Academic literature on the topic 'Landslide Size Distribution'

Abstract. Landslides are natural hazards occurring in response to triggers of different origins, which can act with different intensities and durations. Despite the variety of conditions that cause a landslide, the analysis of landslide inventories has shown that landslide events associated with different triggers can be characterized by the same probability distribution. We studied a cellular automaton, able to reproduce the landslide frequency-size distributions from catalogues. From the comparison between our synthetic probability distribution and the landslide area probability distribution of three landslide inventories, we estimated the typical size of a single cell of our cellular automaton model to be from 35–100 m2, which is important information if we are interested in monitoring a test area. To determine the probability of occurrence of a landslide of size s, we show that it is crucial to get information about the rate at which the system is approaching instability rather than the nature of the trigger. By varying such a driving rate, we find how the probability distribution changes and, in correspondence, how the size and the lifetime of the most probable events evolve. We also introduce a landslide-event magnitude scale based on the driving rate. Large values of the proposed intensity scale are related to landslide events with a fast approach to instability in a long distance of time, while small values are related to landslide events close together in time and approaching instability slowly.

The influence of root reinforcement on shallow landsliding has been well established through mechanistic and empirical studies, yet few studies have examined how local vegetative patterns influence slope stability. Because root networks spread outward from trees, the species, size, and spacing of trees should influence the spatial distribution of root strength. We documented the distribution and characteristics of trees adjacent to 32 shallow landslides that occurred during 1996 in the Oregon Coast Range. Although broadly classified as a conifer-dominated forest, we observed sparse coniferous and abundant hardwood trees near landslide scars in an industrial forest (Mapleton) that experienced widespread burning in the 19th century. In industrial forests that were burned, selectively harvested, and not replanted (Elliott State Forest), swordfern was ubiquitous near landslides, and we observed similar numbers of live conifer and hardwood trees proximal to landslide scarps. We demonstrate that root strength quantified in landslide scarps and soil pits correlates with a geometry-based index of root network contribution derived from mapping the size, species, condition, and spacing of local trees, indicating that root strength can be predicted by mapping the distribution and characteristics of trees on potentially unstable slopes. In our study sites, landslides tend to occur in areas of reduced root strength, suggesting that to make site-specific predictions of landslide occurrence slope stability analyses must account for the diversity and distribution of vegetation in potentially unstable terrain.Key words: slope stability, vegetation, root strength, shallow landslide, debris flow, Oregon Coast Range.

Assessment of landslide hazard across mountains is imperative for public safety. Pre- and post-earthquake landslide mapping envisage that landslides show significant size changes during earthquake activity. One of the purposes of earthquake-induced landslide investigation is to determine the landslide state and geometry and draw conclusions on their mobility. This study was based on remote sensing data that covered 72 years, and focused on the west slopes of the Skolis Mountains, in the northwest Peloponnese. On 8 June 2008, during the strong Movri Mountain earthquake (Mw = 6.4), we mapped the extremely abundant landslide occurrence. Historical seismicity and remote sensing data indicate that the Skolis Mountain west slope is repeatedly affected by landslides. The impact of the earthquakes was based on the estimation of Arias intensity in the study area. We recognized that 89 landslides developed over the last 72 years. These landslides increased their width (W), called herein as inflation or their length (L), termed as enlargement. Length and width changes were used to describe their aspect ratio (L/W). Based on the aspect ratio, the 89 landslides were classified into three types: I, J, and Δ. Taluses, developed at the base of the slope and belonging to the J- and Δ-landslide types, are supplied by narrow or irregular channels. During the earthquakes, the landslide channels migrated upward and downward, outlining the mobility of the earthquake-induced landslides. Landslide mobility was defined by the reach angle. The reach angle is the arctangent of the landslide’s height to length ratio. Furthermore, we analyzed the present slope stability across the Skolis Mountain by using the landslide density (LD), landslide area percentage (LAP), and landslide frequency (LF). All these parameters were used to evaluate the spatial and temporal landslide distribution and evolution with the earthquake activity. These results can be considered as a powerful tool for earthquake-induced landslide disaster mitigation

Accurate and detailed multitemporal inventories of landslides and their process characterization are crucial for the evaluation of landslide hazards and the implementation of disaster risk reduction strategies in densely-populated mountainous regions. Such investigations are, however, rare in many regions of the tropical African highlands, where landslide research is often in its infancy and not adapted to the local needs. Here, we have produced a comprehensive multitemporal investigation of the landslide processes in the hillslopes of Bujumbura, situated in the landslide-prone East African Rift. We inventoried more than 1200 landslides by combining careful field investigation and visual analysis of satellite images, very-high-resolution topographic data, and historical aerial photographs. More than 20% of the hillslopes of the city are affected by landslides. Recent landslides (post-1950s) are mostly shallow, triggered by rainfall, and located on the steepest slopes. The presence of roads and river quarrying can also control their occurrence. Deep-seated landslides typically concentrate in landscapes that have been rejuvenated through knickpoint retreat. The difference in size distributions between old and recent deep-seated landslides suggests the long-term influence of potentially changing slope-failure drivers. Of the deep-seated landslides, 66% are currently active, those being mostly earthflows connected to the river system. Gully systems causing landslides are commonly associated with the urbanization of the hillslopes. Our results provide a much more accurate record of landslide processes and their impacts in the region than was previously available. These insights will be useful for land management and disaster risk reduction strategies.

Abstract. Inventories of landslides caused by different triggering mechanisms, such as earthquakes, extreme rainfall events or anthropogenic activities, may show different characteristics in terms of distribution, contributing factors and frequency–area relationships. The aim of this research is to study such differences in landslide inventories and the effect they have on landslide susceptibility assessment. The study area is the watershed of the transboundary Koshi River in the central Himalaya, shared by China, Nepal and India. Detailed landslide inventories were generated based on visual interpretation of remote-sensing images and field investigation for different time periods and triggering mechanisms. Maps and images from the period 1992 to 2015 were used to map 5858 rainfall-triggered landslides, and after the 2015 Gorkha earthquake, an additional 14 127 coseismic landslides were mapped. A set of topographic, geological and land cover factors were employed to analyze their correlation with different types and sizes of landslides. The frequency–area distributions of rainfall- and earthquake-triggered landslides (ETLs) have a similar cutoff value and power-law exponent, although the ETLs might have a larger frequency of a smaller one. In addition, topographic factors varied considerably for the two triggering events, with both altitude and slope angle showing significantly different patterns for rainfall-triggered and earthquake-triggered landslides. Landslides were classified into two size groups, in combination with the main triggering mechanism (rainfall- or earthquake-triggered). Susceptibility maps for different combinations of landslide size and triggering mechanism were generated using logistic regression analysis. The different triggers and sizes of landslide data were used to validate the models. The results showed that susceptible areas for small- and large-size rainfall- and earthquake-triggered landslides differed substantially.

