ICG2022-5

ICG2022
Forms, Processes and Landscape Change 

The evolution and change of landforms, the mechanisms and quantitative rates of geomorphic processes creating or modifying these landforms, and landscape changes at various temporal and spatial scales are controlled by a range of environmental drivers and anthropogenic activities, exacerbated by the consequences of climate change. This session shall bring together interdisciplinary researchers working across field, experimental, numerical modelling, remote sensing, and dating approaches that are advancing methods and providing new insights into:
i. the analysis of landforms and landform evolution;
ii. geomorphic processes creating or modifying landforms and form-process interactions;
iii. the anthropogenic impacts and societal implications of changing geomorphic processes (including denudational hillslope and fluvial processes) and terrestrial landscape systems, and possible solutions for future sustainable management under ongoing or accelerated global environmental changes.

Conveners: Achim A. Beylich, Luca Mao, Osmar Carvalho, Roberto Verdum, Adélia Nunes
Orals
| Thu, 15 Sep, 09:00–16:30, 17:00–19:00|Room Sala Almedina-C2D
Poster
| Attendance Thu, 15 Sep, 16:30–16:45 | Display Thu, 15 Sep, 09:00–Fri, 16 Sep, 19:00|Poster area

Orals: Thu, 15 Sep | Room Sala Almedina-C2D

09:00–09:15
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ICG2022-551
Larissa A. Naylor and the UK China CZO Team

Critical Zone Observatories (CZOs) explore the deep evolution of landscapes from the bottom of groundwater to the top of vegetation, representing a bridge between geology, geomorphology and ecology. Human impacts on the landscape, notably agriculture and urbanisation, are key drivers of terrestrial landscape change, with these challenges providing a focus of a new class of 3rd generation Critical Zone Observatories (CZOs).  Four of these CZOs were established in China to understand how environmental processes, from the top of vegetation through 10’s to 100’s of metres of soil to bedrock, interact and are affected by land management.  The China CZOs cover vastly different geomorphological settings in karst, loess, and red soil environments that encompass over 1/3 of China’s land area and support 25% of the population. The 4thCZO lies in the peri-urban coastal zone, reflecting urban migration that is growing in China, with over 1/6 of China’s population already migrated from rural areas and 52% of the population in cities.

This talk provides an overview of key geomorphologically relevant findings from these CZOs, obtained by a team of over 50 principal-/co-investigators and many other postdoctoral scientists and students. An over-arching theme is integrating humans into critical zone science to tackle threats to landscape tipping points being crossed, impacting on food and environmental security.  While 2nd generation CZOs capture human impact, the role of human decision-making has been largely overlooked. A 3rd generation approach to CZ science emerged from the China-UK CZO programme (2016-2020). Here, human geography informed knowledge exchange research complemented traditional multidisciplinary CZ science. This provided novel insights into human-environment interactions (and humans as geomorphic agents) that aided the interpretation of empirical data and helped identify the greatest financial pressures on farmers that also adversely impact their local landscape. It also illustrates how scientific sampling in heavily human-modified landscapes can be adjusted to better incorporate the impacts of humans as geomorphic agents. The approach also identified how local people chose to learn more environmentally and economically sustainable farming methods, thereby guiding fit-for-purpose knowledge exchange activities between CZ scientists and key stakeholders. We thus outline the benefits of incorporating learnings about human behaviours and their beneficial impacts into CZO projects. We demonstrate that human geography needs to form a key dimension of multi-disciplinary CZ science approaches to enable identification of the mechanisms underlying human contributions and pressures on CZ functions. Crucially, deep understanding of impacts of environmental and economic stressors on human livelihoods can provide the rationale for policy and local action to achieve resilient social-ecological systems. We thus show how 3rd generation CZOs that combine physical and human geography, underpinned by local knowledge, can provide practical feedback to communities in stressed environments, enabling better achievement of sustainable development goals and planetary health.

 

How to cite: Naylor, L. A. and the UK China CZO Team:  Humans as geomorphic agents: including humans in critical zone science to enhance Anthropocene landscape sustainability , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-551, https://doi.org/10.5194/icg2022-551, 2022.

09:15–09:30
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ICG2022-122
Clement Nkwemoh and Destain Wirsiy

THE ROLE OF MAN ON LAND COVER DYNMICS IN THE JAKIRI AREA,

NORTH WEST REGION OF CAMEROON

By

Clement Anguh Nkwemoh & Destain Wirsiy

The University of Yaounde 1

ABSTRACT

Several Landscape degradation forms have attracted our attention in the Jakiri area on the North Eastern edge of the High Lave Plateau of Cameroon. Landscape degradation has become a major issue in contemporary studies, owing to its impact on society. This study aims to identify mainly various human factors responsible for Land cover dynamics. In order to complete this research, we adopted Classical and Empirical Approaches. These relied on the collection of data from secondary and primary sources. Questionnaires were administered to 310 farmers and 84 pastoralists in 17 villages. Focus Group Discussions and Interviews were equally carried out. The topographic map of Nkambe NB32XVII scale: 1:200 000, was exploited. The MSS, TM and ETM + Enhanced Thematic Mapper Plus as well as ASTER images for 2007 were used. Data was treated with the use of SPSS, ArcGIS and ERDAS IMAGINE software. The study reveals that anthropogenic actions are predominant in degradation meanwhile physical factors are only contributory in the degradation processes that rendered the Jakiri Plateau susceptible to soil erosion and mass movements. The Normalized Different Vegetation Index (NDVI) revealed a decrease in NDVI values from +0.92 in 1988, +0.74 in 2001 and +0.5 in 2020, showing a vegetation decrease. Meanwhile, the Land Cover Classification revealed a change in forest/land cover, from 24.4% in 1988 to 9.83% in 2020 with a decrease in forest cover of 14.5%. On the contrary, built up area, grassland (savannah) and bare surfaces have witnessed an increase in land cover classes from 34.4%, 10%, 31.2% in 1988 to 37.7%, 14%, 38% in 2020. Our study equally identified population pressure, deforestation, rudimentary agricultural activities, overgrazing and the introduction of eucalyptus cultivation as a form of agroforestry that transformed the landscape of Jakiri. The solutions that have been proposed, focus on landscape restoration through improved farming systems such as agroforestry, and also the application of certain technical methods. The solutions are socially just, flexible, adaptable, economically viable and most importantly ecologically sound.

 

Keywords: Anthropic activities; vegetal degradation, GIS, Land cover change; agrarian and

technical measures

 

How to cite: Nkwemoh, C. and Wirsiy, D.: The role of man on Landcover dynamics of the Jakiri Area of the North West Region of Cameroon, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-122, https://doi.org/10.5194/icg2022-122, 2022.

09:30–09:45
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ICG2022-129
Christine Embleton-Hamann and Stefan Premm

Iron ore has been mined in the Erzberg area for at least 900 years, possibly as long as 1500 years. This mining history can be divided into three periods of impact on the landscape. Due to the inefficiency of the early smelting techniques and the low production levels, the first period remained free of serious impacts. A huge demand for energy for ore smelting characterized the second period, resulting in supra-regional deforestation for charcoal production. The third period of mechanized surface mining is marked by the creation of large man-made landforms. In the Erzberg area, both historical documentation and modern recording of the mining activities are exceptionally good and provide an opportunity for i) a qualitative identification and description of the associated landscape changes and ii) a first attempt to quantify them. Qualitative analysis of the documents provided a detailed description of how distinct anthropogenic impacts and landforms have emerged, and identified the procedures that caused medieval supra-regional deforestation. A slope exposure opened along a creek allows interpretation of the geomorphic effects of the historical forest depletion. Quantification of the extent of deforestation was carried out for a forest area close to the mining site. The results allow a reconstruction of the condition of the forest at this site over two centuries. For quantification of the earth material moved by man in mechanized surface mining denudation rates for the Erzberg site were computed and compared with the sediment budget of a nearby river catchment. This comparison suggests that on the local scale man is two to three orders of magnitude more effective in transforming the landscape than geomorphic processes.

How to cite: Embleton-Hamann, C. and Premm, S.: Landscape Change due to Thousand Years of Iron Ore Production in the Erzberg Area (Styria, Austria), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-129, https://doi.org/10.5194/icg2022-129, 2022.

09:45–10:00
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ICG2022-314
Martin Stokes and Shahram Bahrami

Salt domes are bodies of halite-gypsum-anhydrite salt exposed at the Earth’s surface. They typically comprise positive topographic expressions, reaching heights of 10s to 100s m. In plan-view, they display elliptical through to elongated shapes that span metre to km-scale length-width-area-volume dimensions. Salt domes are typically found in drylands, where rainfall-humidity levels are sufficiently low, inhibiting dissolution. Salt is considered to move upwards to the surface by diapiric processes, linked to rock density differences and elevated compressive forces. Thick (>100 m) layers of lacustrine-marine evaporitic sediment are buried to km-scale depths over geological timescales. Salt density = ~2200 kg/m3), becomes buoyant and diapiric due to overburden pressure when buried by >1-3 km thickness of higher density (~2500 kg/m3) sediment cover. Salt movement is further enhanced by tectonics, especially in collisional plate settings. Here, compression provides additional diapiric driving forces, with any resulting folded-faulted strata providing a structural-stratigraphic framework for salt migration pathways. Accordingly, geologists use the term ‘salt diapir’ reflecting the movement-emplacement process, or ‘salt plug’ to reflect its stratigraphic configuration with respect to bounding strata and structures. ‘Salt dome’ is a geomorphological term linked to salt’s surficial geomorphic expression.

Salt dome morphology features widely in geological-geomorphological literature, where dome shape is commonly linked to different stages of diapiric growth. Jahani et al (2007), analysed 43 domes from the Zagros Mountains (Iran), proposing six dome types:  A = buried diapirs, B = high relief active diapirs, C = high relief active diapirs with a salt fountain and glacier, D = like C but with more erosion and without fountain, E = dead and highly eroded diapirs with an empty crater, F = linear diapirs emerging along faults. Although such process-form based classification schemes are well-conceived and likely correct, they surprisingly lack quantitative analytical underpinning of their morphological dimensions. Thus, the purpose of this research is to investigate whether quantitative morphological relationships between salt dome shape and diapiric process-based classification exist.

We focused upon the classic Eastern Fars region studied by Jahani et al (2007) and their 6-fold classification scheme (above). We compiled a spatially expanded database of 67 domes (A = 3%; B = 28%; C = 18%; D = 34%; E = 12%; F = 4%) and their morphological attributes (area [111-0.6km2], relief [1.2-0.7km], length/width ratio [1-6], volume [20- -14km3], hypsometry [curve and integral], slope [mean 33-5°] using 12m TanDEM-X data and satellite imagery for measurement and visualisation purposes. The database was supplemented with geological information sourced from Iranian geological survey maps, including dome relationships to geological units (age/lithology) and tectonic structures (folds/faults).

Results reveal at best a weak qualitative and quantitative relationship between dome morphology and diapir growth and erosion evolution processes. We discuss this finding and suggest that dome location with respect to fold structural configuration as a confinement control provides an improved, and hitherto unexplored, salt dome classification opportunity.

Jahani, S., et al., 2007. The salt diapirs of the eastern Fars Province (Zagros, Iran): A brief outline of their past and present. In Thrust belts and foreland basins. Springer. pp. 289-308. 

How to cite: Stokes, M. and Bahrami, S.: Salt dome morphology: a quantitative analysis of diapiric process-based classification schemes, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-314, https://doi.org/10.5194/icg2022-314, 2022.

10:00–10:15
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ICG2022-76
Mthobisi Masilela, Heinz Beckedahl, and Wisdom Dlamini

Extending some 60 m below ground, and with explored lengths of more than 1 500 m, the Gobholo cave system in Eswatini is one of the largest granite cave systems documented in the scientific literature. The cave system is found in the Gobholo valley, approximately 10 km east of Mbabane. The valley is drained by the Gobholo River, which has a subsurface flow through the cave system for more than 1,8 km. The Gobholo valley itself is located on the Mbabane granite pluton which is made up of the Mswati granite, of 2,7 Ga. in age. It is a porphyritic granite of coarse grain which forms part of the Kaapvaal Craton. The Kaapvaal Craton is an old yet stable landscape composed primarily of granitoids, gneiss, and other metamorphosed volcanic and sedimentary rocks varying in age between 2.5 – 3.6 Ga. The Mbabane Pluton is remarkably affected by tectonics as evidenced by a network of NNE-SSW and NW-SE fault lines and lineations, which account for the deep dissecting and near perpendicular valleys, with the Gobholo Valley being one of these.

A notable feature of this cave system, compared with other granite caves reported in the literature, is that it has elements of both solutional-depositional systems, as well as the ‘typical’ boulder systems in which the interstitial fines have been washed out between large, buried scree-slope boulders. The research focusses on the structure and composition of the granitic bedrock, and compares its mineralogy with the geochemistry of the water of the Gobholo River. Remote sensing and GIS are used to map the spatial arrangement of landforms, geological structure, and digital modelling of the terrain. These are further used to explain the geomorphic processes of the study area. The analysis and modelling of the Gobholo Valley is of key importance in this research, as it informs the discussions and conclusions on the genesis and dynamics of the Gobholo granite cave system.

