Streamflow characteristics of northeastern Tasmania: II. Hydraulic geometry

Relationships describing the adjustment of water-surface width, mean depth and mean velocity to increasing discharge are calculated for eleven sections in northeastern Tasmania. The at-a-station graphs of two sections display distinct discontinuities related, however, to different causes - sub-bankfull channelization and the attainment of overbank stage. Despite intra-reach and inter-fluvial variations in hydraulic geometry, two types of response seem to be dominant, characterised by a high rate of change of either depth or velocity. Two sections do not fit into this pattern and, significantly, they tend to plot poorly on downstream graphs.
Bankfull discharge probably lies between Q1.11 and Q2 at most sites, so both flows are used as reference discharges in analyses of downstream adjustment at the regional scale. The relations at Ql.ll and Q2 are quite similar and they are within the envelope defined by results from other areas. However, the data base is small and the scatter is large enough to render the velocity-discharge relation non-significant. The main residual from regression is the station on the South Esk at Perth which is used for discharge measurements at higher flows. Nevertheless, the hydraulic geometry equations enable estimates to be made of channel flow properties at ungauged sites within the northeastern river system.