How useful are catchment sediment budgets?

Catchment sediment budgeting is an attempt to identify the sources, sinks and pathways of eroded material within catchments. However, the identification of these quantities is not straightforward, and the conceptual underpinnings of sediment budgets make unwarranted and untested assumptions about process stability. Many sediment budgets leave one or more quantities unmeasured and obtain estimates of them by subtraction (assuming budget closure). Consequently, errors in sediment budgets are often hidden and are not quantified. There has been an emphasis on suspended sediment, which, for management purposes, may not be useful. Sediment budgeting can act as a framework for a research agenda on catchment processes. What has been lacking from this agenda has been an adequate consideration of the time taken for sediment to travel via the various pathways to the catchment outlet. The storage term in such budgets has been used as a poor substitute for a thorough understanding of sediment velocity through catchments.