Matjaž Mikoš

Rainfall and runoff erosivity in the alpine climate of north Slovenia: a comparison of different estimation methods

Abstract Rainfall and runoff erosivity is often assessed by using the R factor. For its computation different methods may be used. The aim of this study was to compare some estimation methods for the alpine climate in the Slovenian Alps. Monthly and annual R factor values were calculated according to the RUSLE, using daily precipitation data for the period 1990–2002 in Solčava, which is typical of the alpine region in Slovenia. In this alpine area with rather low rainfall intensities, the expression for computing the rainfall kinetic energy proposed by van Dijk et al. yielded on average 17.9% higher rainfall erosivities than the RUSLE approach. The newly proposed A index yielded on average 40% lower rainfall erosivities than the RUSLE approach. These lower values of rainfall erosivity were caused by the structure of rainfall during erosive events in the alpine region. The analysis in the alpine climate in Slovenia does not support the use of the proposed A index as a replacement for the usually used R factor when assessing rainfall erosivity.

Estimating the R factor from daily rainfall data in the sub-Mediterranean climate of southwest Slovenia / Estimation du facteur R à partir de données journalières de pluie dans le climat sub-méditerranéen du Sud-Ouest de la Slovénie

Abstract Abstract Rainfall and runoff play an important role in the process of soil erosion, which is usually expressed with the R factor. To calculate the R factor, long-term precipitation data are needed with high temporal resolution, typically available for only few locations. The aim of this study was to obtain an approximate relationship between the more commonly available daily precipitation data and the R factor. A set of equations is presented for calculating monthly and annual R factor values based on daily precipitation data for a sub-Mediterranean region in southwest Slovenia, and their applicability is discussed. The sum of squares of daily precipitation was found to be the best descriptor of the monthly R factor. The ratio between the R factor and the sum of squares of daily precipitation varies throughout the year and generally follows the mean monthly temperature, with the efficiency coefficient, e, of 0.869 between predicted and observed data on the annual basis.

Computer simulation of stone falls and rockfalls

The paper gives an overview of the literature on available computer (simulation) models of stone falls and rockfalls, divided into 2D and 3D models. 2D models consider single blocks in the rock-fall mass as lumped mass or a rigid body, and are used to assess the single rockfall runout distance. Opposed to the 2D models, 3D models are composed not only of a dispositional model (depicting rockfall source areas) and friction model (determination of deposition areas and maximum runout distances), but also from a trajectory model (determination of travel areas).

Reinforced concrete shafts for the structural mitigation of large deep-seated landslides: an experience from the Macesnik and the Slano blato landslides (Slovenia)

During the last decade, several rainfall-induced deep-seated large landslides with volumes of the order of 1 million m3 were triggered in various locations in Slovenia (central Europe), each representing a serious threat to the nearby villages and traffic infrastructure and urging to be mitigated. The Macesnik landslide, triggered in 1989, and the Slano blato landslide, triggered in 2000, were the first two large landslides in Slovenia, where a combination of drainage and retaining works consisting of deep reinforced concrete (RC) shafts/wells was successfully used as a mitigation measure. This paper presents the field conditions and a brief history of the two landslides with emphasis on the design approach and method used for the stability analysis and the design of deep RC shafts/wells. In addition, the paper gives an insight into the problems associated with the execution of works and provides data about the behavior of the two landslides after drainage and retaining works were completed. The monitoring data show that the undertaken mitigation measures were efficient to improve the stability of both landslides and significantly reduce the risk.

The ICL Adriatic-Balkan Network: analysis of current state and planned activities

International Consortium on Landslides (ICL) Adriatic-Balkan Network was established in January 2012 as one of eight regional and thematic ICL networks to promote activities of the International Consortium on Landslides and the International Programme on Landslides. This paper presents the annual report of the ICL Adriatic-Balkan Network for the year 2012. The main activity of the regional network was to complete an overview of publicly available data and sources about landslides in the region, scientific and professional practices related to evaluation and mitigation of landslide hazard, as well as related legislative framework. Recommendations for the discussion and endorsement in the course of the ICL Adriatic-Balkan Network activities will be derived from the analysis of strengths, weaknesses, opportunities, and threats related to landslide issues which are present at the national level in Croatia, Slovenia, and Serbia and at the regional level. Discussion and endorsement of the recommendations are planned as a further activity which will be held in March 2013 in Zagreb (Croatia), during the planned first regional symposium on landslides in the Adriatic-Balkan Region.

