The Lake Tyers estuary extends from the sand barrier on the Ninety Mile Beach to Nowa Nowa. The entrance is subject to strong currents and wave action, and sand supply along the beach has frequently closed the entrance.
The area of land subject to inundation when the estuary closes is small. The estuary has a comparatively small catchment and high volumes of water are needed for an opening (artificial and natural) to be successful.
Pattern of closures
For the period between 1983 and 2011 the estuary was closed for 75% of the time, including one closure for over four years.
Strong west and south westerly winds that generate storm waves at an oblique angle to the beach and transport large volumes of sand across the entrance appear to be the major factor influencing closures. There seems to be no pattern of closures directly related to rainfall (and resultant flows) possibly due to the size of the waterway compared to the size of the catchment.
Location of flooding
The steep topography adjoining the estuary means that the area of land subject to inundation when the estuary closes is comparatively small.
Inundation occurs at boat ramps, jetties, and fishing platforms at Nowa Nowa during periods of extended closure. There may also be restricted access to boat ramps and walking tracks at Lake Tyers.
Level required for a successful opening
The water level in the estuary during an extended closure is about 1.7m (indicated by marks on infrastructure surrounding the estuary). The maximum water height, where the entrance either opens naturally or is opened manually, is approximately 2.3m (as indicated on the gauge at the boat ramp). This significant variation underlies that fact that the opening is associated with periods of high intensity rainfall and the corresponding inflows.
Once open the estuary water level drops to close to sea level within 24 to 36 hours and creates a significant entrance through the sand-bar. The duration of the opening varies and depends on the inflows and prevalence of strong westerly winds.
Responsibility for an opening
A natural opening is the preferred outcome. However, if an artificial opening is to be made, this will be done by the East Gippsland CMA and Parks Victoria. The actual opening will be undertaken by Parks Victoria.
Location of gauge
The gauge is attached to the concrete wall beside the boat ramp.
Printed information about estuary entrance management at Lake Tyers can be found here (PDF, 320KB).