ALBERT

Description: Residual shear strength of soils is an important soil parameter for assessing the stability of landslides. To investigate the effect of the shear rate on the residual shear strength of loessic soils, a series of ring shear tests were carried out on loess from three landslides at two shear rates (0.1 mm/min and 1 mm/min). Naturally drained ring shear tests results showed that the shear displacement to achieve the residual stage for specimens with higher shear rate was greater than that of the lower rate; both the peak and residual friction coefficient became smaller with increase of shear rate for each sample; at two shear rates, the residual friction coefficients for all specimens under the lower normal stress were greater than that under the higher normal stress. The tests results revealed that the difference in the residual friction angle фr at the two shear rates, фr (1)–фr (0.1), under each normal stress level were either positive or negative values. However, the difference фr(1)–фr (0.1) under all normal stresses was negative, which indicates that the residual shear parameters reduced with the increasing of the shear rate in loess area. Such negative shear rate effect on loess could be attributed to a greater ability of clay particles in specimen to restore broken bonds at low shear rates.

Description: The objective of this paper is the assessment of bioclimatic conditions in Sebia. A special emphasis has been given to the heat budget bioclimatic Universal Thermal Climate Index (UTCI) whose purpose is to evaluate degree of thermal stress that human body is exposed to during the last twenty years. In addition, the thresholds of daily maximum temperatures are analysed in order to identify increase and frequency of heat waves in Serbia. For this research, daily and hourly (07 h and 14 h) meteorological data from 3 weather station (Mt. Zlatibor, Novi Sad, Niš) are collected for the period 1998–2017. The results show that the most frequent UTCI heat stress categories are strong heat stress and very strong heat stress. The most extreme heat waves events are occurred in 2007, 2012, 2015 and 2017. Moreover, there were three Heat wave events (HWE) in Niš occurred in July, 2007 lasting 3, 10 and 4 days in row. Heat wave events (HWE) In July 2007 (10 days) and July 2012 (9 days) in Niš are occurrences with maximum number of days in row recorded.

Description: For many geotechnical purposes, the proper estimation of shapes and dimensions of landslide rupture zones is of significant importance. Very often this exact delineation is difficult due to the lack of information on rupture zone extents in 3D. Based on a global landslide inventory, this study presents a refined statistical analysis correlating dimension-related and shape-related parameters characterizing a rupture zone in 3D to its volume. Dimension-parameters are approximated by linear regressions increasing with greater volumes, whereas shape-related parameters appear stable throughout the entire range of volumes. Revealing themselves as very stable, these correlations can be used, hence, to extrapolate from a distinct parameter to the volume of a landslide rupture zone. In a second stage, ratios of dimension-related parameters are correlated with rupture zone volumes. Also, this type of correlation delivers very stable results showing that ratios are constant throughout the entire range of volumes. Making use of this ratio consistency, it is possible to deduce one of the two parameters when the other one is given. This latter aspect seems to be promising for remote sensing surveys when initial rupture areas or rupture volumes should be delineated.

Description: A tailings dam accident can cause serious ecological disaster and property loss. Simulation of a tailings dam accident in advance is useful for understanding the tailings flow characteristics and assessing the possible extension of the impact area. In this paper, a three-dimensional (3-D) computational fluid dynamics (CFD) approach was proposed for reasonably and quickly predicting the flow routing and impact area of mud flow from a dam failure across 3-D terrain. The Navier–Stokes equations and the Bingham-Papanastasiou rheology model were employed as the governing equations and the constitutive model, respectively, and solved numerically in the finite volume method (FVM) scheme. The volume of fluid (VOF) method was used to track the interface between the tailings and air. The accuracy of the CFD model and the chosen numerical algorithm were validated using an analytical solution of the channel flow problem and a laboratory experiment on the dam break problem reported in the literature. In each issue, the obtained results were very close to the analytical solutions or experimental values. The proposed approach was then applied to simulate two scenarios of tailings dam failures, one of which was the Feijão tailings dam that failed on 25 January 2019, and the simulated routing coincided well with the in situ investigation. Therefore, the proposed approach does well in simulating the flow phenomenon of tailings after a dam break, and the numerical results can be used for early warning of disasters and emergency response.

Description: Post-event damage assessments are essential to document the effects of high-impact weather events such as floods or strong wind events. Moreover, evaluating the damage and characterizing its extension and intensity can be helpful for further analysis such as completing a diagnostic meteorological case study. This paper presents a methodology to perform field surveys of damage caused by strong winds of convective origin, i.e. tornado, downburst and other types of convective winds. It is based on previous studies and also on 136 fieldworks performed by the authors in Spain from 2004 to 2018. The methodology includes the systematic collection of pictures and records of damages on man-made structures and on vegetation, as well as collection of any available Automatic Weather Station data, witness reports and images of the phenomenon and their location and orientation. Three final deliverables are proposed to synthesize the data recorded: (i) A summary of the fieldwork; (ii) A table consisting of detailed geolocated information about each damage, and (iii) A map or a .kml file containing the previous information ready for graphical display and further analysis. This methodology has been applied by the authors in the past, sometimes only a few hours after the event occurrence and, in many occasions, when the type of convective phenomenon (e.g. tornado, downburst) was uncertain. In the latter case the information resulting from this methodology has proofed very useful to discern the phenomenon type, based on the damage patterns particularly if no witness reports were available. The application of systematic methodologies as the one presented here is necessary in order to build homogeneous databases of severe weather cases and high impact weather events.

