GM7 – Hillslope Geomorphology, Soil Erosion, and Gravitational Processes
Geomorphic processes in the context of land cover dynamics, climate variability and evolving topographic patterns
Analysing the geomorphic response to environmental change is crucial to improve the understanding, interpretation and prediction of surface process activity. Environmental drivers such as land cover and land use change, climate variability and tectonic activity are mutable in space and time, which renders the analysis of their impact on Earth surface dynamics anything but trivial. In turn, geomorphic processes have a strong impact on both natural ecosystems and artificially transformed land surfaces, with consequences ranging from increasing environmental diversity to economic damage.
This session aims to cluster latest advances in land surface research that address interrelationships between land cover dynamics, climate, evolving topography and geomorphic processes. Herein, the focus is set on the analysis, modelling and prediction of land surface processes that are linked to:
1) Natural and anthropogenic land cover dynamics, including land use changes, management practices, cultivation of field crops or grassland management, soil reinforcement of different vegetation types and parameterisation of prediction models.
2) Climate variability on a variety of spatial and temporal scales, from freeze-thaw cycles, monsoonal precipitation and extreme climatic events to Plio-Pleistocene glacial cycles and Late-Pleistocene to Holocene climatic changes.
Studies are welcome that pay heed on the geomorphic response to changes in land cover or climate, as well as the resulting feedbacks between land cover, climate and Earth surface dynamics over different temporal and spatial scales.
Denudational hillslope and fluvial processes, sedimentary budgets, and landscape responses to global environmental changes
Denudation, including both chemical and mechanical processes, is of high relevance for Earth surface and landscape development and the transfers of solutes, nutrients and sediments from slope and headwater systems through the main stem of drainage basin systems to ocean basins. Denudational slope and fluvial processes are controlled by a range of environmental drivers and can be significantly affected by man-made activities. Only if we have a better quantitative knowledge of drivers, mechanisms and rates of Holocene to contemporary denudational processes across a range of different climatic environments, an improved assessment of the possible effects of global environmental changes (e.g., higher frequencies of extreme rainfall events, accelerated permafrost thawing, rapid glacier retreat), anthropogenic impacts and other disturbances (e.g., land use, fires, earthquakes) on denudation can be achieved.
This session combines contributions on denudational hillslope and fluvial processes, sedimentary budgets and landscape responses to environmental changes in different morphoclimates, including both undisturbed and anthropogenically modified landscapes. The presented studies apply a diverse set of tools and data analyses, including up to date field measurements and monitoring techniques, remotely sensed/GIS-based analyses, modelling, geochemical and fingerprinting measurements and techniques, dendrochronological approaches, and cosmogenic radionuclide dating.
This session is organized by the I.A.G./A.I.G. Working Group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE).
Mechanics of mass flows and granular-fluid mixture flows: rheology, modeling and applications
Prediction of the areas threatened by landslides and gravity-driven mass flows are a key part of hazard assessment in mountainous regions. Whatever the material transported (debris, snow, etc.), the granular flow process involves determining the initiation mechanisms, initial volume, physical transport, entrainment processes as well as deposition and phase-separation mechanisms. Because of the number of scientific disciplines needed to solve it, there is a substantial benefit from interdisciplinary research. Furthermore, the definition of a unified rheology that accounts for the different regimes characterizing granular-fluid mixture flows is still lacking. The co-existence of the
collisional regime and the dense regime that have a very different behavior, makes the definition of a proper rheology quite challenging. So is the transition from dilute to dense regimes in granular-fluid
This session aims to bring together new research results from a variety of different approaches to understanding these kinds of processes. In particular, we encourage presentations on physical modelling, innovative laboratory research, theoretical studies on the physics of multiphase and multiscale phenomena and detailed field observations, which yield insight into the triggering mechanisms, the mass movement or mass flow process. Another important aspect, still unclear, that will be addressed in the session, is the mechanism and consequence of grain sorting and particle-fluid separation, entrainment and deposition in debris and hyperconcentrated flows. A proper description of the granular-fluid mixture flow phenomena is fundamental in order to properly define the design criteria of the protection structures and to have reliable risk maps. So, contributions related to the numerical modelling of landslides and granular geophysical flows, including torrential sediment transport, debris flows, rock and snow avalanches, and similar flows are expected.
Selected contributions will be considered for a special issue of a relevant international journal.
