Janusz Wasowski

Engineering Geology for Society and Territory - Volume 1

Dissociation of natural gas hydrate (NGH) in seabed can product amounts of gas. If the soil layer over NGH layer is permeable, gas will escape. Gas escape can on one hand lead to the damage of seabed, on the other hand lead to the decrease of the density of sea water and so threatens the structures nearby. In this paper movement and expansion behavior of gas in water was first studied, then the damage of seabed due to gas escape was studied. Effects of gas pressure, thickness of soil layer were investigated. The expansion angle of gas in the water was obtained. The characteristics of the hole size induced by gas escape with gas pressure and soil thickness were also obtained. These results can be as references of deeper research and practice.

Factors Controlling Seismic Susceptibility of the Sele Valley Slopes: The Case of the 1980 Irpinia Earthquake Re-Examined

Most of the documented slope failures triggered by the 1980 Irpinia earthquake (Ms 6.9) occurred in the upper Sele valley epicentral area (southern Italy). The early investigations revealed some puzzling characteristics of the slope failure distribution, i.e., (i) the higher landslide concentration on the valley slopes located farther away from the earthquake fault; (ii) the predominance of re-activations over first-time movements. The analyses of factors controlling the landslide concentrations indicates that the differences in hydrological setting and in slope were the two main causal factors whereas the seismic shaking, according to the radiation pattern modelling, could have been characterised by a relatively low rate of decrease across the valley. The aspect of the slopes did not play a significant role. The differences in groundwater conditions between the western and eastern valley sides were probably enhanced by the earthquake. In addition to the probable pore-water pressure rise, the seismic shaking caused large increases in the flow of springs draining the western aquifer, and this made the adjacent flysch slopes more prone to landsliding. Data from the available literature suggest that the effects of earthquake-induced groundwater release on seismic landslide distribution is especially important for normal-fault events. The Sele valley case also indicates that the slope of the pre-existing landslides is an important factor controlling their susceptibility to seismic re-activations.

Influence of land-use change and precipitation patterns on landslide activity in the Daunia Apennines, Italy

Abstract The historical variations in landslide activity are investigated in the Rocchetta S. Antonio territory, where sown fields cover 75% of the total area. The perception of the inhabitants is that landsliding has increased in recent years, and climate change has been invoked as a case. However, since 1865 annual precipitation has decreased c. 8% per century in southeastern Italy and local rainfall data for the 1955–2008 period show high inter-annual variability with statistically uncertain trends. In the same decades human alterations to the local environment were considerable. To demonstrate the impacts of land-use changes, detailed landslide and land-use maps spanning the 1976–2006 period have been constructed and the spatial–temporal changes in the context of the local precipitation patterns have been analysed. It is shown that the frequency of landsliding in 2006 was 160% higher than in 1976, even though both years were comparably wet. The sown fields increased by 46% from 1976 to 2006, and the landslide density was 55% higher on the new sown fields; that is, those cultivated after 1976. Thus, the higher susceptibility to landsliding is linked to the land-use changes and especially to the new ploughing for EU-sponsored wheat cultivation that has taken place on the steeper slopes.

Introduction to Geohazards of Central China

This thematic set of papers is intended to raise awareness of the types, nature, effects and impacts of geohazards in Central China. The papers will be published in this and subsequent issues of QJEGH and demonstrate the significant impacts that are wrought on the lives and livelihoods of those who live and work in the mountainous areas of Central China. China is all too often in the news as a result of geohazards that have a severe impact on lives and livelihoods. The mountainous terrain of Central China is subject to frequent hazards of high intensity with recent examples such as the 2008 Wenchuan earthquake and the 2010 Zhouqu debris flow. Rapid economic development brings with it expansion of urban centres and infrastructure networks, which not only increases the exposure of the population to natural processes in a dynamic environment, but can also lead to further strains on a landscape that is only marginally stable. Frequent geohazard events have sparked much research in an effort to better understand processes and material properties that can be used to inform and implement effective strategies to mitigate against the negative consequences of these geohazards. Owing to their location along the eastern margins of the Tibetan Plateau the provinces of Gansu, Sichuan and Yunnan are particularly affected by geohazards (Fig. 1). This tectonically active region is strongly affected by continuing uplift and, towards the east and NE, crustal stress release has resulted in the formation of some very large systems of NNE–SSW- and WNW–ESE-trending strike-slip and thrust fault zones (e.g. Dijkstra et al . 1993). Differences in relative uplift and displacement along these faults have had a significant impact on the present physiography of Central China. Several important geohazard regions can be distinguished and in this introduction we briefly highlight issues in two of …

Introduction to land-use and climate change impacts on landslides

The evidence of a general trend of global warming is overwhelming. It now seems beyond reasonable doubt that increases in greenhouse gas emissions resulting from human activities have led to an increase in the global temperature anomaly, which is, in turn, leading to changes and, indeed, instability in the climate (see Dijkstra & Dixon 2010). The Stern Review (Stern 2007) presented an economic argument in favour of action to limit the potential 5–20% loss of global gross domestic product (GDP) each year that it predicts if climate change were to proceed unabated. An expenditure of 1% of global GPD per annum on actions designed to limit the causes of climate change in the form of reduced greenhouse gas emissions was recommended by Stern and stated to yield a major net positive benefit, although such investment in the next 10–20 years was viewed as critical. Notwithstanding this, the future climate change scenarios that result from global models are somewhat variable. The range and nature of the changes forecast can be substantial when viewed at a global, continental or even, in some cases, a national scale. In addition, the potential range of change forecast, at a given location, may be large even when the results are viewed at a regional level. This may be due to the effects of uncertainty in the levels of future emissions, natural variability (e.g. year-on-year variations) and, of course, uncertainty within the modelling process itself. Natural variability in particular presents certain problems of perception and understanding of the issues around climate change (Pope 2009). As Pope noted, the press often confuses extreme events, which occur within the range of natural variability, as being the direct result of climate change. Clearly, we must be extremely cautious in presenting analyses of such events and attributing their occurrence, either …

