Entrance changes in the Snowy River estuary in response to environmental flow releases

Hinwood, Jonathan Barry; McLean, Errol J

doi:10.7158/c14-004.2014.12.1

Cited by 4 publications

(10 citation statements)

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“…As described under 'Hydrologic response', the mean water level was raised by both EFRs although the change in the 2010 EFR was very small. The bulk movement of water through the estuary from the river to the ocean resulted in much stronger ebb currents and weaker flood currents, biasing sediment transport to scouring, as described above and in Hinwood and McLean (2014). This bulk water movement dominated the salt transport, driving the saltwater downstream, as described in the next section.…”

Section: Hydrodynamic Responsementioning

confidence: 77%

“…Each environmental flow had been preceded by a larger fresh flow and consequently the entrance channel dimensions are likely to have been close to equilibrium for the environmental flows before they reached the estuary. Enlargements of the entrance channel were predominantly by scouring in the intertidal zone, due to a combination of wave action and the lesser consolidation of the intertidal sands (Hinwood & McLean 2014).…”

Section: Discussionmentioning

confidence: 99%

“…A companion paper (Hinwood & McLean 2014) used simple models to examine the tidal and river flow contributions to sediment transport in the entrance and depicted the changes and longer-term trends. Entrance morphology 2010.…”

Section: Geomorphic Responsementioning

confidence: 99%

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Response of the Snowy River Estuary to two environmental flows

McLean¹,

Hinwood²

2015

Proc. R. Soc. Vic.

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The Snowy River is a major river in south-eastern Australia, discharging to the Tasman Sea via a barrier estuary, with its entrance constricted by marine sands. Since the construction of the Snowy Mountains Scheme, river flows have not been sufficient to maintain the river channel. A program of environmental flow releases (EFR) is returning water to the river to restore the fluvial reaches and is now trialling flow regimes that may also benefit the estuarine reaches. This paper documents the response of the estuarine segments of the Snowy River to two EFRs; the release in 2010 was designed to scour the upper reaches of the Snowy River while the larger 2011 release was intended to extend the scouring downstream. For each release, the effects on the entrance morphology, tides and salinity through the flow peak and recovery are described. Each EFR caused minor increases in depth and very minor longshore movement of the entrance channel, although each EFR had been preceded by a larger fresh flow that would have scoured the channels. The small increase in fresh water inflow in the 2010 EFR pushed salinity contours seawards and steepened vertical salinity gradients. The larger inflow in the 2011 EFR purged the upper estuary of saltwater. After the peak flow, salinity recovery was rapid in the principal estuarine channels but took weeks where poorly connected wetlands could store fresh flood waters. Critical flows for scouring the entrance and purging salinity are estimated.

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Section: Hydrodynamic Responsementioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

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Response of the Snowy River Estuary to two environmental flows

McLean¹,

Hinwood²

2015

Proc. R. Soc. Vic.

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“…This is not likely to be true but is a tolerable and necessary approximation as there is no robust method to determine the likely long‐term changes in wave climate, nor the transient response of the coastal system to changing wave climate and sea level. The consequences of the likely errors may be investigated by creating attractor maps with changed parameters (e.g., Hinwood et al, ). Resistance parameters, f and K , and sediment transport parameters, u c and m , are hydraulic constants that are properties determined by bed material and the depth. The ocean tidal period and amplitude are assumed constant, as changes in ocean depths due to climate change will be negligible. The entrance breadth has been assumed to have the constant value B = 150 m. This value has been based on the typical value observed when a period of consistently low flows follows a bank‐full scouring flood (Hinwood & McLean, ). Other breadth values are generated by different river flow histories but the history adopted provides the fastest route to entrance closure.…”

Section: Methodsmentioning

confidence: 99%

Response of a barrier estuary to climate change and river regulation using attractor analysis: Snowy River estuary, Australia

McLean

Hinwood

Williams

2018

River Research & Apps

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The evolution of the entrance channel of the Snowy River estuary in response to river regulation and climate change is predicted. The predictions are made in terms of the physical attractors that define possible long‐term states of the estuary entrance condition. The classification of these attractors shows the dependence of the entrance stability on the catchment inflows and the present entrance depth. The Snowy River estuary in south‐eastern Australia is a barrier estuary with an unstable entrance that tends to closure. The classification from the attractor map shows that the estuary entrance has changed from predominantly stable to a predominantly unstable state attributable to diversion of water from the upper catchment. The introduction of a series of environmental flow regimes, commencing in 2002, has returned 8% rising to 21% of the mean annual natural flow, but this study shows that the releases provide limited improvement in entrance stability. Additionally, the predicted effects of climate change for this region include increased mean sea level (MSL), decreased annual rainfall, and increased incidence of storms. These changes will decrease stability, primarily through the rise in MSL. The rise in sea level will increase the plan area of the tidal basin, increasing the tidal prism, and hence drawing in more marine sand. The application to the Snowy River estuary provides a proof of concept of the attractor classification to support estuary management.

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“…• The hydrodynamic module was validated against a well-validated earlier model (Hinwood and McLean, 2001). • Finally, both the hydrodynamic and sediment modules have been calibrated against field data (Hinwood and McLean, 2014;Hinwood et al, 2012), including reproducing the O' Brien (1931Brien ( , 1969) entrance area-tidal prism relationship.…”

Section: Model Validation and Limitationsmentioning

confidence: 99%