This reprint, named “Landslides in Forests around the World: Causes and Mitigation”, covers various topics, such as the impact mechanism of tree roots on landslide stability, landslide deformation ...monitoring, landslide disaster prevention and control engineering technology, the automatic identification of regional landslides, susceptibility and hazard assessment, and a rainfall-induced mass landslide warning.
Recently, ECMWF has released a new generation of reanalysis, acknowledged as ERA5, able to deliver a comprehensive, free, and operative picture of the past weather, exploiting the data assimilation ...of historical observations from different sources (satellite, in situ, multiple variables) for both atmospheric and soil variables. Experiences concerning flooding issues suggest that ERA5 could support also landslide investigations. In this sense, a number of questions may be raised: (i) can ERA5 data be reliable in reproducing rainfall histories leading to a landslide event? (ii) can ERA5 soil moisture estimations be reliable proxies for antecedent slope wetness condition? (iii) can ERA5 be implemented in a landslide early warning system to improve the performances? This study tries addressing these questions referring to some historical Campanian events (Southern Italy) with a special focus on the fully investigated event occurred in Nocera Inferiore on March 4, 2005. The study shows the following: (i) ERA5 precipitation can appropriately reproduce actual rainfall histories leading to the events occurred in the last years; (ii) ERA5 soil moisture may act as proxy of slope wetness conditions; (iii) ERA5 data could be easily implemented in LEWSs in areas poorly covered by field monitoring networks.
Significant progress has been made in the last few years that has expanded the knowledge of landslide processes. It is, therefore, necessary to summarize, share and disseminate the latest knowledge ...and expertise. This Special Issue brings together novel research focused on landslide monitoring, modelling and data analysis.
The NW-SE-striking fault zone in the Bailong River Basin in the northeastern margin of the Qinghai-Tibet Plateau have the most densely distributed, large complex landslides in China. However, the ...failure of large complex landslides along the fault zone and the causes of their complex geomorphic characteristics are unclear. The purpose of this study was to explore the relationship between the fault zone and the spatial distribution, direction of movement, and geomorphic characteristics of large landslides. We inventoried 29 large landslides in the middle reaches of the Bailong River and described their characteristics. Statistical analysis revealed differences in the spatial relationship between the faults and landslides of different scales. Almost all of the landslide bodies with an area > 1 km2 are distributed on the faults; in addition, the strike of the faults was found to constrain the direction of movement of the landslides to the WNW-ESE direction. Statistical results show that the cross sections of landslides in the study area are asymmetric arc, corresponding to which there are significant differences in the geomorphological characteristics of the north and south sides of landslides. The geometric characteristics, physical properties (i.e., material weakness) of the fault zone and rapid uplift of the hanging wall were responsible for the asymmetric shape of landslide cross sections and the geomorphic difference. We present a conceptual model based on the relationship between the fault zone and landslides, which facilitates an improved understanding of the relationship between the fault zone and landslide evolution.
•Movement direction of landslides is symmetrically distributed along fault zones.•The landslides have geomorphic differences between the north and south sides of the landslide body.•Fault zone control the asymmetric shape of landslide cross sections and the geomorphic features.
Display omitted
•DoD models allowed to determine that landslides remaining in contact with stream channels remain active all the time.•Colluvia are removed from the toe and foot of a landslide in ...periods between floods, which makes these landforms active by setting them in motion at the bottom first, which propagates to the top.•Colluvia are activated within the entire landslide during both major and minor floods starting from the bottom and propagating to the top or through movement propagating in both said directions: top-to-bottom and bottom-to-top.
The paper deals with the problem of the impact of river erosion on the activity level and type of colluvial movement within landslides in two study regions (Foothills and Beskidy Mts.) in the Polish Outer Carpathians. The principal goal of the study was to investigate how landslides that remain in contact with river channels function and to identify primary colluvial movement types depending on hydrometeorological conditions. Five landslides were studied, with three of them found in the Rożnowskie Foothills and two in the Beskid Niski Mts. The research was performed using terrestrial laser scanning (TLS) in the period April 2014 to November 2017. Ten measurement series were acquired during the study period. A total of 9 DEM of Difference representations (DoDs) were produced that showed both quantitative and spatial changes in the studied landslides. It was determined, based on the DoDs produced, that landslides adjacent to river channels remained continuously active due to the influence of continuously occurring fluvial erosion, although the level of activity varied, as it depended on hydrometeorological conditions. Colluvial material was set in motion within the entire landslide during floods. The recording of spatial and quantitative changes in the body of each landslide allowed to identify two key types of colluvial movement occurring during floods: (i) movement starting at the bottom and subsequently activating parts at the top (landslides: Sękówka, Boczkówka, Żabno), (ii) motion propagating in top-to-bottom and in bottom-to-top directions (landslides: Bodaki, Leszczyny). Then again, in periods between floods, colluvial material was continuously removed from the toe of each landslide, which occurred in all the studied landslides. Colluvial material became activated during these periods through movement starting at the bottom and propagating to the top. The amount of colluvium removed by streams varied depending on hydrometeorological conditions. The colluvial material carried away from the studied landslides by streams during floods comprised 60% to 90% of the volume of material removed during the entire examined period.
A characteristic of rainfall‐induced landslides is the gradual loading by infiltrating rainwater that weakens the soil mantle and could progress to abrupt soil mass release. The temporal patterns of ...similar rainfall amounts affect the hydrological response of a catchment and thus influence landslide dynamics. We use a novel catchment scale landslide hydromechanical triggering model to systematically study how different asymmetric distributions of rainfall intensities affect landslide dynamics and hazard evolution. Evaluating rainfall events with similar durations and total amounts shows that early rainfall peak intensity exerts stronger destabilizing effects, relative to delayed rainfall peak intensity. Intense rainfall events reduce landslide triggering relative to uniform‐intensity rainfall events due to reduced water infiltration. With advances in highly resolved and real‐time precipitation observations, the study offers a means for improving prediction of landslide timing and hazard evolution and identifying hydrological scenarios that enhance landslide activity.