Abstract. The 12 January 2010 Port-au-Prince, Haiti, earthquake (Mw 7.0) triggered tens of thousands of landslides. The purpose of this study is to investigate the correlations of the occurrence of landslides and their erosion thicknesses with topographic factors, seismic parameters, and their distance from roads. A total of 30 828 landslides triggered by the earthquake covered a total area of 15.736 km2, distributed in an area more than 3000 km2, and the volume of landslide accumulation materials is estimated to be about 29 700 000 m3. These landslides are of various types, mostly belonging to shallow disrupted landslides and rock falls, but also include coherent deep-seated landslides and rock slides. These landslides were delineated using pre- and post-earthquake high-resolutions satellite images. Spatial distribution maps and contour maps of landslide number density, landslide area percentage, and landslide erosion thickness were constructed in order to analyze the spatial distribution patterns of co-seismic landslides. Statistics of size distribution and morphometric parameters of co-seismic landslides were carried out and were compared with other earthquake events in the world. Four proxies of co-seismic landslide abundance, including landslides centroid number density (LCND), landslide top number density (LTND), landslide area percentage (LAP), and landslide erosion thickness (LET) were used to correlate co-seismic landslides with various landslide controlling parameters. These controlling parameters include elevation, slope angle, slope aspect, slope curvature, topographic position, distance from drainages, lithology, distance from the epicenter, distance from the Enriquillo–Plantain Garden fault, distance along the fault, and peak ground acceleration (PGA). A comparison of these impact parameters on co-seismic landslides shows that slope angle is the strongest impact parameter on co-seismic landslide occurrence. Our co-seismic landslide inventory is much more detailed than other inventories in several previous publications. Therefore, we carried out comparisons of inventories of landslides triggered by the Haiti earthquake with other published results and proposed possible reasons of any differences. We suggest that the empirical functions between earthquake magnitude and co-seismic landslides need to update on the basis of the abundant and more complete co-seismic landslide inventories recently available.

A preliminary analysis of landslide spatial distribution and their geometric characteristics is presented for the area of Slavonski Brod, located in the northeastern part of Croatia and belonging to the Pannonian Basin System. A landslide inventory for the study area of 55.1 km2 is accomplished for the first time, based on the visual interpretation of a high resolution LiDAR digital terrain model. In total, 854 landslide polygons are delineated, corresponding to an average density of 15.5 landslides per square kilometre. The average landslide area is 839 m2, and most of the landslides can be classified as small landslides (76 %). The spatial relationship between landslides and geological units is analysed and expressed as a landslide index. The Late Pannonian sands with silts and gravel interlayers and Pliocene clay, sands, gravels, and coal are determined as the units that are most susceptible to landslide processes. The majority of landslides (85 %) are concentrated within these two units, for which a detailed analysis is performed, determining the morphometric parameters (slope and relief) and drainage network. The parameters’ classes that create favourable preconditions to slope instabilities are defined, based on the landslide density within individual classes. Besides, the geometric characteristics of landslides (size and shape) within these two units are compared. The results serve as the basis for further investigations. They help to foresee the area of future landslides through landslide susceptibility maps, and offer a better understanding of the influence of fluvial-denudation and slope processes on recent landscape evolution and form.

Abstract. The 12 January 2010 Port-au-Prince, Haiti, earthquake (Mw= 7.0) triggered tens of thousands of landslides. The purpose of this study is to investigate the correlations of the occurrence of landslides and the thicknesses of their erosion with topographic, geologic, and seismic parameters. A total of 30 828 landslides triggered by the earthquake covered a total area of 15.736 km2, distributed in an area more than 3000 km2, and the volume of landslide accumulation materials is estimated to be about 29 700 000 m3. These landslides are of various types, mostly belonging to shallow disrupted landslides and rock falls, but also include coherent deep-seated landslides and rock slides. These landslides were delineated using pre- and post-earthquake high-resolution satellite images. Spatial distribution maps and contour maps of landslide number density, landslide area percentage, and landslide erosion thickness were constructed in order to analyze the spatial distribution patterns of co-seismic landslides. Statistics of size distribution and morphometric parameters of co-seismic landslides were carried out and were compared with other earthquake events in the world. Four proxies of co-seismic landslide abundance, including landslides centroid number density (LCND), landslide top number density (LTND), landslide area percentage (LAP), and landslide erosion thickness (LET) were used to correlate co-seismic landslides with various environmental parameters. These parameters include elevation, slope angle, slope aspect, slope curvature, topographic position, distance from drainages, lithology, distance from the epicenter, distance from the Enriquillo–Plantain Garden fault, distance along the fault, and peak ground acceleration (PGA). A comparison of these impact parameters on co-seismic landslides shows that slope angle is the strongest impact parameter on co-seismic landslide occurrence. Our co-seismic landslide inventory is much more detailed than other inventories in several previous publications. Therefore, we carried out comparisons of inventories of landslides triggered by the Haiti earthquake with other published results and proposed possible reasons for any differences. We suggest that the empirical functions between earthquake magnitude and co-seismic landslides need to be updated on the basis of the abundant and more complete co-seismic landslide inventories recently available.

Abstract. In active mountain belts with steep terrain, bedrock landsliding is a major erosional agent. In the Himalayas, landsliding is driven by annual hydro-meteorological forcing due to the summer monsoon and by rarer, exceptional events, such as earthquakes. Independent methods yield erosion rate estimates that appear to increase with sampling time, suggesting that rare, high-magnitude erosion events dominate the erosional budget. Nevertheless, until now, neither the contribution of monsoon and earthquakes to landslide erosion nor the proportion of erosion due to rare, giant landslides have been quantified in the Himalayas. We address these challenges by combining and analysing earthquake- and monsoon-induced landslide inventories across different timescales. With time series of 5 m satellite images over four main valleys in central Nepal, we comprehensively mapped landslides caused by the monsoon from 2010 to 2018. We found no clear correlation between monsoon properties and landsliding and a similar mean landsliding rate for all valleys, except in 2015, where the valleys affected by the earthquake featured ∼5–8 times more landsliding than the pre-earthquake mean rate. The long-term size–frequency distribution of monsoon-induced landsliding (MIL) was derived from these inventories and from an inventory of landslides larger than ∼0.1 km2 that occurred between 1972 and 2014. Using a published landslide inventory for the Gorkha 2015 earthquake, we derive the size–frequency distribution for earthquake-induced landsliding (EQIL). These two distributions are dominated by infrequent, large and giant landslides but under-predict an estimated Holocene frequency of giant landslides (> 1 km3) which we derived from a literature compilation. This discrepancy can be resolved when modelling the effect of a full distribution of earthquakes of variable magnitude and when considering that a shallower earthquake may cause larger landslides. In this case, EQIL and MIL contribute about equally to a total long-term erosion of ∼2±0.75 mm yr−1 in agreement with most thermo-chronological data. Independently of the specific total and relative erosion rates, the heavy-tailed size–frequency distribution from MIL and EQIL and the very large maximal landslide size in the Himalayas indicate that mean landslide erosion rates increase with sampling time, as has been observed for independent erosion estimates. Further, we find that the sampling timescale required to adequately capture the frequency of the largest landslides, which is necessary for deriving long-term mean erosion rates, is often much longer than the averaging time of cosmogenic 10Be methods. This observation presents a strong caveat when interpreting spatial or temporal variability in erosion rates from this method. Thus, in areas where a very large, rare landslide contributes heavily to long-term erosion (as the Himalayas), we recommend 10Be sample in catchments with source areas > 10 000 km2 to reduce the method mean bias to below ∼20 % of the long-term erosion.

