Slow-moving Landslides Research Articles

Dynamic susceptibility mapping of slow-moving landslides using PSInSAR

ABSTRACT A landslide susceptibility map (LSM) is a valuable tool for landslide assessment and land use management. This research proposes a landslide susceptibility dynamic map (DLSM) to increase LSM utility and update the predicted map in a time series. Slope units, as basic mapping units, were produced to define the landslide boundaries and simplify the mapping in the DLSM. The permanent scatterer interferometric synthetic aperture radar (PSInSAR) technique was used to estimate the line of sight velocity (V los). This was then reprojected into the velocity in the steepest slope direction (V slope) to avoid the influence of geometric distortion. The DLSM was produced by integrating, using slope unit aggregate values, the susceptibility (probability) of landsliding predicted by logistic regression based on eight spatial covariates and the V slope predicted using the PSInSAR technique. The DLSM is a dynamically changing susceptibility map in which susceptibility is increased in certain months, particularly where surface velocity increases following the rainy season. The proportion of the study area classified with extremely high susceptibility increased from 22.2% to 44.8% after the rainy season. The DLSM, thus, potentially improves the prediction reliability for slow-moving landslides and, in particular, can help to avoid false negatives. The DLSM can be applied in areas for which radar data are available and can provide more reliable and readily interpretable results to decision-makers.

Characterization and Hydrological Analysis of the Guarumales Deep-Seated Landslide in the Tropical Ecuadorian Andes

The high landslide risk potential along the steep hillslopes of the Eastern Andes in Ecuador provides challenges for hazard mitigation, especially in areas with hydropower dams and reservoirs. The objective of this study was to characterize, understand, and quantify the mechanisms driving the motions of the Guarumales landslide. This 1.5 km2 deep-seated, slow-moving landslide is actively moving and threatening the “Paute Integral” hydroelectric complex. Building on a long time series of measurements of surface displacement, precipitation, and groundwater level fluctuations, we analyzed the role of predisposing conditions and triggering factors on the stability of the landslide. We performed an analysis of the time series of measured groundwater levels and drainage data using transfer functions. The geological interpretation of the landslide was further revised based on twelve new drillings. This demonstrated a locally complex system of colluvium deposits overlying a schist bedrock, reaching up to 100 m. The measured displacement rates were nearly constant at ~50 mm/year over the 18 years of study. However, the measurement accuracy and time resolution were too small to identify possible acceleration or deceleration phases in response to hydro-meteorological forcing. The groundwater and slope drainage data showed a lagged response to rainfall. Finally, we developed a conceptual model of the Guarumales landslide, which we hope will improve our understanding of the many other deep-seated landslides present in the Eastern Andes.

The Niushou landslide in Nanjing City, Jiangsu Province of China: a slow-moving landslide triggered by rainfall

The Niushou landslide is a slow-moving landslide in the Niushou Mountain cultural tourism area, Nanjing City, Jiangsu Province of China. In June 2015, a tension crack appeared on the south side of Niushou Mountain due to the continuous rainfall, which brought great potential safety risk to the scenic area and the construction of the Alila Hotel. From July 2015 to March 2016, emergency rescue works were used to reinforce the south slope of Niushou Mountain. On June 11, 2016, the Niushou landslide occurred on the south side of Niushou Mountain, caused by the heavy rainfall as a result of the 2015–2016 EI Nino event. The movement of the Niushou landslide caused cracks in the land surface, the buildings of Alila Hotel, and reinforced facilities. Field investigations, drilling holes, geophysical prospecting, laboratory tests, groundwater level monitoring, and surface displacement monitoring were carried out to determine the geological features, deformation characteristics, and failure mechanism. Based on analysis of the monitoring data, the main reason for landslide occurrence was the rise of groundwater level, which increased the uplift pressure offered by confined water and decreased the strength in strongly weathered tuff layer, leading to the sliding surface. The construction land of Alila Hotel has been abandoned until now (May 5, 2020) because of the Niushou landslide. The case discussed how the level of groundwater changes would influence landslide deformation and also provided suggestions for the prevention measures of such landslide.

