heights and more consolidated bank materials.

Published, well-described examples of multiple mixed bedrock-alluvial character systems largely pertain to small to medium systems. No descriptions exist for large river systems such as the Mekong River in Cambodia (South East Asia). The published literature concerning the 120km long and up to 5km wide multichannel study reach are outdated and do not provide sufficient levels of detail. Therefore the first part of the thesis offers an amplified portrait of the modern and palaeo-Mekong based upon limited published literature, updated by ground survey data and complemented by analyses of remote sensing data. The second part of the thesis is devoted to applying quantitative channel network characteristics in order to describe the Mekong River but importantly to separate mixed bedrock-alluvial from alluvial multichannel rivers. The key question in this respect is whether the planform characteristics of the river networks reflect whether they are within alluvial settings or are influenced by bedrock controls. The channel metrics comparison is accompanied by a specially designed methodology based upon standard GIS tools so that the results obtained in this study could be later incorporated into subsequent channel network metrics research using a larger dataset for these or other rivers. Geomorphological findings reveal that the multichannel pattern of the Mekong is comprised by primary channels, secondary channels, cross-channels and blind channels, divided by two classes of islands: major and seasonally-inundated islands. The riverbed is represented by outcrops of Mesozoic bedrock and temporally and spatially fixed sand bars whereas the planview variations in the disposition of sand bodies versus bedrock define the extent of longitudinal geomorphological zones. Structurally and qualitatively diverse geological units are dissected by regional and local faults which partially control channel alignments. Topographic and dating control of river terraces and palaeochannel deposits show that the river incised during the Last Glacial Maximum but was essentially within the same course as seen today for at least last 70ka. Distinctive floristic associations emphasise an important role that vegetation plays in channel dynamics in this mixed bedrock-alluvial system. Comparative study of channel network metrics shows that reach-scale standard planform indices (e.g., braiding intensity, channel sinuosity) are less effective than non-standard indices developed at scales less than the reach-scale (e.g., channel network bifurcation angles asymmetry, island convexity) in successfully separating channel patterns. In addition, DEM trend surfaces reveal variable topographic trends generic for the mixed bedrock-alluvial patterns only. Ultimately, it shows that the mixed bedrock-alluvial pattern classification might be more effectively based on channel cross-section properties, e.g. variations between bedrock/alluvium as a part of a channel continuum.

