Landslide Mitigation Measures Research Articles

High-resolution landslide mapping and susceptibility assessment: Landslide temporal variations and vegetation recovery

In mountainous terrains, the frequent landslides and their associated impacts on human lives and the economy is increasing globally. Development of landslide inventory and afterward landslide susceptibility mapping are the main prerequisites for implementing landslide mitigation measures and protection in mountainous regions. The 2005 Kashmir earthquake induced different small and large landslides and some were active for the long term. So far many studies have used medium and high-resolution data to develop landslide inventory. This study aims to develop a 1st detailed, comprehensive and accurate landslide inventory using a very high-resolution image using a semi-automatic technique. The precise landslide inventory is employed to develop an accurate and comprehensive landslide susceptibility map considering the landslide inventory data using a logistic regression training model. Furthermore, the landslide’s temporal recovery from the earthquake and its reactivation due to rainfall in spare vegetation areas have been evaluated. Fine-resolution satellite images of Worldview-2 are applied to develop a detailed landslide inventory using a Support Vector Machine (SVM) classifier. A total of 63,630 landslides were identified using a semi-automatic technique within a study area of 265 km2. From regression modeling, the results show that geology, topography, and road networks have a significant impact on the spatial distribution of landslides. Model performance was evaluated based on the testing data, the model gives an AUC of 0.93 and the kappa value of 0.9353. The spatiotemporal NDVI has been assessed to identify the landslide recovery and its reactivation due to extreme rainfall. The results show that 72.1 % of the landslides occurred in Muzaffarabad formation in the study area. The developed landslide susceptibility map can be further used for land-use planning and implementing mitigation measures for the safety of roads and other infrastructure in the area.

Evaluasi Faktor-Faktor Penyebab Longsor dan Kesesuaian Mitigasi

Management and maintenance of slopes require proper knowledge of slope conditions so that appropriate mitigation measures can be implemented. The activities required for the management of slopes include slope inventory, slope inspection, slope risk level assessment, and risk mitigation measures. The objective of this study was to observe the slope conditions and causes of past slope failures, determine the appropriate mitigation measures, and analyze the suitability of landslide mitigation measures and causes of slope failures. The research locations are road segment No. 36 (Kota Lahat – Simpang Air Dingin), No. 37 (Simpang Air Dingin – Pagar Alam), and No. 38 (Pagar Alam – Tanjung Sakti – batas Bengkulu). The research was initiated by analyzing data collected by the South Sumatra National Road Management Agency (BPJNSS) from 2018 to 2021. The field observation was conducted on ten locations where the slope had been repaired after slope failure events. The suitability of mitigation with the factors that cause landslides was analyzed using the slope management system method suggested by the Ministry of PUPR. The results showed that most slope failures were triggered by high-intensity rain falling on slope surfaces containing high humidity due to previous rainfall. The common types of slope mitigation are reducing the forces that cause movement, increasing the resisting forces by controlling seepage, and the use of anchors.

Internal structure of an active landslide based on ERT and DP data: New insights from the Hofermühle landslide observatory in Lower Austria

Slopes with clay-rich, deeply weathered soils, such as those present in the Flysch Zone of Lower Austria, are prone to landslide processes. Even though generally being of low magnitude and velocity, they can cause substantial economic losses and threaten settlements as well as infrastructure. Previous studies have demonstrated the importance of sub-surface information to further increase our understanding on landslide processes and triggers in different areas as well as to support any decision makers to determine any appropriate landslide mitigation measures. The combination of direct and indirect methods thereby has proven to be an adequate methodology, yet case studies are still needed to develop a universal strategy for the investigation of clay-rich landslides. In this study, we applied Electrical Resistivity Tomography (ERT) and Dynamic Probing Medium (DPM) to further investigate the complex Hofermühle landslide in the Flysch Zone of Lower Austria in order to improve our knowledge on sub-surface conditions. The focus is on the initially activated main landslide area, which has already formed earth-flow-like processes in the past. The methodology facilitated a representative characterization of the sub-surface. We were able to approximate the geometry and depth of slip surfaces, as well as the transition to bedrock, allowing us to delimit those parts of the slope which are likely to fail and, respectively be re-activated in the future. The results show that a range of thicknesses can be found in the investigated part of the Hofermühle landslide. In particular, near the surface, which has been altered by creep displacement and also by anthropogenic alteration, the resistivity is more variable compared to deeper, presumably less disturbed, layers. Furthermore, it is assumed that clay particles are transported with the surface runoff and deposited in the surroundings of the drainage channels, resulting in lower resistivity values and higher saturation at this locations. The location of the slip surface is interpreted to be on the surface of the bedrock, where there is a highly disturbed, clay-rich mass with no interbedded layers. Layers with lower resistivity directly above the bedrock indicate weathered material and remolding of materials during creep.

