山地河川における流砂解析手法の改良事例

抄録

Sediment transportation in mountain streams has been observed by direct and indirect methods. Direct sampling methods are thought to be desirable. However, the instability and difficulties have been a major obstacle. A more radical technological breakthrough remains a holy grail. In the meantime it is imperative to make full use of indirect methods. For quality calibration, an effective application of hydrophone systems is sought out, after 15-year field experience of semi-direct sampling. The systems capture bed load transportation, which can be turned out as sediment-related quantities. There are three chief roadblocks : (1) sampling method itself, (2) estimation of unit section sediment, and (3) cross-sectional and lateral development to obtain total sediment discharges. Comparison among estimation methods, based on full year data retrieval and in site monitoring is made. The result tentatively indicates that the application of hydrophone systems produces more robust estimation, with minor but non-negligible discrepancy with prior estimation.