Quantitative risk assessment of slow-moving landslides from the viewpoint of decision-making: A case study of the Three Gorges Reservoir in China

A large number of landslides in the Three Gorges Reservoir area in China have been reactivated by reservoir impoundment since 2003. Many of them were activated as slow-moving landslides, which caused severe damages to buildings and also pose a significant risk for residents. In this study, a quantitative procedure has been proposed to analyze and assess the landslide risks to buildings and lives by considering the Outang landslide as an example. First, the landslide segmentation was done by considering the sliding history, macroscopic deformation, and monitoring data of displacement. The SLOPE/W and SEEP/W modules of the Geostudio software were used to establish the geotechnical model and analyze the seepage, respectively. Under different scenarios of annual reservoir regulation and return period of rainfall events as determined by Pearson type III (P3) distribution, failure probabilities of every segmented part were obtained with Monte Carlo simulation. Second, the vulnerability of the elements at risk was quantitatively estimated using a model that incorporated the landslide intensity and resistance of the exposed elements. Then, through the analysis and comparison of scenario-based landslide risks, the evolution of landslide risk influenced by different combinations of triggering factors (i.e., reservoir water level and rainfall) was examined. Finally, landslide risks before and after the implementation of several risk reduction alternatives were compared to determine the benefits of alternatives. The risk maps displayed that the risk was the greatest for the scenario of the rapid decline of the reservoir water level in combination with heavy rainfall; the corresponding total annual economic and population risks of the landslide were estimated in 96.88 million ¥ and 216 lives, respectively. In this scenario, the economic risk level of the west deformation zone was the highest, and the total population risk was the highest in the lower unit of the landslide. Results of benefit-cost analysis suggested that real-time monitoring and resident relocation seem to be the most effective alternatives for risk reduction concerning the Outang landslide.

Improved optical image matching time series inversion approach for monitoring dune migration in North Sinai Sand Sea: Algorithm procedure, application, and validation

Sand dune migration poses a potential threat to desert infrastructure, vegetation, and atmospheric conditions. Capturing the patterns of long-term dune migration is useful for predicting probable desertification issues and wind conditions across vast desert areas. In this study, we employed optical image matching and a singular value decomposition approach to estimate the rates of dune migration in the North Sinai Sand Sea using the free Landsat 8 and Sentinel-2 archives. Our optical image matching time-series selection and inversion (OPTSI) algorithm limited the difference in the solar illumination of correlated pairs to decrease shadows and seasonal variability. We found that the maximum annual dune migration rates were 9.4 m/a and 15.9 m/a for Landsat 8 and Sentinel-2 data, respectively, and the results of time-series analysis revealed the existence of seasonal variations in dune migration controlled by wind regimes. The directions of sand movement extracted from the mean velocity solution agreed strongly with each other and with the drift directions estimated using wind data from meteorological stations. We assessed the uncertainty of each solution based on the variance of stable areas. Our results showed that the proposed inversion decreased uncertainty by up to 25% and increased the spatial coverage by up to 20%. This algorithm is also promising for the retrieval of historical time series on the ground displacements of glaciers and slow-moving landslides employing free archives that provide high-frequency images.

Landslide Mapping and Monitoring Using Persistent Scatterer Interferometry (PSI) Technique in the French Alps

