Academic literature on the topic 'Flow-like landslides'

Abstract. Coastal and subaqueous landslides can be very dangerous phenomena since they are characterised by the additional risk of induced tsunamis, unlike their completely-subaerial counterparts. Numerical modelling of landslides propagation is a key step in forecasting the consequences of landslides. In this paper, a novel approach named Equivalent Fluid/Equivalent Medium (EFEM) has been developed. It adapts common numerical models and software that were originally designed for subaerial landslides in order to simulate the propagation of combined subaerial-subaqueous and completely-subaqueous landslides. Drag and buoyancy forces, the loss of energy at the landslide-water impact and peculiar mechanisms like hydroplaning can be suitably simulated by this approach; furthermore, the change in properties of the landslide's mass, which is encountered at the transition from the subaerial to the submerged environment, can be taken into account. The approach has been tested by modelling two documented coastal landslides (a debris flow and a rock slide at Lake Albano) using the DAN-W code. The results, which were achieved from the back-analyses, demonstrate the efficacy of the approach to simulate the propagation of different types of coastal landslides.

Abstract. The morphology of landslides is influenced by the slide/flow of the material downslope. Usually, the distance of the movement of the material is greater than the width of the displaced material (especially for flows, but also the majority of slides); the resulting landslides have a greater length than width. In some specific geomorphologic environments (monoclinic regions, with cuesta landforms type) or as is the case for some types of landslides (translational slides, bank failures, complex landslides), for the majority of landslides, the distance of the movement of the displaced material can be smaller than its width; thus the landslides have a smaller length than width. When working with landslide inventories containing both types of landslides presented above, the analysis of the length and width of the landslides computed using usual geographic information system techniques (like bounding boxes) can be flawed. To overcome this flaw, I present an algorithm which uses both the geometry of the landslide polygon minimum oriented bounding box and a digital elevation model of the landslide topography for identifying the long vs. wide landslides. I tested the proposed algorithm for a landslide inventory which covers 131.1 km2 of the Moldavian Plateau, eastern Romania. This inventory contains 1327 landslides, of which 518 were manually classified as long and 809 as wide. In a first step, the difference in elevation of the length and width of the minimum oriented bounding box is used to separate long landslides from wide landslides (long landslides having the greatest elevation difference along the length of the bounding box). In a second step, the long landslides are checked as to whether their length is greater than the length of flow downslope (estimated with a flow-routing algorithm), in which case the landslide is classified as wide. By using this approach, the area under the Receiver Operating Characteristic curve value for the classification of the long vs. wide landslides is 87.8 %. An intensive review of the misclassified cases and the challenges of the proposed algorithm is made, and discussions are included about the prospects of improving the approach with further steps, to reduce the number of misclassifications.

Landslides that are the major hazards, are concentrated along the river valley, road cut sections, cultivated lands and geologically adverse areas like fault zones, incompetent lithology, steep slopes and overhanging cliffs. Present study represents a small part of the Mahabharat Range within the Lesser Himalaya, where landslide inventory mapping was carried out in the Ramche-Jharlang area because it consists of numerous small to large landslides affecting ecology and society. The main objectives were to delineate both present and past landslides with their characters (geometry, geology, hydrogeology, slope geometry, triggering causes of landslides and their impacts) focusing on the present propagating trends in terms of its cause. The field investigation was carried out by field work in the landslide occurring areas, visual inspection, satellite image analysis, photographical analysis, interaction and interview with the locals and the affected groups. The study reveals nail scratching outlook in most of the hills. The slope failures were debris flow, debris slide, mud flow and deep-seated creeps. The Ramche landslide in the eastern part to the Jharlan-Chhyamthali in the western part, have been devastating and active now and then causing huge casualties. The utmost reasons for occurring small to large scale landslides are inherently weak geological setting along with some adverse geological structures in addition to the triggering factors like concentrated precipitation and earthquakes. Systematic landslide hazard mapping and mitigation measures based on the cause and consequences during the planning and construction stages of infrastructures are fundamental steps to reduce loss from landslide disaster in the region.

Complex flow-like landslides (CFLLs) are important geomorphic agents of Late Quaternary mountain evolution in the Flysch Belt of the Outer Western Carpathians. The CFLLs are characterised by the upper section of deep-seated, retrogressive landslide of structurally unfavourably oriented rocks and lower sections composed of earthflows originated due to liquefaction of material accumulated from the upper slopes. Radiocarbon dating of organic matter incorporated into landslide debris or related deposits suggests that most of the CFLLs collapsed repeatedly throughout the Holocene with typical recurrence intervals of approximately 1–2 ka. Catastrophic landslides that occurred during extreme hydrometeorological events in recent decades displayed evidence of Holocene activity. Most of the CFLLs dammed and steepened adjacent valleys. Our chronological dataset is biased by erosion of older landforms, but most of the dated reactivations correlate to regional increases in humidity identified by previous paleoenvironmetal studies.

