We examine the practicalities of estimating stream channel head location fr
om digital elevation data using single and multiple flow direction algorith
ms within the context of field observations for two small catchments in nor
thern Italy. The main conclusions were: (a) field observed contributing are
as to channel heads vary significantly and suggest that a constant contribu
ting area is not a good assumption; (b) field evidence confirmed an inverse
relationship between drainage area and local slope immediately upslope of
the channel head for one catchment but not the other; (c) when best fit par
ameters for field observed channel heads were used to define slope dependen
t thresholds in the DEM algorithms the resulting drainage densities were to
o high; (d) the single direction algorithms generally produced more extensi
ve channel networks with shorter hillslope flow pathways.