Wednesday, 18 July 2007

An alternative Dune Solution

There have been many theories and talk about a suitable method of restoring our dunes to a safe and acceptable state without extensive costs and risks.
1/ More Sand Sausages.
2/ An artificial reef or bank.
3/ Continual re-supply of sand from the Otago Harbour/Tomahawk
4/ Sand trap fences, as Duke Gilles did in the old days
5/ Relocating Mitre10 Mega as an artificial reef
And all agreed the current action, although necessary is not a solution at all, just a bandaid.

I have had contact with an overseas company (Holmberg Technologies) who have extensive experience and success in coastal dune restoration, and thought it offered an alternative to what is currently proposed, all it would need is the support of the powers that be financially to empower the work. Below is a copy of an email I received back from them:

Hello Nic,

Thank you for contacting Holmberg Technologies Inc. Your contact details have been forwarded to me as the Rep."down under." I've checked your Blog out and it is great! - you and fellow Bloggers appear to share our concerns re conservation of the coastline.

The situation on the coastline in Otago reminds me of the old Chinese proverb which goes something like: - "A crisis is merely an opportunity in disguise!" The crisis on the Otago coastline is an opportunity for our company to assist you through our knowledge and experience and, (I suggest) an opportunity for stakeholders to learn from the past, and open their minds to support a proven alternative.

From your perspective at least stakeholders should have learnt some tough lessons about the limitations of concrete walls and sand filled tubes and (soon to come!) sand replensihment as a means to "defend" the land against the open sea!!!
These methods simply dont work effectively (without adverse effects on the environment) because the basic underlying strategy of trying to defend against the sea is fundamentally flawed.

Holmberg Technologies Inc's strategy is to facilitate reconstruction of a beach profile to create a natural self sustaining beach and dune system - i.e. Holmberg's strategy works with nature rather than the "traditional" engineering approach of working against nature - like most brilliant ideas quite simple really! To do this we use geotextile tubes filled with concrete to
initially (and after storms) trap sand suspended in the system to rebuild the beach profile.
We use concrete because experience has shown that sand filled tubes dont stay intact for long, replenished sand washes away (and eventually money runs out for its replacement etc.) and the new beach needs the solid underpinning of concrete to cope with storm conditions.
The tubes we use become buried out of sight very quickly in open coastal environments and have not been shown to interfere with the surf zone. As you will have probably seen from the examples on the our website Holmberg Technologies Inc has the experience and technology to manage the type and magnitude of situation which you are facing in Otago. What we will need eventually however is the united support of stakeholders. If you have questions please do not hesitate to contact me.
I have attached some introductory information which you may
want to post on your Blogg.

Kind regards,

Chris Johnson,
Australasian Representative
For Holmberg Technologies Inc.


Anonymous said...

exactly. when they built the new wall they destroyed the self sustaining sand effect and yes they now need to introduce a artificial method quickly.
When the wall was built they removed a lot of rocks from the salt water pool end of the beach thinking they were making it look pretty, but they actually destroyed the sustaining effect and lowered the sea floor level
causing all the trouble they have now.

Nic on 18 July, 2007 22:04 said...

I can imagine how that may occur.. I would be very interested to see any kind of study that has been done outlining these effects/acts and consequences. hmm where to start?

boardridingbuddha on 19 July, 2007 08:27 said...

Everybody seems to look at the new sea wall as the major contributor to the loss of sand and that may be a contributing factor .
i'd like to offer a contrary view.
* The new sewerage outfall!(and currently the pier)laying 100 odd meters north if the worst affected area (kettle park)is an underwater groyne placed by the dcc which is having an effect on bottom currents (no pun intended).
* No North swells = sand not replenished.
* More SE swells more sand removed by nature.
* Sand mining at kuri bush and tomahawk beaches ( how much did the council make selling the sand? and how much did the dcc pay the same guys to put some sand back? - wow seems the only winners are the transport companies - wonder if they slashed a sausage or two to compliment their winter slow down)

Anonymous said...

It was interesting to note that the before and after shots of the beach in the companies email bares a stricking ressemblance to Kirra now! I walked around Greenmount club a looked at all the historical photos saw that St Clair was experiencing very simular effects.(erosion and then bandaid measures) The problem that they have now is that since their wise men of the councils laid a pipe from the Tweed river mouth and pumped sand through the once world famous break of Kirra; it is more like a lagoon!But hey;There's plenty of sand as you need to take a pack filled with a days worth of water and food just to reach the waters edge! Can't we find a council member(s) who's willing to listen and get an urgent meeting called to fix the problems?

Anonymous said...

yes I agree with the reasons why the sand has gone from the beach,
but what I don't understand is why the council is not putting a solution in place, trucking heaps of sand in is not really the answer
which unfortunately will be obvious on Tuesday, check out swell map on
Walls or humps perpendicular to the beach to slow the swell down would be a leap in the right direction.

Anonymous said...

Hey Nic, great interview of you in the latest SLIDE mag.


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