Landslides are a frequent natural hazard in Chittagong Hilly Areas (CHA), Bangladesh, which causes the loss of lives and damage to the economy. Despite this, an official landslide inventory is still lacking in this area. In this paper, we present a landslide inventory of this area prepared using the visual interpretation of Google Earth images (Google Earth Mapping), field mapping, and a literature search. We mapped 730 landslides that occurred from January 2001 to March 2017. Different landslide attributes including type, size, distribution, state, water content, and triggers are presented in the dataset. In this area, slide and flow were the two dominant types of landslides. Out of the five districts (Bandarban, Chittagong, Cox’s Bazar, Khagrachari, and Rangamati), most (55%) of the landslides occurred in the Chittagong and Rangamati districts. About 45% of the landslides were small (<100 m2) in size, while the maximum size of the detected landslides was 85202 m2. This dataset will help to understand the characteristics of landslides in CHA and provide useful guidance for policy implementation.

Gli eventi sismici sono riconosciuti come una delle maggiori cause per l’innesco di frane (Keefer, 1984). Le frane sismo-indotte sono documentate sin dal IV secolo (Seed, 1968). È stata condotta un’analisi sulla distribuzione spaziale delle frane sismo-indotte nell’area circostante la sorgente sismogenetica per meglio comprendere il loro innesco in aree sismiche e per delimitare la massima distanza alla quale un sisma con data magnitudo possa indurre frane. Tuttavia, quando si applicano tali approcci a eventi storici si pone un problema legato al sottocampionamento delle frane più piccole, che possono essere obliterate dall'erosione e dall'evoluzione del paesaggio. Per questo motivo è importante caratterizzare accuratamente la distribuzione delle frane, in termini di dimensione, in funzione della distanza dalla sorgente sismica. Sono stati analizzati sei terremoti in tutto il mondo che hanno innescato un significativo numero di frane (Finisterre 1993, Northridge 1994, Niigata 2004, Wenchuan 2008, Iwate 2008 and Tohoku 2011) per meglio comprendere le relazioni esistenti tra la distribuzione spaziale delle frane, l’accelerazione di picco al suolo (PGA), la distanza dalla sorgente, il relief e le litologie presenti nell’area. Si è osservata una forte relazione tra la PGA e la dimensione delle frane, mentre una la relazione tra la loro dimensione e la distanza dalla sorgente non è altrettanto chiara, ciò legato all’interazione tra diversi fattori quali ad esempio il relief e la litologia. Sono state realizzate e analizzate le curve magnitudo-frequenza (MFC) per differenti distanze dall’area sorgente attraverso varie metodologie: stimatore di massima verosimiglianza per distribuzioni di tipo potenza cumulate (Clauset et al, 2009), stimatore di massima verosimiglianza per distribuzioni di tipo potenza non cumulate, regressione ai minimi quadrati per funzioni di tipo potenza non cumulate in scala logaritmica e stimatore di massima verosimiglianza per la distribuzione Double Pareto. Dalle analisi si è potuto osservare un decrescere della densità spaziale delle frane con la distanza, ma un basso impatto della dimensione delle frane. Inoltre la funzione Double Pareto è stata scelta come miglior strumento per il fittaggio dei dati (Valagussa et al, 2014). Allo scopo di definire il rischio legato alle frane sismo-indotte è stata sviluppata una metodologia per la zonazione probabilistica quantitativa del rischio da frane da crollo (Valagussa et al, 2014). Il metodo è stato applicato e dimostrato nell’area del Friuli (Apli orientali) colpita da un terremoto di magnitudo 6.4 nel 1976. Quattro inventari sono stati realizzati sia tramite attività di terreno che da dati storici. La metodologia si basa sul vettore di rischio tridimensionale (RHVmod) le cui componenti includo l’energia cinetica, l’altezza di volo e la frequenza annua. I primi due valori sono calcolati per ogni cella del versante per mezzo del programma Hy-STONE. La frequenza annua è invece determinata moltiplicando la frequenza d’innesco annua per il numero di transiti simulati in ogni cella. La frequenza d’innesco annua è calcolata combinando l’area instabile, calcolata per 10 differenti scenari con differente frequenza annua di occorrenza sulla base di caratteristiche morfometriche e sismiche, e la curva magnitudo-frequenza relativa dei blocchi identificati da attività di terreno. Una serie di analisi discriminanti sono state condotte per determinare le variabili che controllano l’area in frana, sulla base degli inventari redatti e di DEMs a differenti risoluzioni (1 e 10m). L’analisi ha dimostrato il ruolo rilevante della curvatura nella definizione dell’area instabile. Per verificare la validità della mappa di PGA utilizzata nelle analisi, una nuova mappa è stata redatta sulla base delle Precarious Balanced Rocks identificate sul terreno.
Earthquakes have been recognized as a major cause of landsliding (Keefer, 1984), and landslides triggered by earthquakes have been documented since the IV century (Seed, 1968). The spatial distribution of earthquake-induced landslides around the seismogenetic source has been analysed to better understand the triggering of landslides in seismic areas and to forecast the maximum distance at which an earthquake, with a certain magnitude, can trigger landslides. However, when applying such approaches to old earthquakes one should be concerned about the undersampling of smaller landslides, which can be cancelled, by erosion and landscape evolution. For this reason, it is important to characterize carefully the size distribution of landslides as a function of distance from the earthquake source. I analysed six earthquakes in the world that triggered significant amount of landslides (Finisterre 1993, Northridge 1994, Niigata 2004, Wenchuan 2008, Iwate 2008 and Tohoku 2011) to better understand the relation between the spatial distribution of the landslides, the peak ground acceleration (PGA), the distance from the sources, the relief and the lithologies of the area. I observed a strong relationship between landslides size and PGA, while the relationship between the distance from the source and the landslide size distribution is not clear, due to the interaction of different factors such as relief and lithology. I also developed magnitude frequency curves (MFC) for different distances from the source area by using different methods, such as: the maximum likelihood estimator of cumulative power-law distribution (Clauset et al, 2009); the maximum likelihood estimator of non-cumulative power-law function; the least square regression of non-cumulative log power-law function and the maximum likelihood estimator of Double Pareto distribution. I observed a decrease of the spatial density of landslides with distance, with a small effect of the size of these landslides. I also identify the Double Pareto function as the best tool for the fitting of the data (Valagussa et al., 2014a). In order to define the hazard due to earthquake-induced landslides, I developed a methodology for quantitative probabilistic hazard zonation for rockfalls (Valagussa et al., 2014b). I applied and demonstrated the method in the area of Friuli (Eastern Italian Alps) that was affected by the 1976 Mw 6.5 earthquake. Four rockfall datasets have been prepared from both historical data and field surveys. The methodology relies on a three-dimensional hazard vector (RHVmod), whose components include the rockfall kinetic energy, the fly height, and the annual frequency. The values of the first two components are calculated for each location along the slope using the 3D rockfall runout simulator Hy-STONE. The rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency. The annual onset frequency is calculated 2 through a procedure that combines the extent of unstable areas, calculated for 10 different seismichazard scenarios with different annual frequencies of occurrence, and the magnitude relativefrequency relationship of blocks as derived from the collected field data. For each annual frequency of occurrence, the unstable area is calculated as a function of morphometric and earthquake characteristics. A series of discriminant-analysis models, using the rockfall datasets and DEMs of different resolution (1 and 10 m), identified the controlling variables and verified the model robustness. In contrast with previously published research, I show that the slope curvature plays a relevant role in the computation of the unstable area. To ensure the validity of the peak ground acceleration used as seismic parameter in the discriminant function, I also try to define a map of PGA based on the precarious balanced rocks surveyed on the field.

