FEATURES OF THE AREA
The Valle del Medio Tagliamento SCI is conventionally placed between the sites belonging to the Alpine biogeographical region (mountainous part), although the area affected by the project is a part of the dry grasslands in the continental region (plain area). The site is in fact partly developed on the pre-alpine slopes that degrade abruptly toward the Tagliamento and partly in the wide area that includes the gravelly riverbed and in the western area the wet plain of Osoppo. The perimeter of the SCI therefore collects different environments that are very differentiated and characterized by significant natural values. The altitude excursion related to sea level ranges from a minimum height of 158 m (Tagliamento riverbed) to a maximum of 1,478 m (Mt Cuar) with an average height of 450 m.
Around Osoppo Field different geological and geomorphological units of structural importance for the regional landscape are present: the Carnic Prealps to the west, the Julian to the east, the south of the Tagliamento morainic amphitheater, the same river that from the north drifts to southwest flowing into the plain through the narrow strait of Pinzano.
The site arises affecting mainly the western part of the geomorphological complex system that is spanned on either side of Tagliamento river. The main pulse to the formation of this system took place particularly during the Würm glaciation and in the immediate post-glacial period.
The SCI has also been bounded in order to understand the most significant and best-preserved parts of a broadly diversified territory consisting of many ecological and natural elements which are strongly interdependent.
The mountainous part of the site to the west of Tagliamento is characterized by the presence of the Cornino lake, a small basin with water from the incomparable blue-green color, arised on landslide deposits descended from the front foothills. In the same geographical quadrant spreads the limestone cliff rocky verge that toward the Tagliamento delimits Mount Prat-Ledrania plateau. The slope, due to its particular location and exposure, is characterized as a small enclave of Mediterranean microclimate. The mountainous area of the SCI also includes a larger offshoot extended from the west to east-west direction between Mt. Cuar and Arzino Valley.
The plain part arises toward east of Tagliamento: this over the riverbed, whose the stream is characterized by the typical trend in braided paths, also includes the Osoppo plain. The latter is a vast alluvial surface resulting from a post-glacial lake with a water table still fed by the dispersion of the Tagliamento river. To north east of SCI toward Osoppo village some high elevations of Oligocene-origin arises. These elevations constitute the evidence of a delta dating back to the middle Pliocene: the hill of San Rocco (237 meters above sea level), Vergnal hill (198 m above sea level) and Gniva hill (177 meters above sea level).
To the south the SCI is bordered by a morainic amphitheater at the base of which flows the Ledra river, collector of all plain?s tablewaters.
The Tagliamento bed is a great importance element for its breadth and integrity. The strait of Pinzano, located few kilometers downstream, causes some river expansion phenomena in the upstream plain and a bed walk active at same elevations of the whole Osoppo plain (sub-elevated walk) with obvious hydraulic risks. Historically it has been tried to contain the river within the active riverbed and some holmes taking advantage of its vastness.