The Sava Plain: Definition, Denomination, Delineation and Subdivision

The Sava River based its fluvial architecture compromised its upper- and lower courses. The Sava River upper course starts at Radovljica and continues downstream till Krško while from Krško till Belgrade is the Sava lower course. The Sava upper course is positioned in the mountain valley and characterized with headwaters. The Sava lower course positioned in the lowland area of the Pannonian Plain. The Sava Plain (Posavina) is a physico-geographical region, encompass the lowermost, almost flat surface of plain segments of the Sava valley, lower plain segments of its tributaries and adjacent eolian flat landforms. The Sava Plain surface geology composed of Holocene fluvial, as well as Pleistocene alluvial and eolian sediments. According to the Holocene fluvial architecture of the Sava river three significant parts can be defined as the Krško-Samobor Plain, the Upper- and the Lower Sava Plain. The Upper Sava valley represents the Krško-Samobor Basin from Krško downstream till the Podsused Gate. The Upper Sava Plain (Gornja posavina) covers the Sava plain in between Podsused Gate downstream to the Slavonski- and Bosanski Brod (or the Brod Gate). The Lower Sava Plain (Donja posavina) ascends from Brod Gate downstream till the mouth of the Sava to the Danube in Belgrade. The Krško-Podsused Plain and the Upper Sava Plain channel planform type characterized with the gentle meandering river architecture its area composed of Holocene fluvial sediments, while the Lower Sava Plain with meandering river architecture of Pleistocene fluvial and eolian sediments and Holocene fluvial.