No description available.

No description available.

Fine substrate sediments are considered to be important in the management of urban river systems. Urban construction activities have been reported to increase sediment loads causing the temporary siltation of channel substrates within the urban area. Nevertheless fine sediment derived from urban areas frequently carry toxic material well in excess of background concentration levels. While the soluble phase of heavy metals and the importance of their association with suspended sediment has received considerable attention, longer term studies of fine urban river-bed sediments are limited. Furthermore studies of heavy pollutants in active stream sediments, below mine waste tips, have shown the channel substrate can provide a long term store for heavy metals in association with fine sediments. This thesis investigates the variety of impacts that urbanisation has upon the sedimentation of gravel bed rivers. A freeze coring technique and infIltration baskets have been used to study the textural-geochemical properties of fme matrix sediment and its development within an urban river-bed framework, within and below a number of contrasting urban catchments in the U.K. Complex urban hydrological and sedimentological regimes are shown to have a variable influence upon matrix sedimentation. The actual volume of matrix present within the urbanised substrate is influenced by the degree of urbanisation within the catchment. Furthermore this sediment is finer in size and associated heavy metal concentrations are well in excess of natural background levels. Although heavy metal levels do correlate slightly with textural characteristics, the presence of maximum concentrations at depth in the substrate indicate possible mobilisation of metals within the urbanised river-bed. The temporal behaviour of matrix development within an urbanised substrate is shown to differ from natural river-beds. Despite high suspended sediment concentrations the magnitude of the potential rate of supply is lower, by 50 percent, and dominated by organic material. This sediment also contains elevated heavy metal cocnentrations. This contrasts to the inorganic sediment ingress of natural river substrates. It is concluded that fine matrix sediments within urban gravel bed rivers should be at least of concern to public health engineers, water authorities and conservationists.

No description available.

No description available.

Η περιοχή μελέτης εμφανίζει ένα ποτάμιο πλυμμηρικό σύστημα κατά την περίοδο του μέσου/ ανώτερου ολόκαινου. ο οικισμός της αρχαίας Κλειτορίας καταστράφηκε από την δημιουργία πλυμμηρικού φαινομένου.Βέβαια σημαντικό ρόλο στην επιπλέον καταστροφή έπαιξαν και οι ανθρώπινες παρεμβάσεις. Το πλυμμηρικό αυτό γεγονός δημιούργησε ποτάμιες αναβαθμίδες και αλλουβιακές αποθέσεις στην τότε αρχαία Κλειτορία. Τα τείχη του οχυρού παρασύρθηκαν από τη μεγάλη παρόχη του ποταμού και οδήγηση στον αφανισμό του οικιστικού πλέγματος κατά τον 7-8 αιώνα. / Environmental history often reveals the contribution of humans in the modification of natural environment, always in relation with the climatic factors. Archaeological settlements may be preserved through desiccation, however, they are commonly found in floodplain sediments. Archaeological evidences may provide with useful information about the processes and extent of environmental changes, but they may also be used as tools for the analysis of floodplain sedimentation, relative chronology of sedimentation events and for the geomorphological evaluation of the particular archaeological site. The characteristics of archaeological indicators and the deposits in which they occur, may indicate important aspects of their source, transportation way and age. Evidence of river migration may be found in alluvial plains, through careful observations. The study area is located in Kalavrita region in northern Peloponnese. The archaeological excavations carried out revealed the fortification wall of the ancient city of “Kleitor” which is dated between the 3rd and 2nd century BC (Hellenistic Period). It may also provide clues for land surface development, reworking of sedimentary deposits, paleoenvironmental and climatic conditions. Sediments indicating considerable climatic changes are alluvial deposits of considerable thickness, covering areas with human impact. All the aforementioned become a tool for dating the course changes of the rivers and consequently a geomorphological instability. The relationship between geomorphology and history is recognizable also in the settlement distribution. This close relationship between environment and man provides a tool to understanding the landscape evolution from a geomorphological and historical point of view.

No description available.

