2018 Fiscal Year Annual Research Report
Modelling "non-wedge-shaped" groundwater-seawater interactions under climate change and urbanization impacts and its implications for coastal development at the inner Tokyo Bay Area
| Project/Area Number |
17J03852
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Liu Jiaqi 東京大学, 新領域創成科学研究科, 特別研究員(DC1)
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| Project Period (FY) |
2017-04-26 – 2020-03-31
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| Keywords | Numerical modeling / conceptual model / Niijima Island / geophysical survey |
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| Outline of Annual Research Achievements |
Laboratory research activities: To provide understanding of the physical process and driving force for investigating the non-wedge-shaped groundwater-seawater interactions in the Tokyo Bay Area, a conceptual model of variable-density flow and mass transport under horizontal groundwater flow in unsaturated-saturated media was simulated.
Fieldworks: To further confirm the bedrock structure and the position of freshwater-seawater mixing zones, 1-D and 2-D resistivity survey was conducted at the Niijima Island in June
Publications: The simulation results of the conceptual model and the field-based model were presented in JpGU, AOGS, and AGU meetings, and were submitted to the journal Water Resources Research.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In the conceptual model, three flow regimes were identified based on numerical modeling results of variable-density flow and mass transport in unsaturated-saturated aquifers under horizontal groundwater flow conditions. The flow regimes and their driving forces were explained by the dimensionless numbers.
In the study of 2-D modeling, during the tsunami inundation period, the downward hydraulic head gradients controlled the vertical seawater infiltration process. During the post-tsunami period, the flushing of intruded saltwater was controlled mainly by seaward groundwater flow and was affected by the density effect.
The measurement at one site of the 1-D resistivity surveys showed good agreement with our previous microtremor survey, numerical modeling results, and the data from literature.
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| Strategy for Future Research Activity |
Coupled surface-subsurface simulations by using the code HydroGeoSphere are planned to understand the impacts of tsunami inundation conditions and ponded seawater on saltwater intrusion processes.
A geophysical survey is planned to be carried out by using techniques such as surface wave survey, resistivity survey, and seismic reflection survey, to further investigate the bedrock structure in the Niijima
A paper based on the 3-D numerical modeling results is planned to be prepared and submitted to the journal Science of Total Environment. The results of the conceptual model and the field-based model have been accepted and will be presented in JpGU Annual Meeting in May 2019 and in AOGS Annual Meeting in July 2019, respectively.
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