How to cite: Masilela, M., Beckedahl, H., and Dlamini, W.: Understanding the Geomorphology of the Gobholo Granite Cave System in Eswatini, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-76, https://doi.org/10.5194/icg2022-76, 2022.

10:15–10:30
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ICG2022-361
Jessica Williams-Mounsey, Richard Grayson, Alistair Crowle, and Joseph Holden

Peatlands are a globally important wetland habitat, estimated to contain over a third of terrestrial soil carbon, placing their preservation and restoration at the forefront in debates around climate change mitigation. Anthropogenic activities, however, are driving peatland degradation loss both directly and indirectly. One such activity, is the creation of linear disturbances such as roads and tracks. The expansion of these networks, frequently in pursuit of resources, or the desire to explore remote regions, is rapidly outpacing research, with long time lags often experienced before impacts are appreciable.

In 2013 an experiment was established at Moor House, an upland blanket peatland in northern England to examine the impacts of temporary plastic mesh tracks on peatland functioning. A 1.5 km long plastic mesh track was installed and split into five different treatments based on frequency of usage. The tracks were abandoned in 2015/16, and no further vehicular usage occurred. In 2020, 18 7m long sections of this track were removed, to intensively examine the ecohydrological effects of removal compared to leaving the track to overgrow. The impacts of different treatments were evaluated on the ecohydrology; removed vs abandoned track, previous usage frequency, delayed usage, and unsurfaced track. Detailed surficial structural (nanotope) assessments of the tracks were carried out, to compare ruts, centres and controls. Additionally, soil moisture measurements, overland flow sediment, peat cavity strength measurement, hydraulic conductivity, bare peat occurrence and vegetation diversity were recorded.

Across all treatments alteration of the surface nanotopography was observed, loss of vegetation diversity after track removal and a reduction in vegetation height across all treatments occurred compared to controls, both on the track and along track edges. Our nanotope surveys augmented vegetation recovery assessments, demonstrating how different conclusions can be drawn, depending on whether vegetation-only or more complete assessments of surface condition are undertaken. Peat cavity strength on the tracks, measured using a peat specific penetrometer, suggests the persistence of vehicular compaction in the post abandonment and track removal periods. We also present data from overland flow sediment traps, hydraulic conductivity, and soil moisture surveys. Our findings suggest that where mesh track is to be removed, then additional revegetation interventions are required. We demonstrate that because the impacts of tracks, including mesh tracks, even after only light, short duration use, are long-lived, careful consideration of the necessity of tracks is required prior to their construction on peatland.

How to cite: Williams-Mounsey, J., Grayson, R., Crowle, A., and Holden, J.: Temporary tracks, persistent impacts? An evaluation of short-term usage peatland tracks. , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-361, https://doi.org/10.5194/icg2022-361, 2022.

Coffee break and poster session
DENUCHANGE section
11:00–11:15
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ICG2022-644
Juan Remondo, Antonio Cendrero, Luis M. Forte, Achim A. Beylich, and Piotr Cienciala

An analysis and assessment of the effects of human activity on geomorphic processes related to denudation/sedimentation and landscape change, is presented. The analysis focuses on changes occurred during the last couple of centuries and is based on a variety of case studies from different regions as well as global assessments. Data compiled show that certain geomorphic processes are experiencing an important acceleration, in particular since the 1950’s. The acceleration seems to have a global character and suggests a “global geomorphic change” is taking place, largely due to anthropogenic landscape changes.

            Denudation directly caused through activities involving excavation, transport and accumulation of geological materials has increased by a factor of 30 between 1950 and 2015. Direct plus indirectly human-induced denudation (triggered by land surface alteration) is presently at least one order of magnitude greater than denudation due to purely natural processes. A general increase of sedimentation rates seems to have taken place since the end of the 19th century, and more intensely after the mid-20th century. This appears to respond mainly to land surface changes, in conjunction with climate change.

            Slope movements, which represent an important contribution to denudation, sediment generation and landscape evolution, show a clear intensification, in particular after mid-twentieth century. Frequency of disasters related to such movements (an indirect measure of process frequency) in specific regions, as well as continent and global levels, has grown considerably and the general increasing trend observed is not satisfactorily explained by climate change. It rather appears to reflect increasing landscape (land use and land cover) changes. A similar increase in the frequency of flood-related disasters has been recorded.

            The results obtained suggest that the extensive landscape changes described, related to the intensification of human activities affecting land surface, represent a geomorphic change of a global extent. This change shows an acceleration coinciding with the “great acceleration” proposed as one of the manifestations of the Anthropocene.

How to cite: Remondo, J., Cendrero, A., Forte, L. M., Beylich, A. A., and Cienciala, P.: An assessment of geomorphic change and its effects on denudation and landscape evolution, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-644, https://doi.org/10.5194/icg2022-644, 2022.

11:15–11:30
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ICG2022-281
Francesca Vergari, Francesco Troiani, Marco Cavalli, Hazel Faulkner, and Maurizio Del Monte

In the Mediterranean region, natural soil loss susceptibility is enhanced by human pressure, that has a long history and seems to be the main driver of changes in sediment supply during the Anthropocene. Badland areas in non-arid landscapes can be ideal sites to investigate the role of human activities in triggering erosion processes in the current context of global change, as their origin has been related to scenarios of widespread land degradation. So far, little attention has been given to the relationship between slope processes and river morphodynamics in badland landscapes. In this context, the exploration of sediment connectivity can be informative, considering the rapid morphoevolution and consequent off-site effects.

Anthropocene hillslope morphodynamics and sediment connectivity within a representative badland area located in southern Tuscany (Italy) was explored, in order to better delineate the recent erosion dynamics. The relative importance of the role of man activities in the medium-term landscape evolution and how far it can be connected to the triggering and/or mitigation of hillslope processes is discussed.

In order to achieve these general purposes, the research approach included i) a multitemporal survey of the erosion dynamics at catchment scale, ii) the analysis of the land use changes during the last century and iii) the geomorphometric indexing of the structural connectivity of a representative catchment located in the Upper Orcia River valley, starting from a 1 m resolution DEM (Digital Elevation Model) derived from LiDAR (Laser Detection and Ranging).

Starting from the mid-20th century, the area has been subjected to artificial reforestation with conifers (performed mainly on upland areas), impressive land reclamation (many badland areas have been levelled due to the enlargement of croplands), pasture decrease as a consequence of rural land abandonment, with the subsequent increase in the vegetation cover. Everything merges with a recent reduction of hillslope denudation rates, that can be related to the observed channel adjustments during the last decades.

Outcomes of this research can be useful for a deeper comprehension of the effects of man-induced changes on the slope-channel systems and, in a wider context, can be helpful for supporting the decision making in a perspective of sustainable development.

How to cite: Vergari, F., Troiani, F., Cavalli, M., Faulkner, H., and Del Monte, M.: Anthropocene erosion dynamics and sediment connectivity in a central Italy landscape with badlands, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-281, https://doi.org/10.5194/icg2022-281, 2022.

11:30–11:45
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ICG2022-226
Olimpiu Pop

Debris flows (DFs) are widespread geomorphic processes in the high areas of Carpathians, being highly efficient sediment transfer processes from slopes to channel network.  They often damage the transportation infrastructures, inhabited areas and threaten the recreational and other human activities. To minimize the negative impact of DF activity, it is crucial to understand the role of various conditions and factors which lead in the past to debris flow triggering. In this context, information on long-term DF activity needs to be known, to understand the DFs behavior and to predict the future trends of this potential natural hazard in the context of documented climate change. However, in Carpathians, as in most of the mountain areas worldwide, the lack of historical records about past hydrogeomorphic process activity in term of temporal frequency and spatial extent hampers the possibility to have a good knowledge of the past DF activity. Indirect reconstructing methods, e.g., dendrogeomorphic methods can be used to reconstruct past DF activity in forested mountain areas. When DFs along their paths cross the forests, they disturb the trees leaving in their growth rings distinct signs of the past DF events. Dendrogeomorphic approaches are based on the analysis of growth anomalies caused by the mechanical disturbance of DFs on trees and recorded in treir rings, allowing to reconstruct with annual and even seasonal resolution past geomorphic activity. Dendrogeomorphology became in the last decades an established technique applied to reconstruct past geomorphic process activity, helping to understand dynamics of various geomorphic processes.  Dendrogeomorphic methods have been extensively applied to reconstruct DF activity in various mountain regions, while in Romanian Carpathians DF activity has been rarely reconstructed through these methods, and if available the reconstructed activity has focused only on individual case studies at a local scale. The aim of this study is to investigate past DF activity at a regional scale through dendrogeomorphic methods. In this sense, study sites which includes multiple tracks of both natural and anthropogenically-influenced DFs crossing the forested slopes were chosen in Calimani Mountains (Eastern Carpathians). In each investigated site, growth anomalies identified in the rings of disturbed trees sampled allowed to reconstruct DF event chronologies. Analysis of rainfall data recorded at the weather station located close to the study sites revealed that local DF processes may be the result of extreme rainfall events occurring mainly during summer seasons. An increase in DF event frequency in the anthropogenically-influenced areas compared with the DF event frequency in natural areas was observed, suggesting that sediment availability possibly represent another factor for varying DF activity. The dendrogeomorphic reconstructions realized here represents a first attempt to assess the regional patterns of DF activity in Romanian Carpathians, with promising perspectives to extend similar dendrogeomorphic investigations in other regions of the Carpathian Range.

How to cite: Pop, O.: Regional debris-flow chronology reconstructed through dendrogeomorphic methods in Calimani Mountains (Eastern Carpathians, Romania) , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-226, https://doi.org/10.5194/icg2022-226, 2022.

11:45–12:00
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ICG2022-81
Katja Laute and Achim A. Beylich

The upper Driva drainage basin in central Norway (Oppdal-Hjerkinn) is situated in a cold climate and mountainous environment and ranges with a total drainage basin area of 1630 km2 from 220 to 2286 m a.s.l. The mean annual air temperature at Oppdal (545 m a.s.l.) is 4.3°C, and mean annual precipitation at Oppdal amounts to 532 mm. The lithology in the drainage basin is complex and varied, and is dominated by metamorphic rocks (mostly gneisses and schists). Vegetation cover varies between tundra vegetation in the high and rather flat areas of the uppermost drainage basin area, situated at elevations around 900-1200 m a.s.l., tree vegetation (mostly birch and pine) in the lower parts of the incised tributary valleys of the Driva main river and grasslands in the agriculturally used areas close to the lower sections of the main river Driva. Relevant geomorphological processes include chemical and mechanical weathering, rockfalls, snow avalanches, debris flows, slides, wash processes, fluvial erosion, fluvial streambank erosion and down-cutting,  and fluvial solute, suspended sediment and bedload transport.

This ongoing GFL research on sediment sources, controls and spatiotemporal variability of fluvial bedload transport includes detailed field-based studies with extensive granulometric and shape analyses of bedload material, and high-resolution bedload transport measurements applying different tracer techniques, Helley-Smith samplings, and underwater video filming together with impact sensor measurements. Specific focus is on selected stream channel stretches in the six tributary systems Svone, Kaldvella, Stølåa, Tronda, Vinstra and Ålma, and on three selected stream channel stretches of the Driva main river in the upper Driva drainage basin system. Stationary hydrological stations are monitoring runoff continuously as discharge occurs in all tributary systems year-round. The runoff regime is nival with mean annual runoff amounting to 576 mm for the entire upper Driva drainage basin.

The temporal variability of fluvial bedload transport is largely controlled by thermally and/or pluvially determined runoff events. The selected tributary systems display varying grain-size compositions and shape characteristics of bedload material together with different bedload transport rates and yields. These detected spatial variations are explained by different lithologies, different levels of sediment connectivity and spatially varying sediment availabilities in the different tributary systems. The activation of sediment sources is generally strongly determined by thermally and/or pluvially induced events. The clearly highest share of annual bedload transport occurs during the snowmelt period in spring. Altogether, fluvial bedload transport is of high relevance for the total fluvial transport in the upper Driva drainage basin. However, within the different selected tributary systems the relative importance of fluvial bedload transport, as compared to suspended sediment transport and solute transport, ranges from very low in Ålmadalen to very high in Vinstradalen.

How to cite: Laute, K. and Beylich, A. A.: Field-based analysis of sediment sources, spatiotemporal variability and rates of fluvial bedload transport in the cold climate and mountainous upper Driva drainage basin in central Norway, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-81, https://doi.org/10.5194/icg2022-81, 2022.

