RUNOFF PROCESS, SEDIMENT YIELD AND TRANSPORT IN A MOUNTAIN WATERSHED (12)

Observational research of the runoff process, sediment yield and transport have been carriedout in an experimental basin, Ashiaraidani (6.5 km2), which is located in the Northern Japan AlpsRange. In this basin all aspects of sediment transportation which appear in the mountain ravines, namely, bed load, suspended load, wash load, and debris flow can be seen under various rainfalland discharge conditions.Erosion processes of the bare slopes and gully walls and transports of gravels on the steepchannel as contact load and accompanying stream channel variations are discussed in view of theobserved facts in the Ashiaraidani. The process and mechanism of sediment transport duringa flood on the steep channels with sequential falls and pools were considered by means of thepetorological and grain-size classification of transported gravels in reference to the geologicaldistribution in the basin, and the relationships between flow rate and sediment discharge in theHirudani basin (0.85 km2) are explained as a function of sediment storage in the pools.