Steep canyons surrounded by high mountains resulting from large-scale landslides characterize the study area located in the southeastern part of the Tibetan Plateau. A total of 1766 large landslides were identified based on integrated remote sensing interpretations utilizing multisource satellite images and topographic data that were dominated by 3 major regional categories, namely, rockslides, rock falls, and flow-like landslides. The geographical detector method was applied to quantitatively unveil the spatial association between the landslides and 12 environmental factors through computation of the q values based on spatially stratified heterogeneity. Meanwhile, a certainty factor (CF) model was used for comparison. The results indicate that the q values of the 12 influencing factors vary obviously, and the dominant factors are also different for the 3 types of landslides, with annual mean precipitation (AMP) being the dominant factor for rockslide distribution, elevation being the dominant factor for rock fall distribution and lithology being the dominant factor for flow-like distribution. Integrating the results of the factor detector and ecological detector, the AMP, annual mean temperature (AMT), elevation, river density, fault distance and lithology have a stronger influence on the spatial distribution of landslides than other factors. Furthermore, the factor interactions can significantly enhance their interpretability of landslides, and the top 3 dominant interactions were revealed. Based on statistics of landslide discrepancies with respect to diverse stratification of each factor, the high-risk zones were identified for 3 types of landslides, and the results were contrasted with the CF model. In conclusion, our method provides an objective framework for landslide prevention and mitigation through quantitative, spatial and statistical analyses in regions with complex terrain.

Abstract. Digital elevation models (DEMs) representing topography are an essential input for computational models capable of simulating the run-out of flow-like landslides. Yet, DEMs are often subject to error, a fact that is mostly overlooked in landslide modeling. We address this research gap and investigate the impact of topographic uncertainty on landslide run-out models. In particular, we will describe two different approaches to account for DEM uncertainty, namely unconditional and conditional stochastic simulation methods. We investigate and discuss their feasibility, as well as whether DEM uncertainty represented by stochastic simulations critically affects landslide run-out simulations. Based upon a historic flow-like landslide event in Hong Kong, we present a series of computational scenarios to compare both methods using our modular Python-based workflow. Our results show that DEM uncertainty can significantly affect simulation-based landslide run-out analyses, depending on how well the underlying flow path is captured by the DEM, as well as on further topographic characteristics and the DEM error's variability. We further find that, in the absence of systematic bias in the DEM, a performant root-mean-square-error-based unconditional stochastic simulation yields similar results to a computationally intensive conditional stochastic simulation that takes actual DEM error values at reference locations into account. In all other cases the unconditional stochastic simulation overestimates the variability in the DEM error, which leads to an increase in the potential hazard area as well as extreme values of dynamic flow properties.

Abstract. Hazard assessment of shallow landslides represents an important aspect of land management in mountainous areas. Among all the methods proposed in the literature, physically based methods are the only ones that explicitly includes the dynamic factors that control landslide triggering (rainfall pattern, land-use). For this reason, they allow forecasting both the temporal and the spatial distribution of shallow landslides. Physically based methods for shallow landslides are based on the coupling of the infinite slope stability analysis with hydrological models. Three different grid-based distributed hydrological models are presented in this paper: a steady state model, a transient "piston-flow" wetting front model, and a transient diffusive model. A comparative test of these models was performed to simulate landslide occurred during a rainfall event (27–28 June 1997) that triggered hundreds of shallow landslides within Lecco province (central Southern Alps, Italy). In order to test the potential for a completely distributed model for rainfall-triggered landslides, radar detected rainfall intensity has been used. A new procedure for quantitative evaluation of distributed model performance is presented and used in this paper. The diffusive model results in the best model for the simulation of shallow landslide triggering after a rainfall event like the one that we have analysed. Finally, radar data available for the June 1997 event permitted greatly improving the simulation. In particular, radar data allowed to explain the non-uniform distribution of landslides within the study area.

Abstract. Modelling of flow-like landslides is one of the possible approaches that can be used to simulate landslide instability and flow development. Models based on continuum mechanics and associated with a versatile rheological model are usually preferred to predict landslide runout and relevant parameters. A different approach has been used in this research. We have developed a 2-D/3-D finite element code to analyse slope stability and to model runout of mass movements characterised by very large displacements. The idea was to be able to use different material laws already known, tested and verified for granular materials. The implemented materials laws include classical elasto-plasticity, with a linear elastic part and different applicable yield surfaces with associated and non-associated flow rules. The application of Finite Element methods to model landslide run-out, contrasts previous research where typically depth-averaged equivalent-fluid approaches were adopted. The code has been applied to the simulation of large rock avalanches and rapid dry flows in different materials and under different geological and geomorphological conditions.

