Large wood in the Snowy River estuary, Australia

- In estuaries, wind and tide are as important as river flow in transporting and stranding large wood.
- Due to the action of wind and waves, large wood is predominantly parallel to the shore and in contact with the shore.
- Large wood in estuaries generally protects against bank erosion but does not affect the hydraulics or sediment transport.
- Large wood provides roosting and nesting sites for water birds and some shelter against currents and predators for marine life.
- The sparse but clumped distribution in south-eastern Australian estuaries requires more complete sampling rather than representative transect or quadrat methods.
- The use of inexpert undergraduates to perform field work, rather than postgraduates or professional staff, reduced the quality of data but enabled the surveys to cover a much larger area and to sample all the wood.

In this paper we report on 8 years of data collection and interpretation of large wood in the Snowy River estuary in southeastern Australia, providing quantitative data on the amount, sources, transport, decay, and geomorphic actions. No prior census data for an estuary is known to the authors despite their environmental and economic importance and the significant differences between a fluvial channel and an estuarine channel. Southeastern Australian estuaries contain a significant quantity of large wood that is derived from many sources, including river flood flows, local bank erosion, and anthropogenic sources. Wind and tide are shown to be as important as river flow in transporting and stranding large wood. Tidal action facilitates trapping of large wood on intertidal bars and shoals; but channels are wider and generally deeper, so log jams are less likely than in rivers. Estuarine large wood contributes to localised scour and accretion and hence to the modification of estuarine habitat, but in the study area it did not have large-scale impacts on the hydraulic gradients nor the geomorphology.