Tropical Cyclone Oma: How much could she cost us?

Kevin Roche
Swellnet Analysis

In northern NSW and southeast Queensland, migration and continued development of the coast is leading to large concentrations of population, property, and infrastructure at risk to both natural coastal processes and natural disasters. The ever-changing forecast track of Tropical Cyclone Oma may see her arrive in this location over the next week. What could this look like? In 2010 Kevin M. Roche, K. John McAneney, Keping Chen, and Ryan P. Crompton examined a similar scenario.

Approximately ten years ago we looked into the impact of the Tropical Cyclone that made landfall on February 20th 1954, just inside the Queensland border at Coolangatta. Often referred to as TC137, it was never given an official name - a practice not adopted in Australia on a consistent basis until 1964, although some systems were named prior to this.

The objective of the research was to estimate the insured losses that might be expected if a similar event were to occur today and to generalise about the expected economic costs that might occur. Remembering that this was a fairly underdeveloped region back in 1954. These days it is one of the fastest growing regions in Australia with the south-east Queensland region population expected to exceed 4 million by 2026.

The other main objective was to provide a learning tool for future reference. We hoped that if society had a better understanding of historical natural hazard impacts from large scale events that it should lead to reducing the risks to the community from extreme weather events through either mitigation activities and / or community resilience.

At the time, the economic cost of natural disasters across the globe was increasing dramatically and many were keen to attribute this to climate change. On the other side of the argument there was an ever-growing body of evidence (across multiple jurisdictions) that showed that this increase in losses could be largely explained by changing social factors – such as changes in population, wealth, and inflation.

This was the approach we took. In effect, this evidence showed that there were more people living in vulnerable places with more to lose. And this has only increased over the last ten years. Society did not seem to want to learn from its previous mistakes. And sadly it still does not. We continue to build poor quality houses in poor locations. Historically, over 93% of all property destruction due to natural disasters in Australia has been due to weather related events, with tropical cyclones and floods being the most deadly after heatwaves.

Cyclone Track of TC137 (Source: Bureau of Meteorology)

Tropical cyclones are unique in that they can have up to three major impacts from the one event: destructive winds, heavy rainfall, and damaging storm surges. TC137 made landfall on the 20th February near the Queensland / New South Wales border, before heading in a southerly direction for some 500 km where it developed into a rain depression and exited the coast not far from Coffs Harbour.

TC137 was a fairly small cyclone in terms of wind impacts, registering as an Australian Category 1 cyclone. A Cat 1 cyclone is defined by the BOM as having typical wind gusts over open flat land of between 90 and 125 km/h. You would expect to see damage to crops, trees and caravans but negligible damage to houses. But the accompanying rainfall led to nearly all major rivers and creeks in the region experiencing their highest recorded levels right up until TC Debbie (March 2017) decided to take a few of these records for herself.

The Nerang, Tweed, Brunswick, Richmond, and Clarence catchments all flooded simultaneously. Parts of the lower Clarence River were estimated at being 11km wide.

Springbrook, just inside the Queensland border, received 900mm rainfall in 24 hours. The Richmond catchment was hardest hit with most towns including Lismore, Kyogle, Casino, and Nimbin experiencing their highest ever recorded flood heights, as did Murwillumbah.

But of more interest to the surfing population is what happened down in Byron Bay, long before it became the poster child of legal disputes between beachside land owners and the local council. Although Byron these days is full of wealthy escapees from the major cities, backpackers, and those seeking a bohemian lifestyle, it was not always this way. Back in 1954 it was an avid fishing town with an estimated one-fifth of the town employed by the fishing industry.

And overnight the fishing industry was obliterated. The resulting storm surge that arrived with TC137 was the cause. There are limited facts on wave heights and the magnitude of the swell event but the anecdotal evidence is compelling. Wave action breached the sand hills and was reported five blocks back from the beachfront, reaching Marvel Street and the Recreation Ground. It also caused major damage to the wharf.

