Gulam, Vlatko, Pollak, Davor, Aljinović, Dunja, Mihalić Arbanas, Snježana, Gajski, Dubravko, and Žugaj, Ranko
Predmet ovog rada su ogoline koje na području središnje Istre predstavljaju izolirane reljefne jedinice. One nastaju u nepostojanom flišnom kompleksu na kojemu se razvija vrlo erozivni površinski tok vode. Ogoline uglavnom obilježava vrlo oskudan vegetacijski pokrivač te visoki godišnji iznosi denudacije. Također ih označava vrlo zamršen splet egzogenih procesa. Istraživanja prezentirana u ovom radu su imala za cilj određivanje najvažnijih čimbenika nastanka ogolina, te određivanje prosječnog godišnjeg iznosa denudacije na njima. Dostizanje navedenih glavnih ciljeva uvjetovalo je podjelu istraživanja na razinu uzorka, izdanka i regije (sliva). Najvažniji egzogeni proces izučavan na razini izdanka je fizičko trošenje, tj. otpornost na fizičko trošenje – postojanost. Zaključeno je da na postojanost najveći utjecaj imaju uvjeti kojima je na površini terena stijena bila izložena tijekom dužeg vremena. Na razini izdanka je određivan prosječni iznos denudacije i to pomoću tri metode (analogna i digitalna fotogrametrija, profilometarska mjerenja). Utvrđeno je da se on kreće od 1 do 4 cm na godinu, te da je veći tijekom intenzivnih kišnih pljuskova kojima je prethodilo dugotrajno sušno razdoblje. Najvažniji segment regionalnih istraživanja je izrada katastra ogolina kojim je utvrđeno da 2% od ukupne površine istraživanog prostora čine ogoline. Prostornim analizama u kombinaciji s različitim laboratorijskim istraživanjima je utvrđeno da nastanak i opstanak ogolina na području središnje Istre u prvom redu ovisi o pojavi koncentriranog površinskog toka u podnožju strmih padina. Kao krajnji produkt svih analiza provedenih u radu načinjena je karta podložnosti formiranju ogolina. Uz navedenu kartu preporučene su i administrativne mjere zaštite za svaku od na njoj prostorno definiranih kategorija osjetljivosti., The topic of this thesis is badlands which in the central Istria area (west Croatia) represent isolated relief units. They are created in the volatile flysch complex on which surface water flow of high erosivity is developed. Badlands are mainly characterized by a very scanty vegetation cover and high annual amounts of denudation. They are also characterized by very complex exogenetic processes. High amounts of denudation, i.e. high sediment load productions cause problems in the form of filling in of Botonega artificial lake (water supply), and the low durability of flysch sediment causes dispersion of road cuttings and incisions, which often leads to blockage of drainage channels. Research works presented in this paper were aimed to determinate the most important factors for badlands development and the average annual amount of denudation on them. Achieving these major objectives conditioned the division of research into the level of sample, outcrop and region (catchment area). At the level of the sample researches were conducted in the laboratory and in the field. Mineral composition was determined together with physical and mechanical properties of flysch complex. Considering the badlands, the most important feature on the level of sample is the durability which represents resistance to physical weathering. It was determined in the laboratory on 223 samples and it was found that the growth of the ice crystals is the most devastating physical weathering process. It was also determined, indirectly through the mineral composition analysis, that the conditions, under which the rock is on the surface, are the most important factor that influences its durability. Research at the outcrop level was primarily aimed at determining the amount of denudation and the identification of the climatic factors influencing denudation the most. Regarding that, four experimental plots (Šterna, Sv. Donat, Botonega and Boljun) were established in the field. On them, several parameters were monitored: the amount of denudation by 3 methods (analogue and digital photogrammetry and profilometric measurements), the air temperature and the amount and intensity of rainfall using automated measuring instruments (logger). The mentioned researches found out that the average amount of denudation in the central Istria on badland area ranges from 1 to 4 cm per year, and that the greatest amounts of denudation are the result of intense rainfalls (rains/showers), which were preceded by long dry periods. Regional researches, i.e. researches on the level of the catchment area, began by defining the badlands spatial distribution. With this aim the badland cadastre was made by using digital orthophoto maps, scale 1:5000. It was found that in the research area (487 km2) 2% of the area (10.7 km2) is covered by badland. The map of bare surface was obtained from the badland cadastre, which has shown that the catchment areas with mouth in eastern, more tectonically active, part of the Istrian peninsula (catchment areas of Boljunšćica and Raša) are characterized by a larger share of the badlands than the catchment area of Mirna with mouth at tectonically less active western part of Istria. This is explained by the difference in relief development, which is conditioned by slower lowering of erosion base of the catchment areas in the eastern part than the ones in the western part of the Istrian peninsula. Regional studies in combination with various laboratory techniques have yielded the definition of four basic engineering geological units in the explored area and the definition of four badland types on them. By different spatial analysis and field reconnaissance it was found that the concentration of the erosive water flow at the base of the steep slopes is the most important factor in the emergence and survival of badlands in central Istria. It was noted also that the thicker layers of impermanent marl facilitate the emergence of highly erosive Hortonian flow and therefore more frequent emergence of badlands on the parts of the terrain made of such layers. Thick layers of breccias, conglomerates and calcarenites condition the formation of cuesta below which the possibility of badland formation is greater. As the end product of all analyses conducted in the thesis the map of susceptibility to badland formation was created. Four categories were defined on the map: very small, small, medium and large susceptibility to badland formation. Together with this map an administrative control measures were recommended for each of the spatial defined categories of sensitivity.