Controls on land affected by Sea Level Rise

Controlling development on the basis of the natural hazards arising from climate change is no different to controlling development for other natural hazards (wind, flooding, bushfire, etc).

Sea level rise is a natural (unstoppable) hazard (whatever the root cause) and must be taken into account by development consents for exactly the same reason that flooding is accounted for. Councils revise their floor levels regularly when flood studies become available. Similarly, if the rainfall figures are revised by Australian Rainfall and Runoff and floor levels have to be revised, landowners can’t argue that they should be compensated.

We currently raise floor levels above a (previously) predictable flood level by enforcing limits in a development consent (e.g. a 1 in 100 flood level). We live with the risk that this level will be exceeded in some very extreme events. We do this to protect landowners from their own mistake of buying a house in a flood plain.

Protecting people by setting a certain floor level (as some are proposing to do) is not

sufficient for a rising sea level. This does not reduce the risk to a low probability (such as 1 in 100 years) it only postpones the inundation event. We know that sea levels will continue to rise after they reach 0.91m, moving on to 1m, 2m and 3m – the ocean will engulf low lying land, it is only a matter of time!

So, how long will a building last for? Many of the buildings still in use in the Sydney CBD are more than 100 years old (probably 30% currently). Many will easily reach 150 or 200 if they are well cared for. Housing is not so durable, but many houses in older suburbs in Sydney are around 100 years old or more. Suggesting that thousands of houses on low lying land should be constructed with a floor level suitable for 0.91m of sea level rise is not the right approach. All these houses will reach the limit of liability at exactly the same time.

The houses set at the selected floor level are in a very high risk situation, not a low risk situation – the high risk is just postponed to some time in the future. Setting a flood level is a low risk solution where the extreme event will only occur at some random year in a random location (as would happen in the 1 in 100 year flood).

Another point – How is setting a floor level going to protect the house on low property. For many years the land could be tidal before the floor level is reached. The building is useless when it is surrounded by water, so the level of the floor is again NOT the deciding criteria for development. Access must also be taken into account and must at least be available for emergency purposes.

And what about this point – Who is going to pay for the removal of the building when it is inundated? Certainly not those whose property has just been lost to the sea. They will likely be bereft of ready cash to pay for the dozer. We will not be able to leave such buildings to be broken up in the water as the materials will float off and create havoc. Of course the public will have to pick up the tab for the cleanup as well as for finding new housing for those who have just lost theirs.

Remember, not only the individual landowners are affected. The banks that loan them money also lend the rest of us money. The public infrastructure that services the houses is owned by us all. The probabilities all point towards swallowing a bitter pill now, rather than setting up our descendants to submit a large proportion of community capital to the ocean at some date in the future when sea level passes a certain point.

There has to be a mechanism in place to deal with this issue. We need Councils to regulate land subject to sea level rise. The method has to link the planning decision to the sea level and allow for buildings with reasonable expected lives till inundation to be constructed while those with less expected life are restricted. If the mechanism is linked directly to mapping showing sea level rise contours, then when the mapping is revised (as it surely will be) the system can continue to work.

If we don’t recognize and respond to this issue, what will people say in 20 years time when large numbers of properties are being abandoned and yet more are threatened?

[Ed. A previous draft of the above post included reference to Gosford and Wyong Councils. This has been removed following comment recieved to ensure there is no confusion regarding the actions of any specific Council.]

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