Comparative geomorphological observations in two groups of alluvial fans of Sperchios and Eurotas regions, Greece

Στην παρούσα εργασία μελετήθηκαν συγκριτικά δύο ομάδες αλλουβιακών ριπιδίων του ελληνικού χώρου, η πρώτη στην περιοχή του ποταμού Σπερχειού και η δεύτερη στην περιοχή του ποταμού Ευρώτα. Fia το σκοπό αυτό μετρήθηκαν συγκεκριμένα μορφομετρικά χαρακτηριστικά των λεκανών απορροής των ρεμάτων Τσερλιά, Ξεριά, Γοργοπόταμου, Κερασιά, Ρέτσα και Κάκαρη, καθώς και των ριπιδίων τους, έγινε σύγκριση των μετρήσεων αυτών και βγήκαν συμπεράσματα για το σχηματισμό και την εξέλιξη των ριπιδίων. Παράλληλα έγιναν επιμήκεις τομές της κεντρικής κοίτης των ρεμάτων, πραγματοποιήθηκε κροκαλομετρία εντός της κοίτης των ριπιδίων και αποτυπώθηκαν οι οδοντώσεις των ισοϋψών των ριπιδίων. Κατά την κροκαλομετρία έγινε φανερό ότι το μέσο μέγεθος Μ μειώνεται από την κορυφή προς τη βάση των ριπιδίων. Από τη μελέτη των οδοντώσεων των ισοϋψών προέκυψε ότι τα ριπίδια στην περιοχή του Ευρώτα έχουν υποστεί μεγαλύτερη διάβρωση από αυτά της περιοχής του Σπερχειού. Απ' όλα τα παραπάνω συμπεραίνεται ότι τα μελετούμενα ριπίδια παρουσιάζουν σημαντικές διαφορές τόσο μεταξύ τους (κυρίως για την περιοχή του Σπερχειού) όσο και μεταξύ των δύο περιοχών μελέτης. Αυτό οφε^ται κυρίως στον ρηξιγενή τεκτονισμό, την επικρατούσα λιθολογία και το κλίμα. Οι παράγοντες αυτοί είναι εκείνοι που κυρίως καθορίζουν τη γένεση και εξέλιξη των ριπιδίων και επηρεάζουν το σχήμα, την έκταση και τα επιμέρους χαρακτηριστικά τουςIn the present study two groups of alluvial fans from two different regions in Greece were comparetively studied, the first in the region of Sperchios river and the second in the region ofEurotas river. Distinct morphometric characteristics of the drainage basins of the tributaries Ts er lias, Xerias, Gorgopotamos, Kerasias, Retsas and Kakaris, as well as their fans were measured and compared. Furthermore ,the longitudinal stream profiles were mapped, pebble measurements were made and contour crenulations of the fans were studied. In gravelometry, it was found that the mean size M of the pebbles decreases from the apex to the apron of the fan. The crenulation analysis showed that the fans of the streams ofEurotas region have undergone greater erosion than those of Sperchios region. Remarkable differences exist between the fans of the two regions. These results lead to the conclusion that recent tectonism, the prevailing lithology and climate are responsible for the formation and evolution of the fans and also influence their shape, area and all the other morphometric characteristic

RECENT GEOMORPHIC CHANGES AND ANTHROPOGENIC ACTIVITIES IN THE DELTAIC PLAIN OF PINIOS RIVER IN CENTRAL GREECE

The Pinios river delta is a Late Holocene arcuate type delta, located in the southern Thermaikos gulf (Central Greece). In order to determine the processes which contributed in the recent configuration of the delta, a detailed geomorphic map at the scale of 1:5000 has been prepared showing both the deltaic plain and the coastal zone features using GIS techniques. Comparative examinations of aerial photographs taken in different dates and reliable maps of the last two centuries along with field observations depict recent changes of the delta morphology. The most important factors for the development of the delta are fluvial sedimentation, wave activity and longshore currents in a tectonically active area. Land uses throughout the delta plain have been mapped in an attempt to identify socio-economic activities. The dominant feature in the deltaic plain is the numerous abandoned meandering channels. The delta shoreline is generally retreating due to marine processes especially where former river mouths occur. Finally, various future sea-level rise scenarios have been analyzed and an assessment of the impacts of the potential global future sea-level rise to the delta is estimated

GEOMORPHOLOGY AND SEDIMENTOLOGICAL PROCESSES ALONG THE COASTAL ZONE BETWEEN LIVANATES AND AGIOS KONSTANTINOS (N. EVOIKOS GULF, CENTRAL GREECE)

This study deals with aspects of geomorphology and nearshore marine processes in the coastal zone located between Livanates and Agios Konstantinos (North Evoikos Gulf, central Greece). Evoikos Gulf is a tectonic graben bounded by WNW-ESE trending normal faults; it can be further characterized as semi-closed marine basin with water depths exceeding 400m.The Coastal geomorphology is affected by active tectonics with the most prominent morphological features being the uplifted marine terraces and the well-developed deltaic fan of Xerias torrent. In the present investigation, detailed geomorphological mapping at a scale of 1:5000 was performed together with granulometric analysis, while nearshore wave and current activity related to sediment dynamics has been determined on the basis of wind-generated wave regime. The examined coastal zone consists of a series of alluvial cones and fans, Xerias fan being the largest among them, low cliffs, a cuspate foreland and beach zones of limited length, often hosting beachrock formations. The formation and evolution of the study area seems to be controlled by the limited terrestrial influxes, the relatively weak wave regime due to limited wave fetches distances, and the associated longshore currents that induces limited sediment transport