Shallow landslides studies are usually extended over landscape scale, where the investigations about geotechnical and hydrological properties of the soil are limited to some local points and not sufficient to assure an in-depth explanation of failure trigger. The physics of the phenomenon is thus minimized, and resolution in space and time is maximized. Such as approach can be useful to predict landslide occurrences for emergency purposes, but it is not effective to interpret the real triggering landslide mechanism. A local scale analysis become needed to achieve an understanding of the processes leading to the failure. Specifically, a full comprehension requires to provide experimental data from a carefully monitored and controlled landslide field site. The present study focuses on a large-scale device aimed at simulating shallow landslides triggered by heavy intensity rainfall. The physical model consists of an artificial hillslope built with a reinforced concrete box: the maximum height is 3.5 m, with length of 6 m and width of 2 m, so that a 2:3 slope can be built. On each lateral side of the box, 50 openings closed with screw caps allow the insertion on properly chosen positions of the control instrumentation (6 tensiometers and 6 Water Content Reflectometer sensors). The monitoring network, connected to an automatic acquisition system, was completed by two piezometers, and two stream gages able to evaluate both the surface runoff and subsurface contributions to the total outflow. The work developed in this study concerns the design and the performance analysis of the main features characterizing the large-scale hillslope model, up to the performance of two landslide experiments on a 60 cm thick sandy soil layer. A rainfall simulator was designed and built to reproduce an intensive precipitation causing the soil collapse. It was realized with a one-loop network equipped with spray nozzles appropriately chosen to minimize the surface splash erosion. In such a way the effects induced by the simulator concern infiltration dynamics without generating top erosion, which could introduce further factors of more difficult understanding. The nozzle configurations on the network were chosen to reproduce i) the desired range of the rainfall intensity, varying from 50 to 150 mm/h, and ii) the spatial uniformity of the produced rain. A careful analysis of the rain sprayed by a single nozzle was developed on a prototype, in order to recognize the main variables affecting the nozzle functioning and performance. Further investigations were then carried out to test the performance of the final full-scale version of the rainfall simulator, highlighting its flexibility for the regulation and the control of the generated rain intensity. Depending on the desired rainfall range, four different configurations of nozzles, distinguished by the number of active nozzles and their location, were chosen to cover the required intensity interval. A careful analysis about the drop diameters was conducted by recurring to an oil mixture poured in Petri dishes that were exposed to the rain. The drop size distribution thus collected characterizes the induced rainfall and was used for a numerical simulation aimed at estimating the impact energy of the drops falling on the soil. The proposed model calculates the trajectories of the particles injected by the nozzle using a constitutive law of sphere aerodynamics in a 3D space. As a result, the rainfall potential erosion and its spatial distribution were assessed, highlighting the limited surface erosion generated by the proposed rainfall simulator. In a second step, a suitable device was realized to calibrate the WCR (Water Content Reflectometer) sensors. It consists of a 0.6 x 0.5 x 0.6 cubic meters Plexiglas box containing the soil with the top exposed to rainfall and the bottom sustained by a perforated base. The calibration of the WCR sensors pointed to obtain an effective law for an accurate assessment of the water infiltration evolution in the soil during the landslide experiments. Several tests were performed with varying porosity values of the sand sample placed into the Plexiglas box, where three tensiometers and as many as WCR probes were arranged. The final results suggest a calibration relationship linearly depending on the WCR output signal and porosity. Two experiments on the artificial slope were then performed by applying two different porosities of the soil during the placement. The chosen soil consists of a fine sand with high particle size uniformity. The first porosity was obtained by dumping the sand without applying compacting action, such that the sand was in loose conditions. In a second case, the sand was compacted to yield a dense sand. The two experiments were carried out by applying the rainfall at until the sand collapse. The observation of the experiments and the analysis of the recorded data allow to examine the hydrological dynamics leading to the landslide and the triggering factors. With loose sand, the failure occurred suddenly without warning signs; at the failure, the soil appeared like a viscous fluid and the tensiometers recorded an instantaneous peak of the water pressure head. In the case with dense sand, the failure occurred really slowly, and some local detachments of top layer preceded the advance of the whole sand volume. A numerical model solving Richards equation was used to reproduce the hydrological processes leading to failure in the two experiments. A numerical inverse method was adopted to improve the reliability of the numerical solution with respect to the data recorded from the experiments. The comparison reveals a good agreement between the experimental and numerical results for the loose sand experiment. In the case regarding dense sand, the limits of Richards solution does not allow to reach an acceptable agreement with experimental recorded. The causes might be linked with the affection of the air phase in sand pores and the incipient deformation of the soil matrix at micro-scale.
