Snježana Mihalić

The Croatian–Japanese Joint Research Project on Landslides: Activities and Public Benefits

The main activities of the research groups involved in the Croatian–Japanese joint research project on “Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia” include investigations of recent landslides using landslide monitoring, the establishment and development of early warning systems for landslides and the definition of hazard zones using a methodology for assessing susceptibility and hazards based on local geological and landslide conditions. This project is also designated as on-going IPL project 161. The final objective of the joint research is the development of risk mitigation measures that can be instituted through urban planning. Dissemination and use of the results should ensure significant benefits for the local and regional communities that are directly and indirectly threatened by landslides.

Landslide Inventory in the Area of Dubračina River Basin (Croatia)

Systematic landslide mapping was performed for an area of 9.35 km2 of the geomorphological unit of hills in the Dubracina River Basin. Based on the visual interpretation of LiDAR imagery, supplemented by field reconnaissance mapping of damaged roads and structures, 48 landslides were identified. In this first phase of landslide inventory preparation for the area of the Dubracina River Basin, a preliminary landslide inventory map presents data on locations of all identified landslides. Three examples of identification of landslide contours are given to show different possibilities in visual interpretation of airborne LiDAR imagery.

Rockfall Hazard Analyses and Rockfall Protection along the Adriatic Coast of Croatia

During the last decade, large rockfalls occurred on the steep limestone slopes along the Adriatic Coast of Croatia, causing injury to people and serious damage to buildings and traffic facilities. The rockfalls along the limestone slopes were caused by unfavorable characteristics of the rock mass, weathering in combination with heavy rainfall and artificial influences during highway construction. Rockfall protection projects were conducted to protect human lives and facilities from future rockfalls. The rockfall protection program started with rockfall hazard analyses to identify the potential of rockfalls to occur and the potential consequences. At the locations of hazards where related risks were determined, detailed field investigations were conducted. Based on the indentified characteristics of potentially unstable rock masses, analyses of movement and resulting pathways were conducted. The trajectories, impact energy and the height of bouncing are dependent on slope geometry, slope surface roughness and rockfall block characteristics. Two protection measure approaches were adopted: prevention of rockfalls by removing potentially unstable rock mass or installation of rock mass support systems and suspending running rockfall masses with rockfall protection barriers. In this paper, rockfall hazard determination, rockfall analyses and rockfall protection designs for rockfall protection systems at selected locations on the limestone slopes along the Adriatic coast of Croatia are presented.

Landslide Inventory in the Area of Zagreb City: Effectiveness of Using LiDAR DEM

Preliminary results of landslide mapping in the City of Zagreb (Croatia), obtained in the frame of the Japanese-Croatian scientific project, are presented in this paper. The aim of this research is to develop a method for landslide delineation in order to enable land use officials to implement this data to create more useful measures for landslide risk management. Selected landslides in the hilly zone of Mt. Medvednica were identified visually using LiDAR bare-earth DEMs. The results of data analysis will be implemented to perform a more comprehensive study of landslides in the entire pilot area (total area is 180km2).

Three Dimensional Stability Analysis of the Grohovo Landslide in Croatia

The Grohovo Landslide, situated on the north-eastern slope in the central part of the Rjecina River valley, is the largest active landslide along the Croatian part of the Adriatic Sea coast. The Grohovo Landslide is also a key pilot area for implementation of the monitoring activities of the Japanese-Croatian joint research project on “Risk identification and land-use planning for disaster mitigation of landslides and floods in Croatia”. This complex retrogressive landslide was reactivated in December 1996. It is considered that the basal failure surface is positioned at the contact between the slope deposits and the flysch bedrock. Based on the data from boreholes, geological mapping, geophysical surveys and the geological cross-section of the slope, the three dimensional shape and the position of the sliding surface were simulated using the inverse distance weighted interpolation. Using 3D extended Janbu’s simplified method, global stability of the Grohovo Landslide and stability of 12 separate landslide bodies were analyzed.

Japanese-Croatian Project: Preliminary Investigations of the Kostanjek Landslide

In this paper preliminary results of scientific research of the Kostanjek Landslide (the City of Zagreb, Croatia) are presented, which are achieved in the frame of a scientific Japanese-Croatian project. The aim of this research is to develop a base for planning of integrated real-time geodetic and geotechnical monitoring of the landslide. Despite long history of landslide movements (approximately 50 years) and geotechnical investigations conducted in 1998 and 2008, present landslide model does not ensure information about landslide activity state, activity style, activity distribution and velocity of movement. On the basis of preliminary investigations it is concluded that determination of landslide geometry, soil properties and hydrogeological conditions require additional research (geomorphological, geomechanical and hydrological) which need to be conducted before design of monitoring system.

The Role of Engineering Geology in Standardization of Innovative Geological Mapping

The ever-growing development of national digital geological cartographic systems emphasizes the need for standardization of geological mapping. A synthesis of the two existing approaches, which are of interest as starting points in the tremendous process of standardization of innovative geological mapping, is presented. A recent example of the US Geological Survey standardized geological information system for the production of stratigraphic maps is emphasized. A general conceptual model of the database content and structure is presented in brief, considering the main concepts related to standardization of geological mapping procedures and geological terminology. A second issue concerns traditional engineering geological mapping. Its importance lies in the abundance of engineering geological standards and recommendations, which could be directly applied to custom-oriented geological mapping. Therefore, the goal of analyses of engineering geological mapping is to extract the main issues of engineering geological mapping related to standardization of modern geological cartography. The main contribution of this paper is to address the extensions of digital geological cartographic databases with engineering geological data which are required for the production of a wide spectrum of geological custom-oriented maps from the same geological information system.