Mihai Micu

A morphogenetic insight into a multi-hazard analysis: Bâsca Mare landslide dam

Slope–channel coupling in geomorphologically active regions represents a topic with numerous implications, from both fundamental and applied perspectives. Landsliding and erosion combine under the influence of the morphostructural and lithological, seismic, climatic, and anthropic factors, and their interaction may materialize in landslide dams, forms which are conditioning the future slope and river morphology and morphodynamics. The proper understanding of the predisposition and preparing and triggering factors in case of landslide dams could provide significant information in the risk analysis, assessment, and management. The occurrence in July 2013 of a landslide dam in the Buzău Mountains (along the Bâsca Mare river), caused by the partial reactivation of a dormant deep-seated landslide, allowed the outlining of the entire agents–forms–processes framework, offering in the meantime the background data for a future multi-hazard assessment. Since the Vrancea seismic region (area that comprises the Curvature Carpathians of Romania) represents one of Europe’s most slope/channel/seismically active regions, the case–study offers important insight information that allows in the meantime the analysis of multi-hazard at a regional scale.

Scenarios of Land Cover Change and Landslide Susceptibility: An Example from the Buzau Subcarpathians, Romania

Since 1990 the Subcarpathians in Buzau County, Romania have witnessed substantial socioeconomic changes and resulting changes in the land cover. Influenced by the interplay of poor economic conditions, land ownership reforms, and institutional difficulties, these changes have been difficult to manage, resulting in a dispersal of built-up areas. Even though, the spatial extent of land cover changes has not reached critical levels as similar areas in the Carpathians, our analysis suggests that in the future the area might experience more extreme land cover changes. Moreover, the litho-structural traits and the high relief energy of the Romanian Subcarpathians favored the occurrence of various types of mass movements, imposing different levels of risk to people, buildings and infrastructure. Increase of human influence in form of expansion of built-up areas in the area could therefore result in slope instability and changes in the temporal and spatial patterns of hydro-meteorological hazards. This study shows, that possible future changes in land cover will not have a major influence on hazards, however risk might increase due to the increased value and number of elements at risk.

Multi-Temporal Landslide Susceptibility Maps and Future Scenarios for Expected Land Cover Changes (Southern Apennines, Italy)

Human activities, including extensive land use practices, such as deforestation and intensive cultivation, may severely affect the landscape, and have caused important changes to the extent of natural forests during the last century in Southern Italy. Such changes had a strong influence on the frequency of occurrence of natural hazards, including landslides. Being one of the most significant control factors of slope movements, any variation in land cover pattern may determine changes in landslide distribution. The study area is the Rivo Basin which is located in Molise (Southern Apennines of Italy), a region severely affected by landslides. We prepared multi-temporal land cover and landslide inventory maps, aimed at developing different susceptibility maps to evaluate the effects of land cover changes in the predisposition to landslides. Based on the observed land cover trends in the study area, we simulated future scenarios of land cover in the attempt to assess potential future changes in landslide distribution and susceptibility. By investigating the relationship between the spatial pattern and distribution of past land cover settings and location factors (as elevation, slope, distance to settlements), we were able to calibrate a land cover change model to simulate future scenarios. The obtained results give important information both regarding the impact of past trends of land cover changes on landslide occurrence and possible future directions. They could be useful to provide insights toward a better land management for the study area, as well as for similar landslide-prone environments in Southern Italy, contributing to establish good practices for future landslide risk mitigation.

Economic Losses for Rural Land Value Due to Landslides

A high dynamic environment is typically interested by changes affecting the natural processes and their related consequences. Landslides do not only alter the landscape, but substantially affect human activities. When it comes to natural hazards, landslides have been acknowledged as one of the main causes of human casualties or damage to assets. Furthermore, economic losses to rural lands are also significant, despite often being underestimated, especially in rural areas. In territories not densely populated, the main productive activities are in fact often based on the agricultural and pastoral resources. We intend to propose a methodology that helps to investigate the potential loss of value (expressed in EUR) of lands usually exploited for economic profit in rural areas. We test the method on two case studies, belonging to different European Countries with very different economical assets and geological, geomorphological and other environmental conditions. The first study area is situated in the Southern Italian Apennines, in the Molise region, while the second area is located in Buzau County, a region belonging to the Romanian Curvature Carpathians and Subcarpathians Our analysis is focused not only on the actual situation, represented by the past and present landslides, but also on potential future scenarios for 2050. The scenarios foresee future similar socio-economical and technological activities, with no major changes expected. The loss estimation is based on the presence of landslides affecting the rural lands, but it also considers both a present and future landslide susceptibility scenario. This procedure allowed the estimation of the economic losses in the two case-study areas, highlighting how the same natural processes might result in different economic consequences. Following our approach, the results highlight that for the Italian case study there is a loss of 10,45% for 2007 and 9,90% for 2050 of the total land value as concerns landslides susceptibility. In the Romanian case study, on the other hand, the loss corresponds to 29,60% and 29,81% for 2010 and 2050, respectively. In addition, the proposed procedure could be considered a valuable methodological approach to assess landslide-induced economic losses, and be effectively used during spatial planning activities, aimed at supporting decision