Le valutazioni di pericolosità sulle frane superficiali sono in genere estese su scala di versante, le cui limitate indagini geotecniche non consentono una caratterizzazione fedele che miri ad una comprensione dettagliata dei fenomeni di innesco. Per tale motivo, i processi fisici considerati nella spiegazione del fenomeno sono spesso riduttivi e tali da consentire una modesta risoluzione sia spaziale che temporale. Tale approccio risulta utile per valutazioni legate alla previsione di innesco, e quindi, correttamente, non necessitano di un’elevata affidabilità nell’interpretazione del fenomeno idromeccanico, ma risultano compatibili con un’analisi sommaria e generalizzata. Tuttavia, un’analisi a scala locale diventa necessaria quando sia richiesta una comprensione dettagliata del fenomeno di innesco che permetta di riconoscere gli elementi, e la loro intensità, nell’innesco delle frane superficiali. Tale esigenza può essere soddisfatta solo riproducendo dati sperimentali raccolti su siti a monitoraggio elevato. Lo studio presente si occupa di un pendio artificiale per la simulazione dei fenomeni di innesco delle frane superficiali determinate da precipitazioni intense. Il modello fisico consiste di un muro di contenimento in calcestruzzo armato: l’altezza massima è di 3.5 m, la lunghezza alla base è di 6 m e la larghezza di 2 m, così da realizzare una pendenza superficiale di 2:3. Su ogni muro laterale, sono applicate 50 forature realizzate mediante tronchetti flangiati che consentono l’inserimento di 6 tensiometri e 6 sonde WCR (Water Content Reflectometer) nelle posizioni desiderate. La strumentazione è completata con 2 piezometri e due pozzetti per la misura delle portate di ruscellamento e sub-superficiale in uscita. Ogni misura viene acquisita e registrata mediante un sistema di acquisizione. Il lavoro sviluppato riguarda la progettazione e l’analisi delle prestazioni dei principali dispositivi impiegati nel modello fisico, fino alla realizzazione di due prove sperimentali su uno strato di sabbia con spessore verticale di 60 cm. Un simulatore di pioggia è stato progettato e realizzato per generare una precipitazione intensa tale da provocare l’instabilità del materiale posato nel modello fisico. Il simulatore consiste in una rete ad anello chiuso sulla quale sono distribuiti degli ugelli appositamente scelti per evitare erosione sulla superficie del terreno dovuta all’impatto delle gocce erogate. In questo modo gli effetti indotti dalla precipitazione si riconoscono nei soli fenomeni di infiltrazione, senza innesco di processi erosivi che potrebbero aggiungere fenomeni di difficile comprensione. Le configurazioni degli ugelli distribuiti sul simulatore vengono scelte per coprire i) il campo desiderato delle intensità di pioggia, variante tra 50 e 150 mm/h, e per assicurare ii) un’elevata uniformità spaziale della precipitazione prodotta. Un’attenta analisi è stata svolta per caratterizzare un singolo ugello mediante un apposito dispositivo, così da individuarne le principali variabili caratterizzanti il funzionamento e le prestazioni. Successivamente, l’indagine sperimentale è stata concentrata sulla versione finale del simulatore di pioggia, al fine di definire le modalità di gestione e di regolazione della precipitazione riprodotta. A seconda del campo di intensità desiderato, quattro differenti configurazioni di ugelli, distinte per il numero e la posizione degli ugelli attivi, sono state individuate per ricoprire l’intervallo totale di intensità da 50 a 150 mm/h. Inoltre, è stata eseguita un’analisi per valutare i diametri delle gocce erogate mediante olio ad alta viscosità versato in dischetti Petri esposti alla pioggia artificiale. La distribuzione dei diametri così ottenuta è stata successivamente impiegata in un modello numerico per stimare la distribuzione dell’energia di impatto delle gocce sul suolo. Il modello numerico proposto calcola la traiettoria delle particelle erogate dall’ugello mediante una legge costitutiva basata sull’aerodinamica di sfere nello spazio 3D. I risultati hanno posto in evidenza la limitata erosione superficiale determinata dalla precipitazione erogata. È stata poi realizzato un dispositivo per la calibrazione delle sonde WCR (Water Content Reflectometer), impiegate per la stima del contenuto volumetrico d’acqua del terreno. Il dispositivo consiste in un contenitore in Plexiglas di dimensione interne pari a 0.6 x 0.5 x 0.6 m3, contenente il suolo che risulta libero nella parte superiore e, alla base, trattenuto da una piastra forata. La procedura di calibrazione delle sonde WCR ha mirato a definire una legge per una stima accurata dei processi di infiltrazione nel suolo durante gli esperimenti di frana. Numerose prove sono state quindi condotte variando, rispettivamente, la porosità del provino di materiale posato nel contenitore; le caratteristiche del suolo erano costantemente monitorate da 3 tensiometri infissi e da altrettante sonde WCR. Il risultato finale ha restituito una legge di calibrazione dello strumento linearmente dipendente dal segnale di uscita della sonda WCR e anche dalla porosità del terreno. Due esperimenti sul modello fisico di frana sono stati quindi realizzati su uno strato di materiale con due rispettive porosità. Il materiale impiegato consiste in una sabbia fine con distribuzione granulometrica molto uniforme. In un primo caso la sabbia è stata posata senza introdurre azioni di compattazione, a meno di una leggera battitura sulla superficie per evitare eccessive deformazioni successive alla precipitazione. In un secondo esperimento, la sabbia è stata invece posata e compattata per strati successivi, così da raggiungere uno stato addensato. I due esperimenti sono stati rispettivamente eseguiti applicando un’intensità di precipitazione pari a 150 mm/h fino a collasso avvenuto. Le modalità di innesco osservate e l’analisi dei dati raccolti permettono di individuare gli elementi idrologici che determinano il collasso in entrambi i casi, mettendo anche in rilievo le diversità. Con sabbia sciolta, il collasso si verifica istantaneamente, senza segni premonitori che avvertano dell’imminente frana. All’innesco, il volume di terreno ha assunto le sembianze di un fluido ad alta viscosità, e i tensiometri installati registrano un picco istantaneo di pressione idraulica. Nel caso di sabbia addensata, il collasso avviene molto lentamente ed è preceduto da distacchi localizzati di strati sottili di terreno. Un modello per la risoluzione dell’equazione di Richards è stato impiegato per riprodurre le dinamiche idrologiche che determinano l’innesco delle frane nei due casi distinti. Si è ricorso, inoltre, ad una procedura inversa per migliorare l’affidabilità della soluzione numerica rispetto ai dati sperimentali registrati durante le prove di frana. Il confronto esprime un’elevata corrispondenza tra dati numerici e sperimentali nel caso di sabbia sciolta. Nel secondo caso con sabbia addensata, le ipotesi del modello di Richards non sono sufficienti per raggiungere una corrispondenza accettabile con i dati sperimentali. Le cause possono ritrovarsi nell’influenza che la fase gassosa contenuta nei pori può determinare, nonché le deformazioni incipienti a micro-scala che si manifestano durante l’esperimento.