Les gestionnaires de l'Etat français sont aujourd'hui exposés à plus d'un siècle de profondes modifications environnementales des cours d'eau : perturbations des conditions d'écoulement par "chenalisation" et incision du lit, aggravation des risques hydrologiques par végétalisation des corridors fluviaux et diminution des zones humides. La Loire fait partie des cours d'eau concernés par ces perturbations Le lit fluvial réagit par l’érosion de son fond (une incision qui atteint localement une valeur de 2 m entre 1995 et 2010), la migration latérale du talweg et la rétraction de la largeur du corridor fluvial. Depuis maintenant plus de 15 ans, la Loire fait l'objet de lourds travaux d'entretien des ouvrages (levées. épis et digues) et du lit fluvial. Ces interventions s'inscrivent dans le cadre du Plan Loire Grandeur Nature, elles visent la protection des riverains contre les risques d'inondation (ouverture des annexes d'écoulements), la préservation des richesses écologiques et l'enrayement de l'enfoncement de la ligne d'eau à l'étiage.Des travaux de recherche en géomorphologie fluviale sont réalisés parallèlement aux actions d'entretien effectués sous la houlette des services de l'Etat. Notre travail de thèse s'inscrit dans cette perspective de recherche. Les secteurs d'études ont été définis en concertation avec les gestionnaires du fleuve (DREAL Centre, DDT et Conservatoire du Patrimoine de la Région Centre). Trois sites ateliers ont été retenus le site de La Charité-sur-Loire. le site de Mesves et le site de Guilly. Cela afin de déterminer les modalités de l'évolution hydro-sédimentaire de la bande active, d'analyser les processus d'ajustement fluvial et mettre en lumière l'existence d'un dysfonctionnement, ses causes et ces conséquences. Les résultats obtenus montrent clairement l'impact du forçage anthropique et naturels sur l'évolution morpho-sédimentaire de la bande active. Les débits solide et liquide sont perturbés par différents aménagements fluviaux dont certains n'ont plus de fonction aujourd'hui ces ouvrages provoquent une rupture de la continuité sédimentaire. Cela se traduit par une poursuite de l'incision du chenal principal, un exhaussement des îles et des bras secondaires et une extension du couvert végétal. Les résultats de ce travail de recherche sont mis à la disposition des gestionnaires du fleuve pour optimiser les travaux de restauration réalisés au sein du lit mineur. / Managers of the French goverment are now exposed to more th an a century of profound environmental streams changes disruption of flow conditions by channelization and incision of the river bed, increased hydrological risks through the development of vegetation in river corridors and reducing wetlands. The Loire River is one of the rivers affected by such disruption. The river bed reacts by erosion (an incision that is locally a value of 2 m between 1995 and 2010), the lateral migration of the thalweg and narrowing the width of the river corridor. Since 1995, the Loire riverbed has been a field of restoration and maintenance works. These interventions took place within the "Plan Loire Grandeur Nature" and consisted of the following points : the protection of the inhabitants against flooding risks (opening of the secondary channels), the preservation of the ecological assets and the elimination of the water line sinking at its lower level. Research studies in fluvial geomorphology are made parallel to maintenance actions carried out under the leadership of state services. Our research study is part of this research perspective. Areas of study were defined in consultation with the river managers (DREAL Centre, DDT and Conservatoire du Patrimoine de la Région Centre) Three study sites were selected (the site of La Charité-sur-Loire. the site of Mesves and the site of Guilly) in order to : determine the terms of sediment transfer in accordance with flows, obtain evidence of understanding fluvial adjustment and highlight the presence of a dysfunction. its causes and consequences. Results clearly show the impact of natural and human pressure on the morphosedimentary evolution of active channels. Solid and liquid flows are affected by different river engineering (dams and bridges) some of which have no function today. These river installations encourage the continuation of the main channel incision. an elevation of islands, secondary channels and excessive growth of vegetation Results of this research are made available to managers to optimize river maintenance work carried out in the riverbed.

