Natural processes and anthropogenic influences on sedimentary environments in downstream of the Mirna River

U ovome diplomskom radu određene su granulometrijske karakteristike površinskih sedimenata poplavne ravnice, korita i ušća rijeke Mirne te je u njima određen udio karbonata. Cilj rada je na temelju dobivenih terenskih i laboratorijskih rezultata dovesti u vezu karakteristike sedimenta s prepoznatim prirodnim i antropogenim procesima u donjem toku rijeke Mirne. Površinski uzorci poplavne ravnice pokazali su relativno jednoličan granulometrijski sastav. Dominantno su građeni od sitnozrnatih čestica veličine gline i praha, dok su frakcije pijeska i šljunka prisutne u manjim količinama, uglavnom kao biogena komponenta. Povećani nanos takvog sitnozrnatog sedimenta iz gornjih dijelova toka potječe od stijena podložnih eroziji: uglavnom fliša (lapori i pješčenjaci) i manje karbonatnih stijena, zaslužnih za stvaranje delte unutar estuarija. Količina materijala kojeg rijeka Mirna donosi do svoga ušća je značajna, a tome pridonose i prirodni i antropogeni procesi. Sedimentacija je uzrokovana mehaničkom erozijom kojoj potpomažu intervencije čovjeka, deforestacija tijekom prošlosti, nutrije, periodične poplave; procesi koji u svome međusobnom djelovanju mogu podjednako i pozitivno i negativno utjecati ne samo na prirodu, već i na čovjeka.In this graduate thesis, the granulometric characteristics of surface sediments of the floodplain, riverbed and mouth of the Mirna River were determined together with share of carbonates component. The aim of this paper is to link sediment characteristics with the recognized natural and anthropogenic processes in the lower course of the Mirna River, based on the obtained field and laboratory results. Surface floodplain samples showed a relatively uniform granulometric composition. They are predominantly composed of fine-grained (clay and silt) particles, while fractions of sand and gravel are less present, mainly as a biogenic component. The increased deposition of such fine-grained sediment from the upper parts of the stream originates from rocks subjected to erosion: mostly flysch (marls and sandstones) and less carbonate rocks. This deposition led to development of delta within the estuary. The amount of material brought by the Mirna River to its mouth is significant, and both natural and anthropogenic processes contribute to such a deposition. Sedimentation is caused by mechanical erosion aided by human interventions, deforestation during the past, nutria rodents, periodic floods; processes that in their interaction can equally positively and negatively affect not only nature but also a man