Potassium chloride wells used as quick-clay landslide mitigation: installation procedures, cost–benefit analysis, and recommendations for design

Retrogressive development of landslides in highly sensitive clays (quick clays) may extend several hundred metres upslope from an initial landslide, and liquified slide-debris may impact buildings or infrastructure in the run-out zone. By installing wells filled with potassium chloride (KCl) in quick clays, the salt migrates into the surrounding clay and increases its remolded shear strength, reducing its sensitivity. The salt-stabilized, nonquick clay volume may act as a barrier preventing backward retrogression, thereby contributing to reducing both the area susceptible for being involved in a quick-clay landslide, and the area of the run-out zone. Installation procedures and design guidelines for salt stabilization are examined herein. Installation procedures generating temporary, very small excess pore-water pressures were tested at National Geo-Test Site Tiller–Flotten. Although the benefit-to-cost ratios related to these procedures are small compared to conventional landslide mitigation measures, reducing the installation costs to less than 30 USD per m well and increasing the center distance between the wells may justify salt-stabilization as a landslide mitigation measure. This paper describes experience from testing safe installation procedures, evaluations of cost–benefit and environmental impact, and proposed design guidelines, introducing KCl as an alternative to conventional landslide mitigation-measures in slopes with highly sensitive quick-clay deposits.

Performance Assessment of Event-Based Ensemble Landslide Susceptibility Models in Shihmen Watershed, Taiwan

While multi-year and event-based landslide inventories are both commonly used in landslide susceptibility analysis, most areas lack multi-year landslide inventories, and the analysis results obtained from the use of event-based landslide inventories are very sensitive to the choice of event. Based on 24 event-based landslide inventories for the Shihmen watershed from 1996 to 2015, this study established five event-based single landslide susceptibility models employing logistic regression, random forest, support vector machine, kernel logistic regression, and gradient boosting decision tree methods. The ensemble methods, involving calculating the mean of the susceptibility indexes (PM), median of the susceptibility indexes (PME), weighted mean of the susceptibility indexes (PMW), and committee average of binary susceptibility values (CA) of the five single models were then used to establish four event-based ensemble landslide susceptibility models. After establishing nine landslide susceptibility models, using each inventory from the 24 event-based landslide inventories or a multi-year landslide inventory, we identified the differences in landslide susceptibility maps attributable to the different landslide inventories and modeling methods, and used the area under the receiver operating characteristic curve to assess the accuracy of the models. The results indicated that an ensemble model based on a multi-year inventory can obtain excellent predictive accuracy. The predictive accuracy of multi-year landslide susceptibility models is found to be superior to that of event-based models. In addition, the higher predictive accuracy of ensemble landslide susceptibility models than that of single models implied that these ensemble methods were robust for enhancing the model’s predictive performance in the study area. When employing event-based landslide inventories in modeling, PM ensemble models offer the best predictive ability, according to the Kruskal–Wallis test results. Areas with a high mean susceptibility index and low standard deviation, identified using the 24 PM ensemble models based on different event-based landslide inventories, constitute places where landslide mitigation measures should be prioritized.

