Geomorphological investigations on landslide dams

Background: The study of past landslide dams and their consequences has gained a considerable significance for forecasting induced hydraulic risk on people and property. Landslide dams are rather frequent in Italy, where a broad climatic, geological and morphological variability characterize different part of the peninsula, and have already been studied in literature, focusing different geographical regions with different levels of detail. In order to develop specific tools to assess the landslide dam formation and stability, the first step is to realize a large data archive including a big number of data, collected with a consistent methodology to standardize the quality. Description: For this reason, this paper reports the results of an extensive bibliographic work and geomorphologic investigation on landslide dams that lead to the development of the wider systematic inventory in Italy. Through the revision and the update of scientific works and historical reports, three hundreds of landslide dams from the Alps to the Southern Apennine and Sicily were identified. During investigations and through cartographic and aerial photos interpretation, several geomorphic parameters of the landslide, the dam body, the valley and the lake, if any, have been determined, or estimated using historical and bibliographical documents analysis. Conclusions: The collected data were resumed in a database, formed by 57 information fields easy to collect and measure to privilege intuitive usability and future implementation. In order to describe the characteristics of landslide dams in Italy some specific analysis on the different types of landslide movements and their volume, the dam longevity, the main triggers and their geographical distribution were carried out

Geomorphic indexing of landslide dams evolution

AbstractLandslide dams are rather common events in hilly and mountainous areas and they occur when a landslide reaches a valley floor closing the riverbed. If they form a lake basin, unstable landslide dams can have catastrophic consequences when they occur in upstream of populated regions. Landslide dam behavior is not completely understood yet, however several studies suggested implementing geomorphological index in order to assess their formation and evolution. These indexes result from the composition of two or more morphological attributes that characterize the landslide (e.g. landslide volume or length) and the involved river valley (e.g. valley width).The objective of this work is the definition of a procedure, based on the joint use of different indexes, to assess landslide dams evolution over large areas (e.g. entire river catchment or even a region or a nation) and in short times, in order to be used for emergency response or for planning activities.About 300 landslide dam events collected in Italy were analyzed and some state-of-the-art geomorphological indexes were applied to characterize the damming phenomena at the national scale. To overcome some limitations of the aforementioned indexes, we introduce two new indexes: the Morphological Obstruction Index and the Hydromorphological Dam Stability Index. The former combines the river width and the landslide volume, and it can be used to identify the conditions associated to dam formation discriminating between circumstances where a landslide dam is formed and circumstances where it is not. The latter uses a simplified stream power formulation (combining the upstream catchment area and the local slope gradient) to account for the river energy. This index allows evaluating the stability of a dam in near real time as soon as it occurs and can be used to discriminate between stable and unstable dams.If compared with the reviewed state of the art indexes, the newly proposed ones show an improvement in the forecasting effectiveness and have the advantage of being based on morphometric input parameters that can be easily and quickly assessed on a distributed way even over large areas. We propose a tool that is based on the joint use of the newly proposed indexes and that can be used to provide fast and effective assessment on landslide dam formation and stability during emergency or planning activities

Additional file 1: of Geomorphological investigations on landslide dams

Landslide Dams DataBase. Description of data: archive of 300 Italian landslide dams described trough 57 information fields useful for events characterization. Both descriptive data and morphometric data are present. (PDF 4903 kb

Integration of remote sensing and offshore geophysical data for monitoring the short-term morphological evolution of an active volcanic flank: A case study from Stromboli Island

The Sciara del Fuoco (SdF) collapse scar at Stromboli is an active volcanic area affected by rapid morphological changes due to explosive/effusive eruptions and mass-wasting processes. The aim of this paper is to demonstrate the importance of an integrated analysis of multi-temporal remote sensing (photogrammetry, COSMO-SkyMed Synthetic Aperture Radar amplitude image) and marine geophysical data (multibeam and side scan sonar data) to characterize the main morphological, textural, and volumetric changes that occurred along the SdF slope in the 2020–2021 period. The analysis showed the marked erosive potential of the 19 May 2021 pyroclastic density current generated by a crater rim collapse, which mobilized a minimum volume of 44,000 m3 in the upper Sciara del Fuoco slope and eroded 350,000–400,000 m3 of material just considering the shallow-water setting. The analysis allowed us also to constrain the main factors controlling the emplacement of different lava flows and overflows during the monitored period. Despite the morphological continuity between the subaerial and submarine slope, textural variations in the SdF primarily depend on different processes and characteristics of the subaerial slope, the coastal area, the nearshore, and “deeper” marine areas

Recent technological and methodological advances for the investigation of landslide dams

River-damming by landslides is a widespread phenomenon around the world. Recent advances in remote sensing technology and the rising commercial availability of their products enable the assemblage of increasingly more complete inventories and improve monitoring efforts. On the ground, multi-method dating campaigns enhance our understanding of the timelines of dam formation and failure. In comparison to single-dating methods, they reduce uncertainty by using different materials from the landslide deposit, facilitate the advantages of each method, and consider the deposit and the source area. They can pin dates on the time of lake drainage where backwater sediments are included in the dating campaign and thus inform about dam longevity. Geophysical methods provide non-invasive and rapid methods to investigate the properties and interior conditions of landslide dams. By identifying, e.g. evolving zones of weakness and saturation they can aid in the monitoring of a dam in addition to providing information on interior stratification for scientific research. To verify results from geophysical campaigns, and to add details of dam interior structures and geotechnical properties, knowledge of their sedimentology is essential. This information is gathered at sections from breached dams, other (partially) eroded landslide deposits, and through laboratory testing of sampled material. Combining the knowledge gained from all these methods with insights from blast-fill and embankment dam construction, physical and numerical modelling in multi-disciplinary research projects is the way forward in landslide dam research, assessment and monitoring. This review offers a broad, yet concise overview of the state-of-the-art in the aforementioned research fields. It completes the review of Fan et al. (2020) on the formation and impact on landslide dams