Frontiers in Geomorphology - Earth surface interactions, couplings and feedbacks

Landscapes, and how they change over time, provide the foundations of life and affect the ecosystems and human activities that can exist on Earth. Yet, there appears to be no single axis of causality between landscape and Earth surface processes, but rather, each entity can exert a simultaneous influence on the other over a wide range of temporal and spatial scales. We are just starting to realise and explore the modes, trajectories and effects of these coupled systems, and to trace and infer the often non-linear feedback mechanisms.
Geomorphology inevitably stands in the center of an emerging science devoted to the Earth's surface, where strong couplings link human dynamics, biology, biochemistry, geochemistry, geology, hydrology, geomorphology, soil science, and atmospheric dynamics, including past and ongoing climate changes.
Motivated by the importance of understanding Earth surface interactions, couplings and feedbacks on a rapidly changing globe, this session will bring together a series of invited speakers to provide insights and perspectives on this hot topic from across the field of geomorphology.

Including GM Division Outstanding ECS Award Lecture 2021
Convener: Giulia Sofia | Co-conveners: Daniel Parsons, Matteo Spagnolo, Andrea Zerboni
| Thu, 29 Apr, 13:30–15:00 (CEST)

Presentations: Thu, 29 Apr

Chairpersons: Daniel Parsons, Giulia Sofia
GM Division Outstanding ECS Award Lecture 2021
Louise Slater

Many fluvial processes have long been treated as stationary, fluctuating within an unchanging envelope of variability. However, a large body of evidence has revealed that shifts in climate, land cover and river basin management may manifest locally along river networks through hydrological and geomorphic change. Measuring the effect of these changes on the local flood risk requires a large sample approach. Large sample geomorphology has existed for many decades but is currently undergoing a step-change characterised by computational techniques, scalability, and growing interdisciplinarity. This step-change has been assisted by the availability of remotely sensed datasets describing the land surface (including satellite, airborne and ground-based acquisitions), alongside other datasets more conventionally employed in hydro-climatology (including weather and climate observations, reanalysis, and projections). Within this context, data science and AI approaches facilitate pattern detection and the testing of both long-standing and emerging theories, to derive insights about processes and mechanisms at play. Here, we will discuss the value of large-sample geomorphology for understanding nonstationary landscapes and the associated flood risk. We will provide insights into the promise and pitfalls of large-sample approaches within an evolving discipline, and discuss ways forward, with more systematic hypothesis testing and developing projections of future change.    

How to cite: Slater, L.: Detecting flood drivers through large-sample geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12838,, 2021.

Paul Santi and Francis Rengers

Wildfire is a global phenomenon that is expected to increase in extent and severity due to shifting land management practices and climate change. It removes vegetation, deposits ash, influences water-repellent soil formation, and physically weathers rock. These changes typically lead to increased erosion through sheetwash, rilling, rock spalling, and dry ravel, as well as increased mass movement in the form of floods, debris flows, rockfall, and landslides. Post-wildfire changes in these processes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Research has documented increases in erosion after wildfire ranging from 2-1000 times the pre-fire rates. Post-wildfire landscape lowering by erosion has been measured in the western U.S. at magnitudes of 2 mm per year, with sediment delivery at the mouths of canyons increased in the range of 160-1000% during the post-wildfire window of disturbance. Furthermore, post-wildfire sediment transport enhances the development of alluvial fans, debris fans, and talus cones. Debris-flow likelihood is increased following wildfire, such that modest rainstorms with <2 year recurrence intervals are typically sufficient to trigger debris flows with volumes much larger (270-540%) than at unburned sites. In the western U.S., as much as 25-50% of alluvial fan accumulation can be attributed to post-wildfire debris flows and other post-wildfire fluvial transport. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.  Consequently, wildfire is an important agent of geomorphic change.

How to cite: Santi, P. and Rengers, F.: Influence of Wildfire on Earth Surface Processes and Geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-948,, 2021.