12:00–12:15
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ICG2022-413
Waldemar Kociuba

A four-day glacier-melt flood (13-16 August, 2013) caused an abrupt geomorphic change in the proglacial gravel-bed Scott River, that drains the small (10 km2) Scott Glacier catchment (SE Svalbard). This type of floods occur on Svalbard increasingly during periods of abnormally warm or rainy weather in summer or early autumn, and the probability of occurrence grows in direct proportion to the increase in temperature and/or precipitation intensity. In the summer 2013 measurement season, the highest daily precipitation (17 mm) occurred on August 13. During the following four days, it constituted in total 47mm i.e. 50% of the precipitation total for the measurement period of 2013. The largest flood in 20 years, was caused by high precipitation with a synchronous rise in temperature from about 1.0 to 8.6 °C. These values exceeded multi-year averages (32 mm and 5.0 °C, respectively), at average discharge 0.9 m3·s–1 (melt season mean 1986–2011). These conditions caused a rapid and abrupt response of the river with dominant (90%) glacier-fed. The increase of discharge to 4.6 m3·s–1, initiated by the glacial flood, mobilized significant amounts of sediment in the river bed and channel. Geomorphic changes within the alluvial fan as area of 58,820 m2, located at the mouth of the Scott River, were recorded by multi-sites terrestrial laser scanning using a Leica Scan Station C10, and then estimated using Geomorphic Change Detection (GCD) Software. Flood-induced total area of lowering (erosion) covered 38% of the alluvial fan (6,030 m2), resulting in the removal of 1,182 ± 121 m3 of sediment volume. During the final phase of the flood, two times more sediments (1,919 ± 344 m3) was re-deposited within the alluvial fan surface, causing significant aggradation on 62% of its area (17,190m2). These geomorphic changes resulted in an average lowering (erosion) of the alluvial fan surface of 0.2 m and an average rising (deposition) of 0.1 m.

How to cite: Kociuba, W.: Geomorphic Change Caused by Flood at Scott River Alluvial Fan, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-413, https://doi.org/10.5194/icg2022-413, 2022.

12:15–12:30
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ICG2022-24
Ting Zhang, Dongfeng Li, and Xixi Lu

Permafrost degradation by ongoing climate warming has expanded the erodible thermokarst landscapes, enhanced the thermal erosion, and altered the sediment transport processes in cryosphere basins. Thermal-activated sediment sources and enhanced sediment export due to developed hillslope-channel connectivity can increase the annual sediment flux and accelerate the sediment response to hydroclimatic disturbances, thus complicating suspended sediment concentration (SSC) and discharge (Q) relationships and forming various hysteretic patterns. Yet, the commonly used sediment rating curve (SSC=a×Qb with a and b as static fitting parameters) is unable to capture the SSC-Q hysteretic patterns and most single-event-scale hysteresis models mainly emphasize the pluvially enhanced sediment transport (e.g. rainstorms), but overlook the thermally-erosional processes.

To rebuild dynamic SSC-Q relationships and hysteresis in sediment transport in cryosphere basins, we propose a Sediment-Availability-Transport (SAT) model by extending traditional rating curves to incorporate the time-varying sediment availability regulated by thermal-fluvial processes and long-term storage exhaustion. In the SAT-model, increased thermal erosion is represented by basin temperature; enhanced fluvial erosion is represented by runoff increase; sediment transport capacity is represented by total runoff. Specifically, thawing permafrost as temperature rising can enhance sediment generation by forming active layer detachment, retrogressive thaw slump, and thermal erosion gully from hillslopes, and fluvio-thermal erosion along the riverbank, associated with a time-lag in the sediment response due to the time for temperature accumulation to melt cryosphere and long-travel distance from thermal-activated sediment sources to the basin outlet. A surge in basin water supply during intense rainfall and excessive melting with a certain time-lag can increase sediment availability and fluvial erosion by flushing the erodible slope and scouring the river channel. Moreover, sediment storage is assumed to be continuously depleted throughout a hydrological year and leads to sediment exhaustion.

With the support of multi-decadal daily SSC and Q in-situ observations (1985-2017), the SAT-model can be parameterized and validated in the permafrost-dominated Tuotuohe basin on Tibetan Plateau. In Tuotuohe, thermal erosion processes are found to be best captured by an eight-day average temperature, associated with an exponential amplification of SSC. Fluvial erosion is best captured by a two-day runoff increase and shows a linear amplification of SSC. Moreover, the warming-wetting climate over the past decades has expanded the thermokarst landscapes and boosted the slope-channel connectivity by thermal gullies, which leads to the significant inter/intra-annual variation in SSC-Q relationships and reduces the performance of the sediment rating curve. Yet, the SAT-model can robustly reproduce the long-term evolution, seasonality, and various event-scale hysteresis of SSC, including clockwise, counter-clockwise, figure-eight, counter-figure-eight, and more complex hysteresis loops. Overall, the SAT-model can explain over 75% of long-term SSC variance, outperforming the sediment rating curve approach by 20%, with stable performance under an abrupt hydroclimate change.

Part of the results is also published in Water Resources Research: Zhang et al., 2021. Constraining dynamic sediment-discharge relationships in cold environments: The sediment-availability-transport (SAT) model.;. Li et al., 2021. Air temperature regulates erodible landscape, water, and sediment fluxes in the permafrost-dominated catchment on the Tibetan Plateau.

How to cite: Zhang, T., Li, D., and Lu, X.: Basin-scale sediment transport and sediment concentration-discharge relationship modeling in a permafrost-dominated basin, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-24, https://doi.org/10.5194/icg2022-24, 2022.

Lunch break
14:30–14:45
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ICG2022-43
Adeyemi Olusola, Samuel Ogunjo, Olutoyin Fashae, Olumide Onafeso, and Samuel Adelabu

Bivariate relationships have been extensively researched in fluvial geomorphology. The relationship between process-process, form-form, or process-form gives great insight into the dynamics of channel morphological variables. One of the most extensively adopted concepts in bivariate relationships in fluvial geomorphology has been the use of hydraulic geometry.  The hydraulic geometry despite its many advantages and applications has been identified to focus more on general trends rather than innumerable individual variations. In recent times, a growing concept on bivariate observations within fluvial systems is the geomorphic covariance structures (GCS). GCS has been defined as linked bivariate observations of any two river morphological variables along a continuum. These variables could also accommodate the abiotic and biotic variables. In its strictest sense, GCS does not necessarily connote a statistical covariance though sometimes it could, it focuses more on a complete bivariate spatial series. In this study, we investigated coherent patterns for GCS for selected morphological variables along the alluvial-bedrock continuum for 83 reaches within the Upper Ogun River Basin. In interpreting the bivariate spatial series along the alluvial-bedrock continuum, we made use of “in-phase” and “out-of-phase”. In-phase signifies a positive relationship and out-of-phase signifies an inverse relationship. The morphological variables were measured using standard procedures and derived variables were determined using hydraulic equations. As the river flows from an alluvial section into a bedrock section; slope and total stream power were out of phase, hydraulic radius and velocity are in phase across the continuum, bankfull with and slope were out of phase, while slope and total stream power were more in phase within the bedrock section than in the alluvial section and finally, width and total stream power were out of phase. The alluvial section within the Upper Ogun River Basin is either unconfined or partly confined while bedrock channels are confined and underlain by migmatites. Flow within the bedrock channels is restricted while flow within the alluvial channels is more dispersed and free-flowing. The inherent dynamics operating within these two distinct channel types are capable of providing a detailed extent as to the observed bivariate relationships between these selected morphological variables using geomorphic covariance structures.

How to cite: Olusola, A., Ogunjo, S., Fashae, O., Onafeso, O., and Adelabu, S.: Geomorphic covariance structures of selected channel morphological variables across the alluvial-bedrock continuum in the Upper Ogun River Basin, Southwestern Nigeria, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-43, https://doi.org/10.5194/icg2022-43, 2022.

14:45–15:00
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ICG2022-88
Andrej Novak, Marko Vrabec, Tomislav Popit, Goran Vižintin, and Andrej Šmuc

Sieve-lobe deposits are morphological features typical for gravel-rich and matrix-poor alluvial fans. Each sieve-lobe deposit is composed of open-framework, clast-supported, moderately-sorted gravels. Lobes form during sieve-deposition process where gravel is transported as bedload during short and intense rainfall events and abruptly deposited after the water quickly infiltrates into permeable underlying ground. Despite being a common morphological feature qualitatively described in several alluvial fan studies it lacks a detailed sedimentological description based on quantified data. The formative conditions and depositional activity of sieve lobes as well as subsurface architecture of a sieve-lobe built alluvial fan is largely unknown. In this study we present (i) a detailed sedimentary facies analysis based on sedimentary structure and texture of recent sieve lobes, (ii) a three-year aerial survey of sieve-lobe depositional activity, (iii) a direct linkage of depositional activity to specific rainfall triggers, and (iv) a depiction of subsurface architecture of intertwined sieve lobes.

The study was done in the Planica Valley (NW Slovenia), a typical post-glacial alpine valley, where several gravel-rich Holocene alluvial fans are located.  The study was performed on one of the more active alluvial fan, which is predominantly built of sieve-lobe deposits. The sedimentological analysis is based on granulometry, grain morphology, and grain fabric of 11 sieve lobes that differ in size and age. Sieve lobe generation was detected by aerial surveying using Small Unmanned Aircraft (SAM) and photogrammetric modelling of the surface of the deposits. Detected surface changes were temporally correlated with precipitation records from the nearby meteorological station. Ground-penetrating radar (GPR) technique was used to depict architecture and geometry of sieve-lobe built alluvial fan.

Sedimentary analysis reveals that majority of sieve lobes belong to textural group of gravel and some to sandy gravel, containing almost negligible percentage of mud fraction, which rarely exceeds 2.0%. Almost uniformly and regardless of age and size, all sampled sieve lobes exhibit downward coarsening, with distal parts of lobe being significantly coarser than proximal. Clasts are angular to subangular, predominantly moderately to highly spherical and not orientated.

Temporal surface changes are clearly visible on SAM-derived digital orthophoto and digital elevation models. Correlating surface changes to meteorological records shows that sieve lobes form with a subannual frequency, usually after rainfall events exceeding 50 mm of rainfall in 24-hours. During such events more than 1000 m3 of sediment was deposited.

GPR data from a radargram parallel to the direction of sediment transport displays stratified and progradational reflectors with sigmoid shapes that are continuous for 10s of metres and have 10° dip. Radargrams orientated perpendicular to the direction of sediment transport exhibit stratified hummocky and discontinuous reflections of up to 10 metres long. The reflection patterns are interpreted as series of stacked sieve-lobe deposits confirming formation of the studied alluvial fan predominantly by sieve-deposition process.

This study provides the first detailed quantified facies analysis of sieve deposits observed in nature. Monitoring of their deposition shows that they represent major building blocks of gravel-rich alluvial fans, and their deposition is directly linked to intense precipitation triggering events.

How to cite: Novak, A., Vrabec, M., Popit, T., Vižintin, G., and Šmuc, A.: Facies analysis, depositional activity and subsurface architecture of sieve lobe built alluvial fan (Planica Valley, NW Slovenia), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-88, https://doi.org/10.5194/icg2022-88, 2022.

15:00–15:15
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ICG2022-123
Amelia Remers, George Heritage, and Neil Entwistle

The sediment dynamics of river systems are of significant importance from an ecological, social and engineering viewpoint and are defined by complex relationships of numerous variables. It is widely accepted amongst authors that as flow increases as does the amount and size of sediment entrained. Threshold theories surrounding this have been proposed by many authors including Hjulstrom, Van Rijn, Du Boys and Shields. The aim of this research is to investigate thresholds of motion for sediments within bi-modal riverbeds, including examining incipient motion for various particle sizes. Previous research methods which have investigated this have focused on either field methods using small sample populations from sediment traps and sediment tracers or laboratory studies (flume models). In this paper an alternative method is presented utilising repeat UAV imagery of two gravel-bed river reaches in England to identify individual sediment clasts and monitor movement. By determining whether a sediment has moved or stayed and comparing this to a maximum flow rate during the interval between surveys, derived from hydraulic modelling, a maximum local shear stress value can be established for when each grain is mobilised. Initial findings have shown that as flow increases so does the amount of sediment moved. However, the size of mobilised sediment does not necessarily increase. Sediments over a certain size (0.3 m B-Axis length) display little movement despite rising shear stress values. Shielding and exposure are also investigated to examine why these larger sediments remain stable despite increasing local shear stress values. This has shown that in non-uniform gravel-bed rivers bed armouring and sediment sorting can heavily impact transportation. Armouring of coarser sediments consolidates a bed leaving finer sediments exposed to the flow and constantly moving through the system. Furthermore, this bi-modal sediment impacts roughness within the channel. A smooth channel with cohesive material decreases roughness, whereas in a non-uniform channel with larger grains roughness increases; this is turn makes movement of grains more difficult. The conclusions established within this research are of significant importance to understanding the complex relationships and various parameters for sediment dynamics within these systems.

How to cite: Remers, A., Heritage, G., and Entwistle, N.: An investigation into the threshold of sediment motion, in two non-uniform English gravel-bed rivers, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-123, https://doi.org/10.5194/icg2022-123, 2022.

15:15–15:30
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ICG2022-167
Amy East, Joel Sankey, Dongfeng Li, Ting Zhang, and Jonathan Warrick

The societal importance of understanding physical landscape response to rapidly progressing anthropogenic climate change is very high. Detecting geomorphic and sedimentary signals of modern climate change is essential for management decisions affecting human health and safety, infrastructure, economics, energy–food–water security, and ecosystems. This presentation examines challenges in measuring and attributing the influence of contemporary climate change on geomorphic and sedimentary systems, and opportunities for improving these efforts.

