The influence of physical factors on channel morphology and geometric diversity

This study investigates the influence of three external factors (channel confinement, riparian vegetation and the presence of in-channel islands and bars) on the downstream morphology and variability of a 600-m reach of the Turon River, NSW, Australia. Statistical analyses revealed that the magnitude and diversity of longitudinal morphologic variables varied between the external factors. For all factors, the influence of each was more relevant to the diversity of the longitudinal variables than their magnitude. Of these, confined channels were shown to be more heterogeneous than partially or unconfined channels, channels with dense riparian vegetation on both banks were more heterogeneous than those with riparian vegetation on only one bank and channel reaches lacking island or bars were more heterogeneous than those containing islands or bars. These findings are significant in that they demonstrate that heterogeneity, or diversity, can be a more important measure of the influence of an external factor on channel morphology than measures of channel size.