Philip S.J. Minderhoud, Sepehr Eslami, and Gualbert Oude Essink

Deltas have been a focal point for geomorphologists for decades, as these geologically young and transient landforms are formed and influenced by the interplay of many Earth surface processes. Hence delta systems are highly dynamic with sophisticated couplings and feedbacks that often span across multiple scientific domains. Climate change (including sea-level rise) and upstream damming alter the boundary conditions that determine how deltas form, grow, or shrink, however, the impact of human pressures within the delta system is becoming increasingly dominant in driving environmental change. Rapid economic development and urbanization of the world deltas often lead to overexploitation and exhaustion of natural resources, such as fresh water and sand. The impacts of such human-induced overexploitations have recently been shown to be dominant in driving the current geomorphological changes witnessed in the Mekong delta. The overexploitation of fresh groundwater is caused wide-spread decrease in groundwater levels in the aquifer-system, which leads to accelerated rates of land subsidence and salinization of fresh groundwater resources. The extraction of riverbed sand and upstream impoundments deepen the river channels which changes the fluvial and tidal dynamics leading to increased riverbank erosion and surface water salinization.

Recent advances in geomorphological system understanding of the Mekong delta have revealed its critical state and show its disastrous trajectory towards which it is going when current business-as-usual practices are continued in the next decades. The scientific findings from several research groups have been instrumental to the quick increase in awareness and sense of urgency within governmental bodies and has laid the foundation for the development of more system-inclusive delta policy. Although the road towards effective mitigation of the root causes is still long, multi-disciplinary geomorphological research was effective in quantifying gradual but crucial human-induced changes in the delta system. This talk highlights some of the key scientific findings in the Mekong delta and elaborates on how science was instrumental to make the issues visible to a larger community of stakeholders and policymakers.

How to cite: Minderhoud, P. S. J., Eslami, S., and Oude Essink, G.: How geomorphology can shape policy - Advances in system understanding of the Mekong delta reveal large anthropogenic impacts and drive policy change , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2971,, 2021.

Onn Crouvi, Rivka Amit, and Yehouda Enzel

Quaternary loess covers desert margins and vast areas of the Negev, southern Israel. The Negev loess is among the best-studied desert loess, with research going back to the early 20th century. The contrast between carbonate rocks of the Negev and its silicate-rich coarse-silt loess allows determining the loess sources, learning the synoptic-scale paleoclimatology, and exploring processes of coarse silt formation. Here, we present an overview of new perspectives on the origins and climatic significance of the Negev loess, expand on how (a) coarse silts affected soils farther downwind, and (b) how the loess has now turned into an active dust source.

The sources of the Negev loess are the (a) distal Sahara and Arabia delivering fine silts and clays, transported over thousands of kilometers, and (b) proximal sand dunes in Sinai and Negev, advancing and concurrently supplying the coarse silts to the loess accretion through eolian abrasion of sand grains. It was found that the coarse silts which compose the majority of the loess, commenced during the late middle Pleistocene – early late Pleistocene, coeval with the appearance of the advancing Sinai/Negev sand dunes and the first coarse silt accretion in regional soils; The main loess formation episode is ~95-10 ka, when the dunes appeared in the Negev. Within the loess, the dust mass accumulations rates (MAR), and consequently, soil formation rates, spatiotemporally vary according to specific site location and distance relative to the proximal sources. With increasing distance beyond the loess zone, both dust MARs and grain size gradually decrease; thus, whereas Mediterranean mountains located in central Israel, tens of kilometers downwind the loess, exhibit thick soils on top of the carbonate bedrock, the even wetter regions in northern Israel, located hundreds kilometers away from the loess, exhibit only thin soils. Thus, in Mediterranean regions located at the desert fringe, coarse silt influx is one of the main factors in determining the environmental sustainability, rather than only the precipitation amount.

During the Holocene, dust MARs in the Negev were much lower than late Pleistocene ones, and loess was not formed. Recently, the Negev loess became a prime source of dust mainly due to anthropogenic interferences, contributing to the regional dust cycle, and thus, at present the loess zone is a dust source rather than a dust sink. Today, the Negev loess is a non-replenishable natural resource that is slowly eroding and disappearing from the landscape.

How to cite: Crouvi, O., Amit, R., and Enzel, Y.: Geomorphological context of Quaternary desert loess - from dust sink to dust source, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3386,, 2021.