Byron Bay’s first wharf was built in 1888 and had been replaced in 1928 after heavy seas damaged it. This second one was rebuilt in 1948, before approximately 200m of it was washed away by TC137. In those days, the fisherman used to lift their boats up on to the wharf to protect them from heavy seas. On that fateful night, 23 of the 24 boats which made up the Byron fishing fleet were loaded on top of the wharf - and subsequently never seen again. The last of the boats survived as it was stuck up at Brunswick in the river, initially annoyed that they could not make it back down to the so-called safety of the wharf.

The image below shows the wharf in the early 1940’s with a few of the fishing fleet on top.

Byron Wharf in the 1940’s

Almost immediately after TC137, Byron Bay became a whaling town – worthy of another discussion at a different time.

To estimate the cost of TC137 if it had occurred in 2010 we used a combination of local council flood maps, Census information, and Risk Frontiers’ proprietary flood loss model, a model used by many insurance companies. Essentially we used mathematical techniques to take into account that the value of real estate in the region had increased over ten times since 1954 and the population by an order of magnitude, and combined this with our knowledge of the impact a similar type of event would have.

I will not get into the detail too much here but if you are interested you can read more about it here (https://journals.ametsoc.org/doi/full/10.1175/WCAS-D-12-00018.1)/.

TC137 occurred prior to the availability of reliable insurance statistics. Our best estimate of losses in the dollars of the day was approximately £7.5 million with 28 people losing their lives (some reports have this number as high as 30). Our best estimate at the time using 2010 levels of exposure - think houses, people, business, and infrastructure - whilst assuming 100% insurance penetration (in Australia it is about 96%) could reach $3.4 billion, with economic losses approximately twice this. We would expect these losses to be higher if a cyclone was to be more intense when it reached landfall.

Remember these are 2010 numbers. In today’s terms we would expect them to be even higher.

To put this in perspective, here are the top 5 natural disasters (since 1967) ranked as if if they occurred in 2017, taking into account changes in build codes, trades and material costs, population and demographics from the Insurance Council of Australia:

$5.6bn, Sydney Hailstorm, 1999
$5.0bn, Cyclone Tracy, 1974
$4.7bn, Cyclone Dinah, 1966
$4.2bn, Earthquake, 1989
$3.2bn, Brisbane Flooding, 1973

So yes, Tropical Cyclone Oma could potentially be both devastating and expensive.

// DR KEVIN ROCHE

Dr Kevin Roche is an economist who spends his time advising governments and corporates how to manage their exposure to natural hazards and climate change across the Asia-Pacific region.   

Comments

yocal's picture
yocal's picture
yocal commented Friday, 22 Feb 2019 at 8:06am

Interesting Article thanks Kevin,
If the Cyclone sits off the coast as currently forecast, and has sustained gale force winds for 3-4 days, will this cause significant damage or does the real damage occur at the specific locations where a cyclone crosses the coast?

Go deeper Taylor, go deeper!

atticus's picture
atticus's picture
atticus commented Friday, 22 Feb 2019 at 9:00am

The strongest winds are around the eye of the cyclone so it either has to come ashore or brush the coastline for wind damage. Then again, as Kevin's article states, swell can cause damage even when the cyclone is hundreds of kilometers away

le-renard's picture
le-renard's picture
le-renard commented Friday, 22 Feb 2019 at 9:51am

Have to respectfully disagree with the ”We continue to build poor quality houses in poor locations” line. Post-Tracy building regulations are some of the more stringent in the world. Even the lowest design wind category for post-'86 buildings in the region is 40m/s, 144km/h. Flood level restrictions continue to get updated and even pure beachfront sites have scour-zone design considerations, at least on the GC. There will undoubtedly be property damage in any significant weather event, but we're not exactly building shantie towns, as intimated.

psychadeliceahorse's picture
psychadeliceahorse's picture
psychadeliceahorse commented Friday, 22 Feb 2019 at 10:10am

Let's refine it to poor structural systems in poor locations.
Tight regulations but those regulations are only enforced during construction. Standard method of timber frame construction in the majority of houses across Au is not designed to last and will degrade over time due to poor workmanship and cost cutting all around, especially amongst volume builders.
This of course is talking about typical Class 1 buildings for residential and is not taking into account multi storey 4-9 in which the certification process is much more stringent.
My two cents based on a mixture of industry experience and education and anecdotal knowledge so completely ready to be debunked / scrutinised on this call. :)

le-renard's picture
le-renard's picture
le-renard commented Friday, 22 Feb 2019 at 11:14am

