Estuary entrance changes in response to an environmental flow release

An environmental water releases to the Snowy River was made in October 2011 (12,000 ML/day) as part of the Snowy River Increased Flows Program. The effects on the inlet entrance morphology and tidal response were measured on four field trips for each release to cover the flow peak and recovery. Water level recorders were deployed in the principal channels over the period of the releases and for the prior two months at Marlo. The EFR raised waterlevels in the estuary but the change was attenuated by the large storage capacity and the relatively open entrance. Entrance scour was minor as the entrance channel had been enlarged by a previous catchment flow of greater magnitude than the EFR Scour primarily occurred in the intertidal zone, showing that the entrance was close to equilibrium for the EFR. This result was confirmed by analyses of the sediment transport capacity and through use of an attractor plot.