Foremost among the challenges to detecting modern climate-change impacts are short and incomplete records. Because anthropogenic climate change accelerated substantially after around 1970, its detection often requires robust, high-resolution data from before and after that time. For some purposes a small number of data points can be informative (documenting glacier extent using photographs taken decades apart), whereas investigations of other processes require daily or at least sub-annual data (fluvial sediment fluxes; documenting landslide patterns). Direct measurements rarely continue long enough, with consistent sampling frequency and methods, to resolve signals at the level of detail needed to detect or attribute change to climatic effects. Isolating signals in ‘noisy’ natural systems is notoriously difficult; individual extreme events (floods, storms, fires) can remain apparent for decades, obscuring more subtle change. Climatic influence also must be disentangled from land-use and tectonic effects. Data availability is commonly biased toward places with human land use, either because land uses motivated the site selection or because people witnessed and reported disasters. Variable connectivity and storage in sediment-routing systems (e.g., floodplains or dams in river basins) also affects climate signal detection downstream.

However, the scientific community has opportunities to make useful progress. Data are needed from many more locations, at greater spatial and temporal resolution, to resolve the nature and extent of ongoing climate-change effects. This can be done by establishing and continuing time-series measurements with consistent methods and frequency. We can utilize paleo-records wherever possible, such as studying high-sedimentation-rate lake deposits instead of relying on laborious in-stream sediment-flux measurements. Optimal research sites are those with little human land-use influence and a high signal-to-noise ratio—high sensitivity to climatic change (high-sediment-yield, low-storage catchments; steep slopes with little stabilizing vegetation) and places where warming has been fastest, e.g., high-latitude and high mountain settings. For certain landscape processes, it is useful to establish a global list of sites likely to respond earlier and more strongly than other locations, as has been done recently in the landslide community. We can better define the role of superimposed, cascading landscape disturbances and their relative timing and seasonality (e.g., fires, storms, and growth and senescence of vegetation). We encourage sharing data and methodological improvements across disciplinary and national boundaries and building a community network/platform to synthesize such improvements. There are instances where sufficient data exist to detect recent climatic influence but where no signal is apparent yet. Thus, reporting of both negative and positive results, that highlight climate-change effects or lack thereof, is essential to demonstrating rates, regional patterns, and nuances of process.

How to cite: East, A., Sankey, J., Li, D., Zhang, T., and Warrick, J.: Measuring and attributing geomorphic and sedimentary responses to modern climate change: challenges and opportunities, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-167, https://doi.org/10.5194/icg2022-167, 2022.

15:30–15:45
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ICG2022-459
Joel Johnson, Grace Guryan, Sam Anderson, Nicole Gasparini, Lisa Tranel, and Arjun Heimsath

Bedrock channel erodibility is a nonunique model-dependent parameter that scales hydraulic forcing to fluvial bedrock erosion. In landscape evolution modeling, erodibility coefficients are often assumed constant and uniform, and are often empirically calibrated to the form of natural landscapes. This approach lumps a wide range of variables into erodibility, including not only rock properties but also erosion processes (and their possible variations with discharge), climatic controls on hydrographs and rock weathering, and effects of coarse sediment supply.  Our goals are to better understand (a) how field measurements of rock properties could be combined to better quantify bedrock erodibility, (b) how bedrock erodibility may vary with discharge as different fluvial erosion processes become more or less dominant, and (c) how flood discharge variability and coarse sediment load influence “effective” erodibility in simple stream power incision model formulations.

Building on previous work, we first present new equations to calculate erodibility. Our rather complex erodibility model incorporates core-scale (i.e. unfractured) rock strength, discontinuity spacing (fractures, bedding planes), and climate-dependent bedrock susceptibility to weathering (which influences strength and fracturing), and accounts for abrasion and block plucking erosion processes. The model attempts to include feedbacks between these factors in a physical way, using variables that could be constrained from field data. Second, we explore the parameter space of these erodibility equations by modeling bedrock channel profile evolution for a range of conditions and varying rock properties, using preliminary constraints from field data collected in the semi-arid and lithologically variable Guadalupe Mountains, New Mexico and Texas, USA. Finally, we generalize our results by estimating uncertainties that may arise from assuming constant and uniform erodibility coefficients in simple stream power erosion models, compared to erodibilities that potentially vary spatially and temporally.

How to cite: Johnson, J., Guryan, G., Anderson, S., Gasparini, N., Tranel, L., and Heimsath, A.: Modeling bedrock channel erodibility as a function of measurable rock properties and climate, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-459, https://doi.org/10.5194/icg2022-459, 2022.

15:45–16:00
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ICG2022-514
Predicting rill erosion due to extreme rainfall events on a small hillslope in Spain using the Landscape Evolution Model (LEM) 
(withdrawn)
Antonio Minervino Amodio, Pietro P.C. Aucelli, Dario Gioia, Saskia Keesstra, Carmen M. Rosskopf, and Artemi Cerda
16:00–16:15
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ICG2022-204
Vincent Viel, Riadh Bouaziz, Gilles Arnaud-Fassetta, and Salem Dahech

The Kneiss Islands and the outlet of the Wadi Leben watershed (Tunisia), is an internationally recognized site, classified ZICO (1990) and Ramsar (2007) for the high fish productivity of its shallow waters, which makes these areas a favorable breeding ground for migratory birds. The difficulties to access to the sea make these areas slightly degraded. However, the sustainability of this site is now being jeopardized with anthropogenic pressure becoming progressively stronger on this littoral zone and the upstream watershed.

Our objective is to show the original hydro-sedimentary functioning of this Mediterranean watershed, shared between physical characteristics and intrusive agricultural practices in full reconversion (from local/traditional to international/globalized): (i) The upstream zone of the watershed is subject to sediment retention related to the implementation of a hydro-agricultural and anti-erosion system (water and soil conservation works); (ii) The intermediate zone, by its morpho-structural and sedimentogenetic characteristics, has favored the accumulation of sediments in the valley bottoms, which makes it not only a transfer zone but also a sediment-recharge zone that can substitute for the upstream; (iii) The downstream zone, which could be expected to be sensitive to these upstream conditions, which may have altered its morphosedimentary equilibrium and caused a retreat of the coastline and the estuary, and accelerate soil salinization in the coastal plain, records a completely different hydro-morphological behavior, where the role of high-magnitude, low-frequency events (i.e., exceptional floods) is highlighted to understand its recent geomorphological dynamics.

In a methodological point of view, this research is based on a systemic analysis used to better understand the hydro-sedimentary connectivity. Topographic field measurements were carried out on a small representative watershed (7 km²) in order to estimate sediment storage induced by agricultural practices. Results were then extrapolated at the watershed scale (1215 km²) according to a modeling approach. Channel adjustments including the linear and lateral erosion and sedimentation processes were then estimated according to twenty 137Cs and 210Pb dating carried out in the transfer zone as well as in the wetlands (Sebkhas and shotts) located at the outlet of the watershed.

As a conclusion, we indicate that Wadi Leben can be proposed as a model of hydro-morpho-sedimentary functioning showing the efficiency of sedimentary recharge as a key point of equilibrium of the watershed as soon as the river is capable of lateral displacements, thus joining the question of the re-dynamization of rivers in the perspective of the river-bed restoration. A balance sheet leading to the assessment of the sustainability of economic practices (agriculture, industry, tourism, fishing) in the context where change factors (water resources, hydrological regime, sedimentary stock) may affect the hydrosystem in its watershed in the more or less long term is also proposed.

How to cite: Viel, V., Bouaziz, R., Arnaud-Fassetta, G., and Dahech, S.: Systemic analysis of sediment connectivity in the Wadi Leben watershed, Tunisia (Mediterranean): Between morpho-structural potentialities, originality of the hydrographic network and societal reorganizations, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-204, https://doi.org/10.5194/icg2022-204, 2022.

16:15–16:30
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ICG2022-223
Xianyan Wang, Xiaolu Dong, Long Yang, Zhijun Zhao, Ronal Ronal Van Balen, Xiaodong Miao, Tao Liu, Jef Jef Vandenberghe, and Huayu Lu

It has been debated whether gradual, persistent river flows or infrequent outburst floods play more important roles shaping the rugged mountain landscape, partially tied to insufficient evidence based on reliable retrievals of erosion and sediment fluxes from historical outburst floods. The Himalayan Tsangpo Gorge, exhibiting rapid exhumation and outburst floods, provides a perfect avenue to shed light on this debate. Here we report the quantitative erosion and transport capacity of a recent catastrophic outburst flood in Himalayan which occurred in June 2000 by landslide-dam failure with a peak discharge of 105 m3/s. The flood lasted for only ~10 hours, but equivalent to the cumulative effect of 103 years of continuously gradual fluvial transport and erosion. The valley widened three times, triggering a large number of landslides, and extensive boulder bars were formed in the channel. These boulder bars protected the channel bed from incision but promoted extensive lateral erosion through increased roughness, resulting in widespread bank erosion and concurrent landslides, which will continue to do so until the next catastrophic flood remobilizes them. We provide direct evidence that highlights the dominance of recurrent outburst floods on drastic exhumation, deep gorge formation and long-term landscape evolution over rapidly uplifting mountains.

How to cite: Wang, X., Dong, X., Yang, L., Zhao, Z., Ronal Van Balen, R., Miao, X., Liu, T., Jef Vandenberghe, J., and Lu, H.: Outburst floods control the fluvial landscape evolution in Himalayan Tsangpo Gorge, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-223, https://doi.org/10.5194/icg2022-223, 2022.

Coffee break and poster session
17:00–17:15
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ICG2022-565
Marek Ewertowski, David Evans, Aleksandra Tomczyk, and Szymon Śledź

Modern glaciers and processes operating within their foreland are often used as analogues to infer past glacial conditions and interpret dating results. As such, an important research question is how glacial landforms changed over time after being created by ice or released from under the ice, and how confident can we use them as modern analogues of past environments? Proglacial areas exposed because of glacier recession are among the most dynamic landscapes in polar and mountainous regions and are intensively modified by various geomorphological processes associated with ice margin retreat, meltwater activity, and paraglacial adjustment of topography. As these areas contain important traces of the former glacial regime and dynamics, quantification of the recent transformation of these areas is crucial in terms of glacial landsystem studies.

In this study, we quantified recent landscape dynamics in proglacial areas of Fjallsjökull and Hrútárjökull (SE Iceland) based on time series of unmanned aerial vehicle surveys (UAV) from 2014, 2016, 2017, 2018, 2019 and 2021. UAV data were processed using the structure from motion (SfM) approach to generate detailed (0.1 m ground sampling distance) orthomosaics and digital elevation models. Based on the results of geomorphic change detection, five types of landscape dynamics were identified: (1) Degradation of ice-cored moraines and expansion of the lake; (2) Ice margin retreat and melting; (3) Ice margin oscillation and dislocation of the esker; (4) Degradation of buried snout and development of pitted outwash; (5) Degradation of buried ice in the overdeepening. In general, the volume balance for Fjallsjökull/Hrútárjökull foreland over the 2014-2021 period was negative. Large-scale changes were related to the retreat of the glaciers’ margin, ice melting and drainage reconfiguration. A similar magnitude of volume loss was observed in places where the ice-cored moraines degraded, and the lake expanded. Degradation of buried ice and associated collapsing of outwash plain was responsible for minor volume loss. In some relatively small areas, gain in elevation was observed – it was primarily associated with ice margin pushing or transporting sediments during winter re-advances and, to a much lesser degree, by mobilizations of sediments due to debris flows. Relatively large areas of glacial foreland remained stable over the observation period. However, as an example of collapsing outwash indicates, topography adjustment due to the final melting of dead ice might occur several tens of years after the ice margin apparently retreated, and the ground was stabilized and vegetated.

This research was funded by National Science Centre, Poland, project number 2019/35/B/ST10/03928.

How to cite: Ewertowski, M., Evans, D., Tomczyk, A., and Śledź, S.: Mapping and quantification of proglacial landscape changes based on time-series of UAV surveys: A case study of a temperate glacial landsystem of Fjallsjökull/Hrútárjökull, SE Iceland, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-565, https://doi.org/10.5194/icg2022-565, 2022.

