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Coastal erosion goes beyond global warming
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Politicians rely on academics to explain their observations — as the public do. But have academics and the media deceived politicians in their exuberance to make a point in support of ‘global warming’? Their recent tour of the Australian coastline may be a case in point. Coastal erosion happens constantly and has many causes. Spits and points grow too and bays and inlets shallow or disappear completely. There are a series of complex interactions that are site specific that give rise to these events — so they simply cannot be ascribed collectively to the results of global sea level change. A Parliamentary Committee on Climate Change has just finished its tour of the Australian coastline looking at the impact of extreme weather and tidal events and sea level rise. On The 7.30 Report last night MP Jennie George commented:
Another common cause of coastal erosion is the construction of groins, drains and carparks on beaches that stop the seasonal movement of sand along beachers. This is common in Port Phillip Bay. When the winter wind is from the south the sand moves up beaches and around breakwaters that hook to the north and capture the reversed flow of sand when northerly winds occur in summer. Channel Deepening has possibly already caused increased tide heights. Much the same is likely to be happening at Belongil Beach, Byron Bay, where the construction of a large carpark right on the beach many years ago has lead to ongoing problems. Stopping the movement of sand west to it has likely robbed the Belongil Beach periodically, depending on which way the weather comes from. Westerlys push the sand eastwards past the carpark where it is caught and maintains a wide beach adjacent to the Byron Bay township. This problem is further aggravated by housing development and the associated clearing of dune top vegetation. This removes the root mass that stabilises the dunes, destabilising them and leading to erosion. Mowed lawns and hard surfaces that speed up the runoff after rainfall increase erosion, cutting the dunes back from the beaches and undermining houses and gardens. The site of both a whaling station and an Abattoir before becoming beachside backpackers’ accommodation, Belongil has suffered this kind of erosion before too with houses falling into the sea. The solution to these problems lies in making proper scale models of the coastal and engineering structures that enable the movement of sand, stopping development of dunes and revegetating lawns with deep rooted indigenous species. This may sacrifice the view but not the house — as quickly, anyway. Similarly the ingress of saltwater into many freshwater systems is most often not due to sea level rise but the loss of streamflow, or more accurately streamflow persistence. A classic example is the Lakes Entrance system where increasing diversions of major streamflow — like the Thomson River to the Melbourne water supply and power generation — has seen saltwater penetrating ever further up into the Lakes Entrance system. Land clearing, clearfall logging and bushfires also have dramatic impacts on streamflow that can in turn impact the coast. The less vegetation, the more soil that is less penetrable to water after bushfires, the more dramatic the impact of heavy rainfall which leads to more dramatic flooding events than the same rainfall in the past. Many of these problems will not be affected by reducing carbon emissions. The fact that the threat of global warming and sea level rise has drawn attention to the coast is good. However these observations must lead to a more considered site and catchment specific evaluation. Though academic involvement is essential it must be informed by local knowledge and a detailed site specific epidemiology of all the changes back in time that can be tracked. Only through this kind of evaluation can the whole rangeof problems and solutions be clearly identified. |
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13 Comments
Lionel well done. Not often you read a comprehensive evaluation of coastal erosion (both natural and anthropogenic) which shows some understanding of complex coastal processes and the effects that man made structures have on coastal landforms. Of course, what the local council recommends for future management of the Byron bay coastline is well advised. Trouble is landowners have only their own interests to consider and couldn’t care less the longshore effects building a sea wall to save their own property would cause. On the Mornington peninsula many cliffs are slumping into the sea; one cause is the enormous amounts of bore water landowners pour on their lawns…this percolates through the unstructured soils and causes the limestone cliffs to collapse. And so on.
Agreed, excellent and well argued article.
Give thanks for Elmore’s sense of perspective. This country, like all others, is suffering environmental death by a thousand cuts. A myriad acts of thoughtless (or greedy) exploitation. In 1981 I photographed coastal erosion on the Sunshine Coast in Qld, the same phenomena that the Climate Change committee have reported on. Not one scrap of coastal damage thus far can be attributed to global warming. Hypotheses about more storms etc in future are just that, hypotheses. Serious sea level rise remains a prediction, but continued damage to Australia’s coast is a certainty. It remains to be seen if the current AGW push inadvertently benefits the coast. Fingers crossed.
Over and above the problems identified in this article, although on a different time scale is the natural subsidence and raising of the land. Britain used to be attached to Europe, Tasmania to the mainland etc.
As a resident along the Illawarra coastline, there’s been several occurences over the years that led to the spoiling or almost disappearance of some local beaches. One of the main causes was the removal of sand for glass making or other uses. I’ve maintained for many years now, that the beaches and environs belong to all of us, and nobody should be allowed to build along the foreshores, in fact, no buildings on the eastern side of the road(or the western in WA). When did ‘God’ give the land to State govts or the developers etc. Too many homes and buildings (look at the Gold Coast - it’s obscene) along the coast line. They even block the sun for some time on the beach, and in too many cases, the general public are locked out. I don’t have much sympathy for those who are living along these beautiful areas that should have been maintained for public use and pleasure. Now they want local Councils to fix the mess!
There’s a council in Sydney that is going to use land close to a beach for a car park and other ‘facilities’ like restaurants etc? The proposed Shellharbour Marina is going to get rid of a wetland and put houses between the wetland and the new marina. What will happen, not only to the water birds etc but the natural flow in a ‘handmade’ Marina? Time will tell, but I predict, that in a few years time, those homes will be threatened, and who knows what the changes will do to beaches along the coastline. I also predict, that Shellharbour Council will wash its hands of any responsiblity. Removing sand from Windang Beach resulted in Shellharbour Council having to spend many dollars placing sandbags along Warilla Beach (which is the next (south)along from Windang?) I’m not an engineer but I could understand why that happened. It seems that as usual, if human beings don’t learn from past mistakes, we just repeat them - over and over again!
