Field observations and assessment of riverine geomorphologicalenvironments in view of integrated floodplain management

研究了河道漫滩区地下水位随河道水位变化而发生的波动。在宇治河43.0km测站附近的洪泛区，设置了垂直于河道低岸的观测威尔斯井阵列。观测到的地下水位快速上升和缓慢下降的表现清楚地反映了与台风和暴雨相关的洪水阶段的反应。仔细的时间序列分析发现，在上升期间的横向渗透和下降期间的垂直渗透。计算出洪泛区土壤在涨潮期和退潮期的表观渗透系数分别为1.6×10-2~1.32 cm/s和1.9~3.4×10-4 cm/s。水位下降期的剩余水位与河岸侵蚀过程密切相关。讨论了确定未来河流管理的实际意义。

This study focuses on the unconfined groundwater table fluctuations in a floodplain of river channel that occur in response to water level changes of the low channel. The array of observation wells normal to the low channel bank was set up at the floodplain near the 43.0km station of Uji River. The observed performance of a rapid rise and slow fall in the groundwater table clearly captured the response to a flood stage associated with a typhoon and heavy rainfall. Careful time-series analyses identified lateral infiltration during the rising period and vertical infiltration during the falling period. The apparent coefficients of permeability in floodplain soil during the rising and falling period were calculated as equal to 1.6×10-2~1.32 cm/s and 1.9~3.4×10-4 cm/s, respectively. The residual groundwater table during the falling period closely related to a process of bank erosion. A discussion is made to identifying practical implications for future river management.