The aim of the paper was to determine the influence of root systems of chosen tree species found in the Polish Flysch Carpathians on the increase of soil shear strength (root cohesion) in terms of slope stability. The paper's goal was achieved through comprehensive tests on root systems of eight relatively common in the Polish Flysch Carpathians tree species. The tests that were carried out included field work, laboratory work and analytical calculations. As part of the field work, the root area ratio (A IA) of the roots was determined using the method of profiling the walls of the trench at a distance of about 1.0 m from the tree trunk. The width of the. trenches was about 1.0 m, and their depth depended on the ground conditions and ranged from 0.6 to 1.0 m below the ground level. After preparing the walls of the trench, the profile was divided into vertical layers with a height of 0.1 m, within which root diameters were measured. Roots with diameters from 1 to 10 mm were taken into consideration in root area ratio calculations in accordance with the generally accepted methodology for this type of tests. These measurements were made in Biegnik (silver fir), Ropica Polska (silver birch, black locust) and Szymbark (silver birch, European beech, European hornbeam, silver fir, sycamore maple, Scots pine, European spruce) located near Gorlice (The Low Beskids) in areas with unplanned forest management. In case of each tested tree species the samples of roots were taken, transported to the laboratory and then saturated with water for at least one day. Before testing the samples were obtained from the water and stretched in a. tensile testing machine in order to determine their tensile strength and flexibility. In general, over 2200 root samples were tested. The results of tests on root area ratio of root systems and their tensile strength were used to determine the value of increase in shear strength of the soils, called root cohesion. To this purpose a classic Wu-Waldron calculation model was used as well as two types of bundle models, the so called static model (Fiber Bundle Model — FIRM, FBM2, FBM3) and the deformation model (Root Bundle Model— RBM1, RBM2, mRBM1) that differ in terms of the assumptions concerning the way the tensile force is distributed to the roots as well as the range of parameters taken into account during calculations. The stability analysis of 8 landslides in forest areas of Cicikowicleie and Wignickie Foothills was a form of verification of relevance of the obtained calculation results. The results of tests on root area ratio in the profile showed that, as expected, the number of roots in the soil profile and their ApIA values are very variable. It was shown that the values of the root area ratio of the tested tree species with a diameter 1-10 ram are a maximum of 0.8% close to the surface of the ground and they decrease along with the depth reaching the values at least one order of magnitude lower than close to the surface at the depth 0.5-1.0 m below the ground level. Average values of the root area ratio within the soil profile were from 0.05 to 0.13% adequately for Scots pine and European beech. The measured values of the root area ratio are relatively low in relation to the values of this parameter given in literature, which is probably connected with great cohesiveness of the soils and the fact that there were a lot of rock fragments in the soil, where the tests were carried out. Calculation results of the Gale-Grigal function indicate that a distribution of roots in the soil profile is similar for the tested species, apart from the silver fir from Bie§nik and European hornbeam. Considering the number of roots, their distribution in the soil profile and the root area ratio it appears that — considering slope stability — the root systems of European beech and black locust are the most optimal, which coincides with tests results given in literature. The results of tensile strength tests showed that the roots of the tested tree species have different tensile strength. The roots of European beech and European hornbeam had high tensile strength, whereas the roots of conifers and silver birch in deciduous trees — low. The analysis of test results also showed that the roots of the studied tree species are characterized by high variability of mechanical properties. The values Of shear strength increase are mainly related to the number and size (diameter) of the roots in the soil profile as well as their tensile strength and pullout resistance, although they can also result from the used calculation method (calculation model). The tests showed that the distribution of roots in the soil and their tensile strength are characterized by large variability, which allows the conclusion that using typical geotechnical calculations, which take into consideration the role of root systems is exposed to a high risk of overestimating their influence on the soil reinforcement. hence, while determining or assuming the increase in shear strength of soil reinforced with roots (root cohesion) for design calculations, a conservative (careful) approach that includes the most unfavourable values of this parameter should be used. Tests showed that the values of shear strength increase of the soil reinforced with roots calculated using Wu-Waldron model in extreme cases are three times higher than the values calculated using bundle models. In general, the most conservative calculation results of the shear strength increase were obtained using deformation bundle models: RBM2 (RBMw) or mRBM1. RBM2 model considers the variability of strength characteristics of soils described by Weibull survival function and in most cases gives the lowest values of the shear strength increase, which usually constitute 50% of the values of shear strength increase determined using classic Wu-Waldron model. Whereas the second model (mRBM1.) considers averaged values of roots strength parameters as well as the possibility that two main mechanism of destruction of a root bundle - rupture and pulling out - can occur at the same. time. The values of shear strength increase calculated using this model were the lowest in case of beech and hornbeam roots, which had high tensile strength. It indicates that in the surface part of the profile (down to 0.2 m below the ground level), primarily in case of deciduous trees, the main mechanism of failure of the root bundle will be pulling out. However, this model requires the knowledge of a much greater number of geometrical parameters of roots and geotechnical parameters of soil, and additionally it is very sensitive to input data. Therefore, it seems practical to use the RBM2 model to assess the influence of roots on the soil shear strength increase, and in order to obtain safe results of calculations in the surface part of the profile, the Weibull shape coefficient equal to 1.0 can be assumed. On the other hand, the Wu-Waldron model can be used for the initial assessment of the shear strength increase of soil reinforced with roots in the situation, where the deformation properties of the root system and its interaction with the soil are not considered, although the values of the shear strength increase calculated using this model should be corrected and reduced by half. Test results indicate that in terms of slope stability the root systems of beech and hornbeam have the most favourable properties - their maximum effect of soil reinforcement in the profile to the depth of 0.5 m does not usually exceed 30 kPa, and to the depth of 1 m - 20 kPa. The root systems of conifers have the least impact on the slope reinforcement, usually increasing the soil shear strength by less than 5 kPa. These values coincide to a large extent with the range of shear strength increase obtained from the direct shear test as well as results of stability analysis given in literature and carried out as part of this work. The analysis of the literature indicates that the methods of measuring tree's root systems as well as their interpretation are very different, which often limits the possibilities of comparing test results. This indicates the need to systematize this type of tests and for this purpose a root distribution model (RDM) can be used, which can be integrated with any deformation bundle model (RBM). A combination of these two calculation models allows the range of soil reinforcement around trees to be determined and this information might be used in practice, while planning bioengineering procedures in areas exposed to surface mass movements. The functionality of this solution can be increased by considering the dynamics of plant develop¬ment in the calculations. This, however, requires conducting this type of research in order to obtain more data.