@psychadeliceahorse oh i agree re. timber structure maintenance, the Standards defer to homeowners but few would be aware of their responsibilities. But they are at least -designed- to last, within the legal obligations of the designers. The majority of property damage due to winds is from object impacts, of which there are no design considerations required. I do think there are legitimate, serious questions on overall urban development strategies, but more due to population concentrations etc. No-one forces people to buy beachfront properties and any land owner prevented from building as others nearby have built, would have some solid legal basis to challenge that prevention. I think there has to be some individual responsibility on private property development, it's not like rising sea-levels etc aren't discussed ad nauseum.

mowgli's picture
mowgli's picture
mowgli commented Saturday, 23 Feb 2019 at 12:10pm

"....any land owner prevented from building as others nearby have built, would have some solid legal basis to challenge that prevention. I think there has to be some individual responsibility on private property development, it's not like rising sea-levels etc aren't discussed ad nauseum."

These two questions are going to be tested in the planning/land & environment courts very, very soon. Actually already has a little bit but in a fashion not as broad-sweeping. The pre-cursor case has been the (long-running) one involving Byron Shire Council.

It's going to be tricky to draw lines around where local government responsibility ends (i.e. with where they allow people to develop, whether new or replacement), and where the asset owner needs to take responsibility for their own decisions. Caveat emptor and all that.

You watch. There is going to be a huge (and very vocal) push to transfer risk from the private asset owner to the public, particularly in the coastal zone where asset values are very high. The irony being many of those on the frontline are wealthy and tend to vote conservative. You know, voting for those same parties that have actively fought against actions to avert serious climate change despite the warnings of climate scientists that a warming world would lead to the kinds of consequences that we're already beginning to see. The broader public would be wise to pay attention to this and support formation of policies that prevent this risk transfer from occurring, lest they be hit with hefty rate rises to bail out the wealthy.

“Life is a long lesson in humility.”

Smorto's picture
Smorto's picture
Smorto commented Friday, 22 Feb 2019 at 10:17am

Great article but I agree that we have very strict flood and erosion related planning and building regulations. I doubt we will ever see (in our lifetime) the kind of destruction caused by cyclones in the mid-20th century.
Gold Coast Council has just released new flood maps (which take into account sea level rise and storm surge events) which have made developing some coastal areas very difficult or expensive. For example, Palm Beach has just had an 880mm flood level increase meaning that you either need to put heaps of fill onto the site so that the dwelling sits up high, have the house on scour proof stilts or have no habitable rooms on the ground floor.
Its good from a safety perspective but makes it very hard for a Mum and Dad in an old fibro shack from redeveloping their land with a duplex.

memlasurf's picture
memlasurf's picture
memlasurf commented Monday, 25 Feb 2019 at 1:50pm

I don't think you can use fill as it will reduce the flood area and just shift the problem. I know it Victoria it is now a no -no not sure about up north.

Smorto's picture
Smorto's picture
Smorto commented Monday, 25 Feb 2019 at 2:37pm

Yeah you are right its the same up here and the fill option requires the loss of floodplain storage to be balanced out. Either with a tank for small sites or lake for larger sites.

That's why I said it is hard for Mum and Dads on small sites now because the cost of installing a tank basically eats up any profit they were going to make so they are only left with other expensive build options like stilts or suspended slabs.

Although I reckon Council's 880mm flood increase is crazy and way too conservative an increase in a single hit.

hamishbro's picture
hamishbro's picture
hamishbro commented Friday, 22 Feb 2019 at 10:45am

Great review of the event and appropriate that you mentioned Kyogle and Casino because that’s where most of the fatalities were in ‘54. That’s how far the deluge penetrated when the cyclone crossed - enough to fill up the Richmond River which doesn’t collect until you get rain west of Nimbin. The economic damage was huge both inland and on the coast - but it would pale in comparison to a similar event now. And given the much higher concentration of development along the coast, this is where the economic catastrophe would be felt. We all talk about Byron bay, but I reckon it’s parts of the tweed coast which have recently been overdeveloped IMO would get smashed much worse. Interesting to see how modern developments would fare given all the development controls imposed today. I still don’t think they account for these one in a hundred year events - the joke being it’s not if, but when.