Paolo Tarolli

Since geologic time began, Earth’s surface has been evolving through natural processes (geologic and climate forcing). Now a new force of global change is altering Earth’s morphology in unprecedented ways: humanity. Anthropogenic activities are leaving their fingerprints across Earth, driven by increasing populations, technological capacities, and societal demands (e.g. food). The magnitude of this fingerprint is currently growing, with clear impacts upon in biosphere. The recognition and analysis of these changes represent a challenge for understanding the evolution of the Earth's landscape. The purpose of this talk is focus on a specific aspect of anthropogenic landform modifications and their interaction with climate: agriculture. Agricultural landscapes cover large areas of the world, on the plains but also on high steep hillslopes. Such areas are also served by an articulated network of rural roads. Not optimal tillage practices, poor design and lack of maintenance of the drainage systems, and wrong rural road construction could significantly affect runoff patterns, cause severe erosion or even more articulated mass movements, with a direct consequence to the entire agricultural sector (e.g. productivity, cost of restoration) but also people (safety). Climate change is worsening the entire scenario. It is clear that our society should develop more resilient agriculture, where different practices should be adapted to local conditions such as climate, soil properties, but especially geomorphology. With the help of the recent remote sensing techniques and platforms (e.g., LiDAR, drones) is now possible to provide a high-resolution 3D view of terrain (also multitemporal), providing new opportunities for a better understanding of Earth surface processes based on their geomorphic signatures. In the case of agriculture, through a detailed map of concavities and convexities, and surface roughness, it is possible to recognize the alteration, due to different till practices, of important processes such as infiltration, water storage depression, and soil water erosion. It is also possible to represent in detail surface water flow directions and concentrations along rural roads, thus estimating potential soil erosion patterns or even potential landslides activation in high-steep cultivated landscapes. This work provides an overview of some useful case studies, located in low-land but also high-steep agricultural landscapes in Italy. The purpose is to offer a geomorphologic perspective, on the effects of human activities on the Earth. Understanding and addressing the causes and consequences of anthropogenic landform modifications are a global challenge. But this challenge also poses an opportunity to manage environmental resources better and protect environmental values.


  • Tarolli P (2016). Humans and the Earth’s surface. Earth Surface Processes and Landforms, 41, 2301–2304, doi:10.1002/esp.4059.
  • Tarolli P, Cao W, Sofia G, Evans D, Ellis EC (2019). From features to fingerprints: a general diagnostic framework for anthropogenic geomorphology. Progress in Physical Geography, 43, 95–128, doi:10.1177/0309133318825284.
  • Tarolli P, Pijl A, Cucchiaro S, Wei W (2021). Slope instabilities in steep cultivation systems: process classification and opportunities from remote sensing. Land Degradation & Development, doi:10.1002/ldr.3798.

How to cite: Tarolli, P.: The Geomorphology of Life, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3561,, 2021.

Louise Bracken and Jacky Croke

The concept of connectivity has found great traction in understanding the movement of fluxes across the surface of the earth through disciplinary perspectives including hydrology, geomorphology and ecology (Bracken and Croke, 2007; Bracken et al 2013;2015). Connectivity-based approaches have also generated new understanding of structural-functional relationships that characterise complex systems, for instance in computational neuroscience, social network science and systems biology (Turnbull et al., 2018). Whilst the concept of hydrological connectivity has been used widely, at all scales and with respect to fluxes of both water and sediment, critique and development of the concept is less frequent in the literature. In this paper we revisit the existing body of work around hydrological connectivity to examine whether the concept has been used to it’s full potential and explore further ways in which the concept of hydrological connectivity could be expanded to continue to drive geomorphological research. One potential avenue for research is to learn from complex systems and use the concept of connectivity to embrace human dynamics (through managing the landscape and guiding policy and regulation) on one hand and climate change (which drives system inputs) on the other.  This opportunity is explored here using the water sector as a case study where planning, and managing for, water security under growing population pressures and future climate change are explored through this broader interpretation of connectivity. We see this wider coupling between humans and system inputs playing a significant role in shaping earth surface processes and sediment dynamics and a widening of definition may enable hydrologists and geomorphologists to better integrate socio-ecological systems into our research.

How to cite: Bracken, L. and Croke, J.: Using the concept of hydrological connectivity to integrate physical and social systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5520,, 2021.

