In the current paper are presented the results of a multidisciplinary study (stratigraphical, sedimentological, geophysical and geochemical) combined with modern techniques (G.I.S. and remote sensing). This study aims at integrating the natural and anthropogenic factors affecting the Korissia lagoon. It is a shallow coastal lagoon, communicating with the sea via an artificial channel. The area around the lagoon consists of alluvial sediments hosting, in places, newly formed and/or “old” (pre – Holocene) sand-dunes. The broader area constitutes a postalpine sedimentary basin characterised by smooth morphological relief. The lower stratigraphic unit of the post-alpine sequence is a Pleistocene marly formation, which was detected as the basement (5-15 Οhm.m) by the geophysical survey. The resistivity-based basement map implies the existence of a “palaeo-gulf” trending EW. These marls constitute the impermeable basement of a shallow aquifer hosted in the area. The salinity of the lagoon is very high during summer (>40psu) but it does not affect significantly the wells around it. The lagoon is well oxygenated, while the wells have lower D.O. values. Ammonia and nitrates are the main inorganic Nitrogen forms, in the lagoon and the wells, respectively. Phosphorus is the limiting factor for phytoplankton growth. Human activities affect the area that is in need of an environmental management plan in order to prevent ecological degradation.

Korissia lagoon located in the southwest end of Corfu separated from the open Ionian Sea by a narrow (<250 m) stip of land. It has a surface of 4,2 km2 and depths <2m, communicating with the sea via an artificial-dredged channel. The bed of the lagoon consists of fine-grainned sediment (sandy silt – silty sand). Its drainage basin covers an area of 16 km2 and is characterized by low relief. It receives the freshwater inputs form a low relief (maximum elevation 319 m) of the drainage basin. The influx of fresh water is surficial includes also an underground flow, as indicated by the presence of a phreatic aquifer and a large number of wells at its nearby surrounding area. The water budget of the lagoon is characterised by a wet (October-March) and a dry (April-September) period. During the wet period the incoming volume of fresh water (5,3x106 m3 ) is much larger than its total volume (2,5 x 106 m3 ); this implies an outflow of lagoonal waters whilst lagoonal waters are characterised by relatively lower salinity values (<20 ppt) compare to those of the Ionian Sea (38 ppt). In contrast, during the dry period, the fresh water influx (1,2 x106 m3 ) is smaller than the volume of the lagoon; this induces an influx of sea water, which in association with the high levels of evaporation moduled hyper-saline (>50 ppt) hydrologic conditions within the lagoonal basin.

In an effort to investigate the deep geological structure in the broader area of central-western Attica, that suffered severe damage during the destructive Athens earthquake of September 7th, 1999, the Department of Geophysics-Geothermics of the Faculty of Geology and Geoenvironment of Athens University, in collaboration with the Geodynamic Institute of National Observatory of Athens and the Department of Geological Sciences of Durham University, carried out a combined geophysical survey. For the first time in Attica, seismic and gravity geophysical methods were applied along profiles, in such an extensive scale. Within the framework of this investigation the following tasks were accomplished: a) Three (3) seismic lines of about 30 kilometres of total length, two (2) in the area of Thriassion plain and one (1) along the Parnitha-Krioneri-Drosia-Ekali-Dionysos axis (Attica plain) and b) 338 gravity measurements distributed along eight (8) gravity profiles, four (4) of which in Thriassion plain, three (3) in Petroupoli-Aharnes-Thrakomakedones region (Attica plain) and one (1) along Parnitha-Krioneri-Drosia-Ekali-Dionysos axis (Attica plain). Preliminary results of the geophysical investigation combined with existing geological and tectonic data are presented in this paper. Significant variation in the elevation of the alpine basement has been detected, expressed by manifestation of low and high subsurface areas which are well correlated with existing fault zones. In the area of Thriassion plain the thickness of post-alpine sediments is estimated of a few hundred meters (<500 meters) and huge thickness of several hundred meters (~800 meters) of post-alpine sediments were detected in Thrakemakedones and Krioneri areas. The relief of alpine basement is more intense in fault zones areas, such as Thriassion plain (WNW-ESE), Pathitha and Kifissos (NE-SW) as well as along the fault zone outline the Fili and Aharnes graben and is covered by postalpine formations.