Water Levels in the Swan River Estuary: A Personal Observation

I READ with interest an article in The Fremantle Herald newspaper in which global warming was blamed for rising sea levels, which in turn were said to be submerging the mud flats in the Swan River estuary and thus destroying the habitat of migratory birds.

Reading it, I could not but reflect on my own observations of water levels and on the accretion and erosion of mud banks in the Swan River over my life-time. I have known the river intimately since the early 1940s when as a toddler I first paddled in the waters of Freshwater Bay. Over the years I have swum and fished in, and canoed, rowed and sailed on the river. I have cycled around the riverside paths, explored the river’s shores and bushland, walked my dogs at the river’s edge, and enjoyed the wildlife – some of which (like the river cobbler) seems to have disappeared, while other species (like the black swans) appear to be flourishing. I have known the river from Preston Point at East Fremantle to the Perth Causeway and beyond for over 60 years, and since 1980 I have swum regularly at the old Bicton Baths.

Over all this time I have seen the river rise and fall with the ocean tides, respond to flood waters coming down from the Avon, and fill to its brim with the run-off from heavy rain storms. But I have also seen the Point Walter sand spit so far above the water that it has grown a small-vegetated island. And only last summer there were occasions when the water was so low at Bicton Baths that the bottoms of the swimmers’ ladders were exposed and there were acres of temporarily exposed mudflats west of Alfred Cove and along the Como foreshore.

I have also observed the wave-cut benches in the limestone cliffs along Blackwall Reach. These indicate river levels at least 2 metres higher at some time in the geological past, while the current benchmarks do not appear to have changed for decades, perhaps a century.

The literature on sea level rise suggests that global average sea levels are rising at a rate of about 2 mm per year, a trend going back for 150-odd years to the Little Ice Age. But the picture is confusing because in some places sea levels are falling, while in others there is only an apparent rise because the adjoining land is subsiding. In other places still, the rate of rise is much slower. For example, according to the Swan River Trust’s website, the sea level at Fremantle Harbour has risen at a rate of only 1.5 mm/year over the last 100 years (or about six inches in total) and the Trust does not report any sudden recent rise in levels, or in the rate of increase.

Within a tidal estuary connected to a vast inland catchment (as is the case with the Swan River) the picture is particularly complex because of the way mud flats and sand spits are eroded by tides, floods and boat wash, or built up by sedimentation. And if anyone wonders about sedimentation, they need only look at the colour of the river after winter rains inland – the water is stained brown from the topsoil carried down from wheatbelt farms. Much of this goes out into the ocean, but tonnes are also deposited in the estuary.

I do not dispute the data on sea level rises measured over the last 150 years. However the evidence of my own eyes is that there has been no sudden, recent rise in water levels in the Swan River as reported in The Fremantle Herald. It seems to me that the average river level today is pretty much where it was when I first knew it, and that the variation around that average is the same as it has been over the last half-century, a response to predictable and well-known factors such as ocean tides and rainfall in the catchment.

It is possible, of course, to speculate about the future, even to design future scenarios using computer models, and I am well aware of the belief some people hold that sea levels will rise many metres (some say 100 metres) due to the phenomenon of ‘global warming’. I don’t wish to discuss this here, but I would appreciate the presentation of actual data on river levels to help me to understand the true picture. This will enable me to either validate or deny my own experience and observations over more than 60 years, which appear to be different to (or at least less dramatic than) those reported in The Fremantle Herald.

In closing, it is interesting to compare two photographs taken of a well-known feature of the Swan River – the Crawley boatshed.

Screen Shot 2013-06-03 at 12.58.11 AM

The first was published in George Seddon’s book Swan River Landscapes and is a photo taken by Professor Seddon in the late 1950s. The second, of the same scene, was taken fifty-three years later by me.

Apart from the colour scheme, and the absence of the elegant old boats in the Seddon photograph, the river water levels half a century later appear to be virtually the same.

There is an amusing postscript to this story. It was submitted to The Fremantle Herald as a follow-up to the concern that migratory bird habitat was being submerged by rising water levels in the Swan River. It was never published. When I asked why, I received a classic response from Steve Grant, the paper’s Chief of Staff: he queried my qualifications as a climate scientist.

Subsequently The Fremantle Herald has published a story about the impending demise of the Little Penguin due to “a marine heatwave” in the Indian Ocean. Neither the story about rising river levels or the one about endangered penguins drew on the expertise of a climate scientist, nor were any references given to climate science data… but then these were stories that supported the Herald’s position on climate change, and mine did not.