AI-powered landslide susceptibility assessment in Hong Kong

Landslide susceptibility assessment is essential for regional landslide risk assessment and mitigation. Most past studies involved cell-based analysis that takes landslide incidents as geo-spatial points. Nevertheless, given that a landslide is a two-dimensional polygon on maps and a three-dimensional object in the real world, an object-wise assessment is more logical. Fusing with artificial intelligence (AI) techniques, this paper proposes a novel AI-powered object-based landslide susceptibility assessment method to address this issue. First, landslide and non-landslide objects are defined based on an optimal object size determined by statistics of historical landslides. Next, landslide and non-landslide samples are constructed by integrating geoenvironmental data layers derived from multi-source data. Subsequently, AI techniques are applied to learn susceptibility prediction based on the prepared samples. To illustrate the proposed method, a comprehensive case study of Hong Kong is conducted, in which six AI algorithms are evaluated including logistic regression (area under curve, AUC = 0.949), random forest (AUC = 0.951), LogitBoost (AUC = 0.958), convolutional neural network (CNN) (AUC = 0.966), bidirectional long short-term memory architecture of recurrent neural network (BiLSTM-RNN) (AUC = 0.966), and CNN-LSTM (AUC = 0.972), among which the BiLSTM-RNN and CNN-LSTM algorithms are applied in landslide susceptibility assessment for the first time. Results confirm that the proposed object-based method outperforms the traditional cell-based method significantly. Equally importantly, the case study produced the first set of AI-based territory-wide landslide susceptibility maps for Hong Kong. These maps can be used as a fundamental tool for quantifying natural terrain landslide risk and identifying susceptible zones where landslide mitigation measures may be needed.

Recharge response and kinematics of an unusual earthflow in Liechtenstein

Understanding landslide behavior over medium and long timescales is crucial for predicting landslide hazard and constructing accurate landscape evolution models. The behavior of landslides in soil that undergo periodic displacements, termed earthflows or compound soil slides, is especially difficult to forecast at these timescales. This is because velocities can increase by orders of magnitude over annual to decadal timescales, due to processes such as changing recharge conditions, erosion of the landslide toe, and retrogression of the landslide head. In this paper, we provide a detailed analysis of the Schlucher landslide, an unusual earthflow that is perched above the village of Malbun, Liechtenstein. This landslide had been displacing by 10 to 20 cm/year until 2015, when displacements on the order of 2 m/year occurred from 2016 to 2018. These large displacements damaged landslide mitigation measures, caused numerous surface deformation features, and threatened the local population downstream of the earthflow. This landslide has an unusually long monitoring record, with accurate displacement and climatic data available since 1983. We analyze this nearly 40-year monitoring time series to estimate recharge from snowmelt and rainfall, and its correlation with displacement. We also analyze recently collected, high-resolution surface and subsurface data in order to understand landslide response to recharge, landslide kinematics through time, and catastrophic failure potential. We find that interannual displacements can be explained with variations in recharge; however, periodic surges with recurrence times of tens of years must be explained by other mechanisms. In particular, recharge into the landslide during the recent acceleration (2016 to 2018) was not anomalously high. Instead, we argue that loss of internal strength is responsible for this recent acceleration period, and that this mechanism should be considered when forecasting the surge potential for certain earthflows and soil slides.

Landslide susceptibility analysis of Karakoram highway using analytical hierarchy process and scoops 3D

Landslides are prevalent, regular, and expensive hazards in the Karakoram Highway (KKH) region. The KKH connects Pakistan with China in the present China-Pakistan Economic Corridor (CPEC) context. This region has not only immense economic importance but also ecological significance. The purpose of the study was to map the landslide-prone areas along KKH using two different techniques-Analytical Hierarchy Process (AHP) and Scoops 3D model. The causative parameters for running AHP include the lithology, presence of thrust, land use land cover, precipitation, and Digital Elevation Model (DEM) derived variables (slope, curvature, aspect, and elevation). The AHP derived final landslide susceptibility map was classified into four zones, i.e., low, moderate, high, and extremely high. Over 80% of the study area falls under the moderate (43%) and high (40%) landslide susceptible zones. To assess the slope stability of the study area, the Scoops 3D model was used by integrating with the earthquake loading data. The results of the limit equilibrium analysis categorized the area into four groups (low, moderate, high, and extremely high mass) of slope failure. The areas around Main Mantle Thrust (MMT) including Dubair, Jijal, and Kohistan regions, had high volumes of potential slope failures. The results from AHP and Scoops 3D techniques were validated with the landslides inventory record of the Geological Survey of Pakistan and Google Earth. The results from both the techniques showed similar output that coincides with the known landslides areas. However, Scoops 3D provides not only susceptible zones but also the range of volume of the potential slope failures. Further, these techniques could be used in other mountainous areas, which could help in the landslide mitigation measures.

