GM1.2 | General Geomorphology Poster Session
Fri, 14:00
EDI Poster session
General Geomorphology Poster Session
Convener: Matteo Spagnolo | Co-conveners: Laure Guerit, Aayush SrivastavaECSECS, Philippe Steer
Posters on site
| Attendance Fri, 02 May, 14:00–15:45 (CEST) | Display Fri, 02 May, 14:00–18:00
 
Hall X2
Fri, 14:00

Posters on site: Fri, 2 May, 14:00–15:45 | Hall X2

Display time: Fri, 2 May, 14:00–18:00
Chairpersons: Matteo Spagnolo, Laure Guerit, Aayush Srivastava
X2.1
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EGU25-574
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ECS
Using DEMs to map subtle geomorphic expression of Quaternary deformation in the Eastern Cordillera of NW Argentina
(withdrawn)
Ananya Pandey, Manfred R. Strecker, and Bodo Bookhagen
X2.2
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EGU25-3833
Yvonne Martin and Hugh Alvarez

Valley floors influence a range of environmental processes in mountain regions. For example, valley floors serve as a deposition zone for geomorphological processes occurring on hillslopes. Valley floors represent relative low points in the landscape, thereby affecting basin hydrology and influencing soil moisture in these locations. Valley floors also serve as important locations of organic carbon storage in soils and vegetation. While it has been recognized that valley floor widths in mountain regions often show high variability due to complex geology and geomorphology, few studies have quantified and analyzed values and controls of valley floor widths in these settings. Objectives of this study are to measure valley floor widths for three small tributary drainage basins in Kananaskis, Canadian Rockies and to analyze possible controls, including geology and geomorphology, on valley floor widths. First, delineation of valley floor extent for alluvial parts of the channel network in the three study basins is undertaken using GIS-based methods. Valley floor polygons consist of DEM grid cells that fall within a threshold height relative to the channel height. Next, valley floor widths are obtained by measuring width in a direction perpendicular to the channel for valley floor polygons along the entire channel network. The complex geological and geomorphological characteristics in our study region suggest that generalizations about valley floor widths relevant to larger, lowland drainage basins are not likely to be applicable for our study area. Upper Kananaskis Creek and Ribbon Creek basins show overall higher values of valley floor width relative to Porcupine Creek basin, likely due to their topographical positioning, which is expected to result in higher precipitation and discharge values and greater possible impacts of past glaciation. Results show a very high variability in valley floor widths along the channel network for all three study basins. Valley floor widths show distinct fluctuations between groups of below-average and above-average values in an upstream direction, with any particular group often persisting for a relatively short distance before a notable change in valley floor width is observed. Channel junction locations along the channel network are often associated with local increases in valley floor width for all study basins, although such increases sometimes only last for short distances. Bedrock lithology is found to influence valley floor widths in the study basins, with either below-average or above-average values being associated respectively with more resistant Palaeozoic formations or somewhat more erodible Mesozoic formations. Geological structures situated near channel networks are also shown to be a possible control of valley floor width in some situations. Parts of the channel network in Upper Kananaskis Creek basin and Ribbon Creek basin show evidence of glacial activity, with greater valley floor widths often found in these locations.

 

How to cite: Martin, Y. and Alvarez, H.: Variability of Valley Floor Widths in a Mountain Landscape, Canadian Rockies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3833, https://doi.org/10.5194/egusphere-egu25-3833, 2025.

X2.3
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EGU25-7286
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ECS
Benjamin Warsmann and Yvonne Martin

Sediment transfer from hillslopes to valley floors represents a major component of the sediment routing regime in mountainous environments. Valley floors are connected to a range of physical, chemical and biological processes, including hydrological flow routing, soil moisture, vegetation growth and organic carbon storage. The degree of connection between hillslopes and valley floors depends on variables that affect geomorphic process operation on hillslopes, including slope morphology, land cover, rock and/or soil characteristics, and precipitation regimes. This study measures and analyzes the degree and variability of hillslope-valley floor coupling along channel networks in small drainage basins in Kananaskis, Canadian Rockies. First, key morphometric and land cover variables derived from DEM and satellite-based data are analyzed for study basins. These variables influence hillslope sediment transfers to local valley floors. A large proportion of landscapes in tributary study basins is defined as 1st order or 2nd order sub-basins with slope gradients often in the range of 30 degrees to 60 degrees. These landscapes have significant potential for mass movements. Geology and geomorphology are shown to influence the complex arrangement of landscape morphology and land cover within study basins. Ribbon Creek and Upper Kananaskis Creek basins show a greater extent of steep, rock areas compared to Porcupine Creek basin. Next, parts of surrounding hillslopes that have potential for sediment transfer to valley floors are identified. Significant breaks in slope gradient on hillslopes above local valley floors are shown to limit the hillslope length with potential to connect with the valley floor. Lower-order stream links show a higher percentage of surrounding hillslopes that are coupled with valley floors relative to higher-order stream links. Next, coupled parts of landscapes in study basins are classified into categories of mass movement potential based on primary controlling variables (e.g., slope gradient, land cover). Mass movement potential within coupled parts of the landscape determines the degree of hillslope-valley floor coupling. Maps show significant variability in mass movement potential along channel networks in study basins. Variability in hillslope-valley floor coupling results from the complex geological and geomorphological controls on landscape characteristics in this region. Glacial oversteepening of hillslopes is more notable in Ribbon Creek and Upper Kananaskis Creek basins and results in more landscape areas with a high degree of hillslope-valley floor coupling compared to Porcupine Creek basin. Parts of channel networks with resistant lithology typically show relatively uniform, steep hillslopes, with limited buffers between hillslopes and valley floors. In contrast, areas with less resistant lithology often display lower slope gradients and more buffers that limit hillslope coupling with valley floors. Finally, parts of the landscape with overall greater heterogeneity in bedrock lithology show smaller and more complex-shaped units of hillslope connection with valley floors compared to areas with more uniform lithology.

