本研究は急流河川で土砂移動が活発な姫川を対象とし，洪水中の流水抵抗変化を予測して河床高を推定し，それを用いて流量を推定する手法を検討する．姫川の基準点では過去に，観測水位から変換する流量と水文モデルで計算する流量が乖離する例がある．このうち，観測水位から流量に変換する上で誤差が生じる要因は洪水中の流水抵抗の変化や河床変動が挙げられ，土砂移動が活発な姫川ではこれらを考慮することが特に重要である．本研究では，ADCP等を用いた観測結果から洪水中の流水抵抗を分析した上で，表面流速や水位等の水表面から得られる情報から流水抵抗変化を予測しながら河床高及び流量を推定した．その結果，推定河床高からの流量はADCP観測の河床高からの流量を良好に再現し，横断観測結果から固定床を仮定し算出される流量よりも大きくなった．
This study aims to estimate discharge considering river bed evolution during flooding with calculation of hydraulic resistance in the Hime river. The river is a flashy river and has active sediment movement. An observation site of the river has a problem that discharges converted from water level and calculated by hydrological model differ. It is considered that the both have error, and the error of the former is caused by changes of hydraulic resistance and river bed elevation. Hence these changes need to be taken into account to estimate discharge accurately in the river. First, analysis of hydraulic resistance with observed data by equipment such as ADCP is conducted, then river bed elevation and discharge are estimated using the analysis result of hydraulic resistance and hydrological quantities over water surface such as water level and water surface velocity. As a result, discharge calculated with estimated river bed elevation reproduces the one calculated with river bed elevation observed by ADCP, and shows higher values than discharge assuming fixed river bed elevation.
洪水中の河床変動を考慮した流量の推定
JSCE_72_5_I313_I320
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