Saturday, December 18, 2010

How high's the water Papa?

OzCoasts is a new Federal Government site with some simple and heavily qualified projections of the possible effects of increased sea levels at several locations around Australia.
The maps have been prepared by combining a sea level rise value with a high tide value. They illustrate an event that could be expected to occur at least once a year, but possibly more frequently, around the year 2100.
Maps are available to show three sea level rise scenarios: low sea level rise (0.5m), medium sea level rise (0.8m) and high sea level rise (1.1m). These sea level rise scenarios are for a 2100 period, relative to 1990. The sea level rise values are based on IPCC projections (B1 and A1FI scenarios) and more recent science.
Before you view each high resolution image you are required to agree to a disclaimer that states in part:
These images have been developed to help communicate the risks of sea-level rise.
The images are not provided as professional advice, and should not be relied upon for site-specific decision-making or for making financial or any other commitments.
The images use a 'bucket fill' method to determine the extent of inundation and should be considered as approximate only.
The actual impacts may vary as this model does not take account of existing sea walls, storm surge, erosion or other local factors.
The model does not include the dynamic response of unconsolidated shorelines (eg. sand, mud and shell) or the increase in tidal flows in coastal waterways that will result from different coastal configurations in some locations. Nor does the model take account of the effects of catchment flooding from coincident extreme rainfall events.
Despite the heavy qualification of the data, Gold Coast Councillor Peter Young was adament that the Federal Government's data was flawed.

Council rejects rising sea level forecast
Ashlynne McGhee, ABC News

"I would hope that this is worse than the worst scenario ... fundamentally, they're working with data that ... at a very high level, doesn't have the accuracy that we are working with locally," he said.
"They're using all sorts of assumptions that aren't necessarily accurate in the local conditions."

Cr Young says people should not be alarmed by the flood predictions for the coast.
He says it would not stop him buying a house by the water.
"I can't afford it but I absolutely would," he said.
"I don't believe at this point in time any part of the city is so vulnerable that I would discourage people from making an investment there."
"I'm not saying everything is rosy but I do believe we're really well positioned to deal with something that's not only going to affect our city of course, but all coastal areas."
Of course council revenue is in no way affected by land prices. Mouse over the image below (give it time) to see why the councillor might be alarmed.  The first image is the low case scenario, the second the high case.

Image 1 Image 2

Remember the underlined sections of the disclaimer above and recall that Gold Coast Beaches may be vulnerable to storm erosion.

What is interesting about some of these maps is that it is not necessarily the land and suburbs directly adjacent to the coast that are at immediate risk of inundation, but rather the low lying areas adjacent to estuaries and rivers, as in the case shown above. Building a barrage may not help if there is a simultaneous high rainfall event.

What these images show is that coastal living and coastal infrastructure is most likely going to become more expensive and difficult to maintain. Sea level rise not only increases the potential of coastal erosion but will also have an effect on groundwater levels and supply, and increase the risk of inundation and flooding in rivers especially in areas predicted to experience increased storm activity.

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