The quality and quantity of sediment transport in watersheds must be evaluated for comprehensive sediment management in sediment transport systems. Field observations are thus important. Indirect methods, such as the use of turbidity sensors, to observe suspended and wash loads and the use of hydrophones, to observe bed load, have been applied recently in several catchments in Japan. We used these methods to collect data at four points in the Ashiarai�]dani watershed, in the district of the city of Takayama, Gifu Prefecture. This paper reports the results of analysis and three main observations. First, sediment discharge was recognized in each blanch and was influenced by sediment supply from riverbed and side banks. Second, we effectively estimated sediment transport routes during rainfall events by comparing the turbidity curves and changes in hydrophone pulses at two different observation points. Third, the sediment source area of suspended and wash loads was estimated by classifying the relationship between turbidity and water level. Thus, these indirect methods were successfully adapted to monitor sediment discharge in mountain streams.

Key words�Fturbidity, hydrophone, suspended sediment, bed load, hysteresis loop