Japan Geoscience Union Meeting 2023

Presentation information

[E] Oral

H (Human Geosciences ) » H-TT Technology & Techniques

[H-TT13] HIGH-DEFINITION TOPOGRAPHIC SURFACE DATA FOR CONNECTIVITY IN THE ANTHROPOCENE

Wed. May 24, 2023 10:45 AM - 12:00 PM 201A (International Conference Hall, Makuhari Messe)

convener:Yuichi S. Hayakawa(Faculty of Environmental Earth Science, Hokkaido University), Christopher A Gomez(Kobe University Faculty of Maritime Sciences Volcanic Risk at Sea Research Group), Mio Kasai(Research Faculty of Agriculture, Hokkaido University), Takuro Ogura(Graduate School of Education, Hyogo University of Teacher Education), Chairperson:Yuichi S. Hayakawa(Faculty of Environmental Earth Science, Hokkaido University), Christopher A Gomez(Kobe University Faculty of Maritime Sciences Volcanic Risk at Sea Research Group), Takuro Ogura(Graduate School of Education, Hyogo University of Teacher Education), Mio Kasai(Research Faculty of Agriculture, Hokkaido University)



11:15 AM - 11:30 AM

[HTT13-03] Sediment Transfer Rates post-Deglaciation on New Zealand Alpine Fans - Field data, Laboratory and Numerical Simulations

*Christopher A Gomez1, Purdie Purdie2 (1.Kobe University Faculty of Maritime Sciences Volcanic Risk at Sea Research Group, 2.Canterbury University)

Keywords:alluvial fan, sediment flows, Sediment hazards, Fox Valley, New Zealand, Numerical simulation

At the slope-breaks, fan-shaped landforms ranging from steep debris-cones to lower-angled alluvial fans and estuaries, are filling the topographic hinges. The geomorphic activity is dominated by water and sediment-laden flows, eventually turning into hazards and disaster risk in populated areas, on touristic mountain trails (Gomez et al., Purdie et al. 2015) and when sediment supply is suddenly from earthquake activity for instance (Gomez & Hotta, 2021). Although their modeling is dominated by the ‘Exner’ and diffusive differential equations, it also has been demonstrated that rapid collapse followed by a diffusion-base smoothing can generate fan-landforms in a shorter time-span than the sediment transport and supply and the diffusion-based simulation would let one expects (Gomez et al., 2022).
In the present contribution, the author is investigating the role of local sediment stock on the growth rate of Alpine-fans in deglaciating valleys on the West coast of the South Island of New Zealand, using a combination of field investigation, laboratory simulation and numerical modeling.
In the field, GNSS RTK combined with UAV photogrammetry was used to model the 3D topography, and the growth rates were calculated from historical archives showing the glacier retreat. From the field observation, in-valley benches of sediments inherited from the glacier and the valley interaction were added to a table-top flume to simulate the growth of a fan, with and without those, for constant slopes and discharges. The parameters extracted from these simulations were then applied to numerical models of fan development, in order to relate the sediment discharge, the fan growth rate and the spatial distribution of sediments’ volume.
The results from laboratory fan experiments were used to feed the numerical model, in order to explain the field observations.