Sanja Bernat

Review of Monitoring Parameters of the Kostanjek Landslide (Zagreb, Croatia)

Since 2011, in the framework of the Croatian-Japanese SATREPS FY2008 Project, scientists have been working on the establishment of the Kostanjek landslide monitoring system in the City of Zagreb (Croatia). External triggers at Kostanjek landslide are measured with rain gauge and accelerometers. Displacements at the surface are measured by GNSS sensors and extensometers, while subsurface displacement is measured by vertical extensometers and inclinometer. Hydrological measurements consist of groundwater level measurements, discharge measurements, chemical and isotope analysis. Monitoring sensors recorded landslide reactivation due to external triggers in the winter period of 2012/2013. During the period from September 2012 to March 2013 the total cumulative precipitation was 793.7 mm and horizontal displacements were in the range of 9–20 cm. The installed monitoring sensor network proved to provide reliable data for the establishment of relations between landslide causal factors and landslide displacement rates aimed at establishing threshold values for early warning system.

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.

Landslides Triggered in the Continental Part of Croatia by Extreme Precipitation in 2013

The subject of this paper are landslides triggered by the extreme precipitation during winter and spring of 2013. More than 900 landslides were (re)activated in the continental part of Croatia during the analyzed period. This paper presents preliminary analysis results of the relationship between 55 slide-type occurrences and precipitation conditions. The preliminary analysis is based on the sliding data from the hilly area of Medvednica Mt. in the City of Zagreb. The exact landslide location, the slope failure time, information on the precipitation duration D and the mean intensity I, which have resulted in landslide activation, are known for each analyzed landslide event. A comparison of precipitation series and landslides occurrence dates with global rainfall intensity-duration (ID) thresholds showed that precipitation conditions exceeded threshold values and were likely to trigger a landslide. The results will be used for further study of the empirical threshold of landslides in the area of NW Croatia.

Inventory of precipitation triggered landslides in the winter of 2013 in Zagreb (Croatia, Europe)

The subject of this paper is inventory of precipitation induced landslides in Zagreb in the period of extreme weather conditions in the winter of 2013. Long-lasting heavy rainfall and a thick snow cover triggered more than 60 landslides in the hilly area of the Medvednica Mt. which belongs to the City of Zagreb. Basic data about landslide event locations, received from records of the City Office of Emergency Management (OEM), are analyzed. We present the results of preliminary temporal distribution analysis of landslide occurrence during the following extremes: cumulative monthly precipitation in January, February and March in 2013 was 130-190% higher than the average monthly values for the period from 1862 to 2012 ; and cumulative precipitation for a 3-month period in 2013 has the highest value in the last 150 years. Spatial distribution analysis shows that most of the analyzed landslide events were triggered in engineering soils of Pontian age (approximately 1 landslide per 2 km2). Presented landslide inventory map provide a solid basis for organizing further research aimed at the analysis of landslide triggering rainfall thresholds as well as development of landslide inventory map which will depict landslide contours.

The Kostanjek Landslide in the City of Zagreb: Forecasting and Protective Monitoring

Since 2011 the scientists have been working on the establishment of the Kostanjek landslide monitoring system in Zagreb (Croatia) in the frame of the Croatian-Japanese SATREPS FY2008 Project. The system consists of sensors for measuring displacement, hydrological properties and external triggers. The total rain quantity of 455.2 mm, which fell in the winter period of 2012/2013, caused a reactivation of the landslide. Displacements in the range of 9–20 cm have been recorded by GNSS sensors and extensometers in various parts of the landslide surface (an area of 1 km2). This paper briefly presents measured displacements which pointed out the necessity to establish an early warning system (EWS). Monitored data will be used for the prediction of landslide failure and for the establishment of the threshold values for an early warning system. The final user of the early warning system will be the City’s administration for civil protection.

Landslide Knowledge Exchange Through the Regional Cooperation in the Adriatic-Balkan Region

Regional cooperation among ICL members in the Adriatic-Balkan region has been initiated at the beginning of 2012 by establishing the ICL Adriatic-Balkan Network on Landslides which encompasses seven institutions from four regional countries, Albania, Croatia, Serbia and Slovenia. The objectives of regional cooperation are to conduct regional cooperative research and capacity building in landslide study and related risk prevention and mitigation for the benefit of society and the environment. This paper presents an overview of the main ICL ABN activities in the period from the beginning of 2012 to the end of 2013. One of the main activities was launching regional thematic conferences on landslides by organizing the 1st Regional Symposium on Landslides in the Adriatic-Balkan Region (1st RegSyLAB) in Zagreb, Croatia in March 2013. The social and technical program of the symposium enabled the participants from nine regional countries to share their experiences about local landslide research at the regional level and enhance the establishment of relations between scientist in the region which are important for future cooperative research and capacity building. This paper describes in more detail the technical sessions and side events of the 1st RegSyLAB, so as report symposium’s outcomes as they relate to the promotion of landslide science.