Proposal of a simplified method for verifying the effectiveness of landslide mitigation measures

Proposal of a simplified method for verifying the effectiveness of landslide mitigation measures

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.

A geochemical, mineralogical and geotechnical characterization of the low plastic, highly sensitive glaciomarine clay at Dragvoll, Norway

The sediments at the NTNU research site Dragvoll, Trondheim, Norway accumulated in seawater close to the glacier front during the Pleistocene-Holocene transition. A comprehensive site investigation and laboratory test program was carried out to characterize the quick clay at Dragvoll. Downsized block samples, mini-blocks, were extracted and tested in the laboratory. Index testing, constant rate of strain oedometer tests and anisotropically consolidated undrained compression tests were carried out on all quick-clay samples. Pore-water chemistry, bulk and clay mineralogy, cation exchange capacity and specific surface area were determined. Resistivity cone-penetration tests and electrical resistivity tomography surveys were carried out and correlated to the laboratory results. With a clay mineralogy dominated by illite and chlorite, the Dragvoll clay is electro-chemically very active. Leaching has diluted the salt content in the pore water to~0.7 g/L, corresponding to a very low soil conductivity of only 20 mS/m. Due to the low salt content and a composition of cations in the pore-water dominated by sodium (85-92%), the repulsive forces between the clay particles are large. Therefore, the clay liquefies when remolded and has a very brittle behavior. The clay is slightly overconsolidated in top, with an overconsolidation ratio decreasing towards 1 at around 6 m depth. Developing new cost-effective ground improvement methods that may also serve as landslide mitigation measures in quick-clay areas is needed. Detailed knowledge on mineralogy and geochemistry is necessary to fully understand the behavior of clays, and in developing effective ground improvement methods by chemical additives. This paper present geochemical, mineralogical and geotechnical data from the quick clay at Dragvoll. A field experiment at Dragvoll showed that potassium chloride can be used as landslide mitigation in quick-clay areas, inhibiting retrogressive landslides and reducing the risk for progressive landslides.

Comparative evaluation of various approaches for landslide hazard zoning: a critical review in Indian perspectives

The progress of geospatial technique can help to minimise the losses as it emerges as a powerful technique for mapping landslide hazard zonation. Different researchers use different methods for landslide hazard assessment. But, there is not a single method which has been universally accepted for effective assessment of landslide hazard. In Indian subcontinent, 12.6% of land area is susceptible to landslide hazard and the estimated total economic damage due to landslide hazard is 4,500,000US$. This review article represents the temporal development of different methodologies towards landslide hazard zonation up to a recent year and their advantages and disadvantages. The review indicates that mostly three methods i.e., knowledge driven, data driven and physical based method are followed among which, knowledge driven and bivariate analysis are mostly used during last decade but from the twenty-first century onwards multivariate statistical modelling is mostly popularised as it gives the most accurate result of landslide hazard zonation in comparison to other methods. Geospatial modelling of landslide susceptibility is useful for monitoring, mapping and formulating proper management plans that will be helpful for future landslide mitigation measures.

