The Reka-Timavo River System of the Yugoslavian and Italian Karst PAUL B. ALEXANDER* In the late nineteenth and early twentieth centuries Jovan Cvijic published a series of papers which made the Karst regions of Yugoslavia internationally famous. An area which Cvijic chose for his early descriptive works was the high limestone plateau that overlooks the Gulf of Trieste (Figure 1). This region is known to the Yugoslavs as Kras, to the Italians as Carso, and to the Austrians as Karst. The descriptive work done in this area led to its name being adopted as an international type locality. The Cretaceous limestone formations of the plateau have remained conspicuously above the erosional levels of the less resistant Tertiary limes and flysch. This barren region of solution erosion had long been considered a barrier between Mediterranean and Danubian trade. It was an area well known for its lack of water, lack of vegetation, difficult footing, and its wild bora winds. The scarcity of surface water posed a particularly difficult problem along early transportation routes. Adequate vegetation for forage was limited to the widely spaced pockets of terra rosa which accumulated in the karst surface depressions. After man destroyed the forests of the karsts, the soil was rapidly eroded from the limestone ridges. Much of this soil was washed into the underground channel system. A * Dr. Alexander is an Associate Professor of Geography at the University of Montana, Missoula, Montana 59801. This manuscript was presented at the Annual Meeting of the Association at Bellingham in 1968. Research is based primarily on personal investigation of cave records and Slovene public documents on file at the Slovene Karst Institute at Postojna. The cooperation and assistance of the staff of the institute is hereby acknowledged. 157 158ASSOCIATION of pacific coast geographers large portion of the karst became a bare and rugged lapies surface. In late winter the bora, a cold pulsating northeast wind, blows from the higher plateaus across the karst into low pressure systems of the Mediterranean Sea.1 Rora velocities of 38 meters a second ( 137 kilometers an hour) have been recorded in the interior of Slovenia.2 With the advent of rail communications across the karst, large bora walls had to be constructed to protect the rails from drifting snow. The occupance of the karst has been characterized by small nucleated villages based on meager soil resources that have been developed in the isolated karstdepressions. In striking contrast to the dry, barren karst lands are the green slopes and gentle hills of Brkini. This area adjoins the karst on the east and is underlain by Eocine flysch. Figure 2 indicates the extreme changes which occur in the drainage pattern of the Reka-Timavo River as it flows from the flysch to the limestone area. The headwaters of the Reka-Timavo River lie beneath impressive snowcovered Mount Sneznik. For 50 kilometers the river flows across the clay soils of Brkini. Here the drainage network is well developed and surface water abundant. The large flysch region of Brkini sits like a green oasis among the surrounding barren dry karst plateaus. To the south lies the Plateau of Cicarija, to the northeast lies Zgornja Pivka3 and the high limestones of Javorniki and Sneznik, to the west and northwest lies the Plateau of Karst. The soils of Brkini are fertile and sustain productive fields, lush meadows, and intensive horticultural development. At the village of Brenski Britof the flysch thins and the river flows through barren limestone. Here the river has eroded a precipitous and narrow gorge some 2 kilometers in length. At the end of this gorge the Reka-Timavo River sinks beneath the Upper Cretaceous limestones of the Karst Plateau. The river follows its sub1 During the winter months the snow-covered plateaus and mountains of Javorniki, Sneznik, and Velica Gora become exceedingly cold through the influx of Arctic air and radiation. As the pressure gradient between these high areas and the warm Adriatic Sea increases, a katabatic flow of cold air occurs. 2 Bojan Paradiz, "Burje ? Sloveniji," 10 let hidrometeoroloske sluzbe. Ljubljana, Hidrome Teoroloski zavod L. R. S., 1957, p. 160. 3 For a detailed analysis of a typical Slovene karst region refer to...
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Oct 1, 1987
Thomas R Parish + 1
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