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

Recent coastline changes of fan-deltas in the Western Gulf of Corinth, Central Greece

Στην παρούσα εργασία επιχειρείται η εκτίμηση των πρόσφατων μεταβολών της ακτογραμμής των δελταϊκών ριπιδίων των ποταμών Φοίνικα, Θολοπόταμο, Λαγκάδι, Μεγανίτα, Σελινούντα, Κερυνίτη και Βουραϊκού, με τη χρήση μεθόδων τηλεπισκόπησης και ΣΓΠ. Τα δελταϊκά αυτά ριπίδια ηλικίας Ανώτερου Ολόκαινου έχουν σχηματισθεί από ποτάμια μεγάλης μορφολογικής κλίσης που αποθέτουν το αδρομερές φορτίο ιζημάτων τους κατά μήκος των νότιων ακτών του δυτικού Κορινθιακού κόλπου (Β. Πελοπόννησος). Για τους σκοπούς της εργασίας δημιουργήθηκε και οργανώθηκε μια ψηφιακή βάση δεδομένων για την περιοχή αποτελούμενη από λεπτομερή (κλίμακας 1:5.000) τοπογραφικά διαγράμματα και γεωμετρικά διορθωμένες και γεωαναφερμένες αεροφωτογραφίες λήψης 1945, 1996 και 2008. Η σύγκριση των ακτογραμμών των δελταϊκών ριπιδίων κατά τα έτη 1945, 1996 και 2008 οδήγησε στον προσδιορισμό των τμημάτων της ακτογραμμής πουυπόκεινται σε διάβρωση καθώς και εκείνων που προελαύνουν. Η κύρια διεργασία κατά μήκος του μεγαλύτερου μήκους της ακτογραμμής είναι η διάβρωση. Ομεγαλύτερος ρυθμός διάβρωσης ήταν 2,44 m/έτος (μεταξύ των ετών 1945 και 1996) και σημειώθηκε περίπου 150 m δυτικά των εκβολών του ποταμού Φοίνικα. Αντίθετα οι υψηλότεροι ρυθμοί προέλασης μετά το 1945 ήταν 3,10 και 3,00 m/έτος και σημειώθηκαν στις περιοχές των ενεργών εκβολών των ποταμών Βουραϊκού και Σελινούντα αντίστοιχα.This study deals with the assessment of recent shoreline change rates along the fandeltas of Finix, Tholopotamo, Lagadi, Meganitas, Selinous, Kerinitis, and Vouraikos streams by using GIS and Remote Sensing techniques. These Late Holocene fandeltas have been formed by high gradient braided streams that deposit their coarse sediment load along the southern coast (North Peloponnese) of the western Gulf of Corinth. For the purposes of the study a spatial database was constructed, organized and implemented consisting of analogue detailed (at the scale of 1:5000) topographic diagrams, and orthorectified aerial photos taken in 1945, 1996 and 2008. Comparisons of fan-deltas shoreline positions for the periods 1945 vs. 1996 and 1945 vs. 2008 were made and the segments of the coastline along the aprons of the fan-deltas which are subject to erosion accretion were defined. Coastal erosion is the main dominant geomorphic process along a significant part of the fan deltas coastline. The highest retreat rate value (2.44 m/yr for the period 1945-1996) was estimated for the Finix stream fan delta, about 150 m west of the river mouth, while the highest accretion rates since 1945 (3.10 and 3.00 m/yr) occurred at the mouths of Vouraikos and Selinous rivers respectively

Assessment of neotectonic landscape deformation in Evia Island, Greece, using GIS-based multi-criteria analysis

This study deals with the assessment and mapping of neotectonic landscape deformation in the northern part of the Evia Island (Central Greece). Multi-Criteria Decision Analysis (MCDA) utilizing Analytic Hierarchy Process (AHP) andWeighted Linear Combination (WLC) procedures were conducted for the calculation of the Neotectonic Landscape Deformation Index (NLDI). The study is based on the combination of morphotectonic, geomorphological and geological parameters. The GIS-based spatial MCDA led to the classification of the study area into five classes of neotectonic deformation (from very low to very high) and to a neotectonic deformation map. The results were compared with the outputs of a relative tectonic activity classification approach based on quantitative geomorphic analysis at a regional scale, including site-specific field observations. Areas of high and very high deformation are related to the major active faults of Dirfis, Kandili and Gregolimano- Telethrio. Other minor active normal faults of medium to high seismic risk level, affecting the northern and northeastern parts of the island, are also associated with areas of intense landscape neotectonic deformation

Evaluating Spatial Variability in Sediment and Phosphorus Concentration-Discharge Relationships Using Bayesian Inference and Self-Organizing Maps

Given the variable biogeochemical, physical, and hydrological processes driving fluvial sediment and nutrient export, the water science and management communities need data-driven methods to identify regions prone to production and transport under variable hydrometeorological conditions. We use Bayesian analysis to segment concentration-discharge linear regression models for total suspended solids (TSS) and particulate and dissolved phosphorus (PP, DP) using 22 years of monitoring data from 18 Lake Champlain watersheds. Bayesian inference was leveraged to estimate segmented regression model parameters and identify threshold position. The identified threshold positions demonstrated a considerable range below and above the median discharge—which has been used previously as the default breakpoint in segmented regression models to discern differences between pre and post-threshold export regimes. We then applied a Self-Organizing Map (SOM), which partitioned the watersheds into clusters of TSS, PP, and DP export regimes using watershed characteristics, as well as Bayesian regression intercepts and slopes. A SOM defined two clusters of high-flux basins, one where PP flux was predominantly episodic and hydrologically driven; and another in which the sediment and nutrient sourcing and mobilization were more bimodal, resulting from both hydrologic processes at post-threshold discharges and reactive processes (e.g., nutrient cycling or lateral/vertical exchanges of fine sediment) at prethreshold discharges. A separate DP SOM defined two high-flux clusters exhibiting a bimodal concentration-discharge response, but driven by differing land use. Our novel framework shows promise as a tool with broad management application that provides insights into landscape drivers of riverine solute and sediment export