Generally, soil characteristics have a significant influence on landslide occurrence. This issue has, however, not yet been adequately analysed in Kigezi highlands of South Western Uganda. In this study, soil properties such as dispersion, grain size distribution, Atterberg limits, shear strength and clay mineralogy were analysed to establish their contribution to the spatial distribution of landslides in Kigezi highlands. The results demonstrate that deep soil profiles ranging between 2.5 and 7 meters were dominated by clay-pans at a depth between 0.75 and 3 meters. Although the uppermost surface horizons of the soil profile are loamy sand, the clay content is more than 35% especially in the sub soil. This suggests that the soil materials are Vertic in nature. In addition, the upper soil layers predominantly contain quartz, while subsurface horizons have considerable amounts of illite as the dominant clay minerals, ranging from 43–47%. The average liquid limit and plasticity index was 58.43% and 33.3% respectively. Besides, high average computed weighted plasticity index (28.4%) and expansiveness (38.6%) were obtained. These soil characteristics have great implication on the timing and nature of landslide processes in the study area. A change in soil material due to varying moisture content is thought to be a major trigger of landslides in Kigezi highlands of South Western Uganda. This understanding of soil characteristics is a key step in mitigating landslide hazards in the area.

The stability analysis carried out by GEO5 software and uses free sliding analysis by wet and pore saturated weight charting provided the safety factor of 1.35. The safety precautions were followed by inclinometers and wire extensometer measurements. The other pore saturated asphalt bound shear box and unaxial test compression tests were resulted in the geotechnical and geoseismical data over sliding soil /shale inter surface quality and the characteristics of free rock falling risk and discontinuity distribution, sub crack density and distribution on stereo nets were determined. The research was firstly followed the perched water levels on geoseismical data over causing water burst or explosion of highly free mud and landslides. The hazardous rock falls over saturated soil and uncohesive rock explosions. The proposed study was secondly as strengthening methods such as asphalt mixing as precautious on shear stabilization and other wire mesh barriers anchored. The free sliding cracks was filled by asphalt and compressed for stabilization strengthening known as the characteristics of avoiding shear falls in the future. The unconditional expectations related to this study was also defined for this region such as the influence of the ground water, rock cracks and slope design, explosion exchange dynamics leading to landslide.

<em>Abstract.</em>—Wood is recruited to rivers by a diversity of processes, including chronic mortality, windstorms, wildfires, bank erosion, landslides, and ice storms. Recruitment, storage, and transport of large wood in streams can be understood in terms of a mass balance, or quantitative wood budget, similar to the study of other material fluxes in watersheds. A wood budgeting framework is presented that includes numerical expressions for punctuated forest mortality by fire, chronic mortality and tree fall, bank erosion, mass wasting, decay, and stream transport. When used with appropriate parameter values derived for specific conditions or regions, the wood budget equations can be used to make predictions on the importance of various landscape processes on wood abundance in streams in any locale. For example, wood budgets can be used to predict how variations in climate (wet – dry), topography (steep – gentle), basin size (small – large), and land management could affect abundance and distribution of large wood in streams. Wood budgets also can be integrated into numerical simulation models for estimating the natural range of variability, specifically temporal fluctuations of wood supply driven by large storms, floods, fires, and mass wasting, and spatial variability driven by topographic heterogeneity and variations in wood transport. Field studies of wood in streams may be enhanced by the use of a wood budget framework. This includes specifying what measurements are required over what length of stream for estimating recruitment rates of all relevant inputs processes, wood loss by decay, and stream transport of wood. Finally, wood budgets can be used to estimate rates of bank erosion, forest mortality, and landsliding, given appropriate field measurements of wood in streams and riparian conditions.

The Long-Term Ecological Research (LTER) program has not influenced my basic approach to science. The LTER program has reinforced my approach to mentoring, and it has increased my opportunities to mentor students through the LTER-associated Research Experiences for Undergraduates Program. LTER program has greatly enriched my collaborative network and expanded my research in directions that I would not have otherwise pursued; similarly, I have expanded the research and perspectives of my collaborators. My involvement in the LTER program has changed my perspective in reviewing grant proposals and manuscripts. I have been a co–principal investigator or senior personnel at the Luquillo site (LUQ) of the LTER since its inception in 1988. My MS was on fungal population genetics and epidemiology of a plant pathogen, and my PhD work involved a study of the ecology of arbuscular and ectomycorrhizal fungi associated with cottonwood and willow, with a minor in entomology. I was employed as an ecosystem ecologist for the first 9 years of my professional career as a research scientist with the University of Puerto Rico, Center for Energy and Environment Research, which later became the Terrestrial Ecology Division. My early research in the LTER program focused on the role of arbuscular mycorrhizal fungi in plant colonization of landslides in collaboration with plant ecologists and physiologists in the “disturbed plant group.” Hurricane Gilbert struck Jamaica in 1988, shortly after I had measured vegetation there, so I returned to Jamaica with a group that was studying migrant bird habitat and helped to remeasure plants. I used this opportunity to design the tree damage protocol that was used in 1989, when Hurricane Hugo struck the Luquillo Experimental Forest in Puerto Rico (the location of LUQ) (Zimmerman et al. 1994). Consequently, I was nicknamed “Hurricane Hattie” by my collaborators at the Coweeta LTER site. Throughout my career, I have used my graduate training in ecology and soil microbial ecology to make important estimates of fungal and bacterial biomass and nutrient immobilization, and to determine what factors control spatial and temporal patterns in fungal distributions, abundance, and diversity (Lodge and Cantrell 1995; Lodge 1997).

ABSTRACT: The Boise Valley contains several columnar jointed basalt cliffs, which were deposited approximately 1.4 to 0.5 Ma on terraces formed by downcutting of the Boise River. Three runout talus deposits on Whitney Terrace were characterized using unmanned aerial vehicle visual imagery. Although the runout talus deposits were from different areas and were of varying size, they contained roughly the same dimensions and distributions of blocks. Images of the cliff face indicated that blocks were detached from the base of columns along horizontal discontinuities which lacked support (undercut columns) and by toppling of basalt columns. The mapped block sizes in the cliff face were larger than the blocks in the associated runout, indicating the cliff blocks were fragmented during impacts in the runout. 1. INTRODUCTION The movement of geologic materials downslope, commonly referred to as landslides, is one of the most well-known geologic hazards. Varnes (1978) developed the most widely used classification framework for landslides. Since the Varnes classification scheme was developed, various modifications have been proposed and adopted. Still, the goal is to be able to describe the movement(s) and the end result(s) of the landslide using well-known terminology which incorporates the focus of the investigators (Hungr et al., 2014). Our focus is to characterize the runout talus deposits formed from the dislodgement and subsequent downslope movement of rock blocks from columnar basalt cliffs. Columnar basalt, or specifically columnar jointing in basalt, is a type of rock mass that is divided into long prismatic blocks. The formation of the jointing is complex and thought to be a series of events rather than simple cooling of the lava. The vertical discontinuities are continuous and horizontal discontinuities are less prominent and generally end at the edges of the vertical discontinuities (Spry, 1962). Failures of rock masses with columnar jointing have been studied in several geographical locations, including Australia (Dahlhaus and Miner, 2000), Chile (Holm and Jakob, 2009), Spain (Abellán et al., 2011), and Washington State (Guzek, 2019). The failure mechanism most often reported in these studies has been the somewhat generic term "rockfall", even though the studies mentioned above have shown that two failure (detachment) modes occur, rockfalls and rock topples.

