Medium Scale Landslide Research Articles

Distribution of large- and medium-scale loess landslides induced by the Haiyuan Earthquake in 1920 based on field investigation and interpretation of satellite images

Abstract Studying the distribution law and influencing factors of coseismic landslides has important scientific significance and engineering value for understanding the mechanism of seismic landslides and predicting the occurrence of seismic landslides. After a hundred years, these large- and medium-scale landslides induced by the 1920 Haiyuan earthquake are still well-preserved and have extremely high academic research value. About 620 loess seismic landslides induced by the Haiyuan earthquake in 1920 were investigated on site. On this basis, the shape differences between seismic landslides and gravity landslides were summarized; 605 landslides were identified by satellite images, and the Haiyuan earthquake-induced loess landslide database containing seismic information and landslide information was established. The distribution law and morphological characteristics of large- and medium-sized landslides induced by the Haiyuan earthquake were systematically counted according to the conditions of the landslide-intensive area, intensity, and fault upper and lower plates. The influencing factors of loess earthquake landslides were summarized, and the following conclusions were obtained: (1) 1,225 large- and medium-sized landslides were induced by the Haiyuan earthquake in 1920. These landslides have the characteristics of long sliding distance, large single scale, and strong disaster-causing. They are mainly distributed in three concentrated areas of Xiji, Haiyuan, and Pengyang. The landslide morphological characteristics of the three landslide-intensive areas are different because the landslide sliding mechanism caused by topography and lithology is different. (2) The landslide distribution has obvious clustering, zonation, and directivity, and has an obvious river distance effect and fault hanging wall effect. (3) The internal influencing factors such as stratum lithology, topography, fault location, and direction, and the role of water control the occurrence location and scale of landslide. The external factor of an earthquake is an important incentive and control factor for landslide occurrence.

Pre-landslide topographic reconstruction in Baetis Chaos, mars using a CaSSIS Digital Elevation Model

Planview detailed morphological analysis of martian landslides is usually performed using orbital imagery such as from the ConTeXt camera (CTX) at 6 ​m/pix, the Colour and Stereo Surface Imaging System (CaSSIS) at 4.5 ​m/pix or the High-Resolution Imaging Science Experiment (HiRISE) at 0.25–0.5 ​m/pix. However, topographic information is key to fully understand a landslide's formation mechanism and its mobility, by estimating the material volumes mobilised and the spatial distribution of erosion and deposition. Digital Elevation Models (DEM) are required to carry out these analyses; nevertheless, there is currently a gap in landslide-volume studies between those using Mars Orbiter Laser Altimeter (MOLA) dataset at ∼450 ​m/pix or HRSC at 50–200 m/pix and those using HiRISE data at 1–2 m/pix, which is only partially filled by CTX elevation data at ∼20 ​m/pix. The CaSSIS camera on board the ESA/Trace Gas Obiter (TGO) can be used to produce DEMs, but so far, such data have not yet been used to conduct a landslide volume analysis. Here, we use three reconstruction methods (semi-automatic, morphology-based and tilted) on a CaSSIS DEM to estimate the initial topography and hence the volume and the distribution of erosion and deposition of a 6 ​km long landslide in Baetis Chaos. Despite the complex topography of the surrounding area due to the presence of an ejecta deposit beneath the landslide, we were able to estimate the landslide's volume and mass distribution. Using a tilted plane as part of estimating the initial topography produced the best results. We evaluated the success by considering the quantifiable balance between erosion and deposition (given the uncertainties) and more subjectively by considering whether the volume distribution matched with what was expected based on the morphology in images alone. Therefore, we recommend the use of this method for individual landslide studies in complex topography where detailed knowledge of the deposit-thickness distribution is required. The semi-automatic reconstruction method produces satisfactory volume estimates and would be better suited to studies where hundreds of landslides are present. We found that CaSSIS data can be used to successfully conduct such analyses, providing additional DEM coverage to study martian medium-scale landslides or other landforms of similar scale (5–15 ​km) with the notable benefit that it provides single-pass stereo image acquisition. • Digital Elevation Model are needed to estimates landslide's material volumes and distribution in order to fully understand their mobility. • CaSSIS (Colour and Stereo Surface Imaging System) DEM have not yet been used to conduct such landslide analysis. • Three reconstruction on a CaSSIS DEM have been used to estimate the volume and the material distribution of a landslide in Baetis Chaos on Mars. • CaSSIS data can be used to conduct analysis and provide additional coverage to study medium-scale landslides or other landforms (scale 5–15 km).

