LAND-SUITE V1.0: a suite of tools for statistically based landslide susceptibility zonation

In the past 50 years, a large variety of statisti- cally based models and methods for landslide susceptibility mapping and zonation have been proposed in the literature. The methods, which are applicable to a large range of spa- tial scales, use a large variety of input thematic data, differ- ent model combinations, and several approaches to evaluate the models’ performance. Despite the numerous applications available in the literature, a standard approach for suscepti- bility modeling and zonation is still missing. The literature search revealed that several software pro- gram and tools are available to evaluate regional slope stability using physically based analysis, but only a few use statistically based approaches. Among them, LAND-SE (LANDslide Susceptibility Evaluation) provides the possi- bility to perform and combine different statistical suscepti- bility models and to evaluate their performances and asso- ciated uncertainties. This paper describes the structure and the functionalities of LAND-SUITE, a suite of tools for sta- tistically based landslide susceptibility modeling which in- tegrates LAND-SE. LAND-SUITE completes and extends LAND-SE, adding functionalities to (i) facilitate input data preparation, (ii) perform preliminary and exploratory analy- sis of the available data, and (iii) test different combinations of variables and select the optimal thematic/explanatory set. LAND-SUITE provides a tool to assist the user during the data preparatory phase and to perform diversified statistically based landslide susceptibility applications.The implementation and improvement of LAND-SUITE with respect to the version published by Rossi and Reichenbach (2016) were funded mainly using internal funds. Txomin Bornaetxea was financially supported by the postdoctoral fellowship program of the Basque Government (grant numbers POS_2020_2_0010) and hosted by the University of the Basque Country (UPV/EHU, group IT1678) in the framework of a scien- tific collaboration with the Geological Survey of Canada as well as during scientific collaborations with the Geomorphological Group of the Research Institute for the Geo-Hydrological Protection in Perugia, Italian National Research Council (CNR-IRPI

Probabilistic identification of rockfall source areas at regional scale in El Hierro (Canary Islands, Spain)

Abstract Modelling rockfall phenomena is complex and requires various inputs, including an accurate location of the source areas. Source areas are controlled by geomorphological, geological, or other geo-environmental factors and may largely influence the results of the modelling. In the Canary Islands, rockfalls are extremely common and pose a major threat to society, costing lives, disrupting infrastructure, and destroying livelihoods. In 2011, the volcanic event on the island of El Hierro triggered numerous rockfalls that affected strategic infrastructures, with a substantial impact on the local population. During the emergency, the efforts performed to map the source areas and to model the rockfalls in the considerably steep landscape characterising the island were not trivial. To better identify the rockfall source areas, we propose a probabilistic modelling framework that applies a combination of multiple statistical models using the source area locations mapped in the field as the dependent variable and a set of thematic data as independent variables. The models use as input morphometric parameters derived from the Digital Elevation Model and lithological data as an expression of the mechanical behaviour of the rocks. The analysis of different training and validation scenarios allowed us to test the model sensitivity to the input data, select the optimal model training configuration, and evaluate the model applicability outside the training areas. The final map obtained from the model for the entire island of El Hierro provides the probability of a given location being a potential source area and can be used as the input for rockfall runout simulation modelling

Progress in Landslide Susceptibility Mapping over Europe Using Tier-Based Approaches

The European Thematic Strategy for Soil Protection aims, among other objectives, to ensure a sustainable use of soil. The legal instrument of the strategy, the proposed Framework Directive, suggests identifying priority areas of several soil threats including landslides using a coherent and compatible approach based on the use of common thematic data. In a first stage, this can be achieved through landslide susceptibility mapping using geographically nested, multi-step tiered approaches, where areas identified as of high susceptibility by a first, synoptic-scale Tier (Tier 1) can then be further assessed and mapped at larger scale by successive Tiers. In order to identify areas prone to landslides at European scale (Tier 1), a number of thematic terrain and environmental data sets already available for the whole of Europe can be used as input for a continental scale susceptibility model. However, since no coherent landslide inventory data is available at the moment over the whole continent, qualitative heuristic zonation approaches are proposed. For Tier 1 a preliminary, simplified model has been developed. It consists of an equally weighting combination of a reduced, continent-wide common dataset of landslide conditioning factors including soil parent material, slope angle and land cover, to derive a landslide susceptibility index using raster mapping units consisting of 1 x 1 km pixels. A preliminary European-wide susceptibility map has thus been produced at 1:1 Million scale, since this is compatible with that of the datasets used. The map has been validated by means of a ratio of effectiveness using samples from landslide inventories in Italy, Austria, Hungary and United Kingdom. Although not differentiated for specific geomorphological environments or specific landslide types, the experimental model reveals a relatively good performance in many European regions at a 1:1 Million scale. An additional Tier 1 susceptibility map at the same scale and using the same or equivalent thematic data as for the one above has been generated for six French departments using a heuristic, weighting-based multi-criteria evaluation model applied also to raster-cell mapping units. In this experiment, thematic data class weights have been differentiated for two stratification areas, namely mountains and plains, and four main landslide types. Separate susceptibility maps for each landslide type and a combined map for all types have been produced. Results have been validated using BRGM's BDMvT landslide inventory. Unlike Tier 1, Tier 2 assessment requires landslide inventory data and additional thematic data on conditioning factors which may not be available for all European countries. For the Tier 2, a nation-wide quantitative landslide susceptibility assessment has been performed for Italy by applying a statistical model. In this assessment, multivariate analysis was applied using bedrock, soil and climate data together with a number of derivatives from SRTM90 DEM. In addition, separate datasets from a historical landslide inventory were used for model training and validation respectively. The mapping units selected were based on administrative boundaries (municipalities). The performance of this nation-wide, quantitative susceptibility assessment has been evaluated using multi-temporal landslide inventory data. Finally, model limitations for Tier 1 are discussed, and recommendations for enhanced Tier 1 and Tier 2 models including additional thematic data for conditioning factors are drawn. This project is part of the collaborative research carried out within the European Landslide Expert Group coordinated by JRC in support to the EU Soil Thematic Strategy. It is also supported by the International Programme on Landslides of the International Consortium on Landslides.JRC.DDG.H.7-Land management and natural hazard

