11:15 〜 11:30
[HTT13-03] 氷河後退後の扇状地における土砂流： 現地調査、実験室および数値シミュレーション
キーワード：扇状地、土砂量、砂防、フォクス谷と氷河、ニュージーランド、数値計算
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.
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.