Abstract A tsunami earthquake is defined as an earthquake which induces abnormally strong tsunami waves compared with its seismic magnitude (Kanamori 1972; Kanamori and Anderson 1975; Tanioka and Seno 2001). We investigate the possibility that the surface waves (Rayleigh, Love, and tsunami waves) in tsunami earthquakes are amplified by secondly submarine landslides, induced by the liquefaction of the sea floor due to the strong vibrations of the earthquakes. As pointed by Kanamori (2004), tsunami earthquakes are significantly stronger in longer waves than 100 s and low in radiation efficiencies of seismic waves by one or two order of magnitudes. These natures are in favor of a significant contribution of landslides. The landslides can generate seismic waves with longer period with lower efficiency than the tectonic fault motions (Kanamori et al 1980; Eissler and Kanamori 1987; Hasegawa and Kanamori 1987). We further investigate the distribution of the tsunami earthquakes and found that most of their epicenters are located at the steep slopes in the landward side of the trenches or around volcanic islands, where the soft sediments layers from the landmass are nearly critical against slope failures. This distribution suggests that the secondly landslides may contribute to the tsunami earthquakes. In the present paper, we will investigate the rapture processes determined by the inversion analysis of seismic surface waves of tsunami earthquakes can be explained by massive landslides, simultaneously triggered by earthquakes in the tsunami earthquakes which took place near the trenches.

Establishing pipeline failure frequencies enables designers and operators to make informed decisions on the allocation of resources to address different threats. Normally, this would involve the selection and timing of inspection, monitoring and protection activities. Typically, failure frequencies are defined based on the collection of historical statistics. This is difficult for geohazards due to the comparatively low incident rate compared to other hazards, however the consequences tend to be catastrophic. As a result, significant uncertainties are attached to predicted failure frequencies for geohazards. Two principal areas of uncertainty cover the occurrence and nature of loading events and whether the pipeline will survive the loading. This paper addresses both of these key aspects. The occurrence and nature of loading can be determined from the examination of in-line inspection records through different terrains. The pipeline survival rate is based on the efficient execution of multiple analysis runs within a finite element code where the distributions of the key input variables are defined to cover either observed or potential variation in the field. These include landslide size, orientation, movement and soil stiffness values as well as considerations of tensile fracture limits. The calculation of the probability of pipeline failure due to landslide loading is illustrated using a case study.

Pipelines for oil distribution may affect the environment when natural disasters such as landslides and earthquakes damage the infrastructures. Besides natural causes, illegal extraction of oil from the pipelines can produce significant environmental damage and sometimes loss of lives from explosions. During the spill, the fuel flow of the main stream theoretically reduces, but this variation is within the normal flow fluctuation and so it is not possible to detect this illegal activity using fuel flow measurements. Transducers based on Fiber Bragg Grating (FBG) sensors are very attractive for pipeline monitoring. In two previous works we proposed a new transducer for increasing the sensitivity of FBG sensors to detect illegal activities on the pipelines (drilling). In fact FBG sensors attached directly on the surface of the pipe are not capable to detect strain variations induced by a drill. This paper reports an update on the experimental results obtained on a real size pipeline and a theoretical study aimed to explain why a surface attached sensor does not work.

Ground deformation from natural or anthropogenic processes is a significant factor in the integrity management plan for natural gas distribution networks. Rapid or large scale deformation can pose an immediate rupture threat. Smaller, more gradual or repeated ground deformations may lead to material stresses, damage and strain accumulation, posing a longer-term threat. Satellite monitoring can play a key role in pipeline integrity management programs by measuring ground deformation over an entire pipeline network, at high spatial and temporal resolutions with the ability to capture both rapid large scale and subtle, repeated ground movement over a longer period of time. Millimeter accuracy ground deformation estimates are derived from radar satellite imagery using InSAR, a well-established and validated remote sensing technique. InSAR is an effective tool for rapidly identifying new regions requiring ground geotechnical surveys, deriving estimates of deformation rate, extents, and evolution of deformation patterns, for validating or extending traditional ground-based measurements, and for forward-looking operational monitoring. We present the results of InSAR ground deformation monitoring over a natural gas distribution pipeline network in Saskatchewan, Canada. At the case study site, small diameter pipelines (up to 40 years old) have been subjected to ground slumping from a retrogressive landslide affecting multiple lakeshore communities and compounded in recent years by a high water table. Some locations have recently experienced slumping at rates greater than 50 cm/yr leading to important structural issues with roads, buildings, water mains, and gas pipelines. The ground movement analysis is based on RADARSAT-2 satellite imagery acquired at 24-day intervals over a short period in 2015. Thousands of suitable measurement points were identified over two communities on opposite shores of the lake. The measured InSAR deformation time series showed deformation toward the lake. The extents of the deformation are clearly delineated by the InSAR measurements.

Strong motion seismic monitoring systems are often installed at critical industrial facilities located in areas of moderate to high seismicity. The objective of seismic monitoring is to facilitate post-earthquake evaluation and emergency action by providing rapid detection of seismic events and associated data, alarms, and information. Seismic monitoring can play a similar role for pipelines, especially considering the added geohazard risks along right-of-ways that might include landslides, fault crossings, and liquefaction hazard areas. Because of spatial distribution, seismic monitoring for pipelines is more complex than that required for a site-specific facility. In recent years, graphical software known as “ShakeMap,” developed by U.S. Geological Survey (USGS), has been used to rapidly estimate and distribute the distribution and intensity of earthquake ground motions from an earthquake. The ShakeMap solution for ground motions takes into account the distance from the earthquake source, the rock and soil conditions at sites, and variations in the propagation of seismic waves due to complexities in the structure of the Earth’s crust. ShakeMap ground motion data is available for automatic download from the USGS for potentially damaging earthquakes, e.g., Magnitude 5 and greater, within minutes after the event. USGS’ ShakeMap provides the opportunity to implement web-based systems to conduct automatic seismic monitoring for cross-county pipelines or networks of pipelines. A monitoring website can be equipped with a seismic database of fragilities that characterize geohazard vulnerabilities along pipeline right-of-ways as well as support facilities. Website software can be used to process the ground motion data to assess the threat to the pipeline system, advise pipeline controllers on the need for shutdown, and guide post-earthquake inspection on a prioritized basis. Drawing from the authors’ recent seismic monitoring experience for the Trans-Alaska Pipeline and other lifeline facilities, a conceptual plan for web-based seismic monitoring for pipelines is presented. The choice of a software platform can range from the use of open-source software available from USGS (ShakeCast) to custom software making direct use of gridded data downloads. Regardless of implementation strategy, the most convincing point to be made is that a seismic monitoring system need not require the installation of seismic instruments and the associated commitment to maintenance and hands-on seismology; instead it makes use of publicly available scientific data for rapid post-earthquake assessment.