High-volume fast-moving landslides undergo a solid–liquid-like phase transition. In this study we apply the smoothed particle hydrodynamics (SPH) method to simulate the solid–liquid-like phase transition in earthquake-induced landslides based on a unified constitutive model. The feasibility analysis is carried out from two aspects: the governing equations in SPH and the unified constitutive model. A sand-collapse experiment simulating the fluidization motion is performed to verify the SPH model. Strong similarities between the SPH results and the experimental results are observed, confirming that the motion of geo-materials in different states can be simulated by the unified constitutive model. The entire process of the Tangjiashan landslide is reproduced. The SPH simulation shows that during the initiation process, the sliding-mass velocity was low as the geo-materials were in solid state. As shown in Part I of this study, a continuous slip surface formed at about 15[Formula: see text]s. The sliding body gains speed as it enters the fluid state. About 50[Formula: see text]s later, the mass gradually stops moving, reaches a steady state and returns to a solid phase. Besides, the SPH simulation based on elastic–plastic model clearly shows the advantage of the proposed model.

Nowadays, the numerical models are important allies for the study of physical and natural phenomena. They become progressively more complicated because various differential equations are included to consider the different processes involved in a singular phenomenon. The number of parameters used to adapt the numerical results to the real measurements increase consequently. Among the huge quantity of natural phenomena studied, the landslides are definitely important and, among them, the flow-slides are a type, which actually have an increasing occurrence frequency because of the climate change. When the velocity of the flowing material is high, this type of natural hazard becomes even more worrying. The risk and the damage, which may result, are significant, especially when the landslide is located in close proximity to residential areas. The catastrophic effects range from the destruction of buildings and infrastructures, to the most tragic loss of human lives. Three processes of a flow-slide could be individuated: the trigger mechanism, the propagation and the final deposit. Topic of this thesis is the study of the last two phases that occur after the mass collapse has already happened. The propagation and the deposit phases will be here analyzed using a model which integrates the Saint Venant‘s equations developed for the flow of an equivalent homogeneous material according to the shallow water hypothesis. The model is applied before to the simulation of several laboratory experiments and, then, for reproducing a debris flow really occurred in 2010 in Italy. The calibration phase is the basic operation for using a numerical model. The parameters considered have to be smartly defined to reproduce the phenomenon with a satisfactory likelihood. When the parameters have a physical meaning, it is necessary to check if they allow the model to produce reliable results, even when the model necessarily introduces strong approximations. Sometimes, anyway, the parameters to include in the calculation have just a mathematical significance. In this case, it is even more important to calibrate the model paying attention to all the complexities of the phenomenon, because if the calibration strategy does not take into account the various aspects of the case study, the parameters obtained by the back-analysis may be senseless. This thesis wants to show the complexity that may characterize the calibration procedure. Once the numerical model has been adopted and its possibilities and limitations have been evaluated, the analysis of different cases will help to evidence the difficulties that the back-analysis can present. To this aim, in this work, three main case studies are presented: the spreading of a column of cohesive material on a horizontal plane, numerous flume tests performed using three-phases mixtures and, finally, a real debris flow occurred in 2010 along the Rotolon stream, in North-Western sector of Veneto region (Italy). It is important to underline that all the laboratory tests are performed on purpose to apply the back-analysis, paying therefore particular attention to the data acquisition conditions. For all the case studies, many calibration procedures are applied in order to individuate the most suitable to reduce the uncertainty in the determination of the fitting parameters.
Oggigiorno, i modelli numerici ricoprono un ruolo di fondamentale importanza per lo studio di fenomeni fisici e naturali. Essi diventano via via sempre più complessi grazie all’aumento del numero di equazioni differenziali implementate in ciascun modello al fine di tener conto dei differenti aspetti che caratterizzano il fenomeno oggetto studio. Conseguentemente cresce anche il numero dei parametri da valutare per adattare i risultati ottenuti dal modello numerico alle misure reali. Tra tutti i fenomeni naturali che si possono considerare, i frane sono indiscutibilmente molto importanti. Tra i diversi tipi di frane, le colate sono una tipologia che si presenta sempre con maggior frequenza a causa dei cambiamenti climatici in atto e con effetti molto dannosi. Quando, poi, la velocità raggiunta in questi fenomeni diventa elevata, aumenta il loro potere distruttivo. I rischi e i danni che ne possono nascere non sono trascurabili, in modo particolare quando le colate avviene in prossimità di aree residenziali. Gli effetti catastrofici che ne possono scaturire spaziano dalla distruzione di edifici e infrastrutture, fino ad arrivare alla ancor più tragica perdita di vite umane. Quando si studia un movimento di colata, tre processi devono essere presi in considerazione: il meccanismo di innesco, la fase di propagazione ed infine il deposito. Questa tesi riguarda principalmente lo studio degli ultimi due processi che si verificano, cioè, quando il materiale ha già iniziato il suo movimento. Le fasi di propagazione e di arresto sono qui analizzate utilizzando un modello numerico sviluppato integrando le equazioni di Saint Venant per il flusso di un materiale monofase omogeneo in acque basse. Il modello è stato applicato sia per la simulazione di esperimenti di laboratorio sia per riprodurre un debris flow avvenuto nel nord Italia nel 2010. Quando si utilizza un modello numerico, la fase di calibrazione rappresenta un’operazione essenziale affinché si possano ottenere buoni risultati. I parametri utilizzati dal codice devono essere attentamente definiti in modo che il modello possa riprodurre il fenomeno fisico con elevata accuratezza. Quando i parametri hanno un significato fisico, risulta necessario controllare se il loro utilizzo, considerando le approssimazioni che il modello inevitabilmente comporta, permette di produrre risultati affidabili. A volte, tuttavia, i parametri che devono essere inseriti nel modello prescindono dalla natura fisica del caso in esame, ed hanno solamente un significato in termini matematici. Quando questo avviene, risulta ancor più importante calibrare il modello, cercando di cogliere l’intera complessità del fenomeno. Se la strategia di calibrazione non tiene conto dei vari aspetti che caratterizzano il caso di studio, infatti, i parametri ottenuti tramite back-analysis potrebbe non aver alcun senso. Questa tesi si pone l’obiettivo di sottolineare la complessità che può contraddistinguere il processo di calibrazione. Dopo aver deciso quale modello numerico utilizzare ed averne comprese possibilità e limitazioni, lo studio di casi di studio differenti permette di evidenziare le criticità e le problematiche che la back-analysis può presentare. A tale scopo, in questo lavoro vengono considerati principalmente tre casi di studio. Il primo riguarda il collasso di una colonna di materiale coesivo su di un piano orizzontale. Successivamente la procedura è applicata ad un gruppo di prove in canaletta condotte con diverse miscele di argilla e sabbia. Infine, viene analizzata la colata detritica avvenuta nel 2010 lungo il torrente Rotolon, situato in nella parte nord-occidentale del Veneto. È importante sottolineare che tutti i test di laboratorio sono stati eseguiti appositamente per la successiva applicazione della back-analysis, prestando quindi particolare attenzione alle modalità di acquisizione dei dati. Per tutti e tre i casi, è stata ricercata ed applicata una strategia di calibrazione per ridurre l’incertezza nell’identificazione dei parametri ottimali.