Rockfalls, rockslides and rock avalanches: Mechanics, dynamics, and new insights from novel data
Rockfalls, rockslides and rock avalanches are fundamental modes of erosion on steep hillslopes, and among the primary hazards in steep alpine terrain. To better understand the processes driving rock slope degradation, mechanisms contributing to the triggering, transport, and deposition of resulting rock slope instabilities, and mitigation measures for associated hazards, we must develop insight into both the physics of intact and rock mass failure and the dynamics of transport processes. This session aims to bring together state-of-the-art methods for predicting, assessing, quantifying, and protecting against rock slope hazards. We seek innovative contributions from investigators dealing with all stages of rock slope hazards, from weathering and/or damage accumulation, through detachment, transport and deposition, and finally to the development of protection and mitigation measures. In particular, we seek studies presenting new theoretical, numerical or probabilistic modelling approaches, novel data sets derived from laboratory, in situ, or remote sensing applications, and state-of-the-art approaches to social, structural, or natural protection measures.
Large slope instabilities: characterisation, dating, triggering, monitoring and modelling
Large slope instabilities have been frequently recognised in areas with different lithological (sedimentary, igneous, metamorphic rocks) and geological domains (cordillera, volcanic, etc.). Slow to very fast moving, complex mass movements have been recognized and sometimes described as strongly interrelated. Many types of slope instabilities can be grouped within this broad class, each presenting different types of hazard and risk. Some major aspects of these slope instabilities are still understudied and debated, namely:
- their regional distribution and relevance;
- triggering and controlling factors, including possible climatic changes;
- hydrological boundary conditions and evolution or control of internal hydrogeological conditions;
- mechanical controls in terms of physical mechanical properties of failure surfaces and shear zones
- dating of initial movements and reactivation episodes;
- style and state of past and present activity;
- passive and/or active control by structural-tectonic elements of the bedrock geology;
- possible styles of evolution and consequent modeling approaches;
- assessment of related hazard;
- influence of external anthropogenic factors and effects on structures and infrastructures (e.g. tunnels, dams, bridges);
- role on the general erosional and sediment yield regime at the local or mountain belt scale;
- best technologies and approaches for implementing a correct monitoring and warning system and for the interpretation of monitoring data in terms of landslide activity and behavior.
Study of these instabilities requires a multidisciplinary approach involving geology, geomorphology, geomechanics, hydro-geochemistry, and geophysics. These phenomena have been recognized on Earth as well as on other planetary bodies (e.g. Mars, Moon).
Trenching and drilling can be used for material characterization, recognition of episodes of activity, and sampling in slow slope movements. At the same time many different approaches can be used for monitoring and establishing of warning thresholds and systems for such phenomena.
Geophysical survey methods can be used to assess both the geometrical and geomechanical characteristics of the unstable mass. Different dating techniques can be applied to determine the age and stages of movement. Many modeling approaches can be applied to evaluate instability and failure (e.g. displacement and velocity thresholds), triggering mechanisms (e.g. rainfall, seismicity, volcanic eruption, deglaciation), failure propagation, rapid mass movements (rock avalanches, debris avalanches and flows), and related secondary failures (rock fall and debris flows).
Studies of hydraulic and hydrologic boundary conditions and hydrochemistry are involved, both at the moment of initial failure and, later, during reactivation. The impacts of such instabilities on structures and human activities can be substantial and of a variety of forms (e.g. deformation or failure of structures and infrastructure, burial of developed areas, etc.).
Furthermore, the local and regional sediment yield could be influenced by the landsliding activity and different landslides (e.g. type, size) can play different roles.
From slow-spreading to rapid mass-movements in alpine and volcano-tectonic settings. Advances on monitoring, modelling and risk management
Weathering, tectonics, gravitational and volcanic processes can transform the regular sediment delivery from unstable slopes in catastrophic landslides. Mass spreading and mass wasting processes can potentially evolve in rapid landslides are among the most dangerous natural hazards that threaten people and infrastructures, directly or through secondary events like tsunamis.
Documentation and monitoring of these phenomena requires the adoption of a variety of methods. The difficulties in detecting their initiation and propagation have progressively prompted research into a wide variety of monitoring technologies. Nowadays, the combination of distributed sensor networks and remote sensing techniques represents a unique opportunity to gather direct observations. A growing number of scientists with diverse backgrounds are dealing with the monitoring of processes ranging from volcano flak deformations to large debris flows and lahars. However, there is a need of improving quality and quantity of both documentation procedures and instrumental observations that would provide knowledge for more accurate hazard assessment, land-use planning and design of mitigation measures, including early warning systems. Successful strategies for hazard assessment and risk reduction would imply integrated methodology for instability detection, modeling and forecasting. Nevertheless, only few studies exist to date in which numerical modelling integrate geological, geophysical, geodetic studies with the aim of understanding and managing of terrestrial and subaqueous volcano slope instability.