Continuous geodetic measurements in landslide prone regions are necessary to avoid disasters and better understand the spatiotemporal and kinematic evolution of landslides. The detection and characterization of landslides in high alpine environments remains a challenge associated with difficult accessibility, extensive coverage, limitations of available techniques, and the complex nature of landslide process. Recent studies using space-based observations and especially Persistent Scatterer Interferometry (PSI) techniques with the integration of in-situ monitoring instrumentation are providing vital information for an actual landslide monitoring. In the present study, the Stanford Method for Persistent Scatterers InSAR package (StaMPS) is employed to process the series of Sentinel 1-A and 1-B Synthetic Aperture Radar (SAR) images acquired between 2015 and 2019 along ascending and descending orbits for the selected area in the French Alps. We applied the proposed approach, based on extraction of Active Deformation Areas (ADA), to automatically detect and assess the state of activity and the intensity of the suspected slow-moving landslides in the study area. We illustrated the potential of Sentinel-1 data with the aim of detecting regions of relatively low motion rates that be can attributed to activate landslide and updated pre-existing national landslide inventory maps on a regional scale in terms of slow moving landslides. Our results are compared to pre-existing landslide inventories. More than 100 unknown slow-moving landslides, their spatial pattern, deformation rate, state of activity, as well as orientation are successfully identified over an area of 4000 km2 located in the French Alps. We also address the current limitations due the nature of PSI and geometric characteristic of InSAR data for measuring slope movements in mountainous environments like Alps.

Spatial and temporal analysis of debris flow occurrence in three adjacent basins of the western margin of Grande River: Quebrada de Humahuaca, Jujuy, Argentina

ABSTRACTNumerous slides, rock falls and flows occur in the arid mountainous areas of northwestern Argentina. On 10 January 2017, torrential rain caused the acceleration of large-scale and slow-moving landslides mainly in the Los Filtros basin and it produces important damage in the Volcán village causing fatalities, dozens of evacuees and great economic losses, with the total destruction of buildings, services and infrastructure. However, in the two adjacent creek basins, the Coiruro basin to the north and Del Medio basin to the south, the effects were smaller. A morphometric analysis of these three adjacent basins was carried out in order to understand this catastrophic event and to explore its causes. The geological characteristics of the study basins are very favourable conditioning factors in landslide generation. Precambrian-age low grade metaclastics shatter in the frost climate of the higher mountains and poorly consolidated Quaternary deposits along the sides of the gully erode readily and become source material for landslides. Also, the area, shape, relief and slope of the basins would have been other key factors in the debris/mud flow generation in the Los Filtros creek basin. The Melton ratio number has been a key morphometric index to discriminate river basins susceptible to different types of flows. Finally, this study aims to increase knowledge of all the above-mentioned events in order to provide several methods of analysis for landslide prevention and control in adjacent basins whit different dynamics in the Central Andes.

Changes in climate patterns and their association to natural hazard distribution in South Tyrol (Eastern Italian Alps)

In Alpine regions changes in seasonal climatic parameters, such as temperature, rainfall, and snow amount have already been observed. Specifically, in the South Tyrol area, meteorological observations indicate that temperatures are increasing and the number of snow days has generally diminished over time with perennial snow line now observed at higher elevations. Changes in rainfall have also been observed with more events associated with higher temperatures in the summer season. Natural hazards - mainly debris and mud flows, landslides, avalanches, rock falls, and (flash) floods - that affect this area every year, damaging population and infrastructures, are either weather or cryosphere-related. While these events have been recorded sporadically since the beginning of the 20th century, a systematic approach of their inventory has been done by local authorities since the 1990s. So far, Earth observation data has not been exploited to complete or complement existing inventories nor have they been used to investigate the influence of climate perturbation on potentially dangerous natural phenomena. The research presented here thus has three objectives: (i) analyse long time series of climate data and hazard occurrence in South Tyrol to examine if these records exhibit a coherent response of hazards to changes in climate; (ii) measure the spatio-temporal evolution of climatic and natural hazard events recorded, and (iii) explore potential relations between meteorological conditions and the hazard occurrence. In this context, in-situ and satellite-based climate data are exploited to study natural hazard triggers while the potential of Earth observation data is evaluated as a complement to the existing historical records of natural hazards. Specifically, Copernicus Sentinel-1 images are used to detect the spatio-temporal distribution of slow earth surface deformations and the results used for checking the completeness of the actual slow-moving landslide inventories. Hazard-related changes in the South Tyrolian landscape have also been analysed in relation to particular meteorological events at a regional scale, assessing trends and anomalies. Results show that: (i) satellite data are very useful to complement the existing natural hazard inventories; (ii) in-situ and satellite-based climate records show similar patterns but differ due to regional versus local variability; (iii) even in a data-rich region such as the analysed area, the overall response of natural hazard occurrence, magnitude, and frequency to change in climate variables is difficult to decipher due to the presence of multiple triggers and locally driven ground responses. However, an increase in the average annual duration of rainfall events and debris flow occurrence can be observed.

