Case Studies from the Dinaric Karst of Slovenia

UvalasUvalas are large, km-scale closed karst depressionsof elongated or irregular plan form.Their bottoms are undulating or pitted withdolines, seldom flattened by colluvial sediments.Uvalas are always situated above thekarst water table. They are polygenetic featuresand are strongly guided by geological structureand tectonics (Čalić 2009). The word “uvala” iscommon toponym in the Dinaric karst, alwaysdenoting a large depression. In folk language ithas a morphological meaning only.The term was introduced into literature byJovan Cvijić (1893) for dolines with huge diameters,but unfortunately with an erroneousexplanation of their genesis – that the uvalasare transitional evolutional elements betweendolines and poljes, formed by the coalescenceof several dolines which have enlargedand merged towards each other (Cvijić 1901,1960). Because of this erroneous explanation,the term “uvala” is mostly abandoned in professionalliterature outside the Dinaric karst.There is considerable variety among thedimensions, and also the shapes, of the uvalas,but there are also some common generalcharacteristics (Čalić 2009). In most cases theuvalas are developed along tectonically brokenzones of regional extension. Their perimetersare of irregular shape, the plan dimensionsvary from approximately 1 km up toseveral kilometers along the longer axis, whilethe depths below the highest closed contoursare at least 40-50 m, and sometimes exceed200 m. Uvalas are not present on karst leveledsurfaces, but only in areas with more orless dissected relief, so the bottoms are alwaysabove the karst water table.Uvalas have internal karstic drainage; occurrencesof small seasonal surface flows arean exception. Sediments in the bottoms arescarce; their origin is from denudation fromthe slopes. Infill is not threatening to fill up adepression. The inclinations of the slopes aregenerally smaller than those of dolines. Uvalasare formed because of differences in solubilityof the karstified rock, structural elementsand recent tectonics. Formation of such topologicallyclosed areas within larger karst areasneeds only sufficient time and favorable climaticconditions.Uvalas can be found in all of the Dinarickarst except in low positions and on leveledsurfaces. In many uvalas, because of some colluvium,small settlements developed. Someuvalas were affected by glaciation; in some,glacial tongues ended and fluvioglacial till wasdeposited. In them, the lowest temperaturesin the area were observed because of temperatureinversions.DolinesDolines are the most frequent karst depressions.They are centric and mostly roundrelief forms. Dolines commonly have circularto sub circular plan geometry, and a bowl- orfunnel-shaped concave profile. Their depthsrange from a few decameters to a few hundredmeters, and their inner slopes vary from subhorizontal to nearly vertical. Dolines up to tenmeters deep and 100 meters wide dominate.Their genetic definition is difficult becausealthough they formed in very diverse conditions,all the processes led to the same funnelor bowl shape. Morphologically, the same orsimilar dolines can therefore have differentorigins. In order to understand how dolinesand other, closed karst depressions develop, itis necessary to examine their morphology andsize, their relationships with the topographicand geomorphologic settings, their structures,their hydrological behaviour and related solutionprocesses, examples of evolution, and peculiarmorphologies that occur under specificenvironmental conditions (Sauro 2005).Corrosion dolines occurred where verticalpercolation into the karst was possible anddissolution of rock was stronger than in thesurrounding area. The round shape with onelowest point indicates a spatially limited andactive process of rock mass removal. In mostcases, the soil plays a major role due to the37