Šiame darbe nagrinėjamas 3 km ilgio Nemuno vandens kelio ruožas Šilutės rajone ir tiriami įvairūs upės vagos reguliavimo variantai. Pasirinktas Nemuno ruožas Šilutės rajone ties Leitės žiotimis pasižymi sudėtingomis sąlygomis vaginių procesų atžvilgiu. Tai tipiškas, be įprastinių, daugybės antropogeninių veiksnių formuojamas ruožas. Kita vertus, tai labai svarbus ruožas landšafto – gamtosaugos, rekreacijos, kultūros, ekonomikos ir kitais požiūriais, todėl šios Nemuno atkarpos tyrimai turi neabejotiną mokslinę svarbą ir praktinę naudą. Pagrindinis šio darbo tikslas- išanalizuoti ir įvertinti Nemuno vagos priežiūros ir reguliavimo galimybes saugomose teritorijose. Tam buvo panaudoti skaitmeniniai Nemuno dugno reljefo ir dvimačiai hidrodinamikos modeliai. Ruožo modeliavimas buvo atliekamas programomis ArcView ir Danijos Hidraulikos institute (DHI) sukurtu hidrodinamikos modeliavimo programų paketu MIKE 21 HD. Hidrodinamikos modelis suderintas pagal nagrinėjamo ruožo projektinius vandens lygius ir debitus. Analizuojama vagos reguliavimo įtaka upės pralaidumui (debitams) įvairiomis hidrologinėmis sąlygomis. Buvo išnagrinėti įvairūs nagrinėjamo upės ruožo vagos reguliavimo variantai: vagos krantų ištiesinimas ir laivakelio pagilinus nuo 1,5 iki 2,5 m garantinio gylio. Analizuojant modeliavimo rezultatus įvertintos Nemuno vagos priežiūros ir reguliavimo galimybės atsižvelgiant į galiojančius teisės aktus. / In this work researching 3 km length the Nemunas river waterway in Šilutės district and searching various variants of the riverbed. This Nemunas river waterway in Šilutės district beside the Leitė river mouth has complicated situation of the river bed process. This is typical, without odd, the strip formed with many anthropogenic factors. In other way, this is very essential strip of landscape – ecology, recreation, cultural, economical and in other aspects, wherefore this research of channel section of the Nemunas river has undoubted scientific and practical substantiality. The main purpose of this paper is to analyse and evaluate the possibilities to maintain and regulate the Nemunas river bed in the protected areas. The digital models of the relief of the Nemunas bed and the two-dimensional models of hydrodynamics have been used for this purpose. Modelling of the section has been made by using the application ArcView and the software package for hydrodynamics modelling developed by the Danish Hydraulic Institute (DHI), i.e. MIKE 21 HD. The model of hydrodynamics is matched for the designed water levels and yields of the section under examination. The influence of levelling the shores of the bed in the section under examination, deepening the channel from 1.5 up to 2.5 m of the depth guaranteed and has been analyzed. While analysing the results of modelling, the possibilities of maintenance and regulation of the Nemunas river bed have been evaluated, taking into... [to full text]

Aurimas Bieliauskas, Nemuno vagos reguliavimas būnomis: magistro tezės/ mokslinis vadovas doc. Arvydas Šikšnys. Darbo apimtis: 50 psl., 1 lentelė, 21 paveikslas, 7 priedai. Šiame darbe nagrinėjamas 3 km ilgio Nemuno vandens kelio ruožas ties Leitės žiotimis ir tiriami įvairūs upės vagos reguliavimo variantai. Skaitmeniniuose hidrodinamikos modeliuose buvo tiriamas vagos reguliavimo poveikis upės hidrauliniam režimui esant įvairioms hidrologinėms sąlygoms. Išnagrinėtas vagos reguliavimas būnomis, kurių pagrindinė paskirtis - sumažinti vandens tėkmės greičius prie kranto linijos ir apsaugoti upės krantus nuo vandens erozijos, o laivakelio zonoje - padidinti tėkmės greičius ir sumažinti čia nusėdančių nešmenų kiekius. Pasirinktas Nemuno ruožas ties Leitės žiotimis pasižymi sudėtingomis vaginių procesų sąlygomis. Tai be įprastinių, daugybės antropogeninių veiksnių formuojamas ruožas. Kita vertus, tai labai svarbus ruožas kraštovaizdžio – gamtosaugos, rekreacijos, kultūros, ekonomikos ir kitais požiūriais. Darbo tikslas – išanalizuoti ir įvertinti Nemuno vagos reguliavimo būnomis įvairiais variantais poveikį upės hidrauliniam-hidrologiniam režimui. Modeliavimui buvo panaudota programa MIKE 21, buvo išanalizuoti 3 skirtingi vagos reguliavimo variantai, nustatyta būnų įtaka upės hidraulinėms charakteristikoms, apskaičiuoti darbų kiekiai. / Aurimas Bieliauskas. The riverbed regulation with spurs of the river Nemunas: master theses/ scientific guide doc. Arvydas Šikšnys. The amount of work: 50 pages, 1 tables, 21 pictures, 5 supplements. In this work is analyzed the modeling of riverbed of the Nemunas 3 km length the Nemunas beside the mouth of the Leitė river mouth. In the numerical hydrodynamic models there were searching effects of the river bed regulation of the river hydraulic regime in various conditions. In the analytical part there is analyzed the process of the riverbed regulation which the main purpose there is the reduction of the water velocity near banks and conservation of the banks from the water erosion. Another purpose there is the regulation of the water velocity in the waterway zone and reduction in the silt there. This is typical, without odd, the strip formed with many anthropogenic factors. In other way, this is very essential strip of landscape – ecology, recreation, cultural, economical and in other aspects, wherefore this research of channel section of the Nemunas river has undoubted scientific and practical substantiality. The aim of this work is to analyzing and estimation of the waterway regulation in numerous aspects and influence on the river hydraulic- hydrologic regime. The modeling had been made with program MIKE 21 and had analyzed free different variants of the river bed. While doing analysis there was found the influence of the river hydraulic characteristics and there was... [to full text]