Slow-moving landslides: kinematic analysis and movement evolution modeling

Three of the most well-known historical landslide areas in Western Greece were examined, concerning their temporal and kinematic evolution. Long-term ground displacements based on inclinometer data were analyzed. The aim of this study is to estimate the velocity trend type of movement through the years. The total time frame of kinematic evolution regarding the three currently studied landslide locations, was over 20 years for Panagopoula (1995–2017), 10 years for Karya (2005–2017), and 6 years for Platanos (2011–2017). All three landslides occur in soil or soft rock of Flysch and Neogene formations. In addition, two statistical approaches, time series decomposition, and autoregressive integrated moving average (ARIMA) method, were applied to identify the specific kinematic features as well as model movement evolution. In general, these techniques are used to improve forecasts as to better understand the time series characteristics. As a result, the movement evolution over time is substituted into a model that explains the behavior of the displacements time series. The models extracted from this analysis could overcome a common problem in long-term monitoring regarding measurement missing data due to technical matters or non-recorded periods.

Multi-year, three-dimensional landslide surface deformation from repeat lidar and response to precipitation: Mill Gulch earthflow, California

Slow-moving landslides are often the dominant process that shapes hillslopes and delivers sediment to channels in weak lithologies. Understanding what controls their velocities is therefore essential for deciphering their role in landscape evolution and estimating hazards. In this study, we used four sequential airborne lidar data sets to derive the three-dimensional (3D), 1-m spatial resolution surface velocity field of the Mill Gulch earthflow, northern California, for three periods of time spanning a decade. Phase correlation, an image processing technique, applied to the precisely aligned lidar digital elevation models confidently resolved horizontal velocities from 0.2 to 5 m year−1. The velocity field defined three distinct kinematic zones of the landslide with different sensitivities to precipitation, such that the head moved slowly at 0.3–0.5 m year−1, the transport zone moved fastest at 2–5 m year−1, and a forked toe moved intermittently at 0–4 m year−1. Inverting the 3D surface velocity field to infer landslide thickness suggested that the head was underlain by a 6-m-deep, concave-up slip surface, while the transport zone likely had a 1–2.5-m-deep translational slip surface. We hypothesized that velocity in the head was least sensitive to changing precipitation because of its greater inferred depth, which likely dampened the amplitude of pore pressure fluctuations. A lack of major head scarp retrogressions also may have contributed to the relatively steady velocity in the head, while buttressing and debuttressing interactions between the landslide’s toes and the creek running in Mill Gulch may have contributed to the more dramatic changes in velocity in the transport zone and toes. Although predicting landslide velocity from precipitation data alone may therefore be challenging, producing detailed 3D deformation fields from repeat topographic data can be an important tool for deciphering interactions between internal controls, such as changes to landslide geometry, and external controls, such as climate, on landslide motion.

Rain and small earthquakes maintain a slow-moving landslide in a persistent critical state

In tectonically active mountain belts, landslides contribute significantly to erosion. Statistical analysis of regional inventories of earthquake-triggered-landslides after large earthquakes (Mw > 5.5) reveal a complex interaction between seismic shaking, landslide material, and rainfall. However, the contributions of each component have never been quantified due to a lack of in-situ data for active landslides. We exploited a 3-year geodetic and seismic dataset for a slow-moving landslide in Peru affected by local earthquakes and seasonal rainfalls. Here we show that in combination, they cause greater landslide motion than either force alone. We also show the rigidity of the landslide’s bulk clearly decreasing during Ml ≥ 5 earthquakes. The recovery is affected by rainfall and small earthquakes (Ml < 3.6), which prevent the soil from healing, highlighting the importance of the timing between forcings. These new quantitative insights into the mechanics of landslides open new perspectives for the study of the mass balance of earthquakes.