Anabranching fluvial networks recently have become the focus of attention from environmental specialists, especially in the hydraulic field. Anabranching networks can be found in different physical environments; however, the hydraulic and geomorphological natures of such river networks are still not well known leading to on-going discussions on the definition and nature of the networks. Even though, alluvial anabranching networks generally have common features like vegetated islands, low water surface slope and stable channel planform, bedrock-confined anabranching networks also have their own characteristics inherited from the geological and structural controls imposed on the single channels that compose the network complex. This thesis focuses on the provision of a benchmark describing the bulk hydraulic characteristics of a large bedrock-confined, anabranching river network, located within southern Laos. The network can be separated into: (i) the upper river network constituted by two bifurcations and one confluence with an interpolated bathymetry based on soundings of cross-sections along the navigation channels; and, (ii) the downstream river network characterised by a complex anabranching network with five bifurcations and five confluences for which there is no bathymetric survey. The river network as whole is a ‘composite’ – partly bedrock (especially the channel-bed) and partly alluvial-filled and as such it does not accord fully with any prior description or classification of anabranching channel networks (e.g. Huang and Nanson, 1996). To understand the hydraulic nature of the river network, the energy approach in a onedimensional (1D) steady-flow hydraulic model (HEC-RAS) was applied to the network. Significant challenges arose due to the lack of boundary conditions throughout the model, namely: (i) unknown splitting discharge ratios at each bifurcation; (ii) partly non-survey bathymetry; and, (iii) ungauged downstream boundary condition of one of the channel outlets. To determine the discharge entering each channel, the splitting discharge ratio at each bifurcation was defined originally by the ratio of the cross-sectional area of the first crosssection of each downstream channel and then adjusted based on the Flow Optimization function in HEC-RAS to minimize any rise or drop of the modelled water surface around a junction. For the channels with non-surveyed bathymetry, a SPOT satellite image was processed to construct a pseudo-bathymetry showing a range of elevations, including shallow and deep portions of channels, rather than detailed bed elevations as would be obtained from a measured bathymetry. To define the boundary condition of the ungauged channel outlet, the water surface elevation was interpolated and validated according to predefined assumptions (i.e. the water surface slope along the ungauged channel was interpolated according to the available DEM and cross-sectional width extracted from a SPOT image for low discharge conditions was assumed to be similar to the gauged channels for flooding discharges). In general, the study has helped to develop methods to model the complex river network with data constraints (i.e. the boundary conditions). The findings include: (i) the developed pseudo-bathymetry based on a SPOT image is useful to model a large river network using the energy approach in a 1D hydraulic model in which the cross-sectional area is important in modelling the bulk hydraulic parameters but the influence of the cross-sectional shape is subordinate; (ii) the in-channel hydraulic roughness coefficient at each cross-section may be significantly different from neighbouring values due to the variation in the local bedrock roughness and the roughness of intervening alluvial reaches; and, (iii) the hydraulic roughness of the riparian land cover along the floodplains does not contribute noticeably to the modelled stage along the river network nor to the planform extent of flooding for overbank flooding discharges. Rather, changes in land-cover, and hence the riparian roughness, are registered as small, but measureable, changes in the local velocity over the riparian floodplain and in the average in-channel velocity. Citations: Van, P.D.T., 2009. Hydraulic modelling and flood inundation mapping in a bedrockconfined anabranching network: The Mekong River in the Siphandone wetlands, Laos. Unpublished PhD thesis submitted to the Faculty of Engineering, Science and Mathematics, University of Southampton, England.

Aid In Action Porthcawl (a registered South Wales Charity Organisation) has been carrying out charity work in the town of Rubik in the Mirdita Region of North Albania for many years. Rubik lies within the Catchment of the River Fani which is remote, ungauged and characterised by frequent flooding, erosion and deforestation. Over the years these processes have had a huge environmental and socioeconomic impact on the residents of Rubik. Aid In Action was concerned about this situation and wished to provide a sustainable solution. Following discussions with staff at the University of Glamorgan, it was agreed that a sustainable solution was the development of an integrated hydrological decision support system for the whole River Fani Catchment. Hydrological models can be a valuable tool, providing a common platform for experts, decision-makers and stakeholders for the sustainable management of catchments, especially when used within the framework of a Geographic Information System (GIS). Such models and systems require quantitative data of good quality over appropriate spatial and temporal scales. For remote mountainous ungauged river catchments in developing countries the development of a catchment model and management system is often complicated due to limited availability of such data. Very often, any available data are difficult to obtain; they could, for example, be scattered among local authorities and are generally in the national language of the country concerned, thus adding the challenge of having records translated into the study language. Over the last few decades, advances in hydrological data capture (e.g. using remote sensing) and data management systems (e.g. GIS) have provided opportunities for overcoming some of the challenges of modelling ungauged catchments. However, the data captured is often from different sensors and sources and at different scales. This research project sought out to creatively use multi-source and multi-scale data to develop a GIS based hydrological model of the River Fani Catchment in the North of Albania to provide, a long term solution for the sustainable management of the Fani Catchment, thus improving the quality of life for the residents of Rubik and the rest of the Catchment. Data from various remote sensing sensors (e.g. Landsat, MODIS, ASTER) and other sources such as published maps, limited gauged flow and rainfall records, local library archives, digital datasets (e.g. CORINE and radar rainfall) and interviews with residents were used to develop the integrated GIS-based hydrological (using WMS hydrological modelling environment) and hydraulic (HEC-RAS) model of the Fani Catchment. The model was then used to not only map significant environmental change in the Catchment (e.g. deforestation using various vegetation indices), but also to assess flooding impact and to analyse various “What-if” scenarios of conservation strategies (e.g. deforestation, afforestation and provision of runoff attenuation systems). The results suggest that the changes in vegetation cover (apart from farming practices) are not considerably extensive in the Catchment between 1984 and 2000. It was observed that afforestation as a flooding mitigation measure did not play a decisive role in runoff reduction compared with attenuation measures. This study has demonstrated the effectiveness of remote sensing and GIS in generating quantitative information on land classification, change detection, soil erosion and general catchment management for remote and ungauged catchments in developing countries. This has been particularly so, owing to recent developments in sensor technologies and increasing available datasets from data providers and the global scientific community at little or no cost.

