Marine Threat Tsunami Warning What Does That Mean for Lane Cove Residents?

As a result of an eruption of HUNGA TONGA-HUNGA HA’APA in the Tongan Islands at 3.10 pm AEDT Saturday 15 January 2022, the Bureau of Meteorology (BOM) issued a Marine Threat Tsunami Warning for the NSW Coastline, Lord Howe Island and Norfolk Island.

At 2.45 pm Sunday 16 January 2022, the BOM issued the following statement:

“Throughout Saturday night Tsunami wave action continued to be observed along
parts of the East Coast. The Tsunami Warning for the marine environment is
expected to stay in place Sunday until there has been a clear period of several
hours where observations show the threat level has eased. Warnings will be
updated each hour for the duration of the event.”

NSW State Emergency Service (NSW SES) is the lead combat agency for a Tsunami in NSW.

To keep members of the community safe, all NSW beaches have been closed (January 16 2022). NSW SES has asked the public to stay out of the water until it is safe to do so.

What is a Marine Tsunami Warning?

A Marine Tsunami Warning could have the following impacts: dangerous rips and waves, strong ocean currents and some localised overflow onto the immediate foreshore.

It’s the second-highest Tsunami Warning Alert Level.

While land evacuations are not necessary for Marine Threat areas, people are advised to get out of the water and move away from the immediate water’s edge.

Why are Beaches Closed During a Marine Tsunami Warning?

The BOM advised Tsunami waves were more powerful than beach waves of the same size.

NSW SES Commissioner Carlene York told the media that swimmers risked “injury or death” if they go in the water as a marine tsunami threat means there will be unusual currents and dangerous rips.

The SES Commissioner said:

“A lot of people will be disappointed that it’s going to be a very humid day and the Australian way is to get into the beach but to protect this community, the beaches are closed, and Surf Life Saving has removed the flags and we’re making sure that people don’t go down the water”.

“It’s also important not to go down and look at the tsunami. In past tsunami warnings, we’ve had people get in their vehicles and go down to the beach. That is exactly the wrong thing to do.”

“We want to make sure that whoever is in the nearby vicinity, we can evacuate people safely and we can have the roads as clear as possible.”

“Because once that wave if it does come, [when] it’s coming it’s very vital and very urgent to get people away from the areas.”

The SES Commissioner also said:

“Members of the public considering looking to local rivers as an alternative for swimming are reminded that due to recent heavy rain, some river systems across the state are swollen, and may present dangerous swimming conditions.”

Categories of Threat Levels within Tsunami Warnings

In order to assist the community, tsunami threat levels warnings are categorised into three levels with required community responses; these have been determined in consultation with emergency management authorities. These Threat Levels are specified for the same coastal areas that are used for routine BOM Bureau Coastal Waters Forecasts, already known to marine users.

No threat  – An undersea earthquake has been detected, however, it has not generated a tsunami, or the tsunami poses no threat to Australia and its offshore territories.

Marine and immediate foreshore threat – Warning of potentially dangerous rips, waves and strong ocean currents in the marine environment and the possibility of only some localised overflow onto the immediate foreshore.

Land inundation threat – Warning for low-lying coastal areas of major land inundation, flooding, dangerous rips, waves and strong ocean currents.

How Do You Keep Up to Date on the Tsunami Alerts?

The Bureau of Meteorology has a Tsunami Alert Page here.

The SES also updates its Facebook page here.

Which Areas in the Lane Cove Council Area Are Impacted?

If the alert had been at the highest level (land inundation threat), it would have implications for Lane Cove residents.

In June 2016, the NSW SES  launched Tsunami Evacuation Maps. The maps cover the whole NSW coast and show those areas that lie under 10 m above sea level, are 1 km or less inland and are 10 km up an estuary.

Areas of Lane Cove (including Northwood, Lane Cove West, Lane Cove, Longueville, Lane Cove North and other areas that border the Lane Cove River) were noted on the maps as possible land-based tsunami areas.

The SES stressed the maps were released in the very unlikely event of a land threat tsunami.

However, if there was ever a land threat tsunami the NSW SES would request people in the red zone to seek shelter at least 10 m up in a sturdy concrete building or to move outside the red zone area to an area of lower risk.

NSW SES being the combat agency for flood, storm and tsunami released the mapping as part of their work to build preparedness and community resilience.

At the time the maps were released the NSW SES stressed the maps show areas that would be evacuated and not areas that would be inundated with water.

The SES also stated:

“Marine-threat tsunamis occur once about every six years but are usually only dangerous to swimmers and boaters because of the dangerous currents. There is no record of a land-threat tsunami in Australia since the European settlement.”

The area in red is the evacuation area for a land-based Tsunami alert for the 2066/2065 area.

It is important to note that these maps are not inundation maps, and represent the areas considered most at risk from modelling of potential tsunami and effects observed elsewhere. The NSW SES is working on getting more data and refining maps to show potential inundation and evacuation routes in the future.

The NSW SES has on their website all the information you need about Tsunami’s in Australia –  It includes safety and preparation advice – click here.

Water Quality After Periods of Heavy Rains

The NSW Department of Planning, Industry and Environment (DPIE) have the following warning about water quality after heavy rain:

“Beaches in NSW mostly have very good water quality. In fact, they’re among the best in the world. But there are times, particularly after heavy rain, when stormwater runoff and overflows from the sewage system can enter our waterways. If you swim after heavy rain, there’s an increased risk of contracting illnesses like gastroenteritis and ear, eye and throat infections.”

DPIE has issued the following general warnings for safe swimming:

• Avoid swimming during and at least one day after heavy rain at ocean beaches, and for at least three days at harbour beaches.
• Avoid swimming near stormwater drains or sewage outfalls.
• Avoid swimming if you see signs of pollution such as discoloured water, oil or scum on the water, and litter or other debris floating in the water or on the tide line.

Each year the NSW Government releases a water quality report which monitors the water quality of 228 NSW swimming sites – read more about how our local swimming sports and water quality here.

You can also check water quality each day for both ocean beaches and harbourside beaches here.