One scrap of ongoing and measurable coastal damage is that which has been caused by sea level rise. Now of course, some people won’t connect sea level rise to global warming and that is their prerogative. But no one is denying that, even since 1981, there has been a small rise in sea level. Most state governments predict sea level rises of between 300 - 500mm this century. In all those ghastly canal estates (and every state has at least one) every single millimetre of sea level rise weakens revetment walls, threatens local government infrastructure and decreases capacity to withstand inevitable natural events like storm surges and king tides - particularly on the Sunshine (or cyclone) Coast and points north from there.
Regardless of what insurance companies might do about damaged houses in canal estates, if the earthworks underlying the reclaimed land are damaged, taxpayers fund the repairs through disaster assistance because the state is obliged to make good damaged development on state land. So the developers and ultimate buyers of this artificially created ‘land’ have their gambles guaranteed by taxpayers. A land rort of the highest order. New canal estates should not be built until developers and governments can prove that sea levels are falling.
In my judgement Rudd and Garrett are dead scared the national press gallery will latch onto the 5.88 million gallon oil spill at West Atlas, north west shelf in WA. As pointed out on Crikey with the monsoon season soon that could all end up on … the coast they are so concerned to protect re rising sea level.
How big and bad is this oil spill situation? Exxon Valdez was 10.8 million gallons in Prince William Sound in Alaska. So we are already at 1/2 way to that global infamy.
The concern of course is to play all this down, undermining as it does the case for the $50 billion Gorgon gas and oil deal on the pristine Kimberley coast.
This is a international scale disaster for the ocean and maybe coast of Australia and West Timor neighbours. And it’s still unfolding every day. There is coverage in The Australian today as the whole oil and gas industry turns on the West Atlas rig operators for failing safety systems. The poo is going to hit the fan.
All credit to Senator Siewart (The Greens) for exposing the likely real rate of discharge at 2000 barrels a day in Estimates on October 21st. And crikey for their story last Monday and ABC Unleashed profile too yesterday.
You could see how big the stakes were when Siewart was slurred by Laurie Oakes back on 4th Sept in national News Corp press, no doubt based on govt and industry false backgrounders, only to see the Green’s Senator vindicated by evidence to Senate Estimates last week. Oakes traversed the topic with Senator Brown of the Greens last Sunday Today 9 as if to redeem the error.
Another tell tale sign was the day Siewart did her flyover of West Atlas, August 28th, just happend to be the day Garrett decided to shoot his biggest PR ammo - a 2 million ha national park in Arnhem Land to mitigiate the national coverage The Greens started to generate on West Atlas.
This oil spill is a monster up there like Exxon Valdez and Rudd and Garrett have to go to extraordinary lengths to smother that. Of course anything like this bipartisan support with WA MP Washer (Perth mining club?) to boost credentials for Copenhagen will do, but they have no answer to the oil spill that’s threatening a huge section of the NW Shelf. And that’s got me as an ecologist very worried.
Lionel - “…the construction of groins, drains and carparks… “. Cop that storm surge right in the wedding tackle, mate! I think you meant ‘groyne’. Good article. Alex
Congratulations….on an articulate and thoughtful article. We need more of these to balance the increasingly hysterical (and worrying) discussion about global warming. Global warming is underway (even if not at a uniform rate) but its important to not allow ourselves to blame it for every challenge we face.
It seems its going to happen (as the political imperative will not allow the kind of human response that’s needed to make a difference)….so we had better get on with working out how to deal with it. This will be a much more intellectually challenging task than most of our current politicians are capable of….or dare to speak of (yet). I think we are more likely to get somewhere if the debate moved on to how we are going to live with increasing temperatures and higher sea levels (even if either is quite moderate).
Incidentally, its worth taking a look at Ninety Mile Beach (Victoria) and Bass Strait as an example of previous sea level changes. Having been involved in hydrographic and land surveys there, it is clear where two previous beach systems used to exist. One is in approx. 60 metres of water and is obvious along the whole coastline and the other is back from the current beach and approx 6 metres above current sea level. No matter what the cause, sea levels do change and have changed quite dramatically in the past. The beach that’s at +6m really leaves me wondering!
The sea-level rise is long-standing, and according to U Colorado running at about 3.2 mm a year: http://sealevel.colorado.edu/. If continued this would lead to a rise of 30mm in 100 years. As we know from the stock market, trends sometimes reverse themselves, and it is dangerous to simply project the current trend out in linear fashion indefinitely.
Lionel’s multi-factorial approach and sensitivity to local and regional effects is much better.
Oops! I meant to say 30 cm in 100 years.
There is an old song about the wise man building his house upon a rock and the rain come tumbling down and the house stands firm while the foolish man built his house upon the sand and his house fell down splat.
This was something that humans once knew. I am not sure why others should bail out those people who insist on being foolish and making sure their house falls down, by building on sand, in places that require engineering solutions, which in turn create even more problems.
Everyone seems helpless in the face of this and the huge oil leak in the seas close to Western Australia. What is happening is probably worse than anyone imagined. After all just think of all that money which is being lost forever in the oil spill. It shows the vulnerability of important oceans Who will bear the cost of the clean up and will pay to save the coastline?
CO2 is too easy an answer.
An interesting website that lets you see the impact of sea level rise (approx) is:
http://flood.firetree.net/?ll=-27.8390,138.1640&z=13&m=7
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