Creep properties of clastic soil in a reactivated slow-moving landslide in the Three Gorges Reservoir Region, China

Most slow-moving landslides in the Three Gorges Reservoir (TGR) region of China are characterized by pre-existing shear surfaces. The large deformation within the shear zones usually gives rise to clastic soil formation. The creep properties have large influence on the kinematic feature of landslides. In this paper, we report an in-situ direct shear creep test carried out in the shear zone of a reactivated slow-moving landslide in the TGR region. Correspondingly, some laboratory ring shear creep tests are carried out to interpret the movement pattern of this landslide. The shear zone soil exhibits similar non-attenuating creep responses in both the in-situ direct shear and laboratory ring shear creep tests. At the same stress level, however, the in-situ direct shear creep test yields a larger rate of creep displacement due to shearing along the landslide direction. In the ring shear creep tests, at the prepeak stage, the critical creep stress that triggers creep failure is slightly lower than the peak shear strength but much larger than the residual strength; at the postfailure stage, the critical creep stress of the shear-zone soil is equal to the residual shear strength. The rate-dependent residual shear strength may account for the stepwise movement pattern of the landslide.

Modern Farming Kick-Starts Large Landslides in Peruvian Deserts

Large-scale irrigation programs have triggered giant, slow-moving landslides in arid valleys, leading to the destruction of both traditional and modern farmland.

Satellite interferometry for mapping surface deformation time series in one, two and three dimensions: A new method illustrated on a slow-moving landslide

Space-borne Differential Interferometric Synthetic Aperture Radar (DInSAR) has been extensively used in the last two decades to measure ground surface deformation, providing key information for the characterization and understanding of many natural and anthropogenic processes. However, conventional DInSAR technique measures only one component of the surface deformation (i.e. the satellite's line-of-sight (LOS)), causing the interpretation of DInSAR measurements to be challenging and potentially narrowing the understanding of the mechanisms and dynamics of the deformation processes at work. Presently available methods that estimate 3D surface deformation from DInSAR generally operate on individual interferograms and therefore do not produce 3D surface deformation time series. However, the availability of time series is essential for studying surface deformation processes, bringing information on, e.g., temporally and spatially-variable external forcing conditions and characteristics of future deformation patterns. The Multidimensional Small Baseline Subset (MSBAS) method was already able to produce 2D (east and vertical) surface deformation time series from multi-tracks and multi-sensors DInSAR data. Here we propose a novel version of the MSBAS (MSBAS-3D) method that can produce 3D (north, east, and vertical) surface deformation time series from ascending and descending DInSAR data. This new method proposes measuring the surface deformation for processes producing motion parallel to the surface, such as landslides and glacier flows, while conserving the DInSAR accuracy. The ability of MSBAS-3D to capture the full 3D deformation pattern of processes with a surface signature is illustrated for a large, slow-moving, deep-seated landslide, for which long DInSAR and dGNSS time series, as well as ground truth data, are available. Surface deformation is measured over a four-year period using 1D (LOS), 2D and 3D MSBAS methods, and the advantages and limitations of each approach are described. In this case, the novel MSBAS-3D technique produces superior results that greatly simplify interpretation of the processes at work. The MSBAS-3D software can be downloaded from http://insar.ca/.