Update of the European Landslide Susceptibility Map (ELSUS Version 2)

We present an update of the initial version of the European Landslide Susceptibility Map (ELSUS Version 1) that was released in 2012 through the EU Joint Research Centre (JRC) European Soil Data Centre (ESDAC). The susceptibility evaluation methodology employed for the updated map ELSUS Version 2 presented in this paper is identical to the previous approach, and comprises the differentiation of the analyzed European area into seven climate-physiographical model zones, the use of a reduced set of spatial susceptibility predictors (shallow subsurface lithology, slope angle, and land cover), and model zone-specific heuristic spatial multicriteria evaluations (SMCE) for susceptibility mapping. The most important improvement for ELSUS version 2 is the replacement of the original “lithology” data set consisting of soil parent material information derived from the European Soil Database (ESDB) by new information derived from the digital version of the International Hydrogeological Map of Europe at scale 1:1.5 Million (IHME 1500). IHME lithology describes both consolidated and unconsolidated shallow geological materials over Europe and can be shown to have a higher significance for landslide susceptibility evaluation than the soil parent material derived from ESDB. Other improvements consist in the change of the mapping unit from 1 km to 200 m grid size and the incorporation of terrains not covered by ELSUS version 1 (e.g., Iceland, the Faroers, the Shetlands, and Cyprus). Additionally, the new ELSUS version 2 was calibrated and validated with an updated pan-European landslide inventory now containing more than 155,000 landslides (30% more than used for ELSUS version 1). The enhanced and updated landslide inventory and the higher quality of the “lithology” data enabled us to establish more consistent SMCE-schemes for the individual model zones. The enhancements of ELSUS Version 2 result in an overall increase of the predictive power of the map for about 10%, as indicated by ROC curve metrics obtained with the updated landslide inventory. However, the assessment still suffers from missing landslide information in many European terrains. It can be suspected that more distributed landslides information in specific model zones will further enhance the accuracy of ELSUS in the future.JRC.H.5-Land Resources Managemen

Geotechnics for rockfall assessment in the volcanic island of Gran Canaria (Canary Islands, Spain)

The island of Gran Canaria (Canary Islands, Spain) is characterized by a large variability of volcanic rocks reflecting its volcanic evolution. The geological map provided by Geological Survey of Spain at 1:25.000 scale shows more than 109 different lithologies and it is too complex for environmental and engineering purposes. This work presents a simplified geotechnical map with a small number of classes grouping up units with similar geotechnical behaviours. The lithologies were grouped using about 350 rock samples, collected in the seven major islands of the Archipelago. The geotechnical map was used to model rockfall hazard in the entire island of Gran Canaria, where rockfalls are an important threat. The rockfall map was validated with 128 rockfall events along the GC-200 road, located in the NW sector of Gran Canaria. About 96% of the events occurred along sections of the road where the number of expected trajectories is high or moderate.This work was carried out in the framework of two projects funded by the European Commission, Directorate-General Humanitarian Aid and Civil Protection (ECHO): SAFETY (Sentinel-1 for geohazard prevention and forecasting. Ref. ECHO/SUB/2015/718679/Prev02) and U-GEOHAZ (Geohazard Impact Assessment for Urban Areas. Grant Agreement No. 783169). This work has been partly funded by the University of Alicante in the framework of Quality Improvement Grant of PhD Program in Materials, Structures and Soil Engineering: Sustainable Construction, Salvador de Madariaga Mobility Program from the Spanish Ministry of Science (PRX18/00020) and the Industrial PhD Project GEODRON (IND2017/AMB-7789). We also appreciate the contribution of the MACASTAB project (Ref.: MAC/3.5b/027). The laboratory tests were carried out in the Laboratories of Building and Public Works from the Canarian Government. The methodology is also developed in the framework of the RISKCOAST project (Ref: SOE3/P4/E0868) funded by the European Regional Development Fund - Interreg programme (3rd call for proposals)

Exploitation of large archives of ERS and ENVISAT C-band SAR data to characterize ground deformations