Landslide detection based on height and amplitude differences using pre- and post-event airborne X-band SAR data

The recognition of landslides and making their inventory map are considered to be urgent tasks not only for damage estimation but also for planning rescue and restoration activities. Owing to the capability of synthetic aperture radar (SAR) for day-and-night and all-weather imaging, various studies utilizing SAR data for landslide detection have been reported to date. Among the detection methods utilizing SAR data, those based on height differences accompanying landslides are attractive and should be further improved, since they can directly contribute to damage estimation through a volumetric estimation of landslides. In this context, we propose in this paper a landslide detection method utilizing height differences derived from pre- and post-event SAR digital elevation models (DEMs) combined with amplitude differences. The proposed method was applied to the landslides triggered by the 2016 Kumamoto earthquake. The application results demonstrate that SAR DEMs with a high altitudinal resolution can improve the detection ability and that the incorporation of the amplitude differences is effective for decreasing the number of false detections. Although the reliability of the proposed method is deemed moderate when evaluated on the basis of the kappa coefficients derived through an accuracy assessment, most of the outliers are correctly filtered out and large- and medium-scale landslides are detected. Therefore, the inventory maps derived from the proposed method are thought to be effective at the initial stage of planning rescue and restoration activities.

Landslide inventory and susceptibility zoning across SE Australia

Abstract A landmark Australian landslide research project, that will produce a series of medium-scale landslide inventory and susceptibility zoning datasets for substantial areas of Australia, is proposed. The project will produce a series of planning tools to facilitate the implementation of the AGS 2007 Landslide Risk Management (LRM) guidelines within government, and also address the new paradigm in risk management of due diligence. The project will also summarize the current variable status of landslide regulations around the country at both state and local government levels. This project will complement the earlier National Disaster Mitigation funding of the Australian Geomechanics Society and will address the difficulty in assembling a meaningful landslide inventory, essential for the development of susceptibility and hazard maps in landslide risk management practice. Susceptibility maps are seen as the best product from which to produce planning and development control areas for use in local government planning schemes addressing landslide issues. The development of a National Landslide Inventory framework would enhance data collection standards for this hazard across Australia. The costs associated with landslide damage and management are poorly documented within Australia and this project will also contribute to enhancing this element. Preliminary figures from early work in this area suggests government spending in the Wollongong area alone is at least $5 million annually since 1950 on landslide related costs. The project will also result in a series of regional to local zoning inventory and susceptibility zoning datasets and associated maps ranging from 1:250 000 and perhaps in some areas up to 1:25 000 scales for substantial areas of Australia. A modelling process will also be documented to promote transparency and to facilitate subsequent review and revisions. Achieving appropriate levels of funding to undertake this project remains a priority for the team. However, substantial elements are being developed already (some of which are summarized in this paper) and the authors are confident this project will come to fruition.

A novel integrated model for assessing landslide susceptibility mapping using CHAID and AHP pair-wise comparison

ABSTRACTThis article uses an integrated methodology based on a chi-squared automatic interaction detection (CHAID) model combined with analytic hierarchy process (AHP) for pair-wise comparison to assess medium-scale landslide susceptibility in a catchment in the Inje region of South Korea. An inventory of 3596 landslide locations was collected using remote sensing, and a random sample comprising 30% of these was used to validate the model. The remaining portion (70%) was processed by the nearest-neighbour index (NNI) technique and used for extracting the cluster patterns at each location. These data were used for model training purposes. Ten landslide-conditioning factors (independent variables) representing four main domains, namely (1) topology, (2) geology, (3) hydrology, and (4) land cover, were used to produce two landslide-susceptibility maps. The first landslide-susceptibility map (LSM1) was produced by overlaying the terminal nodes of the CHAID result tree. The second landslide-susceptibility map (LSM2) was produced using the overlay result of AHP pair-wise comparisons of CHAID terminal nodes. The prediction rate curve results were better with LSM2 (area under the prediction curve (AUC) = 0.80) than with LSM1 (AUC = 0.76). The results confirmed that the integrated hybrid model has superior prediction performance and reliability, and it is recommended for future use in medium-scale landslide-susceptibility mapping.

Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain)

In the present work, we show the case of Marina del Este resort, located in the southern Mediterranean coast of Spain (Costa del Sol). A medium-scale landslide has been recognized when the area was virgin. In 1977 started the initial works for urbanizing the area; later, buildings and facilities expanded uphill covering the landslide body. This case is characterized by a long history of corrective drainage and mitigate measures without success. An analysis of the landslide activity has been carried out by applying different approaches and based on the combination of the following: (1) geomorphological analysis, (2) PSInSAR technique application (ENVISAT 2003–2009), (3) an assessment of building and infrastructure damages, (4) rainfall time series analysis and (5) ground monitoring (2010–2011) data interpretation. Results show that, from 2003 to 2009, the landslide was active with velocities ranging from 5 to 15 mm/year. During the exceptional rainy period in winter 2009–2010, the movement velocity increased about ten times (velocities ranging from 40 to 90 mm/year) causing widespread damages in the resort. Buildings with high degree of damage are located at the toe of the landslide, close to the marina, where some dwellings have been evacuated. Marina del Este is a good example to show that landslides on coastal and steep slope areas are very vulnerable to reactivations and require thorough studies before any anthropic modification.