Plain Language Summary
Rainfall‐induced landslide triggering is associated with rainwater infiltration that may load and weaken soil mantle and lead to abrupt soil mass release. Temporal rainfall patterns may affect the infiltration process and control landslide dynamics and hazard evolution. We investigate the effects of rainfall temporal patterns of similar durations and total amounts on landslide dynamics by forcing a catchment scale landslide hydromechanical triggering (LHT) model with artificial rainfall time series with different timing and magnitudes of peak intensity. With identical duration and total amount, rainfall patterns with early peak intensity promote landslide activity compared with late peak intensity. High peak rainfall intensities reduce total rainwater infiltration and thus hinder landslide triggering relative to more uniform rainfall time series. With the rapid advances in high spatiotemporal resolution precipitation measurements, the results of this study may improve landslide prediction and provide useful guidelines for real‐time landslide early warning.
Key Points
Rainfall intensity temporal patterns influence simulated infiltration amounts and thus affect timing and volumes of shallow landslides
With identical rainfall amount and duration, early peak rainfall intensity contributes to greater instability than later peak intensity
Uniform‐intensity rainfall events promote landslide activity relative to extreme rainfall of similar total rainfall amount and duration
On 8th August 2017, a magnitude Ms 7.0 earthquake struck the County of Jiuzhaigou, in Sichuan Province, China. It was the third Ms ≥ 7.0 earthquake in the Longmenshan area in the last decade, after ...the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake. The event did not produce any evident surface rupture but triggered significant mass wasting. Based on a large set of pre- and post-earthquake high-resolution satellite images (SPOT-5, Gaofen-1 and Gaofen-2) as well as on 0.2-m-resolution UAV photographs, a polygon-based interpretation of the coseismic landslides was carried out. In total, 1883 landslides were identified, covering an area of 8.11 km2, with an estimated total volume in the order of 25–30 × 106 m3. The total landslide area was lower than that produced by other earthquakes of similar magnitude with strike-slip motion, possibly because of the limited surface rupture. The spatial distribution of the landslides was correlated statistically to a number of seismic, terrain and geological factors, to evaluate the landslide susceptibility at regional scale and to identify the most typical characteristics of the coseismic failures. The landslides, mainly small-scale rockfalls and rock/debris slides, occurred mostly along two NE-SW-oriented valleys near the epicentre. Comparatively, high landslide density was found at locations where the landform evolves from upper, broad valleys to lower, deep-cut gorges. The spatial distribution of the coseismic landslides did not seem correlated to the location of any known active faults. On the contrary, it revealed that a previously-unknown blind fault segment—which is possibly the north-western extension of the Huya fault—is the plausible seismogenic fault. This finding is consistent with what hypothesised on the basis of field observations and ground displacements.
Rainfall‐induced shallow landslides scar the Earth surface and deliver sediment pulses into fluvial systems and thus play an important role in landscape evolution. Previous landslide legacy affects ...local soil depths and soil regeneration rates thus modifying future landslide susceptibility and sediment dynamics. Here, we couple an advanced hydromechanical landslide model with a soil depth regeneration model and quantify landslide legacy effects by placing landslide dynamics in a perspective of landscape soil depth evolution. Results show increased landslide susceptibility near recently failed regions due to alteration of hydrological processes in a thinner soil mantle that imposes constraints on released soil volumes. Landslide recurrence in failed regions levels off when soil depths are gradually restored to steady state pre‐failure values. Cumulative effects of past landslides divert future landslide activity from steep hillslopes to alluvial channels and valley margins thus affecting sediment dynamics and yields. Consideration of landslide legacy improves landslide prediction and quantification of landslide erosion and fluvial sediment yield rates.
Key Points
Past landslide signatures are linked mechanistically with future soil failure dynamics and landscape soil depth evolution
Soil generation rates and rainfall characteristics jointly determine the persistence of past landslide signatures on future susceptibility
Effects of past landslides shift future soil stripping to less steep regions of the landscape and affect fluvial sediment yields
Landslides are the most destructive geological hazard in the hilly regions. For systematic landslide mitigation and management, landslide evaluation and hazard zonation is required. Over the past few ...decades several techniques have been developed that can be used for landslide evaluation and zonation. These techniques can broadly be classified into qualitative and quantitative approaches. Qualitative approaches include geomorphological analysis and heuristic techniques whereas quantitative approaches include statistical, artificial intelligence and deterministic techniques. In quantitative techniques prediction for landslide susceptibility is based on the actual realistic data and interpretations. Further, the quantitative techniques also overcome the subjectivity of qualitative approaches. Each of these techniques may consider different causative factors and utilizes various means for factor evaluation and analysis. When compared, each of these techniques has its own advantage and disadvantage over other techniques. The selection of appropriate technique for landslide hazard evaluation and zonation is very crucial. The factors that need to be considered to adopt an appropriate approach are; investigation purpose, the extent of the area to be covered, the type of mapping units, the scale of map to be produced, type of data to be used, type of landslides, availability of resources, capability and skill set of an evaluator and the accessibility to the study area. The main aim of this article is to present a comprehensive review on various techniques and approaches available for landslide susceptibility and hazard zonation mapping. Further, attempt is also made to assess the effectiveness of these techniques in landslide hazard zonation studies.
PDF
