2018 Fiscal Year Final Research Report
Estimation of flood control function in unconfined aquifer of alluvial fan
| Project/Area Number |
16K06507
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Hydraulic engineering
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| Research Institution | Gifu University |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 扇状地の洪水調節 / 自由地下水 / 広域の透水係数 |
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| Outline of Final Research Achievements |
Water storage volume in unconfined aquifer of alluvial fan and its flood control capacity was estimated. In Nagara River's alluvial fan located Gifu City, macroscopic coefficient of permeability was about 0.04 m/s based on observation of lost river discharge and hydraulic gradient of water table. The value was one oder larger than the local coefficient from permeability test. By using river and groundwater simulation program, River2D, water movement among 2013-2014 was calculated. In the flood of August 2014, water storage volume was 63 million m3 as flood control capacity, which was 5 % of total inflow volume.
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| Free Research Field |
河川工学
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| Academic Significance and Societal Importance of the Research Achievements |
洪水時の河川表流水が扇状地の地盤内に浸透して一時的に貯留されることで，洪水流量を軽減し氾濫の危険性を低減していることが明らかになった．研究対象とした岐阜市長良川扇状地における2014年8月の洪水では総流入量の5%に相当する6,300万m3が扇状地地盤に貯留されていることが数値計算から明らかになり，正確な河川流量の把握には地盤内の貯留量を考慮する必要性があることが示された．また，扇状地の洪水調節能力を推算する過程において，広域の透水係数の決定手法，河川表流水と地下水を統合的に解析する数値計算の有効性も確認された．
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