Nearly all physically based models of soil erosion and landform evolution i
nclude an equation for the sediment transport capacity of flow, yet the cho
ice of relation varies from one model to another. This raises the question
of the empirical and theoretical support for particular choices. We review
descriptions of the effect of discharge and slope on sediment transport cap
acity of overland flow. A limited range of relations is defined for which t
here is strong theoretical and empirical support. Nevertheless, suggestions
are made for improved experimental designs that further evaluate theories
of sediment transport capacity and reduce uncertainty in its application to
catchment modelling of sediment transport.