Scientists working in the fields of hazard mapping, modelling, monitoring and early warning are invited to present their recent advancements in research and feedback from practitioners and decision makers. We encourage multidisciplinary contributions that integrate field-based on-shore and submarine studies (geological, geochemical), geomorphological mapping and account collection, with advanced techniques, as remote sensing data analysis, geophysical investigations, ground-based monitoring systems, and numerical and analogical modelling of volcano spreading, slope stability and debris flows.
Prediction and forecasting of landslides (including Sergey Soloviev Medal Lecture by Kyoji Sassa)
Landslides are ubiquitous geomorphological phenomena with potentially catastrophic consequences. In several countries landslide mortality can be higher than that of any other natural hazard. Predicting landslides is a difficult task that is of both scientific interest and societal relevance that may help save lives and protect individual properties and collective resources. The session focuses on innovative methods and techniques to predict landslide occurrence, including the location, time, size, destructiveness of individual and multiple slope failures. All landslide types are considered, from fast rockfalls to rapid debris flows, from slow slides to very rapid rock avalanches. All geographical scales are considered, from the local to the global scale. Of interest are contributions investigating theoretical aspects of natural hazard prediction, with emphasis on landslide forecasting, including conceptual, mathematical, physical, statistical, numerical and computational problems, and applied contributions demonstrating, with examples, the possibility or the lack of a possibility to predict individual or multiple landslides, or specific landslide characteristics. Of particular interest are contributions aimed at: the evaluation of the quality of landslide forecasts; the comparison of the performance of different forecasting models; the use of landslide forecasts in operational systems; and investigations of the potential for the exploitation of new or emerging technologies e.g., monitoring, computational, Earth observation technologies, in order to improve our ability to predict landslides. We anticipate that the most relevant contributions will be collected in the special issue of an international journal.
Wildfire in the Environment: Causes, impacts and management.
Wildfire is a global phenomenon responsible in each summer for tremendous environmental, social and economic losses. In the last two years, many lives were lost during the fires occurred in Portugal, Greece and California. The conjunction of land abandonment, long drought periods, flammable monocultures, lack of forest management and urban development planning, resulted in an unprecedented destruction. This phenomenon have become a persistent threat worldwide, and this risk may increase in the future due to the combination of future fire-prone climate, together with the recent trends of afforestation, land abandonment and fire suppression.
A reflection focused in these variables is essential to understand the recurrence of these extreme fires, and the consequent fatalities that occurred in Portugal, California and Greece. These high-severity mega-fires have also an important impact on the environment as a result of the reduction of vegetation cover and high volatilization of nutrients. Despite the fact that several ecosystems such as the Mediterranean have a high resilience to fires, the high wildfire recurrence is reducing their capacity for recuperation, contributing importantly to land degradation.
The aim of this session is to join researchers that study fire effects on the ecosystems, from prevention to suppression, wildfire modelling, climate change impacts on fire and post-wildfire impacts, either by means of laboratory, field experiments, or numerical modelling. It is time for scientists to join their strengths to give accurate answers to prevent and mitigate the effects of wildfires.
Control works and soil conservation techniques for watershed management and forest protection: effect evaluation and novel design criteria
Structures and techniques aiming at controlling sediment transport-related or erosion-related issues are numerous and sometimes very old. Hillslope management and bioengineering, reforestation, and torrent control works using transverse structures, as check dams and more recently open check dams, are common all over the world to curtail soil erosion and torrential hazards. These actions may be launched for the control of sediment supply (i) to the stream fans and valley rivers for flood protection, (ii) to dam reservoirs for water storage, and basically, (iii) for the mere mountain soil conservation and agriculture protection. The profound objectives of each action are diverse and vary depending on the geomorphic context and local state of the sediment cascade, where the implementation takes place. The lack of sufficient understanding of soil erosion processes, sediment (dis)connectivity activation and torrential hazards propagation continues to make soil erosion prevention and torrent control complex topics with insufficient implementation criteria and long-term effect assessment methods. Consequently, some projects still experience disappointing results due to many different reasons, such as poor construction quality, inadequate location or lack of adequate design criteria. In addition, these actions induce secondary effects (e.g., block of the downstream transfer of water and sediments), which should be better controlled or possibly prevented. This EGU session aims at gathering the whole community interested in human actions on control works and soil conservation techniques at the waterhed scale. Any contributions to the understanding of soil erosion control and sediment transport management based on detailed field experiences, high-quality laboratory works, validated numerical models and effectiveness assessment methods are welcome. Using the knowledge gaps identified above as a starting point, the proposed EGU session wishes, for the third year, to join and share scientific and technical opinions from all around the world, related to the legacy effects of soil erosion control and (open) check-dam design criteria, highlighting the role of the complex interactions between ecological elements, geomorphic processes and engineering activities.
