Dražen Perica

Groundwater quality in selected caves in Ravni kotari (Croatia)

Complex mechanisms of pollution transport in karst underground and the fact that contaminated cave water can be a health hazard if used for human consumption, imposes the need for monitoring the cave water quality. In order to determine groundwater quality, water samples were collected in four caves in Ravni kotari (Croatia) and analyzed for microbiological and chemical indicators of pollution. Microbiological analyses showed increased concentration of various coliform bacteria at all four locations. Probable sources of pollution are inadequately built septic tanks in nearby villages and bat guano in caves with bat colonies. Chemical analyses indicated values of possible pollutants to be much lower than the permitted values, which reflects the fact that agriculture, as a frequent source of chemical pollution in rural regions, is not as developed as it used to be, thus posing no serious threat to the groundwater quality.

Morphogenesis of karst poljes on Vis Island, Croatia

Karst poljes are the most characteristic feature of Dinaric karst area. The number of poljes identified on the island of Vis (Croatia) differs according to the various authors who have studied the island. Considering the various existing definitions of polje in previous studies, in this paper we propose a set of criteria for identifying poljes in karst terrain using Geographic Information System. This enabled the identification of six poljes on the Vis Island, whose formation is predetermined by tectonic structures. Moreover, processes are frequently inferred by neotectonic (both uplift and subsidence) according to the analysis of longitudinal and transverse profiles gradients affecting balance of these morphologies. Since they are not hydrologically active in present hydrological conditions, poljes on Vis Island can be considered to be paleo - overflow or structural poljes.

The influence of nivation and cryofraction on periglacial relief formation on Velebit Mt. (Croatia)

The peak areas of the Velebit mountain range display an interesting periglacial geomorphology. The appearance of forms is the result of the interdependent geological, geomorphologic, climatic, vegetational and pedological characteristics of the area. The structural and lithological properties of the rock complex, and the inclination of the slope, play a significant role in periglacial relief modelling. Climatic elements are also important, as they influence the intensity and duration of the processes. Low temperatures and relatively high precipitation during the last ice age (Wurm III), served to intensify the activity of periglacial processes and relief modelling of the entire Velebit area. Nivation and cryofraction are the predominant periglacial processes which are represented by snow avalanches and stone streams. Air temperatures and soil temperatures (at 30, 60, 90 cm depth) were measured, presented and reviewed, together with other attributes and the slope inclination of the area. The interactions between ground temperature, snow cover and wind patterns play important roles in frost action. In addition to slope inclination, the penetration of warm winds ( jugo ) and warming of snow on the NE slopes are also important factors in destabilizing the snow cover and triggering avalanches. Snow avalanches are most intensive on slopes with declinations from 35° up to 50°, especially on the parts without vegetation cover.

Quantitative-geomorphological and environmental-historical impact on the ecological soil depth; northwestern croatia

With regard to its geographical position, role and significance, North-Western Croatia represents the key area of the Republic of Croatia. It is the area of a long-lasting continuity of population and a great, although regionally differentiated, agrarian density. A long and intensive pressure on the environment is one of the most important factors which have influenced the ecological depth of soil. Because of the presumed influence of the quantitative geomorphological features (average height, relative height, slope length, length and relative height index, inclination, surface regularity, expositions) and lithology features (rock strength coefficient) on the volume and intensity of slope processes, a multiple regression analysis has been carried out for the dependent variable of ecological depth and the quoted variables as independent assessors.