Irrigation-triggered landslides in a Peruvian desert caused by modern intensive farming

Intensification of agriculture leads to stress on the environment and subsequently can have strong societal and ecological impacts. In deserts, areas of very high sensitivity to land-use changes, these local-scale impacts are not well documented. On the arid southwestern coast of Peru, several vast irrigation programmes were developed in the 1950s on the flat detritic plateau surrounding narrow valleys to supply new farming areas. We document the long-term effects of irrigation on the erosion of arid deserts in the Vitor and Siguas valleys, south Peru, using 40 yr of satellite data. We demonstrate that irrigation initiated very large slow-moving landslides, affecting one-third of the valleys. Their kinematics present periods of quiescence and short periods of rapid activity, corresponding to landslide destabilization by their headscarp retrogression. This analysis suggests that the landslide motion continues long after their initiation by irrigations. Those landslides affect the fertile valley floors, leading to the destruction of villages and agricultural areas. We conclude that modern intensive farming can strongly impact traditional agriculture in desert areas where water management is particularly critical. Slow-moving landslides in two valleys in Peru were initiated by irrigation programmes in the region, suggest analyses of 40 years of satellite data.

The September 16, 2017, Linjiabang landslide in Wanyuan County, China: preliminary investigation and emergency mitigation

This paper reports on a typical slow-moving landslide that occurred in Shuitianba village in Wanyuan County, Sichuan Province, China, on September 16, 2017. The landslide in Wanyuan County is regionally outstanding for its features and well-developed landslide morphology. Hence, this event can provide a good case study for understanding the possible triggering conditions of the occurrences of all the landslides examined in Wanyuan County. The 225 residents of Shuitianba village did not flee the village because the deformation of the landslide was extremely slow. However, the primary emergency tasks are still necessary to reduce the landslide risk that may affect the residents. Detailed field investigations, boreholes, and exploratory trenches were performed to investigate the characteristics and triggering factors of this landslide. Rainfall and anthropogenic activities (such as informal, unplanned settlements and deforestation) were revealed to be the main triggering factors. The main engineering control measures, including anti-sliding piles, an anti-sliding retaining wall, and intercepting ditch, were applied to stabilize the landslide. However, landslide mitigation measures have not been finished, and hence, some interim measures are suggested to effectively reduce landslide risk.

Analysis of Damage to Buildings in Urban Centers on Unstable Slopes via TerraSAR-X PSI Data: The Case Study of El Papiol Town (Spain)

Persistent Scatterer Interferometry (PSI) data, deriving from the processing of SAR images acquired by high-resolution sensors such as TerraSAR-X, provide accurate measurements of displacements affecting structures (e.g., buildings) and linear infrastructure networks (e.g., roads, bridges, embankments, and pipelines). Such widespread displacements, when available on buildings on unstable slopes, offer new perspectives for their integration in procedures pursuing the analysis and the prediction of the physical vulnerability of exposed buildings. In this letter, both deterministic and probabilistic cause (differential settlements)—effects (damage) relationships are generated by using PSI-derived building settlements and the results of building damage surveys. The procedure is applied to El Papiol town (Spain), whose urban area has been suffering diffuse damage of different severity to buildings and roads due to extremely slow-moving landslide phenomena.

Slope structural health monitoring method against rainfall-induced shallow landslide

The structural health monitoring of a slope against rainfall-induced shallow landslides has become an important issue in Japan with the recent instances of extreme weather. In particular, the early detection of a sudden rainfall-induced shallow landslide is well known to be relatively difficult compared with that of a slow-moving landslide. Thus, local governments or civil-structure management companies provide residents or users with early warning information of a disaster via rainfall-based data. However, rainfall information is not enough to predict the risk of individual slope disasters because it does not directly reflect the soil-moisture condition of a slope. To solve this problem, a soil moisture-based index (iQS) is proposed. The applicability of iQS in a real slope was evaluated using the result obtained by monitoring a real slope during heavy rainfall along an expressway. The monitoring results of the real slope were seen to agree well with the results of past laboratory experiments. This implies that slope deformation owing to the rise in water level does not occur unless the volumetric water content exceeds the IQS of the real slope. Based on this result, iQS can be used for predicting the risk of shallow landslides at an early stage.