Numerical simulation is an efficient tool for the run-out analysis of rapid flow-like landslide. In this thesis, I address three topics related to the modeling of flow-like landslide which were not sufficiently investigated in the previous studies. Three improved depth-averaged models are used to simulate the selected typical flow-like landslides and related phenomena. In the first topic, a two-layer depth-averaged model is proposed to simulate the frontal plowing phenomenon in some rapid flow-like landslides. The propagation process of a loess landslide in Shaanxi Province, China and its interaction with the terrace material is analyzed. The second topic is related to the influence of the slope gradient and gully channel on the run-out behavior (especially the entrainment and deposition characteristics) of rockslide-debris flow. The run-out process of the Verghereto landslide in Italy is analyzed by using an improved depth-averaged model. The third topic is related to the numerical assessment of the impeding effect of check dam on debris flow. Another improved depth-averaged model, which takes both entrainment and the impeding effect of check dam into account, is proposed and adopted to analyze the interaction of debris flow and check dams in a debris flow gully in Sichuan province, China. The model is then used to assess the efficiency of the actual check dams in this debris flow gully. The main purpose of this thesis is to investigate the capacity of the improved depth-averaged models on the simulation of rapid flow-like landslides and the related phenomena (frontal plowing, entrainment, and interaction between debris flow and check dam). The simulation results of the case studies in this thesis show that these improved models perform well in simulating the rapid flow-like landslides and the phenomena mentioned above, which demonstrates the potential application ability of these models for the risk assessment of rapid flow-like landslides.

AbstractThe interaction of flow-like landslides with protection barriers is analyzed for their design. Three recent analysis approaches are briefly presented and applied to different landslide geometries. Approach no. 1 (empirical) allows estimating the impact force and flow kinetic energy over the time. Approach no. 2 (analytical) additionally provides the displacement of the barrier due to the impact. Approach no. 3 (numerical) fully simulates the Landslide-Structure-Interaction (LSI) also including the estimate of the amount of landslide volume overtopping the barrier. The required input parameters and the results achievable through the three approaches are illustrated and compared.