Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544km 2 landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98Mkm 2 (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.

The south-western part of Croatia, i.e. the area of central Istria, comprises the research area, (approximately 500 km 2 ). It is characterized by a fl ysch complex with a great number of isolated relief landforms, termed badlands. The importance of badlands (areas with sparse or no vegetation) lies in the fact that sediment production from these areas is 8000 times higher than from areas with vegetation. Here, the badland inventory presents 5568 distinguishable badlands (polygons) with a total badland area of 10.7 km 2 . Spatial analysis of the badland inventory showed that erosive channel fl ow at the steep slope foot is the most important factor in badland formation and development for the area of central Istria.

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In March 2018, a landslide in Hrvatska Kostajnica completely destroyed multiple households. The damage was extensive, and lives were endangered. The question remains: Can it happen again? To enhance the knowledge and understanding of the soil and rock behaviour before, during, and after this geo-hazard event, multi-level sensing technologies in landslide research were applied. Day after the event field mapping and unmanned aerial vehicle (UAV) data were collected with the inspection of available orthophoto and “geo” data. For the landslide, a new geological column was developed with mineralogical and geochemical analyses. The application of differential interferometric synthetic aperture radar (DInSAR) for detecting ground surface displacement was undertaken in order to determine pre-failure behaviour and to give indications about post-failure deformations. In 2020, electrical resistivity tomography (ERT) in the landslide body was undertaken to determine the depth of the landslide surface, and in 2021 ERT measurements in the vicinity of the landslide area were performed to obtain undisturbed material properties. Moreover, in 2021, detailed light detection and ranging (LIDAR) data were acquired for the area. All these different level data sets are being analyzed in order to develop a reliable landslide model as a first step towards answering the aforementioned question. Based on applied multi-level sensing technologies and acquired data, the landslide model is taking shape. However, further detailed research is still recommended.

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The area of the City of Zagreb is relatively large (~ 640 km 2 ) and urbanized (> 800,000 residents). The general geomorphological setting of the City is on the alluvial plane of the Sava River, on the southern slopes of Medvenica Mountain and on the northern slopes of Vukomeričke Gorice, i.e. hilly area. Within this area geohazard events occur, for example: numerous landslides during last decades, great flood in 1964 and on 22 nd March 2020 Zagreb was struck by an M5.5 earthquake. These events cause great damages and can endanger or even take lives. Seismic and geological zonation of the part of the City of Zagreb area (~ 175 km 2 on the southern slopes of Medvednica Mountain) was carried out as one of the geohazard mitigation measure. The zonation was financed by the City of Zagreb government and performed according to Eurocode 8 in the period of 2017-2019. The results of zonation were presented in Study where the geological, geotechnical, geophysical and seismic characteristics of the research area were compiled and addressed. The data sets were organized and presented in GIS project, i.e. in form which is easily usable by officials or public users. At the same time the Study contributes to better understanding of soil and rock properties of the research area and increases the available data and knowledge fund. The research results were also presented on developed Seismic zonation map in accordance with Eurocode 8 in scale of 1:25,000 where areas of equal soil amplification relative to the bedrock are depicted. The developed map can provide (thematic) basic seismic background info necessary for urban planning. Different thematic (geohazard) zonation maps are necessary in modern and quality urban development and they are prerequisite in development of quality hazard and risk management.

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