Graeme Murdoch's picture
Graeme Murdoch's picture
Graeme Murdoch commented Friday, 22 Feb 2019 at 12:01pm

Apologies for kinda unrelated observation, but one thing that'll be pretty telling to observe – especially in comparison with events of previous decades – is the amount of plastic and rubbish that'll wash ashore over this next week. Here on the NSW North Coast it feels like there's been an alarming increase in plastic along the tideline, even in the last six months, so am wondering if this exponential ratio will go fricken ballistic post-cyclone.

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Friday, 22 Feb 2019 at 8:21pm

Very interesting actually. Is there any way of telling if the plastic would be locally used, or if it came from sealanes far away?

eg parts of local craypot vs milk container with different language on it

https://www.weforum.org/agenda/2017/05/the-untouched-south-pacific-islan...

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Friday, 22 Feb 2019 at 12:05pm

https://www.themorningbulletin.com.au/news/debbie-the-second-most-costly...
GC locals were led to believe TC Debbie as Qld's most expensive Cyclone.
Debbie's extended posh seachange tour skyrocketed the damage bill.

Get sued billions for a quick hosedown delaying Hedges Ave Oz CEO's.

SEQ also experiences Australia's most damaging expensive 'storms'.
Single most obvious reason that we Qlders rule out DLS.
More people in harms way at peak hour in storm season is mass suicide.

SE/Qld DLS would incur greatest emergency costs in Oz peacetime history.
Recent example: Cops in Townsville earnt around $6,000 each during floods.

Qlders don't wish to idle as lightning rods on golf courses.
Ask! What irresponsible Premier would order masses into Oz worst storms.
Qld has no choice but to curfew folk indoors during summer storm season.

We thank Oz for allowing us to cower in shelters smack bang in Stormbelt.
We're not so selfish to burden triple time paid Thunderbirds 1/2/3/4/5.

memlasurf's picture
memlasurf's picture
memlasurf commented Monday, 25 Feb 2019 at 1:53pm

I wish I could understand you TBB as beneath the labyrinth of the verse there seems to be something there.

freeride76's picture
freeride76's picture
freeride76 commented Friday, 22 Feb 2019 at 7:36pm

bring back the Byron Jetty

truebluebasher's picture
truebluebasher's picture
truebluebasher commented Saturday, 23 Feb 2019 at 8:28am

The human & financial burden of summer storms increases with DLS.
Real Estate adds to clean up bill.

This weekend Qld Premier reveals day of the week as an equally costly affair.

BOM weekend forecast is for TC' Oma to weaken intensity and backtrack.

Qld Premier is neon flashing a supersized all inclusive [ BEACH CLOSED ]
Weekend Ban includes (SURFERS) + Threats of Criminal Charges. WTF
So why does Premier order Pro surfers from WSR if Cyclone is backing out?

Cyclonic surf has befallen a weekend. (This changes everything).
Premier is obligated to save Volunteers lives & reduce burden on the State.
1. As mentioned Civic Police servants command top dollar on weekend alerts.
2. 'Volunteer' SES/SLSA ...High alert insurance lacks 'Workplace Powers'.

Premier's Message: "It's too expensive to rescue you a/h on weekends!"
Now add that Fishermen/Surfers burden earliest am hours + latest pm hours.
In short Fishing/Surfing is Qld's most expensive storm season pastime.
Cyclone Oma [WSR]... is Millionaires Row for a few million privileged surfers.

Qld Premier: [ "DON'T GO SURFING" ]
SLSQ: [ WE WILL CALL THE COPS ]

In the wash up...real estate/DLS escalate cost but also the day of the week.

Perfect Storm: Friday Twilight Cyclonic landfall @ Glitter Strip
Not because target size but it escalates top dollar a/h 'Weekend' mop up.

Come Friday Night mid cyclone Season our Premier says: [ NO SURFING ]

redmondo's picture
redmondo's picture
redmondo commented Monday, 25 Feb 2019 at 3:07pm

Dodged a bullet.

Victory!