Delineation of risk area in Log pod Mangartom due to debris flows from the Stoze landslide

The paper shows in detail the case of delineation of risk area in the village of Log pod Mangartom in the Koritnica River valley due to possible debris flows that might in future be triggered on the Stože slope above the Mangart Mountain pasture. On the basis of field and laboratory investigations of the debris flow of November 17, 2000, that devastated the Koritnica River valley, the possible scenarios of triggering new debris flows on the Stože slope were investigated. For the determination of debris flow hazard area in the Koritnica River valley, the results of one- and two-dimensional modelling of selected debris flows of known magnitudes and different viscosities were applied. For the determination of risk area, the existing and the possible new infrastructures were taken into account, and the risk area was divided into 3 zones. The paper presents the expert bases summarised by the legislator in the relevant decree issued by the Government of the Republic of Slovenia on the conditions and limitations governing the construction in the debris-flow risk area of Log pod Mangartom. This regulation is the first of its kind in Slovenia.

Institutional repository as an important part of scholarly communication

Institutional repositories have been established as a good practice for quite some time. The European Commission requires archiving of research articles in institutional repositories in order to grant international project funding. Therefore, the interest in institutional repositories should increase in Slovenia as well. In 2011 the institutional repository DRUGG was built at the Faculty of Civil and Geodetic Engineering of the University of Ljubljana. By the end of 2012 more than 1400 scholarly publications (B.Sc., M.Sc., and Ph.D. theses) and nearly 150 research articles were archived in it. The repository DRUGG provides open access to scholarly publications and increases the visibility of the Facultys scientific publications. Building a repository is a complex project, in which the whole institution has to be involved. Library offers all technical support to the authors by archiving publications to the repository. Thus, the importance and the reputation of the library have increased, since it brings a significant added value to the quality of all activities at the faculty. The statistics of repository visits and downloads confirms its importance in Slovenia and abroad.

The impact of flow regulation by hydropower dams on the periphyton community in the Soča River, Slovenia

Abstract The effects of hydropower dams and, in particular, the impacts of reduced river flows on the periphyton community were assessed in the Soča River, Slovenia. Sampling sites were selected upstream and downstream of the Podsela and Ajba dams. Sampling was carried out in 1998 during a period of low flows. Reaches downstream from the dams experienced prolonged periods of reduced flows, and a corresponding decrease in flow velocity and water depth. The chain of hydropower dams has stopped sediment inflow from the upstream reach. Below the dams, the oscillations of water temperature, dissolved oxygen and oxygen saturation are much larger than at unregulated sites upstream. The impact of prolonged periods of reduced flows, a lack of sediment supply from upstream and changes in physicochemical variables has caused high periphyton biomass, proliferation of green algae and increases in the number of periphytic algae species below the dams. This has significant implications for the design of environmental flow strategies that provide a sediment supply to maintain a healthy periphyton community. Editor Z.W. Kundzewicz; Associate editor M. Acreman Citation Smolar-Žvanut, N. and Mikoš, M., 2014. The impact of flow regulation by hydropower dams on the periphyton community in the Soča River, Slovenia. Hydrological Sciences Journal, 59 (5), 1032–1045.

Mechanism of Active Landslides in Flysch

Triggering mechanisms and active landslide dynamics are to a large extent a function of rock and soil types involved. Among different types of active landslides in Slovenia, in the last few years, those in flysch have been of specific research interest. Different field and laboratory investigations have been carried out on several active landslides in flysch, mainly on the Slano Blato landslide in SW Slovenia. The research activities have been focused on the prevailing mechanisms of active landslides in flysch, specifically they have been directed into investigations on soil suction and its relationship with water content and shear-strength characteristics. These research activities have been carried out in the framework of the World Center of Excellence “Mechanisms of landslides in over-consolidated clays and flysch” of the Faculty of Civil and Geodetic Engineering of the University of Ljubljana, and the IPL-151 Project “Soil matrix suction in active landslides in flysch – the Slano Blato landslide case”. This paper presents the main results obtained.

Detecting flooded areas with machine learning techniques: case study of the Selška Sora river flash flood in September 2007

Abstract Floods seem to appear with increased frequency from one year to another. They create great damage to property and in some cases even result in lost lives. However, a quick and effective response by rescue services can greatly reduce the consequences. Machine learning techniques can reduce the time necessary for flood mapping. We test various machine learning methods to find the one with the highest classification accuracy. We also present the most important points for quick and effective machine learning procedures on remote sensing data. First, the data must be prepared correctly. We use satellite images, digital terrain models (DTMs), and the river network. The data in its primary form (e.g., bands of multispectral satellite images or DTMs) is insufficient. We also need certain derived attributes, such as the vegetation index or the slope derived from the DTM. Second, we must select suitable training samples and a suitable machine learning method. This approach to determining floods is presented in a case study of flash floods in the Selška Sora river valley. Machine learning techniques have proven successful in quickly determining flooded areas. The best results are produced by the J48 decision tree algorithm. The success of the ensemble machine learning methods is comparable to the J48 algorithm, while the JRip classification is not as good.