17:15–17:30
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ICG2022-689
Jon Gardoqui, Alejandro Cearreta, Ane García-Artola, María Jesús Irabien, José Gómez-Arozamena, and Víctor Villasante-Marcos

Coastal marshes from the northern Atlantic Iberian margin are unique sedimentary environments filtering and storing chemical pollutants, nutrients and terrestrial carbon,proxies that may allow deciphering their environmental transformation. The Nalón estuary marshes (Asturias, N Spain) have been severely impacted by human activities such as construction of dikes, land reclamation and coal and mercury mining effluents. We analyzed foraminiferal assemblages from 18 surface samples collected from salt marsh and tidal flat settings along the axis of the estuary and a 50-cm-long core recovered from the lower estuary San Juan de la Arena salt marsh in order to understand recent coastal sedimentation and erosion processes. Salt marsh surface samples are characterized by Trochammina inflata, Entzia macrescens, Miliamminafusca andHaplophragmoideswilbertitaxa in the living and dead assemblages. Tidal flat samples from the middle estuary are dominated bythe living speciesHaynesina germanica, Ammonia tepida, Cribroeplhidium excavatumand M. fusca. In turn, deadassemblages reveal an elevated proportion (max. 95%) of salt marsh taxa, much higher than those determined in other tidal flats from this coastal region, that could derive from the ongoing erosion of adjacent salt marsh areas.The stratigraphy of the sedimentary core is distinguished by two intervals with characteristic microfossil assemblages,whose depositional environment has been inferred from those analogues represented by the surface samples. The lowermost unit (50-28 cm), with a mixture of H. germanica, M.fusca, A. tepida and C. excavatum,has been interpreted as an intertidal flat environment, deposited before the development of the San Juan de la Arena salt marsh, namely previous to the 1950s, as observed in aerial photographs. The second unit (28-0 cm) is characterized mainly byE. macrescensand T. inflata, followed by M. fusca and H. wilberti, representing a salt marsh environment. The salt marshwas developed after the 1950s probably in response to an important accumulation of sediment in the lower estuary. However, as observed in aerial photographs, this salt marsh is no longer active owing to very active erosional processes, possibly associated to the construction of a dock in front of this area in ~2004-2006. On the whole, the foraminiferal analysis of the Nalón estuary sedimentary record hasrevealedsignificant changes in the sedimentation and erosion processesalong the middle and lower estuary during the 20th and 21st centuries.

Acknowledgements: Research supported by the Spanish MINECO RTI2018-095678-B-C21(MCIU/AEI/FEDER, UE) project.

How to cite: Gardoqui, J., Cearreta, A., García-Artola, A., Irabien, M. J., Gómez-Arozamena, J., and Villasante-Marcos, V.: Recent sedimentation-erosion processes along the Nalón estuary (Asturias, N Spain), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-689, https://doi.org/10.5194/icg2022-689, 2022.

17:30–17:45
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ICG2022-596
Carolina Coelho Giorio do Vale, Nelson Ferreira Fernandes, Renato Villela Mafra Alvesda Silva, and Lúcia Maria da Silva

Both internal and external Earth’s dynamics are constantly changing the landscapes and one of the most influent external components are the fluvial processes, altering the relief through erosion and fluvial deposition, as well as through its respective drainage network’s reorganization. The drainage basins dynamics seeks to achieve a balance between tectonic uplift and river erosion. The use of parameter Chi (χ) allows a comparison of basins in different scales, erosion and uplift rates, making it possible to determinate its steady or transient state and comprehends the dynamics de divisor migration of basins. Although the great advances have been reached in last decades, there are still many questions without answer. For the accomplishment of this study, two areas in the Serra do Mar of São Paulo and Paraná were chosen due to the presence of important river captures, which generated significant reorganizations in the drainage network. Furthermore, cosmogenic isotopes (10Be) data from existent literature in Serra do Mar of Paraná allows the estimation of the denudation rate of these basins in the long term. In this study, these rates are analyzed combined with values of Chi, verifying the influence of the captured rivers, which contribute to the understanding of landscape evolution. This study uses the Digital Elevation Model (DEM) SRTM 30m. The DEM data were treated in ArcGIS and analyzed in MATLAB, where oceanic and continental basins were selected, considering sea level as the base level. The analysis was made through functions of Topographic Analysis Kit (TAK), integrated to TopoToolBox, to generate longitudinal and elevation-Chi profiles and Chi maps plotted with knickpoints data and, for the Paraná basins, the product obtained were simultaneously analyzed with 10Be data. From the analysis of these data, was possible to notice the ocean basins are capturing the continental basins and, therefore, that these basins are in a transient state, which means that their divisor is migrating towards higher Chi values, thus, towards the interior of the continent. In Paraná basins, the retreating areas of the Serra do Mar escarpment directly related to places of high erosion rates on the oceanic slope. These results, although preliminary, attest the potential of analysis methods used, proving the influence of river captures in the disruption of the steady state between adjacent drainage basins located on the oceanic and continental slopes, as well as their influence on the differentiated retreat in the Serra do Mar escarpment.

How to cite: Coelho Giorio do Vale, C., Ferreira Fernandes, N., Villela Mafra Alvesda Silva, R., and Maria da Silva, L.: Effects of drainage captures in the retreat of Serra do Mar: an analyze using the combination of numerical models and cosmogenic isotopes , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-596, https://doi.org/10.5194/icg2022-596, 2022.

17:45–18:00
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ICG2022-266
Liran Goren, Elhanan Harel, Eitan Shelef, Onn Crouvi, and Hanan Ginat

Drainage reversals occur when a channel reverses its flow direction by 180o while exploiting its antecedent valley. This reorganization mode can critically impact landscapes' hydrologic and geomorphic functionality, but the processes inducing reversals and the related landscape dynamics have not been studied in detail. Reversals are commonly attributed to tectonic tilting. However, in many cases, independent evidence for tilting is missing. Furthermore, when reversals occur toward great escarpments, as was documented in many terrains around the globe, isostatic tilting is expected to occur away and not toward the escarpments.

The current study explores a natural laboratory for drainage reversals in the southeastern Negev Desert, Israel. We identified in this field area tens of highland channels that reversed their flow direction eastward and toward the Arava Valley Escarpment.

Reversals are established by observations of (1) barbed tributaries that join the main trunk with junction angles > 90o and preserve the antecedent pre-reversal drainage topology; (2) a valley confined drainage divide (windgap) that separates the reversed channel from the antecedent, beheaded channel; and (3) series of terraces that grade west, toward the windgap and opposite to the active flow direction.

Based on field observations and morphometric analysis, we propose a new, tilting-independent, mechanism for inducing flow reversals. According to this mechanism, reversal is linked to localized windgap migration within the antecedent channel and away from the escarpment. Migration is driven by slope imbalance across the windgap with steeper slopes at the escarpment side, and by erodibility differences between the hard rocky interfluves and the more erodible valley fill.

Using a new algorithm for quantifying valley width, we find that the scaling between drainage area (A) and width (W) differs between reversed, beheaded, and non-reorganized valleys. In addition to providing markers for reorganization, the unique A-W scaling leads to feedback that promotes further windgap migration and generates longer reversals.

The oppositely grading terraces that accompany some reversed channels present an outstanding opportunity for quantifying the dynamic and rate of windgap migration. We hypothesize that the abandonment age of each terrace reflects the timing at which the paleo-windgap migrated past the location of the terrace, promoting the incision of the reversed channel that generated the terrace. Accordingly, the abandonment ages of the terraces can inform us about the timing and dynamics of windgap migration.

Absolute ages of terrace abandonment were constrained by luminescence dating, with complementary relative ages inferred from chronosequence of reg soils, which develop on abandoned terraces in hyper-arid environments. In agreement with the reversal model, we found that the degree of soil development and the abandonment ages of terraces increase with distance from the windgap eastwards. The average windgap migration rate has been ~1 mm/yr since 200 Kyr, an order of magnitude greater than the vertical incision rate of the reversed channel. The age-distance relations of the terraces indicate episodic windgap migration with a recent stalling. A similar age for other dated windages in the region hints at a regional, possibly climatic control on windgap migration.  

How to cite: Goren, L., Harel, E., Shelef, E., Crouvi, O., and Ginat, H.: Landscape evolution related to drainage reversals toward escarpments: Insights from the southeastern Negev Desert, Israel , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-266, https://doi.org/10.5194/icg2022-266, 2022.

18:00–18:15
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ICG2022-103
Lotem Robins, Joel Roskin, Lotan Edeltin, Revital Bookman, LuPeng Yu, and Noam Greenbaum

Aeolian-Fluvial (A-F) processes along dunefield margins document environmental changes in arid zones around the world. In the present study, at the northwestern Negev dunefield (Israel) margins, high-resolution chrono-stratigraphic analysis of marginal Vegetated Linear Dunes (VLDs) and fine-grained alluvial plains was conducted. Nineteen stratigraphic sections were analyzed in detail. Dating included pre-measurements using Portable Optically Stimulated Luminescence (POSL), which were used to decipher representative samples for OSL dating. Selected hearth and vegetation samples were radiocarbon dated as well.

A-F processes along dunefield margins may generate reliable and detailed palaeoarchives, by combining POSL and OSL analyses. VLDs, prone to defined periods of activation and stabilization, control a gradual and lagged shift from aeolian to fluvial domination in the dune-dammed dunefield margins, succeeding dunefield stabilization.

In an aeolian-dominated environment, either fully or partly dammed fluvial systems aggregate upstream-sourced sediments along the dunefield margins, forming an alluvial plain. Dune-dam waterbody deposits include three distinct types: (a) event-based couplets, (b) massive structureless loam and (c) fine-laminas. These deposits that may remain preserved for substantial times bury usually truncated dune remains. Aeolian deflation of fine-grained sediments from dune-dam waterbody deposits, percolated into adjacent marginal VLD, initiating pedogenic processes. Altogether, dune-dam impoundments were found to be spatially dynamic processes, in which the dune-dammed fluvial system gradually propagates downstream from the dunefiled margin into the dunefield. Each impoundment was generated by slightly or distinctly different A-F mechanisms depending on the location of the damming-dunes in relation to the dunefield margins.  

In the northwestern Negev, three major sand incursions into <180 km2 fluvial systems during the LGM, Heinrich-1 and Younger-Dryas, resulted in localized and usually seasonal waterbodies, utilized by EpiPalaeolithic hunter-gatherers . This study also revelaed that during the early Holocene a climatic shift, which left a signature in the Mediterranean Basin in the form of Sapropel-1, was recorded along the dunefield margins, forming the last, upper and significant portion of the alluvial plains. This aggregative environment was also utilized by Neolithic and Chalcolithic man in some basins, locally reactivating VLDs. After dune-dam breaching, a fluvial-dominated environment developed, characterized by floodplain deposition, and scour and fill patterns.

How to cite: Robins, L., Roskin, J., Edeltin, L., Bookman, R., Yu, L., and Greenbaum, N.: Late Quaternary aeolian-fluvial palaeoarchives along dunefield margins, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-103, https://doi.org/10.5194/icg2022-103, 2022.

18:15–18:30
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ICG2022-199
Filip Duszyński, Wojciech Bartz, Barbara Woronko, Kacper Jancewicz, Piotr Migoń, and Francesco Sauro

The research conducted in recent years has revealed that processes operating at depth play an important role in the morphogenesis of stepped tablelands in Central Europe (SW Poland, N Czechia), underlain by alternating layers of sandstone and fine-grained rocks of the Upper Cretaceous age. It has been demonstrated that underground erosion significantly contributes to the in situ disintegration of the marginal parts of sandstone plateaus and mesas, thereby producing distinctive ruiniform assemblages. They comprise chaotic boulder clusters replacing the cliff-lines, joint-aligned corridors, clefts opened due to the loss of mass from beneath, as well as plazas and courtyards with negligible surface runoff. While the widespread occurrence of sandy cones at the outlets of vertical fissures and allochthonous sandy aprons on the subjacent slopes testifies well to the efficiency of underground erosion, the mechanisms of detachment of sand grains remain unknown. This research aims to elucidate which processes are making the sandstone mechanically incoherent and susceptible for mechanical erosion at depth.

In older views weathering processes acting upon sandstone cliff-lines have either remained unspecified or a priori assumed to be mechanical breakdown. Yet, the presence of joint-aligned and highly disintegrated zones, often mimicking the grikes of the ‘classic’ karst terrains, as well as the widespread evidence of sandy detritus removal via subsurface drainage, allowed us to hypothesise that dissolution may be an important but neglected factor responsible for the loss of coherence of the sandstone rock mass.

Sandstone samples were collected from both disintegrated and non-disintegrated sandstone cliff-lines, as well as fresh debris originating from a recent rockfall event in one of the rock cities in Czechia. Loose grains of sand, already removed from the caprock and deposited at the foot of rock walls, were investigated too. Scanning electron microscopy equipped with energy dispersive spectrometer (SEM-EDX) was used to study micromorphological changes, diagnostic of intensive chemical weathering. This was supplemented by studies using the polarizing light microscopy, i.e. study of thin sections as well as x-ray diffraction (XRD) accompanied by thermal analysis (DSC-TG) to evaluate mineralogical composition of sandstone and to assess the secondary rock porosity.

The preliminary results revealed high degree of etching, mainly of syntaxial quartz overgrowths, with a number of v-shaped or irregularly shaped pits as well as large embayments. Interestingly, SEM-EDX analysis showed the presence of kaolinite, which might conform to the advanced chemical weathering of sandstone as well. It is supposed that solutional processes not only have prepared the rock for further erosional processes and the resultant development of ruiniform relief, but they also contribute to a variety of catastrophic mass movements due to the significant decrease of intact rock strength.

The results presented are the first outcomes of the new Q-MESA project (no. 2020/39/D/ST10/00861) funded by the National Science Centre, Poland.