Numerical Models of Unstable Slopes in Seismic Areas—Based on 3D Geomodels

This paper presents a series of new integrated 3D models of landslide sites that were investigated in very distinctive seismotectonic and climatic contexts in NW and SE Europe as well as in Central Asia (Tien Shan). First, we analyse ancient landslides with likely seismic origin marked by deep-seated failures, by a steep scarp and a massive failed body, by rock structures favouring static stability as well as by scarp initiation near the mountain top, far from river erosion processes. However, we present also one case study for a site near a major river, for which predictive slope stability models had to be developed: the right-bank slope located immediately downstream from the Rogun dam construction area. Multiple survey inputs and outputs were compiled in 3D geological-geophysical models and combined with high-resolution remote sensing data of the ground surface. Those models were used as inputs for 2D, 2.5D and 3D dynamic numerical simulations completed with the UDEC (Itasca) software. For some sites, a full back-analysis was carried out to assess the possibility of a seismic triggering of the landslide. For others, we simulated a series of possible future earthquake scenarios affecting the slopes. Simulations with discrete element codes also allowed us to model very large deformation and even dam formation. Interpretation of the complex inputs and outputs was enhanced by 3D stereo visualisation using a headset system allowing for full immersion in a virtual environment. We work now on the development of systems that allow several people to be immersed in the same virtual 3D model and to share their experience with each other.

Geomorphic services for landslide risk evaluation in the RO-RISK Project

The paper presents the steps undertaken within the RO-RISK (Disaster Risk Evaluation at National Level) project with the aim of achieving landslide hazard and risk evaluation at the national level, as well as the close interand transdisciplinary collaboration through the involvement of specialists and stakeholders during the whole research process, the results of which can be assigned to geomorphic services. A common methodology to analyze all the selected risks has been followed within the project, mainly focusing on hazard and impact analyses. At the end, three national and two local scale landslide scenarios have been analyzed into detail in order to provide risk figures as estimations on the location and magnitude of possible physical impacts on the population, the built-up environment and the transportation network, as well as economic and sociopsychological impacts, all of which were needed to finally estimate risk acceptability. Keywords— landslides; risk assessment; geomorphic services; environmental changes; RO-RISK; Romania

Open image in new windowIntegrated Geological-Geophysical Models of Unstable Slopes in Seismic Areas

We will present a series of new integrated 3D models of landslide sites that were investigated in distinctive seismotectonic and climatic contexts: (1) along the Hockai Fault Zone in Belgium and (2) in the seismic region of Vrancea, Romania. Both sites are deep-seated failures located in more or less seismically active areas. In such areas, slope stability analyses have to take into account the possible contributions to ground failure. Our investigation methods had to be adapted to capture the deep structure as well as the physico-mechanical characteristics that influence the dynamic behaviour of the landslide body. Field surveys included electrical resistivity tomography profiles, seismic refraction profiles (analysed in terms of both seismic P-wave tomography and surface waves), ambient noise measurements to determine the soil resonance frequencies through H/V analysis, complemented by geological and geomorphic mapping. The H/V method, in particular, is more and more used for landslide investigations or sites marked by topographic relief (in addition to the more classical applications on flat sites). Results of data interpretation were compiled in 3D geological-geophysical models supported by high resolution remote sensing data of the ground surface. Data and results were not only analysed in parallel or successively; to ensure full integration of all inputs-outputs, some data fusion and geostatistical techniques were applied to establish closer links between them. Inside the 3D models, material boundaries were defined in terms of surfaces and volumes. Those were implemented in 2D and 3D numerical dynamic models (presented in a companion paper).

Landslide Types and Spatial Pattern in the Subcarpathian Area

The Romanian Subcarpathians are the most representative landslide-prone areas of Romania in terms of typological complexity. Conditioned by a wide range of predisposing, preparing, and triggering factors, landslides are playing a determinant role among the present-day geomorphic processes, posing in the mean time a major threat to a large number of elements at risk throughout one of Romania’s most densely inhabited regions. Within this chapter, the landslides characterizing the main morphostructural and physiographic subunits of the Subcarpathians are discussed in terms of typology imposed by the litho-structural predisposition, anthropic preparatory factors and climatic and seismic triggers. Based on the above-mentioned considerations, a regional distribution reflecting their spatial pattern is attempted through a synthetic map.

The Systematic of Landslide Processes in the Conditions of Romania’s Relief

Landslides are extremely active slope-shaping processes. Their broad spectrum of processes and forms, alongside different types of displaced material is conditioned by a wide range of predisposing, preparing, and triggering factors. There are numerous attempts to classify them homogeneously, but quite often, the heterogeneity of the phenomenon imposes different criteria, depending on regions or scientific schools and approaches. Criteria like morphology and morphogenesis always found a common usage; meanwhile others like age or morphodynamic behavior are still debated. In Romania, the wide range of processes and forms, as well as the potential consequences inflicted to the socio-economic environment is well reflected within an extended geomorphologic literature, dealing with both fundamental and applied considerations. If for a long period of time, landslide systematic in Romanian geomorphology was predominantly descriptive, during the last two decades, one faces an almost completely shifted approach, changing from fundamental aspects to predictive studies, in the form of susceptibility, hazard, and risk. Through an in-depth review of the most important outcomes of the last 100 years’ literature in the field of landslide systematic, several milestones might be set up. The relationship between geomorphology and other geonomic sciences, as well as the connections between national and international literature are discussed in terms of common or uncommon criteria of classification. A concise description of the main types of landslides (according to modern literature) throughout Romania is given in terms of synthetic regional descriptions.