Colin Pain

Applied geomorphic mapping for land management in the River Murray corridor, SE Australia

Abstract The River Murray Corridor, in SE Australia, was the subject of a large integrated project aimed at providing answers to a number of important land and environmental management questions and guidance for land use planning. Airborne electromagnetic (AEM) surveys were carried out in conjunction with a light detection and ranging survey in 2007. These data were combined with various satellite remote-sensing data and field observations to produce a number of maps, including maps of landforms and surface materials. These latter maps were used to assess the value of the AEM data, identify potential surface and sub-surface flow pathways and map potential recharge on the Murray River floodplain surface. This allowed the assessment of potential salt storage and the impact of various land use options on salt storage and mobilisation.

Geomorphological Evolution of the Navua River, Fiji

The Navua River on the main island of Fiji displays anomalous drainage features and associated fluvial forms. The River course makes a right-angled bend approximately halfway along its course, beyond which it flows through a narrow gorge cut into hard volcanic rocks. Several tributaries enter the gorge as high cascades from hanging valleys. It is proposed that the former course of the palaeo-Navua River flowed east in a straight line along the modern Waidina River, and eventually discharged into Fijis Rewa River system. Evidence for this is the presence of a spectacular dry gorge (a wind gap) at the head of the Waidina River. Previous ideas of river capture fail to explain the evolution of the local fluvial geomorphology. Instead, tectonic uplift probably dammed the palaeo-Navua and diverted it to its present short course to the sea. This new hypothesis provides a more plausible, simultaneous account for all the major fluvial geomorphic features, their geographical distribution and their relationship with geology in the Navua region.