How to cite: Duszyński, F., Bartz, W., Woronko, B., Jancewicz, K., Migoń, P., and Sauro, F.: Another one bites the quartz? How silica dissolution contributes to the development of ruiniform relief in the Central European sandstone tablelands?, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-199, https://doi.org/10.5194/icg2022-199, 2022.

18:30–18:45
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ICG2022-287
Aaron Micallef

Groundwater has been implicated as an important geomorphic agent in valley development. In unconsolidated sand and gravel, field observations and numerical simulations have shown that groundwater can lead to the formation of theatre-headed valleys. However, the temporal scale at which these valleys form and the influence of geologic heterogeneities on valley evolution remain poorly constrained. In bedrock, the development of valleys by groundwater remains controversial, and other processes (e.g. plunge-pool erosion, megaflooding) have been proposed to explain such landforms.

Here I will present two case studies, from the Canterbury coastline of New Zealand (unconsolidated sediments) and the Maltese Islands (limestone), to address these knowledge gaps.

In the first case study (New Zealand), I integrate field observations, luminescence dating, multi-temporal UAV and satellite data, time-domain electromagnetic data and slope stability modelling to show that theatre-headed valley erosion by groundwater in sand and gravel is an episodic process that occurs once every 227 d on average, when rainfall intensities exceed 40 mm/d. Valleys can be elongated at rates of 30 m/d via the formation of alcoves and tunnels by groundwater seepage, followed by retrogressive slope failure due to undermining and a decrease in shear strength. Valley location is determined by the occurrence of hydraulically conductive zones, such as relict braided river channels, and sand lenses.

In the second case study (Maltese Islands), I combine field and remote sensing observations from Gnejna Valley with numerical modelling to demonstrate that groundwater seepage is the key driver of theatre-headed valley formation in jointed limestones over clays. Erosion takes place via widening of joints and fractures by fluid pressure and dissolution, and creeping of the underlying clay layer, both of which lead to slope failure at the valley head and its upslope retreat. The talus is removed by creep and sliding on the valley bed. The location and width of the valley are determined by the location of a master fault and the extent of the damage zone. An exponential decrease of seepage away from the master fault gives rise to a theatre-shaped head.

How to cite: Micallef, A.: The role of groundwater in forming theatre-headed valleys in unconsolidated sediments and bedrock, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-287, https://doi.org/10.5194/icg2022-287, 2022.

18:45–19:00
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ICG2022-133
Avni Yoav

The geomorphological process creating the birth and development of large-scale erosional surfaces remains somewhat unclear. In this regard, new insights on the process leading to the creation of such large-scale surfaces were revealed during intensive study on the morphotectonic evolution of the Sinai-Israel micro-plate.

A major erosion surface developed during the Oligocene – Early Miocene, (34-20 Ma) in the northern Red Sea and southern Levant as a result of the combined effects: the formation of an ~3000 km × 1500 km crustal dome above the Afar plume, affecting the northeastern sector of the Afro-Arabian continent, and widespread fluvial erosion that gradually truncated the northern edge of this dome. The truncation of the northward tilted Sinai-Israel plate exposed the Precambrian basement rocks at its southern tip, while a series of sandstone and carbonate units were exposed at its central and northern sector. The Syrian Arc anticlines, developed in the Late Cretaceous, were deeply truncated, exposing their Triassic – Jurassic section. During this event, a geological section, estimated to be 2000-500 m, was removed from the entire region. The Oligocene Regional Truncation Surface (RTS) developed by a continues fluvial and chemical erosion acting on a gentle uplifted region, on which the rate of tectonic uplift was smaller than the ability of the erosive agents to erode and transport the eroded products out of the region, deposited them in the eastern Mediterranean basin. These clastic sediments are holding large-scale gas reservoirs. The reconstruction of this erosive surface is important for detection of the tectonic activity that predates the plate separation of the Sinai-Israel plate and the development of the Dead Sea Transform, initiated in 18-16 Ma along a preexisting suture line. The development of the truncation surface was followed by the deposition of Early Miocene fluvial sediments, deposited within broad channels and valleys, gently incising the original Oligocene erosion surface.

General uplift, tectonic depressions and dome structures developed during the Middle Miocene to Early Pleistocene (16–1.5 Ma), locally deforming the general flat relief left by the previous erosional stage. This rapid tectonic activity promoted the breakup and evolution of the Sinai-Israel microplate generated the development of a deeply incised drainage system, bordered by large-scale cliff. This new erosive pattern is best demonstrated by the deeply incised valleys developed within the core of the Syrian Arc anticlines. The interaction between the anticlinal structure and the Oligocene truncation surface is dictating the configuration of the oval valleys, while their development as deeply incised valleys evolved during younger tectonic events in the Miocene. Another modification to the former flat landscape was caused during the 1.5-1 Ma tectonic event that uplifted and tilted the Negev region toward the Dead Sea Rift. At this stage, a new drainage system was developed, deeply incising the former flat surface. However, despite these modifications, the original Oligocene erosive surface is still dominating the present skyline in the entire Middle East. During most of the time, the landscape evolutionary processes were active under arid climates, contributing to good preservation of diverse geomorphological features.

How to cite: Yoav, A.: The genesis and development of large-scale erosion surfaces – insights from the Sinai-Israel micro plate, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-133, https://doi.org/10.5194/icg2022-133, 2022.

Display time: Thu, 15 Sep 09:00–Fri, 16 Sep 19:00

Poster: Thu, 15 Sep, 16:30–16:45 | Poster area

Chairpersons: Katja Laute, Adélia Nunes, Achim A. Beylich
P20
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ICG2022-47
Achim A. Beylich and the DENUCHANGE Team

The working group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE, http://www.geomorph.org/denuchange-working-group/) was approved as a new working group of the International Association of Geomorphologists (IAG) during the 9th International Conference on Geomorphology, 6-11 November 2017, New Delhi, India.

The key question of DENUCHANGE is:

What are the contemporary chemical and mechanical denudation rates in different morphoclimatic zones on the Earth?

Denudation is controlled by a range of environmental drivers and can be significantly affected by anthropogenic activities. The better understanding of possible effects of ongoing and accelerated environmental changes on present-day denudation requires systematic and quantitative studies (environmental monitoring) on the actual drivers of denudational processes. Only if we have an improved knowledge of drivers and quantitative rates of contemporary denudational hillslope and fluvial processes as well as of the (dis)connectivity in landscapes and between hillslope and fluvial systems across a range of different selected climatic environments, possible effects of global environmental changes on denudation can be better assessed. Special focus is given to selected morphoclimatic zones that are expected to react particularly sensitively to ongoing and accelerated environmental changes, and the key focus of DENUCHANGE is therefore on (i) cold regions (including glacierized, glaciated and unglaciated cold climate environments), (ii) temperate regions, (iii) arid / semi-arid regions and (iv) tropical regions. The different morphoclimatic zones are defined by morphometric characteristics/signatures detected in the various zones.

DENUCHANGE

  • Provides a detailed compilation and comparison of contemporary chemical and mechanical (drainage-basin wide) denudation rates in selected and clearly defined drainage basin systems in selected cold regions, temperate regions, arid / semi-arid regions and tropical regions worldwide;
  • Provides a process-oriented, coordinated and integrated analysis and compilation of the respective key drivers of contemporary denudation occurring under the different present-day morphoclimates;
  • Addresses the key question how environmental changes are affecting contemporary denudation rates in different morphoclimates. This also includes human activities in different morphoclimatic zones, in the context of environmental changes in the Anthropocene.

DENUCHANGE test site fact sheets were developed and key catchment information together with meteorological and hydrological data have been collected from 35 accepted DENUCHANGE field test sites (by March 2022). The collected catchment information and data will be compiled in a database.

The DENUCHANGE field test site catalogue has been published in February 2022 as an interactive PDF-file including short and well illustrated presentations of 22 accepted DENUCHANGE field test sites which are currently in operation within the DENUCHANGE network. Each presented field test site is linked to an interactive map. Key information on each field test site includes short descriptions of the field sites and the methods and techniques applied, and key meteorological and hydrological data. Both field test sites with available longer data records and newly established field sites are included in the catalogue.

Two special issues to the scientific journals Landform Analysis (2018) and Geomorphology (2021) have been produced by the DENUCHANGE group, and synthesis/review papers related to the defined key questions and tasks of DENUCHANGE are currently in preparation.

How to cite: Beylich, A. A. and the DENUCHANGE Team: The IAG Working Group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE): Scientific need, activities and outcomes since the year 2017, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-47, https://doi.org/10.5194/icg2022-47, 2022.

P21
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ICG2022-46
Achim A. Beylich and Katja Laute

Denudation, including both chemical and mechanical processes, is of high relevance for landscape development and the transfer of solutes and sediments from headwater systems through main stem of drainage basin systems into sinks like lakes or the sea. Denudation is controlled by a range of environmental drivers and is in most environments and landscapes worldwide significantly affected by anthropogenic activities.

In the boreal mountain environment of central Norway the regulated lake Selbusjøen, situated at ca. 160 m a.s.l. with an area of 58 km2 and connecting the upstream main mountain river Nea and the downstream main river Nidelva, forms a significant sink for sediments being transferred from its drainage basin area of in total 2876 km2.  The significant sediment trapping efficiency of lake Selbusjøen is causing a sediment deficit and locally increased fluvial erosion and down-cutting in the downstream river Nidelva which drains into the Trondheim fjord.

This ongoing GFL research on natural and anthropogenic drivers and the spatiotemporal variability of contemporary chemical and mechanical fluvial denudation rates and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen is based on statistical analyses of high-resolution meteorological data, detailed field and remotely sensed mapping, computing of morphometric catchment parameters, and year-round process geomorphological field work. Geomorphological field work includes detailed field observations, repeated photographic documentations of selected stream channel stretches and slope surface areas, and field monitoring and frequent measurements with snow, rain water, stream-water and bedload samplings for the analysis of solute and suspended sediment concentrations and the study of atmospheric solute inputs, and the quantification of fluvial solute and sediment transport. Field work is carried out in a number of defined catchments/drainage areas draining into Selbusjøen. The selected catchment/drainage area systems are all characterized by large surface areas with a nearly closed and continuous vegetation cover mostly composed of boreal forests and bogs, and represent a range of different catchment sizes, catchment morphometries, orientations/aspects, and sediment sources and availabilities. In addition, different types and intensities of anthropogenic impact like, e.g., agriculture, forestry and modifications of natural stream channels (e.g., dams, steps, bank protection) and channel discharge for water power purposes are found in various catchments.

Runoff is occurring year-round and the natural runoff regime is nival. Annual runoff in the area amounts to 684 mm. Most fluvial transport is occurring during peak-runoff events generated by snowmelt, rainfall events or combinations of snowmelt and rainfall.  Altogether, chemical denudation is moderate but dominates clearly over mechanical fluvial denudation. Both chemical and mechanical fluvial denudation show a significant spatial variability which can be related to the varying characteristics of the selected catchment/drainage area systems. Agriculture and forestry are generally increasing mechanical fluvial denudation rates whereas anthropogenic stream channel and channel discharge modifications are leading to reduced fluvial bedload transport rates into lake Selbusjøen. Ongoing and accelerated climate change is expected to increase both chemical and mechanical fluvial denudation and sediment transport rates into lake Selbusjøen, particularly in the surface areas that have been modified by anthropogenic activities.

How to cite: Beylich, A. A. and Laute, K.: Climate and anthropogenic impacts on denudation and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen in central Norway, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-46, https://doi.org/10.5194/icg2022-46, 2022.

P22
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ICG2022-231
Luca Mao and Ricardo Carrillo

Steep mountain streams are usually narrow, confined, and characterized by coarse sediments, and cascade or step-pool morphology. Step sequences are quite stable geomorphic units, but high magnitude floods can destroy and reform these features and lead to significant channel changes. However, our current knowledge of channel changes due to floods of different magnitude is still limited to few field sites, and limited evidence are available for high-gradient streams. However, the increased use of unmanned aerial systems to collect photos, and structure-from-motion algorithms able to generate high resolution point clouds from photos, provided unprecedented chances for acquiring multi-temporal sets of digital terrain models. The study was conducted on the Estero Morales, a 27 km2 glacierized Andean catchment located in central Chile. Runoff is dominated by snowmelt in late spring, and glacier melt from December to March. Autumn rainfall events can also generate infrequent but high-magnitude flood events. The study site is a 150-m long, step-pool/cascade reach. A high-magnitude flood generated by an ENSO event occurred in April 2016. The flood destroyed a bridge and caused considerable damages downstream. Detailed topographical surveys of the reach were taken before and after the flood and geomorphological changes due to the flood event were assessed by comparing the pre- and post-flood DEMs. The flood event, which is estimated to have recurrence interval higher than 30 years, was able to move boulders up to 2 m, and caused remarkable changes in the study sites. The channel avulsed in several points, and the morphology changed considerably. The number of steps along the study sited were 25 and 17 before and after the flood event, respectively. However, only 4 of the original 25 steps remained stable in the channel. The number of pools remained constant before and after the flood, but only 9 of the 26 pools remained in their place. The DoD revealed that the study reach experienced vertical changes up to 1m, especially due to bank erosion. Overall, the volume eroded and deposited within the study reach was about 359 and 680 m3, respectively, for a net volumetric change of 321 m3.