Roger Underwood
March 10, 2012


33 Responses to Water Levels in the Swan River Estuary: A Personal Observation

  1. Graeme M June 4, 2013 at 7:03 am #

    Interesting story and observations Roger and consistent with those of others that have commented here.

    Just don’t mention this over at Deltoid…

  2. cohenite June 4, 2013 at 8:12 am #

    It is a great photo comparison; 53 years and not a skerrick of sea level rise.

  3. Neville June 4, 2013 at 8:13 am #

    Graeme, deltoid just love BS. Anyhow according to even the satellite data SLR is about 3mm year.
    Or 26 cm by 2100 or about 10.4 inches. Not much different than the last 100 years. But the boat shed photos say it all for me, that there is zip difference since 1958.

    But now even Karoly admits that large temp increases are unlikely for another century and we also have their own models on SLR to fall back on. Zip again for another 300 years.

  4. Mike Mellor June 4, 2013 at 9:20 am #

    Roger Underwood says

    “…the sea level at Fremantle Harbour has risen at a rate of only 1.5 mm/year over the last 100 years (or about six inches in total)…”

    That’s 1.5mm per decade, not per year?

  5. Neville June 4, 2013 at 9:43 am #

    Roger it’s 1.5mm per year or 15mm per decade or 150mm per century or about 6 inches.

  6. Neville June 4, 2013 at 9:45 am #

    Sorry Mike not Roger above.

  7. Robert June 4, 2013 at 10:19 am #

    You can tell if a guy is really interested in your actual sea level rise or just teasing. If he’s studying the period from the late 1700s to the 1860s, that’s a sign of commitment to the real thing. But most boys are just trying to get published, egged on by their peers. Show-offs with one track minds!

  8. spangled drongo June 4, 2013 at 10:31 am #

    Thanks for those obs Roger. They agree with the PSMSL tide gauge for Fremantle going back to 1897:


    Like you, I too have knocked about the waterfront but on the east coast around Moreton Bay since the early ’40s [where I was totally fascinated by the doings of WW2 and got into all sorts of trouble for bringing home hand grenades etc that were just lying on the beach for kids to play with.]

    There has been no visible SLR here either. In fact the reverse is true. King tides were higher 70 years ago in Moreton Bay than today. The highest cyclone surge that has historically occurred here [and there have been many over the years] was back nearly 80 years ago in 1934.

    At Fort Denison [Pinchgut] in Sydney, the highest surge was in 1974 but there too, virtually nothing has been happening over the last century.

    Have the coastlines around Perth been sinking? I seem to recall I read something about that but can’t find it now.

  9. spangled drongo June 4, 2013 at 11:06 am #

    Found this:

    There are claims of somewhere between minus 50mm and minus 5mm a year subsidence around Perth so by that measure, SLs are actually falling.

    Even if it was only minus 1.5 mm a year there would be no SLR:

    “First, there is no independent supporting evidence for the -50 mm/yr subsidence reported by Ng & Ge (2007) and sensationalised by the Western Australia news media. Evidence from reprocessed InSAR imagery and independent CGPS suggest that the subsidence is closer to -5 mm/yr, but the exact values are spatially and temporally variable (Table 1).”


  10. John Sayers June 4, 2013 at 1:34 pm #

    Roger, on a recent trip back to Auckland where I grew up as a child I went to the beach I played on back in the late 40s, early 50s. My measurement was a crop of rocks that go under water at high tide and are exposed as the tide went out – I knew them backwards as I’d spent hour upon hour exploring them as a child and knew exactly the tidal heights as you could easily get swamped when the tide came in.

    The high tide also was no different as it came up against our house’s wall which has been there since the 30s.

  11. cinders June 4, 2013 at 4:01 pm #

    Roger, minimal sea level rise in this photo comparison on ABC open that shows my ‘local’ beach, and compares a recent photo to one stated to be around the 1990’s https://open.abc.net.au/contributions/kingston-beach-jetty-36wo9fv/in/places/kingston+beach+tas

  12. jennifer June 4, 2013 at 5:52 pm #

    I’ve just deleted several off topic comments. Please keep this thread about sea level change. There is a new open thread for unrelated comments and information.

  13. John Sayers June 4, 2013 at 5:58 pm #

    I started to watch Q&A and Bill McKibben is an idiot! His ranting should be seriously questioned – He’s a Canadian version of Tim Flannery – he claims there is full consensus regarding AGW yet obviously he’s unaware of what the Met Office has admitted, he’s unaware of the latest paper on climate sensitivity yet everyone applauds his opinion.