How to cite: Warsmann, B. and Martin, Y.: Hillslope-Valley Floor Coupling Along Steep Mountain Channel Networks, Kananaskis, Canada , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7286, https://doi.org/10.5194/egusphere-egu25-7286, 2025.

X2.4
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EGU25-6836
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ECS
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Laure-Anne Gueguen and Gottfried Mandlburger

Photo bathymetry is the use of photogrammetry for the reconstruction of the underwater topography. The imaging systems are located above water and the optical rays go through two different media, air and water, which means the rays are refracted at the water surface according to Snell’s law. This refraction leads to a blur in the images and an error in the reconstruction of the topography, and represents today the main limitation to achieving high accuracy photo bathymetry. A 3D model of the water surface at the time of capture of the topography is therefore a prerequisite to correct the ray paths. Our method aims to solve the problem of simultaneous reconstruction of the water bottom and the water surface. In this contribution, we present the setup and the results of an experiment carried out in the measurement lab of TU Wien.

We have borrowed a complete camera rig from IfP Stuttgart. This setup is composed of four cameras and lenses, an Arduino Leonardo and the associated cabling. The Arduino serves as a controller and synchronizes the cameras by sending a trigger signal in user-definable intervals via a cabled USB connection. Two cameras are used to capture the water surface, looking obliquely from the side, and the other two to capture the water bottom, looking nadir from above. A water tank is filled with water and two layers of stones to obtain a textured topography. Finally, we use an indoor fountain pump to create a dynamic water surface. Prior to the data acquisition, we first installed an array of coded photogrammetric targets on the floor, walls, and measurement pillars in the corner of the lab and measured the 3D coordinates with sub-mm precision with a total station. These targets served as control and check points in the bundle block adjustment. In a second step, we measured the topography of the empty water tank with a conventional image block using a Structure-from-Motion and Dense Image Matching approach to obtain a reference model that will serve as validation.

How to cite: Gueguen, L.-A. and Mandlburger, G.: Lab experiment for simultaneous reconstruction of water surface and bottom with a synchronized camera rig, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6836, https://doi.org/10.5194/egusphere-egu25-6836, 2025.

X2.5
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EGU25-15044
Ching Fang, Cheng-Hao Lu, Neng-Ti Yu, and Lih-Der Ho

Huolongtan is located in the east of Baisha Island, Penghu, Taiwan. It was formed by the 1986 typhoon and is the youngest sandbar island in Penghu. This study explores its changes at different time and space scales, focusing on the interaction between tropical typhoons and the northeast monsoon. The influence of its terrain.

In this study, multi-period UAV photogrammetry was used to analyze the erosion and sedimentation status before and after typhoons and northeast monsoons using a DSM of difference (DoD). Grain size analysis and marine meteorological data were combined to explore natural variation factors. The USGU Digital Shoreline Analysis System (DSAS) was used to analyze shoreline changes.

The research results show that the sandbar erosion and siltation responses showed different spatial trends during the three typhoons. The maximum wave height of Typhoon Koinu was 567 cm, and the volume of sedimentation was -7657.2m3, with a ratio of -0.03. During the passage of this typhoon, the wind was mainly from the north, causing accumulation on the south bank and erosion on the north bank, and its sand tail gradually swing south to change. During the northeast monsoon, the volume of sediments recovered, with a volume of 9048.5m3and an increase of 0.04, but the sandbar islands were eroded again in the late northeast monsoon. In addition, this paper found that the intertidal zone of several kilometers in the north would protect the terrain of the northern shore, and significant erosion would only occur with high wave heights or long-term monsoon waves. Comparison of the zero-meter contour lines shows that the main island of Huolongtan has a tendency to move southwest and sand tail has a tendency to move north. The maximum erosion of the coastline changes in the medium and short time intervals is 21.3m/y (end point rate (EPR)) and 8.2m/y (linear regression rate (LRR)); the maximum accumulation is 30.0m/y (EPR) and 16.4 m/y (LRR), and the Kalman filter was used to predict that the north bank would erode more landward and the south bank would advance toward the sea in 10 years.

The research results can be applied to the sustainable development of recreational areas and seabird habitats on Huolongtan sandbar under climate change and frequent extreme events. This will also help management units to adapt to climate change in a changing environment.

Keywords: UAV, Particle size analysis, DSAS, Coastal change

How to cite: Fang, C., Lu, C.-H., Yu, N.-T., and Ho, L.-D.: Spatio-Temporal Morphodynamics of Huolongtan Sandbar, Penghu islands Taiwan - Using Short-term Monitoring from 2020 to 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15044, https://doi.org/10.5194/egusphere-egu25-15044, 2025.

X2.6
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EGU25-15045
Application of Rockfall Hazard Rating System and UAS for Rockfall Monitoring and Recreational Risk Assessment on Whale Cave, Hsiaomen island, Penghu Archipelago
(withdrawn)
Hung-Huei Sung, Cheng-Hao Lu, Neng-Ti Yu, and Lih-Der Ho