Ο ρόλος των γεωμορφολογικών χαρακτηριστικών του υδρογραφικού δικτύου του Σαρανταπόταμου στον πλημμυρικό κίνδυνο του Θριάσιου Πεδίου = Geomorphological characteristics of Sarantapotamos drainage network as causative factor of flooding in Thriassion Plain (Attica, Greece)

Περίληψη

This paper investigates the natural (geomorphological) factors responsible for flooding events in the environmentally fragile urbanized and economically developing broader area of Thriassion plain, located in west Attica, Greece. The study focuses on the Sarantapotamos River drainage network which drains an area of 812.95 km2 and is one of the main watercourses of the plain. A catalogue of the most severe flood events that affected the study area over the past 50 yearsis presented including 24 and/or 48 hour rainfall records from the nearest meteorological station. For the purposes of the study a spatial database for the drainage network and its corresponding basin has been organized and implemented utilizing ESRIs ArcGIS10 software. The quantitative morphometric characteristics of Sarantapotamos river drainage basin (number of channels per stream order, channels length, and drainage basins area) were measured and analyzed. The hierarchical drainage by stream order was investigated and the longitudinal profiles, as well as the stream power diagrams of the main stream and its major tributary, were constructed and analyzed. Among the most important natural flood causes are extreme rainfall and the geomorphological characteristics of the drainage network. The quantitative geomorphological analysis showed that these features include high bifurcation, steam length and basin area ratio values especially between the 4th and the 5th order streams as well as irregularities in the number of channels that drain directly into streams of higher order. An additional reason for intense discharges along the lower Proceedings of the 10th International Congress of the Hellenic Geographical Society 22-24 October 2014, Thessaloniki, Greece Special Session 4 1365 reaches of the main channel is the relatively high slope of the streams at the upper parts of the main watercourses and the gentler slopes at their lower reaches. A crucial flood factor is also intense urbanization and human interference, along the channels of Thriassion Plain without integrated flood defense measures at the broader catchments area and especially at their mountainous parts.