Cost-based analysis of mitigation measures for shallow-landslide risk reduction strategies

Landslide risk assessments are usually permeated by a certain degree of subjectivity. In order to reduce it, we have developed an original methodology which enables risk assessments to be carried out in fully quantitative terms, integrating both physical and economic science techniques. This risk assessment combines geomorphological studies, probabilistic modelling and cost-benefit analyses (CBA). We applied the methodology to an area of north-west Italy that was affected in 2011 by a dramatic rainfall-induced landslide event, and where a risk management program is necessary for avoiding future losses. We analyzed the cost-effectiveness of several landslide mitigation measures applying the proposed procedure. The results demonstrate that measures previously considered as suitable for mitigating shallow landslides were inappropriate from the economic viewpoint. The applied techniques also served to optimize economically the most appropriate mitigation measure. Moreover, our methodology allowed to calculate the maximum affordable investment on a cost-effective mitigation measure; this result will be a reference for designing innovative solutions to mitigate landslides in the study area.

Occurrence of landslides in Nepal and their mitigation options

Landslides are very common occurrences in Nepal that have been affected development infrastructures, lives, and properties of the people every year. Many hill villages are situated on or adjacent to unstable slopes and old landslides are reactivated from time to time. The rapidly increasing construction of infrastructure, such as roads, irrigation canals, and dams without due consideration of natural hazards is contributing to triggering of landslides and debris flows. Thus, this paper has explored the cause and characteristics of landslides occurrences and their mitigation practices in Nepal. Topographic, geologic and triggering factors, and human intervention causing landslides are characterised to suggest the suitable mitigation options that can be implemented in the mountain hill-slopes. Among the wide range of slope stabilisation measures which are available to practitioner engineer, the lowering of groundwater level in combination of controlling of surface infiltration (e.g. sealing of tension cracks) of water into landslide are the most cost effective options for mountainous terrain because the rise in pore water pressure is one of the basic cause of landslides during the rainy season. In addition, removing of unstable slope debris, surface drainage, and retaining walls are the useful landslide mitigation measures depending on site conditions, availability of budget, and specific requirements. Various support systems and elements can be crafted for creative solutions of the slope instability problems in Nepal.

An integrated approach for evaluating the effectiveness of landslide risk reduction in unplanned communities in the Caribbean

Despite the recognition of the need for mitigation approaches to landslide risk in developing countries, the delivery of ‘on-the-ground’ measures is rarely undertaken. With respect to other ‘natural’ hazards, it is widely reported that mitigation can pay. However, the lack of such an evidence base in relation to landslides in developing countries hinders advocacy amongst decision makers for expenditure on ex-ante measures. This research addresses these limitations directly by developing and applying an integrated risk assessment and cost–benefit analysis of physical landslide mitigation measures implemented in an unplanned community in the Eastern Caribbean. In order to quantify the level of landslide risk reduction achieved, landslide hazard and vulnerability were modelled (before and after the intervention), and project costs, direct and indirect benefits were monetised. It is shown that the probability of landslide occurrence has been substantially reduced by implementing surface-water drainage measures and that the benefits of the project outweigh the costs by a ratio of 2.7–1. This paper adds to the evidence base that ‘mitigation pays’ with respect to landslide risk in the most vulnerable communities—thus strengthening the argument for ex-ante measures. This integrated project evaluation methodology should be suitable for adoption as part of the community-based landslide mitigation project cycle, and it is hoped that this resource, and the results of this study, will stimulate further such programmes.

Rain-triggered landslide hazards and mitigation measures in Thailand: From research to practice

Recently, the frequency of rain-triggered landslides in Thailand has been on the increase and has gained momentum, coincident with the effects of climate change. In this regards, the impact of landslide on roads and highways in the hilly and mountainous terrains has also increased. Non-structural landslide mitigation measures, including early warning and hazard mapping, as well as structural mitigation measures with the application of geosynthetics, have been exploited in localities where rain-triggered landslides are a potential threat to human life and property. For early warning, the use of critical Antecedent Precipitation Index (API) is proposed to be most appropriate. Furthermore, deterministic hazard mapping technique incorporating the modern day geospatial technologies can also provide a useful platform to analyze a number of scenarios including rainfall and land cover/land use variations. Finally, a parametric study on a designed and constructed reinforced soil slope with polyester polymer geogrids revealed that the stiffness of backfill is very sensitive to moisture contents or wetting due to rainfall which can influence the performance of reinforced slope structure.