How to cite: Mao, L. and Carrillo, R.: Morphological changes due to a high-mangitude flood in a steep Andean stream, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-231, https://doi.org/10.5194/icg2022-231, 2022.

P23
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ICG2022-537
Daniel Germain and Ludwig Stabile-Caillé

Scree slopes offer an environment conducive to the occurrence of several gravity-driven geomorphic processes, the frequency and magnitude of which are highly variable in time and space. These processes locally prevent vegetation colonization, despite the climatic warming that favors a general progression and consolidation of forest fronts, and this from an altitudinal as well as a latitudinal point of view. The position of the forest front is therefore due, in addition to the climate, to the geomorphological dynamics of mass transfer processes on these steep slopes. Rarely observed in a cold temperate climate, at low altitude and enclosed in the forest environment, this makes the Northern Gaspé region (Province of Quebec, Eastern Canada) unique and complex for studying the interactions between geomorphic processes, talus slope geometry and morphology and forest dynamics during the Holocene.

The mapping inventory of 43 active talus slopes in the coastal valleys of the Northern Gaspé, and their geometric characteristics, allowed the identification of statistically significant variables that explain scree slope morphology in relation to two groups of dominant geomorphic processes, namely: 1) snow avalanches and debris flows, and 2) frost-coated clast flows and rockfalls. The first group is found on East and North facing slopes while the second is found on West and South facing slopes. The variables indicative of high geomorphic activity (active area, altitudinal treeline, Ho/Hi ratio) all suggest increased geomorphic activity on West and South facing slopes. Conversely, the East and North facing slopes are largely stabilized, but occasionally disturbed by debris-flow channels and snow-avalanche corridors. The location and intensity of these disturbances depend essentially on the morphology of the rockwall and the talus slope, in addition to climatic parameters.

The evolution of the West and South facing slopes is more complex as geomorphic processes have continued to disrupt the vegetation colonization, started 7250 years BP, on the slopes where the rockwalls are still active. However, the reasons for the presence or absence of frost-coated clast flows having a notable impact on the sediment budget and the altitudinal treeline remain unclear.

How to cite: Germain, D. and Stabile-Caillé, L.: Dynamics of scree slopes in forested environments: processes, modelling, and Holocene evolution, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-537, https://doi.org/10.5194/icg2022-537, 2022.

P24
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ICG2022-461
Giorgia Macchi, Stefano Crema, Gabriella Boretto, Giovanni Monegato, Barbara De Fanti, Lorenzo Marchi, and Marco Cavalli

The extreme meteorological event “Vaia storm”, which occurred between the 27th and 30th October 2018 over Northeastern Italy, caused widespread windthrows, generated slope instabilities and floods, and damaged several anthropic structures. The Liera catchment (37.7 km2), in the Dolomites, was severely affected by the Vaia storm: an intense flash flood occurred in the valley floor, shallow lansdlides affected soil-mantled slopes, and 34 sub-basins featured debris flows. These severe impacts, together with the availability of high-resolution multi-temporal topographic data, make the Liera catchment an excellent case-study for the analysis of the geomorphic processes caused by the Vaia storm. To this end, several activities were carried out in the frame of the Interreg SedInOut project (2019-2022) encompassing: (i) the creation and comparison of pre- (2015) and post-event (2019) sediment sources inventories, (ii) the analysis of landforms evolution and (iii) the quantification of debris-flow mobilized volumes. The study methods include field surveys, orthophotos interpretation, rainfall analysis, and the processing of high-resolution (1 m) multi-temporal LiDAR-derived DEMs. The main outcomes of this study include: (i) the identification of new sediment sources generated by the Vaia storm, (ii) the quantitative estimation of mobilized material from each sub-basin through DEM of Difference (DoD), and (iii) the assessment of the debris yield rate (i.e. the volume eroded for unit channel length) for homogeneous channel reaches. The structural setting and lithological variety of the valley led to different debris-flow triggering mechanisms. Event rainfall characterization shows that the Liera catchment is located near the edge of one of the convective precipitation belts of the final phase of the Vaia storm; important rainfall gradients occurred between the two valley flanks, which affected more severely the right side. The 2015 pre-event mapped sediment sources cover a total area of about 1.88 km2 while the 2019 inventory covers an area of 2.40 km2, pointing out an increase of 22%. The amount of sediment mobilized from the sub-basins was 307,000±63,500 m3, and the total net volume balance exiting the basins was -64,000±14,500 m3. The latter value encompasses the volume that entered the Liera stream and the material that has been removed during and after the emergency operations. Despite the great impact of the event, only a limited amount of the total mobilized material reached the Liera thalweg. A key to explaining this behavior is sediment connectivity: the presence of large buffering areas as large alluvial fans plays a fundamental role in decoupling the subcatchments featuring the greatest debris-flow magnitudes. The proposed approach, devised and tested in the Liera catchment, enabled to recognize sediment sources and to assess debris-flow mobilized volumes at the event and catchment scales, leveraging the availability of multitemporal high-resolution topographic datasets and detailed field surveys for event characterization. 

KEY WORDS: Geomorphic  changes, debris flows, sediment delivery, extreme event

How to cite: Macchi, G., Crema, S., Boretto, G., Monegato, G., De Fanti, B., Marchi, L., and Cavalli, M.: Assessing debris-flow activity and geomorphic changes caused by an extreme rainstorm: the case study of the Liera catchment (Dolomites, northeastern Italy), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-461, https://doi.org/10.5194/icg2022-461, 2022.

P25
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ICG2022-55
Maíra Oneda Dal Pai, André Augusto Rodrigues Salgado, Michael Vinicius de Sordi, Osmar Abílio de Carvalho Junior, and Eduardo Vedor de Paula

Drainage rearrangement is a critical process in the dynamic evolution of landscapes. Two approaches have been used to identify, analyze, and describe drainage rearrangement and, consequently, divide migration: classical geomorphological studies based on morphological and sedimentary evidence; and geomorphometric analysis, highlighting the χ index and Gilbert's three metrics (gradient, relief, and elevation). The present study uses classical and geomorphometric methods to analyze migration in the drainage divide between the Uruguay and Paraná rivers (two of the largest basins in South America). The study area is the Espigão Range (Santa Catarina State in Brazil), composed of inland plateaus with low relief and low rates of tectonic uplift. The results indicate that the methods express distinct periods of relief evolution. Investigations using classical methods reveal a history of past captures and bidirectional migration of watersheds in low relief areas. In opposition, topographic metrics indicate the current stability trend in drainage migration. After the fluvial channel capture events, there is an adjustment period for the new drainage configuration to reach stability. Therefore, Plateau's drainage divide suggests a contrast throughout the area with phases of relative stability and phases with more accentuated drainage migration. Finally, the results show that the χ index and the three Gilbert metrics (gradient, relief and elevation) should be used with caution when evaluating because, in these areas, present, past, and future divide migrations are not unidirectional, and thus may not be correctly modeled by these computation tools. Likewise, the classical geomorphological studies based on morphological and sedimentary evidence should also be used with caution because this method cannot always show the current stability or instability in drainage divide migration.

How to cite: Oneda Dal Pai, M., Rodrigues Salgado, A. A., de Sordi, M. V., de Carvalho Junior, O. A., and Vedor de Paula, E.: Combining morphological and sedimentological investigation with χ index and Gilbert metrics for analysis of drainage rearrangement and divide migration in a plateau region, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-55, https://doi.org/10.5194/icg2022-55, 2022.

P26
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ICG2022-566
Maciej Dłużewski, Joanna Oliwia Tomczak, and Joanna Rotnicka-Dłużewska

Aeolian bedforms formed on sandy beaches include ubiquitous aeolian ripples and less common sand patches which sometimes may evolve into barchans. Except for small ripples, which are the quick response of a dry sandy surface to wind above the threshold speed, the formation of even small dunes on the beach requires the interaction of many factors. The aim of the study was to determine the boundary conditions and the time necessary for the development of small barchans on a tideless beach. The research was carried out on the beach of Łeba Barrier, the South Baltic coast, within the Słowiński National Park (Poland), in May 2020. The field work included GPS RTK survey of 1-km-long fragment of coast where barchans developed as well as sampling of surface and subsurface sands for the assessment of sand moisture. Based on obtained Digital Elevation Model main morphometric parameters of barchans and sand patches, foredune height and inclination of its seaward slope, the width and height of the beach, and the length of the potential available fetch were determined. Additionally, hourly data from the meteorological station located on the foredune, 2.5 km from the study site, and from the two nearby mareographs (in Łeba and Ustka) were used. Parameters such as wind speed and direction (including the angle of wind attack in relation to the shoreline), the amount and intensity of precipitation, air temperature and humidity, and sea level were analysed in three periods, i.e. before barchans formation, and at the time of their development and then destruction. The obtained values were considered representative for the conditions favourable for the development of barchans. To confirm the obtained results these parameters were also analysed in selected periods between 2000 and 2020, when the occurrence of such barchans was documented.

The studied barchans were 0.54-1.09 m high, their windward slopes were 9.0-12.03 m long, and a total length equalled to 9.4-17.6 m. Their volume was estimated at 116.5-284.8 m3. They formed a chain of bedforms with crest perpendicular to the shoreline and migrated alongshore. Boundary wind conditions of their formation have been determined as follow: the minimum potential wind energy (DP) is 1.9, minimum potential resultant wind energy (RDP) - 1.5 and wind direction variability (RDP/DP) – not greater than 0.83. The results also indicate that such barchans may also develop during oblique onshore wind whose angle of attack is up to 45° to the coastline. In such a case, the near surface air flow can be deflected in the alongshore direction when the seaward slope of the foredune is inclined more than 20° and foredune relative height is greater than 10 m. Under favourable conditions the time needed for the development of barchans is less than 24 hours. The results also shows that barchans form in spring and summer, when events of beach flooding by storm waves are rare and surface layer of dry sand is thick enough to supply the right amount of sand. 

This study was supported by Polish National Science Centre (grant no. 2016/23/B/ST10/01700).

 

How to cite: Dłużewski, M., Tomczak, J. O., and Rotnicka-Dłużewska, J.: Boundary conditions of barchans development on a tideless sand beach, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-566, https://doi.org/10.5194/icg2022-566, 2022.

P27
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ICG2022-232
António Martins, Noel Moreira, António Araújo, and Diamantino Pereira

Since the 1990s, detailed studies on the relief units of the central and upper Alentejo region have been lacking. Previously, tectonics were used to explain most of the relief units, even those in which lithological differentiation is remarkable, such as the dolomitic plateaus of Elvas and Estremoz. The morphotectonic reliefs like Serra d’Ossa and Serra de S. Mamede were previously explained by vertical tectonics, in a horst-graben system, difficult to understand under the Cenozoic compressive tectonic regime affecting the Western Iberian margin.

The superposition of geological maps with digital terrain models suggests a more complex genesis in the formation of the morphotectonic regional reliefs. The Serra d’Ossa (652 m) develops in a WNW-ESE general trend (N80ºW), slightly asymmetrical with a 200 m high north-facing escarpment, much steeper than the south-facing slope. The north-facing escarpment (Ossa Fault – OF) is transversal to the NW-SE variscan structures (N40ºW). Thus, this escarpment cannot be explained by differential erosion. Indeed, Feio (1983) already hypothesized a tectonic origin to the Serra d'Ossa, although without presenting a tectonic model.

The western termination of the Serra d‘Ossa small scarps, with NE-SW orientation, coincide with the horse tail terminations of the NNE-SSW left strike-slip Graça do Divor fault (GDF). If both GDF and OF are connected, the Serra d’Ossa can be interpreted as a push up deformation of the South Portuguese Planation Surface (SPPS).

In this work, a greater relevance of differential erosion is highlighted in the individualisation of Elvas and Estremoz plateaus, as well as the Serra de Monfurado.

Towards the north of the town of Évora, the landscape is formed by broad-bottomed valleys at 240 m, with gentle slope and flat uplands at ca. 320-340 m. Looked in Davisian terms, the valleys looks like a mid-cycle maturity landscape. The flat upland level corresponds to the SPPS, well developed in the upper Alentejo (Nisa and Alpalhão), while the bottom of the valleys correspond to a younger level, embedded ca. 80–100 m in the SPPS. The valley bottoms widens to downstream forming a flattening surface (named N1 fluvial surface) related with the beginning of the incision of the drainage network in the SPPS and with the first (older) terraces of the Tejo and Guadiana rivers.

The prominence in the landscape of the Serra de Monfurado should be understood as a resistant ridge, whose summits were not completely flattened due to the lithological diversity and to the geographic location in the watershed limit of the Tejo, Guadiana and Sado rivers, where the flattening of the SPPS was difficult to achieve. Differential erosion during the formation of the N1 fluvial surface is thought to be the main responsible for the prominence of this ridge in the central Alentejo landscape, as well as other resistant reliefs as the Monsaraz inselberg.