In the last few years, several advances have been made in the use of radar images to detect, map and monitor ground deformations. DInSAR (Differential Synthetic Aperture Radar Interferometry) and A-DInSAR/PSI (Advanced DInSAR/Persistent Scatterers Interferometry) technologies have been successfully applied in the study of deformation phenomena induced by, for example, active tectonics, volcanic activity, ground water exploitation, mining, and landslides, both at local and regional scales. In this paper, the existing European Space Agency (ESA) archives (acquired as part of the FP7-DORIS project), which were collected by the ERS-1/2 and ENVISAT satellites operating in the microwave C-band, were analyzed and exploited to understand the dynamics of landslide and subsidence phenomena. In particular, this paper presents the results obtained as part of the FP7-DORIS project to demonstrate that the full exploitation of very long deformation time series (more than 15 years) can play a key role in understanding the dynamics of natural and human-induced hazards. © 2013 by the authors

COMPARISON OF SRTM ELEVATION DATA WITH CARTOGRAPHICALLY DERIVED DEMS IN ITALY

In this study we evaluated the quality of the DEM acquired by the Shuttle Radar Topography Mission(SRTM) for Italy through comparison with cartographically derived DEMs, available for the Italian territory.Comparison was carried out analyzing differences in elevation and slope angle at regional scale. Thecomparisons carried out at the regional scale disclose a general increase in slope angle values with thechange in resolution and a moderate difference in mean elevation. From these results, we highlighted thatimproved surface-based DEMs, based on advanced SAR, have vertical values that approach or exceedthat of current medium resolution surface products. Moreover, this study helps to provide a benchmarkagainst which future DEM products can be evaluated

Approaches for Delineating Areas Susceptible to Landslides in the Framework of the European Soil Thematic Strategy

In the framework of the European Soil Thematic Strategy, and the associated preparation of a directive on the protection and sustainable use of soil, landslides were recognized as a soil threat requiring specific strategies for risk assessment and management. The criteria for harmonized risk area delineation proposed by the Soil Information Working Group (SIWG) of the European Soil Bureau Network (ESBN) adopt a nested geographical approach based on ¿Tiers¿ and exploit thematic and environmental data of different type, quality, and resolution using a variety of methodological and technological approaches suitable for the spatial evaluation of any specific soil threat. The main requirement for a continent-wide ¿Tier 1¿ assessment for the delineation of areas subject to soil threats in Europe is the availability of relevant input data. At present, such a continent-wide assessment of landslide susceptibility in Europe is feasible only when adopting a qualitative evaluation technique since high-quality, pan-European landslide conditioning- and triggering factor data is available, but a European-wide coverage of landslide locations is missing. ¿Tier 1¿ landslide susceptibility evaluations are described to serve for general risk/priority area identification and must at least be able to discriminate areas subjected to more detailed spatial assessments against those where no further action has to be taken. Quantitative evaluations of landslide susceptibility according to a ¿Tier 2¿ assessment require the availability of landslide inventory maps and databases. We outline the current advances towards the development of a common methodology for assessing the landslide threat in Europe. We refer to limitations, data needs and future work to be carried out, and present examples of nationwide assessments.JRC.H.7-Land management and natural hazard

Improvements in pan-European landslide susceptibility assessment: The ELSUS Version 2 map

An update of the initial European Landslide Susceptibility Map (ELSUS 1000 Version 1) released in 2013 through the EC Joint Research Centre (JRC) European Soil Data Centre (ESDAC) is presented. As in the previous map, the methodology employed for the updated map ELSUS Version 2 comprises the division of the analyzed European area into seven climate-physiographic model zones, the use of a reduced set of spatial susceptibility predictors (slope angle, shallow subsurface lithology, and land cover), and specific heuristic spatial multicriteria evaluations (SMCE) of model zones for susceptibility mapping. However, in the improved new version of ELSUS the original “lithology” data set consisting of soil parent material information derived from the European Soil Database (ESDB) is replaced by new information obtained from the International Hydrogeological Map of Europe at 1:1.5 Million scale (IHME 1500). IHME lithology describes both consolidated and unconsolidated shallow geologic materials over Europe, showing a higher significance for landslide susceptibility assessment than the soil parent material above. Additionally, in version 2 the mapping unit cell size increases from 1 km to 200 m and new areas such as Iceland, Cyprus, the Faroes, and the Shetlands are covered on the map. Moreover, the new ELSUS Version 2 has been calibrated and validated with an updated pan-European landslide inventory now containing more than 155,000 landslides (30% more than used for ELSUS Version 1). A further improvement is the geographic adjustment of the slope angle, lithology and land cover spatial susceptibility criteria to uniform coastline information derived from VMAP 1000 data now allowing for an area-wide susceptibility mapping of European coastal areas. The expanded and updated landslide inventory and the higher quality of the “lithology” data have enabled us to establish more consistent SMCE schemes for the individual model zones. The enhancements of ELSUS Version 2 result in an overall increase of the predictive power of the map of about 10%, as shown by ROC curve metrics obtained with the updated landslide inventory. It can be assumed that more distributed landslide information in specific model zones will further improve the accuracy of ELSUS in the future.JRC.H.5-Land Resources Managemen