Storm Surge or Tsunami? You decide!

About 0000 hrs UTC on Sunday 11 November 1990, I was testing out a new toy: a camcorder, on the southern Australian coast.

Standing at Point Roadknight, looking NW across the shallow bay, the camera caught a very large storm surge, or maybe a tsunami.

The only way to be sure is to correlate this (roughly timed) event with the historical seismic record.

Additional notes:

* The previous night had been very stormy across a vast swathe of the Southern Ocean and nearby Bass Strait.

* the first camera angle is from an opposite vantage point across the bay, looking towards the south-east, and the bay appears reasonably full i.e. the tide is NOT right out.

* after walking to the vantage point from which the surge/tsunami was observed (maybe 30 minutes later) the bay appears almost totally drained of water at the time the surge appears on screen from the right of screen.

* after the surge washes into the bay, the water level appears to stay at the new higher level (more video footage of that shot would have been useful, so as to see how long the water really lingered in the bay).

* there is strong visual evidence (for people who know this bay well at all tide levels) that the bay had significantly drained of a _lot_ of water in the half hour before the big surge rushed in. This is the main thing that makes me think it could be a tsunami.

Apologies about the quality, but the clip was originally filmed on VHS-c mini cassette, transferred to large format VHS for the family archive, stored in a hot attic for 25 summers, and only recently converted to digital media on a low-tech Linux box.

Category:

Science & Technology

Tags:

• tsunami
• storm
• surge
• 1990
• Bass
• Strait
• Victoria
• Australia

[Murrangurk2]

Pt Roadknight, high tide, big swell. Standard behaviour.

[TheOnlyEVG]

what a crappy vid lol, no surge and no tsunami, just a bunch of small waves on banks and reefs

if that was abnormal for that area then that area is very boring in terms of tides and waves lol

if it was a surge it would of gone past the high water marks, which it didnt, if it was a tsunami you would not of been standing on the beach watching it pass you like a little ripple and again would of gone past the beach front

[toffgooglification75]

at 2:20 it looks like there might be a bay to the left of the rocks that the dudes standing on if theres a shelf or sandbar across the mouth of the bay this might cause erratic tidal levels when the tide goes in or out??

[twas500]

that was a normal wave if anything big it would be a storm surge but how big was the waves?

[djcesare]

mild tidal surge

[amp3cx10000a7jp]

not tsunami. this wave make blown in wind.

[funmasterchris]

its just a abnormal wave. not a tsunami!

[Gebora]

its a surnami!

[marbleworkslover3471]

That was years ago.

[mryellow123]

Being southern Australia the tidal variation is low. Maybe there is a shelf.

Looks like a "set" from the video, tho hard to say as there is no real shot of the bay draining or where the levels are before and after.

In a lot of places the sets come in 7's with every 7ths wave being a harmonic larger harmonic from all the super-positioning of waves on top of each other.

It's possible this was just a set from a longer harmonic series.