Description: Since drought is a multifaceted phenomenon, more than one variable should be considered for a proper understanding of such extreme event in order to implement adequate risk mitigation strategies such as weather or agricultural indices insurance programs, or disaster risk financing tools. This paper proposes a new composite drought index that accounts for both meteorological and agricultural drought conditions, by combining in a probabilistic framework two consolidated drought indices: the Standardized Precipitation Index (SPI) and the Vegetation Health Index (VHI). The new index, called Probabilistic Precipitation Vegetation Index (PPVI), is scalable, transferable all over the globe and can be updated in near-real time. Furthermore, it is a remote-sensing product, since precipitation are retrieved from satellite and the VHI is a remote-sensing index. In addition, a set of rules to objectively identify drought events is developed and implemented. Both the index and the set of rules have been applied to Haiti. The performance of PPVI has been evaluated by means of the Receiver Operating Characteristics curve and compared to the ones of SPI and VHI considered separately. The new index outperformed SPI and VHI both in drought identification and characterization, thus revealing potential for an effective implementation within drought early warning systems.

Description: Combined with the spatial data processing capability of geographic information systems (GIS), a three-dimensional (3D) landslide surge height calculation method is proposed based on grid column units. First, the data related to the landslide are rasterized to form grid columns, and a force analysis model of 3D landslides is established. Combining the vertical strip method with Newton's laws of motion, dynamic equilibrium equations are established to solve for the surge height. Moreover, a 3D landslide surge height calculation expansion module is developed in the GIS environment, and the results are compared with those of the two-dimensional Pan Jiazheng method. Comparisons show that the maximum surge height obtained by the proposed method is 24.6 % larger than that based on the Pan Jiazheng method. Compared with the traditional two-dimensional method, the 3D method proposed in this paper better represents the actual spatial state of the landslide and is more suitable for risk assessment.

Description: This study aims to test the capacity of Flow-3D regarding the simulation of a rockslide impacting a water body by evaluating the influence of the extent of the computational domain, the grid resolution, the corresponding computation times and the accuracy of modelling results. A detailed analysis of the Lituya Bay event (1958, Alaska, maximum recorded run-up of 524 m a.s.l.) is presented. A focus on the tsunami formation and run-up in the impact area is accomplished with the numerical model. Several simulations with a simplified bay geometry are accomplished in order to test the concept of a denser fluid for the impacting rockslide material compared to the water in the bay. Further, a real topography and bathymetry of the impact area are set up. The observed maximum run-up in the impact area can be reproduced using a uniform grid resolution of 5 m, where the wave overtops the hill crest on the opposite side of the impact area, then flowing diagonally along the slopes. The model is enlarged along the entire bay to simulate the propagation of the wave. The tsunami trimline is best reproduced when using a mesh size of 15 x 15 x 10 m. The trimline mainly results from the primary wave, but in some locations also from reflected waves. The dense fluid is a suitable, simple concept to recreate a sliding mass impacting a water body, in this case with impact velocities of 94 ms−1. The tsunami event and the related trimline are well reproduced using the 3D-modelling approach with the density evaluation model available in Flow-3D.

Description: Recovering from major earthquakes is a challenge, especially in mountainous environments where post-earthquake mass movements and floods may cause substantial impacts. We monitored the reconstruction of Longchi town in Sichuan, China, over a period of 11 years, following the 2008 Wenchuan earthquake. Seven inventories of buildings, land use, roads and mitigation measures were made by using remote sensing image interpretation and field surveys. Most of the buildings were rebuild by 2010 and reconstruction was completed by 2012. The total economic value of the new buildings in 2010 was much more than the pre-earthquake situation in 2007. Unfortunately, post-seismic hazards were not sufficiently taken into consideration in the recovery planning before the catastrophic debris flow disaster in 2010. As a result, the direct economic loss from post-seismic disasters was more than the loss caused by the earthquake itself. The society showed an impact – adapt pattern, taking losses from disasters and then gaining resistance.

Description: In this study, time-dependent probabilistic tsunami hazard analysis (PTHA) is performed for Tuzla, Istanbul in the Sea of Marmara, Turkey, using various earthquake scenarios of Prince Island Fault within next 50 and 100 years. Monte Carlo (MC) simulation technique is used to generate a synthetic earthquake catalogue which includes earthquakes having magnitudes between Mw 6.5 and 7.1. This interval defines the minimum and maximum magnitudes for the fault in the case of entire fault rupture which depends on the characteristic fault model. Based on this catalogue, probability of occurrence and associated tsunami wave heights are calculated for each event. The study associates the probabilistic approach with tsunami numerical modelling. Tsunami numerical code NAMI DANCE was used for tsunami simulations. According to the results of the analysis, distribution of probability of occurrence corresponding to tsunami hydrodynamic parameters are represented. Maximum positive and negative wave amplitudes show that tsunami wave heights up to 1 m have 65 % probability of exceedance for next 50 years and this value increases by 85 % in Tuzla region for next 100 years. Inundation depth also exceeds 1 m in the region with probabilities of occurrence of 60 % and 80 % for next 50 and 100 years, respectively. Moreover, Probabilistic inundations maps are generated to investigate inundated zones and the amount of water penetrated inland. Probability of exceedance of 0.3 m wave height, ranges between 10 % and 75 % according to these probabilistic inundation maps and the maximum inundation distance calculated among entire earthquake catalogue is 60 m in this test site. Furthermore, at synthetic gauge points which are selected along the western coast of the Istanbul by including Tuzla coasts. Tuzla is one of the area that shows high probability exceedance of 0.3 m wave height, which is around 90 %, for the next 50 years while this probability reaches up to more than 95 % for the next 100 years.