 

Acknowledgments: The authors acknowledge the funding provided by the Institute of Earth Sciences (ICT), under contract with Science and Technology Foundation (UID/GEO/04683/2019).

References:

Feio, M., 1983. O Relevo da Serra de Ossa: uma interpretação tectónica. Finisterra, XVIII, 35, 5-26.

 

How to cite: Martins, A., Moreira, N., Araújo, A., and Pereira, D.: The central Alentejo plateaus: a review of the regional relief units, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-232, https://doi.org/10.5194/icg2022-232, 2022.

P28
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ICG2022-270
Andréia Nunes and Roberto Verdum

Of the human enterprises that modify the landscape, one that is in evidence of studies and discussions is the wind farms (WF). Starting from the premise of a source of low environmental impact, with public policies to encourage and finance private business, WF expanded rapidly in Brazilian territory. Currently, Brazil has 809 WF in operation, totaling 21.5GW of installed power. Of these, 81 parks and 1.83GW are located in Rio Grande do Sul (RS), the main producer of wind energy in southern Brazil (ANEEL, 2022).

The operation of wind turbines in Brazilian spaces introduces new functions, values ​​and intentions, changing the materiality of the landscape and, consequently, the concreteness of the symbolic representations of society. These morphological changes on landscape are not harmless and must also be analyzed in the context of social practices (LUCHIARI, 2001). Therefore, it must be considered that the landscape does not reside only in the object (nature), nor in the subject (society), but in the complex interaction between these two entities that are mutually related (BERQUE, 1994).

Alterations of the landscape frequently appears in studies on the most relevant negative environmental impacts of wind farms. However, some questions about this impact still remain unanswered, namely: What is this alteration? In what perspective was this change carried out? How to manage the impact in question? How to mitigate this impact that remains on the landscape in the medium to long term (at least 20 years)?

The studies for environmental licensing of these projects (Environmental Impact Studies and Simplified Environmental Reports) must be based on the existing regulations that guide the potential to understand, evaluate and manage the alteration of the landscape. However, after a detailed analysis of these available studies, this was not the reality observed in the wind farms of RS. Of the fourteen studies analyzed, only five carried out a landscape analysis, presenting a detailed theoretical and methodological framework. It is possible to affirm that the other eight studies did not analyze the landscape, they just cited it in a disorderly way.  This analysis allowed us to conclude that, in general, with exceptions, the environmental studies that guide wind farms in RS present the understanding of the change in the landscape only as a modification of what is seen from the inclusion of new forms in the areas studied. That is, considering it in a static way and not in its dynamics and complexity, in terms of changes in the forms, structures, functionalities and dynamics of the landscape.

This study is part of the doctoral thesis project that will seek to present a methodology for landscape analysis in WF environmental studies. Starting from a consistent theoretical basis, it is expected to contribute to applied studies about the landscape. Disseminating the use of landscape as a category of analysis with recognized and due theoretical and methodological basis enshrined in the international academic literature.

How to cite: Nunes, A. and Verdum, R.: The landscape in environmental impact assessments of wind farms in Rio Grande do Sul, Brazil, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-270, https://doi.org/10.5194/icg2022-270, 2022.

P29
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ICG2022-289
Karla Cassiano and Roberto Verdum

The coastal region of the state of Rio Grande do Sul is markedly delineated by lake and lagoon landscapes resulting from the regression and transgression movements of the South Atlantic Ocean, which occurred during the Pleistocene and Holocene. This process resulted in the Patos Lagoon and Mirim Lagoon, connected by the São Gonçalo Channel, whose flow directly interferes with their dynamics, especially in Mirim Lagoon. This channel presents flow reversion in the function of the relative levels of these water bodies, whose main mouth is located in an estuarine environment. During the summer, when the Mirim Lagoon is deficient and its water level is low, the São Gonçalo Channel transports brackish waters from the Patos Lagoon. These waters penetrate further or further into the Mirim Lagoon, according to the hydrological conditions, making it more brackish. Although the flow is predominantly in the Mirim-Patos direction (about 80%) in dry periods, it can be inverted, which allows saline water to enter the channel and the Mirim Lagoon itself. The construction of a lock dam has generated changes both in this dynamic and São Gonçalo Channel landscape. The construction was done to avoid saltwater intrusion from the Patos Lagoon into the Mirim Lagoon so that the water resources upstream could be used for irrigation of rice production, benefiting large and medium landowners who practice this activity in the region. From 1977, the year the dam started operating, there was an expansion of large-scale irrigated rice farming on the Channel's plain, advancing to its margin, even though it is a Permanent Protection Area. The supervised classification of Landsat images from 1973, before the dam, 1993, and 2018, after the dam, shows the expansion of rice farming, mainly in the municipality of Capão do Leão (RS/Brazil), northwest of the channel. The São Gonçalo Channel plain also encompasses the municipalities of Pelotas, Rio Grande, and Arroio Grande, all with a significant increase in the area devoted to rice farming. In 1994, the area harvested for rice more than doubled (84,400 hectares) compared to 1974 (34,970 hectares). The impacts of the implementation of the dam are in appearance and also in essence since together with the rice crops there are landscape transformations, among which are those that refer to the dynamics of the river channel on the São Gonçalo Channel plain.

How to cite: Cassiano, K. and Verdum, R.: Landscape and rice culture of the São Gonçalo Channel Plain (Rio Grande do Sul - Brazil), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-289, https://doi.org/10.5194/icg2022-289, 2022.

P30
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ICG2022-723
Renato Emanuel Silva, Antonio Avelino Batista Vieira, Francisco da Silva Costa, and Silvio Carlos Rodrigues

The aim of this study is to present how anthropogeomorphological aspects, generated from the construction, renovation and maintenance of channels in northern Portugal, have hydrogeomorphological repercussions on these slopes and valley bottoms. This research was possible from the cross-checking of documentary data found in the historical archive of the Portuguese Environment Agency, and from field activities carried out in the Levada do Rei, in Abadim, and in the Levada de Piscaredo, in Mondim de Basto. The main aspects raised were the cuts in the slopes, the compartmentalization processes of the water volume, and the interactions promoted along the slopes, both by erosive and depositional processes. The documentary survey reveals that the channels are old and date back to the middle ages, having both undergone renovations in the 1970s that promoted the covering by impermeable slabs (rock cuts) and improvements in the aspects of erosive processes management and water flow. In the field it was possible to identify that from the Abadim Levada the water flows can be practically suppressed from the natural channel by the action of the transposition, which is not observed in the Piscaredo channel, since the supply flows from the rivers Cabril, Cabrão and Ribeira Velha are sufficient to maintain the transposed flow and the natural volumes. The study areas, although they are inserted in identical geological context (granites and schists), differ at the level of geomorphology and, especially, in the slope inclination. Thus, the erosive processes are more pronounced along the Piscaredo Levada, where the maintenance works are more incisive in attempts to control these processes, with cuts in the slopes that exceed two and a half meters and dozens of points with road crossings, gutters, dams, and walled sections. For this levada, works were identified as debris passages, collected from the upper half of the slopes, walls to stabilize erosive forms, and dams to collect water in natural water lines. The sediments deposited along the artificial channel generate demands for cleaning, which are maintained by the users and the competent regulatory agency. From this maintenance, the anthropic marginal dikes are reinforced by the sediments, previously transferred from the hillside to the channel. In the Abadim levada, as observed in the field, the smoother slopes considerably reduce the demands for erosive form containment works. The lower interaction between artificial channel and slopes reduces the number of gutters to divert flows from the slopes and also the demands for cleaning, not promoting significant marginal anthropic dikes. The investigation reveals how the interactions between natural processes and anthropic demands generate substantial changes in the landscape, from the shapes of the slopes, both in the cut for opening the channels, as well as the erosive forms and anthropic dikes accommodated in their margins. Considering that the natural fluvial systems are also impacted by dams, sediment retention and alteration of the flow, knowing these aspects in a more detailed way helps to improve the efficiency of these structures, reducing operation costs and water loss.

How to cite: Silva, R. E., Avelino Batista Vieira, A., da Silva Costa, F., and Carlos Rodrigues, S.: Hydrogeomorphological repercussions of anthropic topographical signatures in the north of Portugal: the documented cases of the Abadim and Piscaredo Levadas, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-723, https://doi.org/10.5194/icg2022-723, 2022.

P31
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ICG2022-387
José Oliveira, Leonardo Santos, and Lionel Siame

The Brazilian northeastern is composed of a mix of Precambrian crystalline rocks and Mesozoic sedimentary basins. In this region, the landscape evolution model is illustrated by a great regional uplift after the cretaceous rift followed by regional denudation. The most resistant rocks from sedimentary Cretaceous basins and the old hard granites support the actual existent high hills. However, the regional landscape evolution scenarios left behind some questions, according to the AFT data, about 1000-2500 m of sediments were deposed and eroded after Cenomanian, resulting in erosion rates higher than 60 m/Myr after Miocene. These scenarios are opposed to the model based on morpho-stratigraphic observations that suggest erosion rates below 10 m/Myr. Surrounded by large planation surfaces, the Chapada do Araripe (Chapada = plateau), located on the border of the states of Ceará, Piaui, and Pernambuco, is part of the drainage divide of 3 large Brazilian watersheds, and is the higher representant of the post cretaceous uplift in the Borborema structural province, with late Aptian–Albian marine sediments (Santana Group) at elevations between 700-800 m a.s.l. That combination of characteristics makes the Chapada do Araripe a landscape with huge potential to assist the understanding of the landscape evolution over the last 70 Myers in the Brazilian northeast. One of the most visible characteristics of the chapada is the difference between the sides. Meanwhile, the north side (Jaguaribe basin) has a steeper relief the south face (São Francisco basin) has longer and less sloping slopes. This abstract is part of a Ph.D. thesis that aims to illustrate the regional relief perspective from a combination of cosmogenic nuclides and digital topographic analysis. The following discussions are based on digital elevation model derivates indices, longitudinal profiles analysis, and fieldwork observations. The north side of the Chapada (Jaguaribe drainage basin) shows indices that indicate a relief with greater geomorphic variations in most of the basin. In contrast, the south side (São Francisco drainage basin) shows smaller variations, with lower altimetric amplitudes and average slopes. These observations can be seen on both the morphometric indices and longitudinal profiles. In the longitudinal profiles, the curves show superior proximity of the equilibrium profile in the streams located in the São Francisco basin when compared to those located in the Jaguaribe basin. From the 290 knickpoints identified, only 15% are in the São Francisco basin. On both sides, 65% of the knickpoints are linked to lithological changes or faults, evidencing the landscape's strong presence of lito-structural controls. The application of morphometric indexes allowed detailing the two sides of the Chapada, contributing to the morphological characterization. Ongoing analyzes at LN2C-ASTER to measure basin-wide denudation rates using in situ produced 10Be and 26Al around the Chapada will complement the results found in this work and will allow a better background to the discussion of the plio-quaternary relief evolution.

How to cite: Oliveira, J., Santos, L., and Siame, L.: Morphologic evolution of a Semiarid Relief: The case of Chapada do Araripe (Ceará, Brazil) , 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-387, https://doi.org/10.5194/icg2022-387, 2022.

P32
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ICG2022-695
Adélia Nunes, João Gonçalves, and Albano Figueiredo

Soil erosion is the most important process of land degradation in Mediterranean Europe, resulting from the combination of intensive rainfall regime, during specific periods of the year, and the absence of vegetation cover, very often promoted by specific land use patterns.

This work aims to assess how changes in land use and land cover alter the risk of soil erosion in Mediterranean agricultural landscapes after recent significant changes in terms of land-use regime, namely due to the increase of intensive uses based on irrigation, which are replacing by traditional extensive uses. For this study, the Beira Baixa Region, one of the areas with the highest susceptibility to desertification, was used as reference.

During a first stage, the period of the year with higher susceptibility to erosion was identified based on the use of vegetation indices, aiming to assess the existence of differences in terms of vegetation cover considering different land uses. Such information was crossed with records of inter- and intra-annual intense rainfall episodes for the last 2 decades, aiming to identify the period of the year that is critical in terms of erosivity potential.

In order to evaluate the effective soil loss in the period with the highest risk of erosion (lowest vegetation cover + highest records of intensive precipitation), rainfall simulations were performed in different land uses at the end of the summer period, considering the most common land uses in the region, and trying to compare intensive and extensive land use systems.

The results obtained show that soil loss in intensive and super-intensive land uses, associated to crops installed in the last 5 years, with no or residual vegetation cover, is significantly higher compared to traditional extensive uses, which maintain an annual vegetation cover based on herbaceous communities, even dry. The results of the simulations also showed that the high values of erosion observed in intensive orchards might be mitigated through the implementation of a vegetative cover able to protect the soil from the direct impact of rainfall.

How to cite: Nunes, A., Gonçalves, J., and Figueiredo, A.: Soil erosion response to land-use change in landscapes sensitive to desertification: a study case in Beira Baixa (Portugal), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-695, https://doi.org/10.5194/icg2022-695, 2022.