Extensive fieldwork, laboratory analyses and secondary research on the glacial and coastal phenomena in Lewis and Harris have cast some light on the effects which glaciations had on the development of the coastline. Contrary to previous ideas, Harris and the major part of Lewis were probably covered by a large local ice cap, while the northern tip of Lewis and the Tolsta Head Peninsula were overridden by external ice during the last glacial phase. According to a C-14 date, this phase occurred after about 27,300 B.P. There are indications that a larger part of north Lewis was occupied by external ice during a previous glacial phase. The coastline developed in close correspondence to the pattern of glaciations. The oldest recognisable marine element is represented by a raised shore platform and cliff with an average cliff-base height of 8 m. above the modern cliff base. Because the raised shore platform is widely developed in resistant Lewisian gneiss and overlain by glacial and non-glacial sediments, the episode of abrasion at the higher level probably pre-dates the Devensian. Beach gravel which tops the raised shore platform in places is believed, on the basis of its well-rounded nature and stratigraphic position between two glacial tills, to be of Ipswichian age. The absence of the pre-Devensian rock platform and cliff and beach gravel in central Lewis, south Lewis and Harris may reflect destruction under subsequent ice advance. In this greater part of the island, differential glacial activity of generally higher intensity produced distinct coastal landforms and sediments. There is no unambiguous evidence that the sea around the island rose above its present level during the late Devensian and/or Flandrian. On the other hand, numerous Occurrences of peat below high water mark and one incidence of cemented sand below low water mark point to recent submergence. A dated peat sample form -3 m. O.D. at Holm indicates that, at around 8,800 B.P., the land/sea interface was at least 5 m. lower than at present. The indirect effects of global glaciations on eustatic sea level are considered as having been of greatest consequence to the long-term development of the coastline of Lewis and Harris since the Pleistocene.

River mouths are characterised by a conflict between marine and fluvial processes, in which the planimetry of the mouth is dependent on the relative contribution of wave, tide and current, which may be manifested in spit and barrier accumulation forms, and the often opposing force of river discharge. Analysis of historical geomorphological evidence shows that the Donmouth has a history of constant change. In 1975-74, in order to assess the relative importance of fluvial and marine factors in explaining this change, monthly and seasonal tacheometric and sediment sampling was undertaken on the spit-bar which extends north across the mouth, and on the updrift beach. The dynamics of both form and material were measured. Hydro™ . graphic surveys of the estuary, nearshore and offshore morphology and material, and measurements of waves and currents were also conducted in the field. Field'data was analysed in_the laboratory and-by computer to produce quantitative results which serve to complement the qualitative description,. Results of the various analyses serve to illustrate a model example of rlver-mouth variability and dynamic equilibrium. The Donmouth Is located in a stretch of soft coastline characterised by a strong south to north wave and current energy continuum, which is reflected in northerly increases in elements of beach, nearshore and offshore form, process and material, out of the wave shadow provided by the rock headland at the southern extremity of th© bay. a s part of this continuum, the Donmouth is largely characterised by a marine-formed spit-bar, whose dimensions are dependent on the level of river and estuarine discharge. Models of spit-bar variability and of river-mouth planimetry were thus facilitated and are presented.

No description available.