A catchment-scale assessment of anabranching in the 143 000 km2 Fitzroy River catchment, northeastern Australia

Abstract

This paper presents a catchment-scale investigation of anabranching in the moderately large 143 000 km2 Fitzroy River catchment in north-eastern Australia. The primary aim is to determine whether mapped and remotely sensed data can provide useful information about the characteristics of anabranching in a catchment of this scale. Anabranching comprises 6% of the total channel network by length, and 24% of higher-order channels (those with catchment areas over 100 km2). Three anabranching planform morphologies are described, which occur in geographically distinct regions, and add to previous descriptions of anabranching rivers. Sinuosity and link length are calculated for all channels of the mapped channel network (a link is a stretch of river between two stream junctions). Slope, mean floodplain width, mean annual rainfall and underlying and catchment geology parameters are calculated for links of a stream network derived from a digital elevation model (DEM), in which each link has either a single channel or anabranching morphology. Anabranching and single channel links do not occupy different ranges of attribute values, and a logistic regression analysis was unable to predict anabranching. However, slope, catchment area, mean floodplain width, length and sinuosity parameters all have significantly different means when comparing single channel with anabranching links, although it is shown that the difference in mean floodplain widths is the result of its correlation with catchment area. Anabranching channels have a tendency towards shorter link lengths, lower sinuosities and lower valley slopes and occur at larger catchment areas than single channels. These differences are discussed in the context of published hypotheses regarding the cause of anabranching. However, the spatial resolution and precision of our data limit our ability to investigate controls on anabranching, which will require detailed measurement of variables at a reach scale. Copyright © 2007 John Wiley & Sons, Ltd.