DInSAR applications to landslide studies

Operational monitoring of slope instabilities by SAR interferometry poses a number of challenges due to the limited spatial extent of the landsliding areas and the rainy conditions usually associated with mass movement events. In this work, we present applications of DInSAR techniques to the assessment of the stability of landslide-prone areas. A long-term analysis over single, stable scatterers can be attempted, in order to overcome the intrinsic low-coherence conditions associated with landslide sites. The technique, known as the permanent scatterers approach, has been shown to give excellent results over areas with high densities of man-made targets. In this work, some aspects of the PS processing are reviewed and possible improvements are proposed to bring the method to give reliable results over sites with low urbanization such as the rural settings associated with landslide-prone areas in Southern Italy.

Multi-scale Robust Modelling of Landslide Susceptibility: Regional Rapid Assessment and Catchment Robust Fuzzy Ensemble

Landslide susceptibility assessment is a fundamental component of effective landslide prevention. One of the main challenges in landslides forecasting is the assessment of spatial distribution of landslide susceptibility. Despite the many different approaches, landslide susceptibility assessment still remains a challenge. A semi-quantitative method is proposed combining heuristic, deterministic and probabilistic approaches for a robust catchment scale assessment. A fuzzy ensemble model has been exploited for aggregating an array of different susceptibility zonation maps. Each susceptibility zonation has been obtained by applying heterogeneous statistical techniques as logistic regression (LR), relative distance similarity (RDS), artificial neural network (ANN) and two different landslide susceptibility techniques based on the infinite slope stability model. The sequence of data-transformation models has been enhanced following the semantic array programming paradigm. The ensemble has been applied to a study area in Italy. This catchment scale methodology may be exploited for analysing the potential impact of landscape disturbances. At regional scale, a qualitative approach is also proposed as a rapid assessment technique – suitable for application in real-time operations such as wildfire emergency management.

Use of InSAR data for landslide monitoring: a case study from southern Italy

Use of InSAR techniques in the study of unstable slopes has been suggested in recent works. However, in the ease of mass movements, which typically occur in high-relief terrain and are of limited areal extent, the detection of ground surface deformation is difficult. Moreover, the presence of vegetation cover and atmospheric effects introduces coherence loss and resolution problems in the analysis of interferometric pairs. Thus, extreme care must be taken in every step of interferometric SAR processing in order to obtain results that can be easily interpreted and be of practical utility in landslide hazard studies. The authors present the results of the application of InSAR and DInSAR techniques to a landslide test area located in the Southern Apennines. A number of SAR images was selected, whose dates coincide with periods of mass movement activity documented by in situ controls. DInSAR processing was conducted in order to assess the potential of satellite radar data for landslide monitoring. Coarse resolution is an important limiting factor for effective information extraction. Advanced processing approaches may help to overcome this limit.

Persistent Scatterers Interferometry Provides Insight on Slope Deformations and Landslide Activity in the Mountains of Zhouqu, Gansu, China

We present the results of Persistent Scatterers Interferometry (PSI) applied to investigate slope instabilities in a remote high mountain region of Southern Gansu, known to be prone to large magnitude (M7-8) earthquakes and catastrophic slope failures. The PSI processing of high resolution (~3 m) COSMO/SkyMed (CSK) satellite images produced spatially dense information (more than 1,000 PS/km2) on ground surface displacements in the area of Zhouqu, a town located in the Bailong River valley. A substantial portion of the radar targets showed significant displacements (from few to over 50 mm/year), denoting widespread occurrence of slope instabilities. In particular, the PSI results provided valuable information on the activity of some very large, apparently slow landslides that represent a persistent hazard to the local population and infrastructure. Monitoring movements of large long-lived landslides is important especially when, as in the case of the Bailong valley, they are known to undergo periods of increased activity resulting in river damming and disastrous flooding. Given the general lack of monitoring data on large landslides at Zhouqu and on other similar major failures that are common in Southern Gansu, the PSI-derived displacements offer unique information, which, following expert judgment, can be used for preliminary wide-area assessments of hazards linked to landslide activity. Furthermore, this study shows that with the high resolution CSK data resulting in high radar target density, PSI can also assist in slope/landslide-specific assessments.

Land-Use Change and Shallow Landsliding: A Case History from the Apennine Mountains, Italy

We investigate temporal variations in land use and landsliding in a small catchment characterized by the predominance of clay-rich materials and known to be prone to shallow slope failures. The results demonstrate a pronounced change from land use dominated by grassland pasture (~53 % in 1955) to wheat-based agriculture (~74 % in 2011). The temporal series of landslide inventories also indicate significant variations in landslide activity in the same period. In particular, the highest susceptibility to landsliding has been registered in recent years on the sown fields which had initially (1955) been used for pasture and grazing. The data also reveal that with time the steeper and apparently more landslide-prone slopes with grassland-pasture have been given over to new wheat cultivation. The introduction of ploughing for the new wheat cultivation on the often steep slopes that had originally been covered by grass is considered to be a significant factor in the increased susceptibility to landsliding. The negative impact on slope stability can be related to the decrease in effective strengths of soil resulting from modification of the existing cover from grass that is present all year to wheat characterized by a few month growth period per year, which implies increase in groundwater levels, and mechanical disturbance of soil caused by tillage. Finally, for the studied period (1955–2011) the local precipitation data indicated high inter-annual variability without the presence of any statistically significant trends.