Using 137Cs and 210Pbex measurements to investigate the sediment budget of a small forested catchment in southern Italy

Concern for the sustainability of the soil resource and for the detrimental impacts of fine sediment on downstream river systems and aquatic ecosystems has directed attention to the need for information on the suspended sediment loads of rivers. However, traditional measurement programmes focus primarily on quantifying the sediment load at a catchment outlet. Such information, whilst useful, may be of limited value in establishing rates of soil degradation, because much of the sediment mobilised within a catchment may be deposited before reaching the catchment outlet. Furthermore, it may also be of limited value in the design and implementation of sediment management and control programmes, because this requires an understanding of the key sources of mobilised sediment, the transport pathways involved and the importance of storage within the catchment. Information on the sediment budget of a catchment must be seen as an increasingly important requirement. However, such information is difficult to obtain using conventional traditional monitoring techniques. Fallout radionuclides, including caesium-137 (137Cs) and unsupported or excess lead-210 (210Pbex) have been shown to offer considerable potential for use as sediment tracers in sediment budget investigations. They are able to provide distributed information on rates of soil and sediment redistribution within the catchment, which represents a valuable complement to information on sediment output. This contribution reports the results of a study aimed at exploring the use of both 137Cs and 210Pbex measurements to establish the sediment budget for the small (1.39 km2) forested Bonis catchment, located in southern Italy. The results confirm that 137Cs and 210Pbex measurements can provide a valuable tool for quantifying both erosion and sediment redistribution within a catchment and therefore for establishing its sediment budget.