Abstract | 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. |
Abstract (english) | 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. |