Assessing soil erosion in a small Sicilian basin by caesium-137 measurements and a simplified mass balance model

The caesium-137 technique affords both an alternative to conventional measu rement methods and an effective quantitative estimate of soil redistributio n at the basin scale. Among the available calibration relationships which l ink the degree of increase or depletion of the Cs-137 activity relative to the baseline Cs-137 input and sediment yield, the mass balance approach has received increased application for its physical basis. First, the applicab ility of the refined simplified point-based mass balance (RSPMB) model of Z hang et ai. (1999) at the scale of the morphological unit is proposed herei n. The Cs-137 spatial distribution measured in a small Sicilian basin and t he spatial distribution of the sediment yield calculated by a sediment deli very distributed approach are used to estimate values of the two key parame ters of the RSPMB model, phi (1) and phi (2), the fraction of Cs-137 fallou t incorporated into soil and a particle size correction factor, respectivel y. Finally, the best procedure for experimental testing of a distributed se diment yield model by using caesium-137 measurements is investigated.