uvala

An uvala is a large closed karst depression formed by the coalescence of several dolines (sinkholes) into a single, irregular cavity. In karst terminology, it is intermediate in size between a doline and a polje, typically elongated or circular in outline and bounded by higher bedrock rims. The floor is often flat or gently inclined and may be partially filled with alluvium or seasonal sediments.

Uvalas occur mainly in Dinaric karst regions where limestone is extensively dissolved by groundwater. They are common along the Adriatic karst areas of Croatia, Bosnia and Herzegovina, Montenegro, and Slovenia. The appearance and size of uvalas can vary, but they generally present as a prominent depression within a landscape of sinkholes and hills.

Hydrologically, uvalas are usually characterized by intermittent surface drainage. Water may accumulate on the floor seasonally and is frequently drained or lost through underground channels, ponors, or swallow holes, reflecting the dominant role of subterranean karst systems in their hydrology. Surface streams are uncommon within the uvala itself, although surrounding topography can influence local flow patterns.

Formation processes combine dissolution of soluble rocks, collapse of subsurface cavities, and the coalescence of neighboring dolines over geological timescales. Tectonic structures and joint patterns guide where dissolution is most active, shaping the final form of the uvala. As a landform, it complements other karst features such as dolines and poljes and contributes to the distinctive hydrology and ecology of the karst landscape.