engleski

Application of semi-automated GIS procedure for river terrace delineation on high resolution LiDAR data in Sava river valley NW of Zagreb, Croatia – First results

Three aggradational terraces of Sava River generally composed of poorly consolidated gravels and sands were formed during Holocene time. In spite of their economic significance, spatial relationships and extent of the two older Holocene Sava River terraces and the recent terrace near Zagreb are not undoubtedly established. This is due to relatively weak morphological expression, vegetation cover and anthropogenic changes in the terrain associated with flood protection structures, traffic infrastructure and agriculture. In the past two decades stratigraphic history of Quaternary sediments in the area has been reconstructed to a great detail through extensive analysis of borehole data. However, present knowledge about spatial relationship and extent of Sava River terraces is mostly based on the geological map published in 1979 and represents summary of the field information and geological exploratory work completed at that time. LiDAR data with high vertical and horizontal resolution have been proven in various studies as a good basis for the application of automatic algorithm based procedures for extraction of river terraces. In this work TerEx ArcGIS extension developed by Justin C. Stout and Patrick Belmont was applied. Several morphologic parameters were varied in the iterative process until most probable result coinciding with the known extent of terraces was obtained. After manual editing of the presumed terrace geometry, the heights of the terraces above the current river course were also extracted by the same tool. The results of the applied semi-automated river terrace extraction process indicated in some sections different spatial relations than previously established. To assess their validity, the results will be checked in the field and compared to the data obtained during preparatory works for gravel excavation and to a new 3D visualisation of water supply borehole data.

Sava River terraces, Holocene, NW Croatia, TerEx (GIS)

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