Rills often act as sediment sources and the dominant sediment and wate
r transport mechanism for hillslopes. Six experiments were conducted o
n two soils and a uniform sand using three experimental methodologies,
The results of this study challenge the assumption often used in hydr
ologic and erosion models that relationships derived for sheet flow or
larger channel flow are applicable to actively eroding rills. Velocit
y did not vary with slope, and Reynolds number was not a consistent pr
edictor of hydraulic friction. This result was due to interactions of
slope gradient, flow rate, erosion, and the formation of rill roughnes
s, bed structures, and head cuts. A relationship for rill flow velocit
ies was proposed, Stream power was found to be a consistent and approp
riate predictor for unit sediment load for the entire data set, while
other hydraulic variables were not. The data for stream power and sedi
ment load fit the form of a logistic curve (r(2)=0.93), which is promi
sing relative to recently proposed erosion models which are based on p
robabilistic particle threshold theory.