    We’ve got a long way to go!

  14. Luke June 4, 2013 at 6:00 pm #

    Yay – Jen’s policing thread context for off-topic rat dirt. My question before I get gonged – so what level of sea level change does establishment science says Fremantle/Swan Estuary should have experienced since 1958?

    So pls no hysteria about Robin Williams having a bad hair day and talking crap – what does the science say?

    Looking at the photo – the walkway is different – that’s OK – renewed. But the piles under the bridge look different or is it just the camera angle. Not making excuses – just asking.

  15. John Sayers June 4, 2013 at 6:00 pm #

    sorry Jen – I posted without seeing your latest post.
    I’ll post somewhere else.

  16. spangled drongo June 4, 2013 at 7:03 pm #

    “But the piles under the bridge look different or is it just the camera angle.”

    Luke, what bridge? Do you mean the piles under the boat house or the footbridge?

    That’s a good point. I’d say they have both been replaced and for this reason and the fact that there have been many changes and renovations, the subject photo is not a good indicator of constant sea levels.

  17. Luke June 4, 2013 at 7:16 pm #

    Whoops boat house I meant – too much coffee. So if you think they have been replaced rather undermines the pictorial value. But I’d be interested to know if they’ve been replaced. Jen?

  18. spangled drongo June 4, 2013 at 7:26 pm #

    Just checking the tide range there and it seems that there is very little. During neap tides the highs and the lows have a difference of only a few centimetres so probably a replacement of piles would not involve a measureable change in pile height. And when you are restumping a modest building like this you usually do it one stump at a time to keep life simple so that would result in a very similar floor level.

    Still, it does affect its believability as an indicator.

  19. Graeme M June 4, 2013 at 7:40 pm #

    Something I would like to see would be a record over time for max tide height. After all, MSL at any location is largely irrelevant in terms of physical impact surely? No-one builds below high tide level and of course all infrastructure/mitigation/management construction will be on average somewhere between low and high, but it’s the effect of the high point that counts.

    So for SLR to have a negative effect, it’d be an increasing high water mark that is the deciding factor. Does anyone know if there are records for say high water values for Fremantle for the past 100 years? My suggestion would be that if the highest high water mark for the period 1930-1960 is not exceeded by the highest mark for the period 1980-2010 then little has happened.


  20. Robert June 4, 2013 at 9:46 pm #

    I have to agree with Luke that we have no way of knowing if the piers and other things have not been altered over the years. Nor do we know the kind and time of tides occurring at the time of the photographs. Or do we?

    Of course, anybody who hangs about the water’s edge knows that the whole thing’s a beat-up. A bit of erosion or subsidence near water somewhere in the world is all our Green Betters can come up with. Which is nothing. Of all the lame climate beat-ups, this one may be the lamest.

    Anyone remember Marian Wilkinson’s front page evacuation plan for the NSW coast? It was around 2008. Maybe Fairfax were getting a little high on the Obama thing and his soaring rhetoric about sea levels, but we were shown all the awful things that would happen to the coast, with pre-tabloid Fairfax lavishness. (The tree-hugger SMH sure was a ravenous tree-gobbler back then.)

    Hilarously, there ensued some controversy because Marian neglected to cover the danger to estuaries in the same detail as she’d covered the beaches. She offended the Posh Left and the Doctors’ Wives, something Malcolm Turnbull knows you must never do. Our first case of Beachism…or maybe Estuarism? Discrimination is everywhere! No wonder the silly rag is now a tabloid going broke.

    And the coast and estuaries? Everything is still where it was, needless to say.

  21. cinders June 4, 2013 at 10:14 pm #

    Perhaps the basis of the Fremantle Herald article and Swan river Trust information http://www.ioci.org.au/publications/doc_download/21-how-our-regional-sea-level-has-changed.html

  22. Luke June 4, 2013 at 10:58 pm #

    Sorry just pressed the return key after a phone call and now noticed Cinders same reference at 10:14

  23. Robert June 4, 2013 at 11:38 pm #

    SLR has been an interesting process over the last couple of centuries and more. Those bigger decadal rises up to the 1860s make one curious. Odd how they don’t make the climatariat curious. Well, I’m being coy. It’s not odd at all.

  24. Luke June 5, 2013 at 12:07 am #

    So Robert I’m curious how many of the sea level papers by the establishment have you read – just rattle a few off.

  25. Robert June 5, 2013 at 1:16 am #

    Just read the one paper quite some time ago, by that Russian chick. Forget her name. Do I sound like some scientist? But none of this have ever been in dispute. Look at your WA stuff that covers the 20th century. SLR coincided with with the warming periods between the wars and after 1980. And it also coincided with the temp plunges of the mid-century.

