NH
Natural Hazards

Geomorphology

Alpine rock instability events and mountain permafrost

Alpine rock instability events and mountain permafrost
Rockfalls, rock slides and rock avalanches in high mountains

The terms rockfall, rock avalanche and rockslide are often used interchangeably. Different authors have proposed definitions based on volume thresholds, but the establishment of fixed boundaries can be tricky. Rockfall can be defined as the detachment of a mass of rock from a steep rock-wall, along discontinuities and/or through rock bridge breakage, and its free or bounding downslope movement under the influence of gravity[1,2]. Usually, we use this term when the volume is limited, and there is little dynamic interaction between rock fragments, which interact mainly with the substrate. Rockslides involve a larger volume (up to 100,000 m3) and the blocks often break in smaller fragments as they travel down the slope. In both rockfall and rockslide, the blocks move downslope mainly by falling, bouncing and rolling. On the other hand, rock avalanches involve the disintegration of rock fragments to form a downslope rapidly flowing, granular mass demonstrating exceptionally high mobility[3]. The size of these rock failures can vary from single boulders to several million cubic meters (e.g. the catastrophic failures of Triolet, 1717, and Randa, 1991).

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InSAR Norway: the big eye on Norwegian unstable rock slopes

InSAR Norway: the big eye on Norwegian unstable rock slopes

Marie Keiding is a researcher in the Geohazard and Earth Observation team at the Geological Survey of Norway. Together with her colleague, John Dehls, who is leading the project, she works to develop and operate the new mapping service called InSAR Norway.

Before we start, let’s briefly describe what is InSAR. First, the Synthetic Aperture Radar (SAR) is a day and night operational imaging system that can be operated from satellite aircraft or ground and has high capabilities of penetrating clouds because it uses microwaves. Its ‘interferometric configuration’, Interferometric SAR or InSAR, uses two or more SAR images to generate maps of surface deformation or digital elevation models. This is made by calculating differences in the phase of the waves returning to the sensor, as a function of the satellite position and time of acquisition.

Measurements of phase variations are possible only in those pixels of the image where the signal maintains a sufficient coherence between different acquisitions. For this reason, InSAR techniques are particularly suitable to monitor relatively small deformations, in the order of millimetres to centimetres.

Hi Marie, can you tell what is InSAR Norway?

InSAR Norway is the first free and open, nationwide, [Read More]

Anthropogenic changes of the landscape and natural hazards

Anthropogenic changes of the landscape and natural hazards

In this post, I had the pleasure to interview Paolo Tarolli, a very active member of the EGU community and a brilliant scientist. He is Professor in Water Resources Management and Integrated Watershed Management, and head of Earth Surface Processes and Society research group at the Università degli Studi di Padova (Italy). He has a PhD in Environmental Watershed Management and Geomatics and has worked as academic staff at the Università degli Studi di Padova since 2011. He was Visiting Professor at several universities (e.g. China University of Geosciences, Guangzhou University, National Cheng Kung University, EPFL), and Adjunct Professor at University of Georgia and Università Politecnica delle Marche.

Paolo Tarolli is also very active in science dissemination, being Executive Editor of the open access journal Natural Hazards and Earth System Sciences (NHESS) and Science Officer of the Natural Hazards division (NH6 remote sensing & hazards) at the European Geosciences Union (EGU). He is also a member of the European Geosciences Union, the American Geophysical Union, and the British Society for Geomorphology.

His fields of expertise include digital terrain analysis, earth surface processes analysis, natural hazards, geomorphology, hydro-geomorphology, lidar, structure-from-motion photogrammetry; new research directions include the analysis of topographic signatures of human activities from local to regional scale.

1) Humans are having an increasing impact on the Earth, and the term Anthropocene is now commonly used to define the period we are living in to highlight the strong influence of human beings. How are humans shaping the Earth?

 

Conceptual diagram of long-term changes in sociocultural systems, cultural inheritances, societal scale, energy use and anthropogenic geomorphic features (source: Tarolli et al. 2019, Progress in Physical Geography, doi:10.1177/0309133318825284)

Human societies have been reshaping the geomorphology of landscapes for thousands of years, producing anthropogenic geomorphic features ranging from earthworks and ditches to settlements, agricultural terraces, ports, roads, canals, airports and constructed wetlands that have distinct characteristics compared with landforms produced by natural processes. Human societies are transforming the geomorphology of landscapes at increasing rates and scales across the globe. These anthropogenic patterns, directly and indirectly, alter Earth surface processes while reflecting the sociocultural conditions of the societies that produced them. In my recent paper published in Progress in Physical Geography[1] (a research collaboration with some colleagues with a different background, e.g. geomorphology, ecology and archaeology), we introduced the concept of “sociocultural fingerprints”. We connected the novel Earth system processes provided by the emergence and evolution of human societies with their continuous shaping and reshaping of Earth’s geomorphology from the deep past into the foreseeable future. We underlined the opportunity to recognize the geomorphic signatures of sociocultural fingerprints across Earth’s land surface using high-resolution remote sensing[2] combined with a theoretical framework that integrates the natural and sociocultural forces that have and will shape the landscapes of the Anthropocene. Doing so, the long-term dynamics of anthropogenic landscapes can be more effectively investigated and understood, towards more sustainable management of the Earth system.

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Combining geomorphology, geomorphometry and natural hazards research: the way forward

Combining geomorphology, geomorphometry and natural hazards research: the way forward

Today I have the honour to introduce a friend and a brilliant scientist that recently won the 2019 Arne Richter Award for Outstanding Early Career Scientists of the EGU, Dr Giulia Sofia. Dr Sofia is currently Assistant Research Professor at the University of Connecticut (USA) in the Hydrometeorology and Hydrologic Remote Sensing group. She received a B.S. and M.S. in Forestry Science, and PhD (2012) in Water Resources, Soil Conservation & Watershed Management from the University of Padova (Italy). Her area of research is geomorphology and digital terrain analysis, with a special interest in feature extraction from high-resolution topography. Her recent research interest concerns anthropogenic landscapes, incorporating the related human-induced processes. Her interdisciplinary research background is the reason behind today interview, to shed some light on the interrelation that geomorphology has with natural hazard research.

1. Hello Giulia. Can you please tell us what geomorphology and geomorphometry are?

Think about looking at a landscape, and working out how each earth surface process, such as air, water, and ice, can mould it. Think about piecing together the history and life of such a landscape place by studying landforms and sediments, and how they interact(ed). Well, this is geomorphology: the science of landforms, their processes, forms and sediments at the surface of the Earth, and sometimes other planets. Geomorphometry, on the other hand, is the science of quantitative land-surface analysis. It draws upon mathematics, computer vision, machine learning, image-processing techniques and statistics to quantify the shape of earth’s topography at various spatial and temporal scales. [Read More]