River channel width controls blocking by slow-moving landslides in California's Franciscan mélange

Abstract. To explore the sensitivity of rivers to blocking from landslide debris, we exploit two similar geomorphic settings in California's Franciscan mélange where slow-moving landslides, often referred to as earthflows, impinge on river channels with drainage areas that differ by a factor of 30. Analysis of valley widths and river long profiles over ∼19 km of Alameda Creek (185 km2 drainage area) and Arroyo Hondo (200 km2 drainage area) in central California shows a very consistent picture in which earthflows that intersect these channels force tens of meters of gravel aggradation for kilometers upstream, leading to apparently long-lived sediment storage and channel burial at these sites. In contrast, over a ∼30 km section of the Eel River (5547 km2 drainage area), there are no knickpoints or aggradation upstream of locations where earthflows impinge on its channel. Hydraulic and hydrologic data from United States Geological Survey (USGS) gages on Arroyo Hondo and the Eel River, combined with measured size distributions of boulders input by landslides for both locations, suggest that landslide derived boulders are not mobile at either site during the largest floods (&gt;2-year recurrence) with field-measured flow depths. We therefore argue that boulder transport capacity is an unlikely explanation for the observed difference in sensitivity to landslide inputs. At the same time, we find that earthflow fluxes per unit channel width are nearly identical for Oak Ridge earthflow on Arroyo Hondo, where evidence for blocking is clear, and for the Boulder Creek earthflow on the Eel River, where evidence for blocking is absent. These observations suggest that boulder supply is also an unlikely explanation for the observed morphological differences along the two rivers. Instead, we argue that the dramatically different sensitivity of the two locations to landslide blocking is related to differences in channel width relative to typical seasonal displacements of earthflows. A synthesis of seasonal earthflow displacements in the Franciscan mélange shows that the channel width of the Eel River is ∼5 times larger than the largest annual seasonal displacement. In contrast, during wet winters, earthflows are capable of crossing the entire channel width of Arroyo Hondo and Alameda Creek. In support of this interpretation, satellite imagery shows that immobile earthflow-derived boulders are generally confined to the edges of the channel on the Eel River. By contrast, immobile earthflow-derived boulders jam the entire channel on Arroyo Hondo. Our results imply that lower drainage area reaches of earthflow-dominated catchments may be particularly prone to blocking. By inhibiting the upstream propagation of base-level signals, valley-blocking earthflows may therefore promote the formation of so-called “relict topography”.

Assessment of building behavior in slow-moving landslide-affected areas through DInSAR data and structural analysis

Slow-moving landslides are a natural hazard which affects wide areas in the world and often are cause of significant damage to structures and infrastructures. Analysis of landslide evolution and of their interaction with existing man-made structures plays a key role in risk prevention and mitigation activities. To this purpose, a considerable interest towards innovative approaches has grown among the scientific community and land management institutions. In this work, Synthetic Aperture Radar data acquired by C-band and X-band sensors, combined with numerical analyses, have been successfully applied as a tool to detect spatial and temporal landslide-induced effects, in terms of deformations and structural behavior of a building affected by ground instability. Such approach has been applied to Moio della Civitella urban settlement (Salerno province, Italy), whose whole territory is interested by several slow-moving landslides. In detail, performance of a masonry building aggregate and the efficacy of restoration works have been investigated through an integrated assessment of displacement time-series pre- and post-repair intervention, and structural analysis performed with numerical code.Historical DInSAR data have permitted firstly the interpretation of building displacement time-series corresponding to pre- and post-works configurations; subsequently, the analysis of interpolated interferometric products has allowed to define gradient maps of vertical and horizontal displacements and to identify part of aggregate which can suffer a greater susceptibility to damage as a consequence of deformation gradients. Finally, the comparison of satellite and numerical data showed a substantial agreement with local failures and damage surveyed, thus confirming the capability of DInSAR technique to investigate building performance where no in situ displacement measurements were available.