Potential tsunamigenic landslides at Stromboli Volcano (Italy): Insight from marine DEM analysis

Seafloor mapping and morphometric analysis of landslide scars can provide useful insights for marine geo-hazard assessment, as demonstrated by several studies performed on different geological settings. The availability of high-resolution Digital Elevation Models (DEMs) obtained through swath bathymetry allows us to apply this approach to the submarine portions of Stromboli volcano, affected for about 90% of their extension by mass-wasting features. Two main kinds of tsunamigenic landslides have been recognized and analyzed. Large-scale sector collapses are catastrophic events that mobilize up to few km 3 of material, generating huge tsunami waves that may affect Stromboli and propagate in surrounding areas. The related hazard is not very high as these collapses show recurrence periods of some (or more) thousand years. Conversely, medium-scale landslides are more hazardous as they occur at higher frequency with respect to the previous events, i.e. from some hundreds up to a few tens of years. These events are able to generate local but severe tsunamis when occurring in shallow-water, as demonstrated by the recent 2002 tsunamigenic landslides that struck the Stromboli coasts with waves up to 10 m high. Medium-scale landslides mobilize volumes up to some millions of cubic meters and may also evolve landwards through retrogressive processes, thus affecting coastal sectors. This study highlights that the main predisposing factors controlling medium-scale slope failures at Stromboli are high slope gradient and sedimentation rates; eruptive activity also plays a key role, as recently witnessed by the 2002 landslide.

Hillslope-channel coupling in the Nepal Himalayas and threat to man-made structures: The middle Kali Gandaki valley

In mountain areas, the confinement of valleys favours landslide interaction with rivers, causing channel changes or short-lived dams and lakes that may threaten trails, roads and human settlements. Their impacts may occur successively in space and time, and they affect randomly the functioning of the sediment fluxes. The present study focuses on the interaction patterns between unstable mountain slopes and the Kali Gandaki River, in the Nepal Himalayas. In this valley, the deepest on earth, a road linking the Myagdi and Mustang districts has been under construction for the past 5 years, either cutting into the bedrock or crossing areas affected episodically by debris slides, earth flows, debris flows and rock slides. On the basis of the geomorphic evolution observed over the last three decades, we assess the potential threats that now arise following completion of the road. We mapped three areas of recurrent mass wasting features characteristic of the most frequent situations encountered in this valley. We analyzed the combination of the hydro-geomorphic processes involved. With the use of a DEM, we assessed the volume and spatial impact of temporary river dams on infrastructure located along the valley floor. We estimated hydraulic parameters to document the geomorphic efficiency of river flooding after dam breaching. We reconstructed the spatial extent of (1) areas threatened by backwater flooding upstream of the dams and (2) areas threatened by the collapse of the dams. We describe the current geomorphic and sedimentary adjustments still at work along the valley sides. Our findings confirm that in the High Himalaya, medium scale landslides (10 5–6 m 3) play a major role in the overall process of denudation and sediment transfer. They highly influence the transient nature of bedload transport in the channel. In reducing the residence time of sediments in temporary, spatially limited traps of the valley bottom, they enhance the vulnerability of land and people attracted by a roadside location.

A quantitative approach for improving the BIS (Indian) method of medium-scale landslide susceptibility

In India, the Bureau of Indian Standards (BIS) recommends a heuristic method for medium-scale (1:25,000/1:50,000) landslide susceptibility mapping. This is based on fixed ratings of geofactors, without the inclusion of landslide inventory information. In BIS method, the pre-defined ratings of geofactors are applied over diverse areas, irrespective of the terrain-specific spatial inter-dependence of geofactors and landslide types, which leads to rather moderate prediction. In this paper, we evaluate the effectiveness of the existing BIS method in Darjeeling Himalaya through a quantitative method adapting weights of evidence (WofE) modeling. The quantified spatial associations between specific geofactors for different landslide types and failure mechanisms that were generated, using this method showed improved prediction rates as compared to the BIS method of fixed ratings of geofactors. We therefore recommend adjusting the existing BIS guidelines by inclusions of weights, derived locally through quantitative spatial analysis of landslide inventories and geofactor maps.

Landslide susceptibility mapping using the Matrix Assessment Approach: a Derbyshire case study

Abstract Civil engineering schemes such as new highways and railway lines, regional planning and large-scale land-management projects in areas known to have a landslide problem require regional landslide susceptibility evaluation. The Matrix Assessment Approach (MAP) is introduced as a medium-scale landslide hazard mapping technique for establishing an index of slope stability over large areas. The method allows the relative landslide susceptibility to be computed over large areas using a discrete combination of geological/geomorphological parameters. MAP was applied to a region in the Peak District, Derbyshire. The model identified key geological/geomorphological parameters involved in deep-seated failures, provided an effective means of classifying the stability of slopes over a large area and successfully indicated sites of previously unmapped landslides. The resultant regional landslide susceptibility index provides useful preliminary information for use at the desk study and reconnaissance stages of large-scale civil engineering works such as highway construction.