Key controls and scale effects on sediment budgets: Recent findings in agricultural upland Java, Indonesia

This study presents recent field research in a small agricultural catchment in upland West Java, and identifies the key controls, and scale effects, on sediment yields. Vegetative cover proved the dominant control on surface runoff and sediment generation, with additional variation attributed to slope and soil surface structure. Vegetation also provided the link between the water, sediment, and carbon cycles. Use of a process model to replicate and upscale field measurement to hillslope scale, highlighted the lack of a predictive theory linking vegetative cover to rainfall infiltration, as well as problems associated with the unaccounted covariance of terrain attributes that promoted sediment generation. At the hillslope to catchment scale, changes in slope gradient, and the presence of less erodible substrates became additional constraints on sediment yield. A conceptual framework to describe the changing importance of different sediment transport and deposition processes with increasing spatial scale was developed.