Landslide investigation using Remote Sensing and Geophysics
Remarkable technological progress in remote sensing and geophysical surveying, together with the recent development of innovative data treatment techniques are providing new scientific opportunities to investigate landslide processes and hazards all over the world. Remote sensing and geophysics, as complementary techniques for the characterization and monitoring of landslides, offer the possibility to effectively infer and correlate an improved information of the shallow -or even deep- geological layers for the development of conceptual and numerical models of slope instabilities. Their ability to provide integrated information about geometry, rheological properties, water content, rate of deformation and time-varying changes of these parameters is ultimately controlling our capability to detect, model and predict landslide processes at different scales (from site specific to regional studies) and over multiple dimensions (2D, 3D and 4D).
This session welcomes innovative contributions and lessons learned from significant case studies using a myriad of remote sensing and geophysical techniques and algorithms, including optical and radar sensors, new satellite constellations (including the emergence of the Sentinel-1A and 1B), Remotely Piloted Aircraft Systems (RPAS) / Unmanned Aerial Vehicles (UAVs) / drones, high spatial resolution airborne LiDAR missions, terrestrial LIDAR, Structure-from-Motion (SfM) photogrammetry, time-lapse cameras, multi-temporal Synthetic Aperture Radar differential interferometry (DInSAR), GPS surveying, Seismic Reflection, Surface Waves Analysis, Geophysical Tomography (seismic and electrical), Seismic Ambient Vibrations, Acoustic Emissions, Electro-Magnetic surveys, low-cost (/cost-efficient) sensors, commercial use of small satellites, Multi-Spectral images, Real time monitoring, in-situ sensing, etc.
The session will provide an overview of the progress and new scientific approaches of Earth Observation (EO) applications, as well as of surface- and borehole-based geophysical surveying for investigating landslides. A special emphasis is expected not only on the collection but also on the interpretation and use of high spatiotemporal resolution data to characterize the main components of slope stability and dynamics, including the type of material, geometrical and mechanical properties, depth of water table, saturation conditions and ground deformation over time. The discussion of recent experiences and the use of advanced processing methods and innovative algorithms that integrate data from remote sensing and geophysics with other survey types are highly encouraged, especially with regard to their use on (rapid) mapping, characterizing, monitoring and modelling of landslide behaviour, as well as their integration on real-time Early Warning Systems and other prevention and protection initiatives. Other pioneering applications using big data treatment techniques, data-driven approaches and/or open code initiatives for investigating mass movements using the above described techniques will also be considered on this session.
We invited prof. Denis Jongmans (Isterre, Université Grenoble Alpes, France), as guest speaker for the session.
Field and modelling approaches for the assessment of hydrogeological and engineering problems in the complex karst environment
Karst environments are characterized by distinctive landforms and unique hydrologic behaviors. Karst systems are commonly extremely complex, heterogeneous, and very difficult to manage because their formation and evolution are controlled by a wide range of geological, hydrological, geochemical and biological processes. Further, karst systems are extremely vulnerable due to the direct connection between the surface and subsurface compartments through conduit networks.
The great variability and unique connectivity may result in serious engineering problems: on one hand, karst groundwater resources are readily contaminated by pollution because of the rapidity of conduit flow; on the other hand, the presence of karst conduits that weakens the strength of the rock mass may lead to serious natural and human-induced hazards. The plan and development of engineering projects in karst environments thus require: 1) an enhanced understanding of natural processes that govern the initiation and evolution of karst systems through both field and modelling approaches, and 2) specific interdisciplinary approaches aiming at at better assessing the associated uncertainties and minimizing the detrimental effects of hazardous processes and environmental problems.
This session calls for abstracts on research related to geomorphology, hydrogeology, engineering geology, and/or hazard mitigation in karst environments in the context of climate change and increased human disturbance. It also aims to discuss various characterization and modelling methods applied in each specific research domain, with their consequences on the understanding of the whole process of karst genesis and functioning.