Alessio Rovere, Deirdre Ryan, Matteo Vacchi, Alexander Simms, Andrea Dutton, and Colin Murray-Wallace

The standardization of geological data, and their compilation into geodatabases, is essential to allow more coherent regional and global analyses. In sea-level studies, the compilation of databases containing details on geological paleo sea-level proxies has been the subject of decades of work. This was largely spearheaded by the community working on Holocene timescales. While several attempts were also made to compile data from older interglacials, a truly comprehensive approach was missing. Here, we present the ongoing efforts directed to create the World Atlas of Last Interglacial Shorelines (WALIS), a project spearheaded by the PALSEA (PAGES/INQUA) community and funded by the European Research Council (ERC StG 802414). The project aims at building a sea-level database centered on the Last Interglacial (Marine Isotope Stage 5e, 125 ka), a period of time considered as an "imperfect analog" for a future warmer climate. The database is composed of 17 tables embedded into a mySQL framework with a total of more than 500 single fields to describe several properties related to paleo sea-level proxies, dated samples and metadata. In this presentation, we will show the first results of the global compilation, which includes nearly 2000 data points and will discuss its relevance in answering some of the most pressing questions related to sea-level changes in past warmer worlds. 

How to cite: Rovere, A., Ryan, D., Vacchi, M., Simms, A., Dutton, A., and Murray-Wallace, C.: WALIS - Towards a global database of Last Interglacial sea-level proxies., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9827,, 2021.

Tobias Bolch, Owen King, James Ferguson, Nico Mölg, Andreas Vieli, and Francesca Pellicciotti

Debris-covered glaciers and ice-debris landforms such as rock glaciers are common in many mountain areas of Earth, are important for the debris transport system and contain a significant amount of ice. The presence, amount and characteristics of debris can strongly alter ice melt and the evolution of glaciers and ice-debris landforms. However, debris cover and debris content exhibits strong spatial variations. To understand the evolution and physiognomies of ice-debris complexes it is important to consider both debris supply and transport as well as deposition, which are impacted by climatic conditions, topography and lithology. A holistic approach to the investigation of these coupled complex systems seems thus crucial.

In this talk we present findings from our work based on in-situ investigations (e.g. geophysical methods), multitemporal high resolution remotely sensed imagery (including historical aerial images, Corona KH 4 images and recent  data) and modelling (including surface ablation, englacial debris transport and ice flow) conducted on selected debris-covered glaciers and ice debris landforms worldwide.

Results show that a significant amount of ice is buried beneath debris cover in glacier forefields, ice cored moraines and rock glaciers under permafrost conditions. The response of rock glaciers to climate change is heterogenous with overall increasing velocities and on average only slight surface elevation changes. Slight increases in surface elevation occur their termini while debris-covered glaciers show on average a clear signal of surface lowering and decreasing velocities. The heterogeneity of debris cover can to a large extend be explained by the different debris sources and the characteristics of the headwalls while englacial and supraglacial streams favour the evolution of rough surface topography on debris-covered glaciers with the presence of ice cliffs. The findings will be illustrated with specific examples from the Swiss Alps, the Himalaya and the Tien Shan.

How to cite: Bolch, T., King, O., Ferguson, J., Mölg, N., Vieli, A., and Pellicciotti, F.: Evolution and hydrological importance of debris-covered glaciers and ice-debris landforms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14966,, 2021.

Ronald E. Pöppl, Saskia D. Keesstra, and Anthony J. Parsons

In the past two decades, connectivity has emerged as a relevant conceptual framework for understanding the transfer of water and sediment through landscapes. In geomorphology, the concept has had particular success in the fields of fluvial geomorphology and soil erosion to better explain rates and patterns of geomorphic change in catchment systems. Sediment (dis)connectivity in geomorphic systems is generally governed by the spatial arrangement of sediment sources, transfer pathways and sinks (i.e. the structural component) as well as the interactions between landscape compartments and the frequency-magnitude relationships that dictate the relative effectiveness of geomorphic processes (i.e. the structural component; Poeppl et al., 2020). This presentation will provide a short general overview on existing concepts of connectivity in geomorphology, further highlighting and discussing recent developments in geomorphological connectivity research.


Ronald E. Poeppl, Kirstie A. Fryirs, Jon Tunnicliffe, Gary J. Brierley (2020). Managing sediment (dis)connectivity in fluvial systems, Science of The Total Environment, Volume 736, 139627

How to cite: Pöppl, R. E., Keesstra, S. D., and Parsons, A. J.: Connectivity in geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16314,, 2021.