    There was an Arctic melt after the Napoleonic Wars, but there was a major refreeze by the end of the 19th century, and SLR just continued through all that. By the way, no need to tell me SLR is fantastically complex and variable. I’d add what ought to be obvious: very little is known.

    We inhabit the insulating crust of a massive ball which is mostly hot. I’d put it to you that we have visited very little of the oceans, and know nothing much at all about the hot, plasticky stuff not too far under them. Trenches, abysses…and yet, like the crust we know a bit about, the hydrosphere is tiny compared to that hot, active ball called Earth, about which we are kind of in the dark. It’s odd how some very learned people can pretend it’s not there or doesn’t count. I’d happily see billions spent on finding out more. (By “finding out” I don’t mean that thing which Flannery and Million Degree Al do.)

    Time for science-science: the long, messy stuff you can’t get to the end of. It won’t be me, Luke…but maybe it can be you? Cut loose, get curious. Use your loaf. You’ve got a good one. Just stay away from all models not called Kardashian (actually, stay away from her too) and try not to publish till you know something – or at least till you know you don’t know.

  26. Luke June 5, 2013 at 7:04 am #

    “Just read the one paper quite some time ago, by that Russian chick. Forget her name.” uh-huh. And so you know what might make the climatariat curious eh? Uh-huh. OK. “Very little is known” right

  27. jennifer June 5, 2013 at 7:19 am #

    1. The boat house picture

    Just got an email from Roger… He said that the boat house could have been re-stumped. He agrees that the stumps on the jetty look different. He also said that the water levels vary enormously in one day in response to the tide and also inflows from the Avon catchment.

    2. Sea level papers

    Regarding recent papers on sea level rise, before leaving for the UK I had a little look around and was interested to find Shennan et al. 2012 (Late Holocene vertical land motion and relative sea-level changes: lessons from the British Isles. Journal of Quaternary Science, volume 27, pages 64-70).

    I see it concludes that the British Isles show general uplift broadly centred on the deglaciated mountains of Scotland. That is relative sea-level fall! But of course we mostly hear about the SE of England which is subsiding… into the English channel.

    3. Affect of ENSO on sea level

    Thanks Cinders and Luke for the above link re. what affects sea levels at Fremantle. I was interested to see the extent of the impact of ENSO on sea levels for Perth. I would have thought this affect would have been mostly concentrated in the Pacific. What is the affect of ENSO on sea levels at Cleveland … thinking of that great photo from Spangled.

  28. spangled drongo June 5, 2013 at 7:54 am #

    Ex-tropical cyclone Oswald in January produced a very high sea surge in Moreton Bay, not because of its intensity but because its centre was inland and the winds came from the north east whereas cyclone winds come from the east to south east.

    MB doesn’t have much “fetch” from the SE but is a huge funnel pointing NE so the hydrological forces were greatly increased.

    This can give the impression of SLR when it is not, like ex-hurricane Sandy in the US.

  29. Robert June 5, 2013 at 8:17 am #

    It can hardly be new to anybody with an interest:
    Generalised, fiddled, but not too trashy. Really, does anybody doubt the 19th century SLR? I thought the trick was just not to mention it.

    As to what makes climate, not only do we lack observations, but we lack the means of observation. That happens. First one to admit it is a climate scientist! (Well, a baby proto-scientist on training wheels.)

  30. Neville June 5, 2013 at 8:54 am #

    Robert the greatest rate of GMSL at your link is from about 1925 to about 1960. This is much steeper than the rate from 1960 to 1990s.
    We know that GMSL couldn’t be driven by co2 emissions during that earlier period, so what caused it? Co2 emissions up to 1960 were about 312ppmv, not that much above pre- idust rev levels of 280ppmv.

    Here is an analysis of global SLR and the Author looks at actual measurements and how they are gathered.

    Specifically he looks at the Church, White 2006 paper.


  31. Robert June 5, 2013 at 9:32 am #

    Nev, I suppose you’re right about that period pre-1960. My own stunt of talking about big decadal rises in the 19th century relies on fluctuation rather than steady rise. That’s if the graph info is half-way decent. You never know your luck.

    Why does any of this happen? Wish I knew, but the oceans are quite large things, good for more than just hiding mysterious lumps of heat in remote abysses.

  32. old44 June 5, 2013 at 11:17 pm #

    You can’t fool me with those photographs, that flagpole from 1958 is now completely under water.

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