Claim- coastal Northland homes flooded in 100 years

According to an article in the Stuff environment section on sea level rise and coastal mapping-

“Much of Alamar Cres​ (Mangawhai) is expected to be flooded in 100 years, especially when rapid sea level rise is taken into account”.

How horrifying would this news be to you if you lived in said Alamar Cres? While most of inland New Zealand is making a killing on real estate, your property has just been deemed practically worthless by the stroke of an environmentalist’s pen.

A newly released report designates a “coastal flood zone” where 20,000 properties are at flooding risk. The updated data also puts a further 2500 properties at risk from erosion. All up, that’s 22500 Northland properties facing dire risk from flooding or erosion caused by expected sea level rise.

Here’s the thing. Property owners effected have asked councils to reduce their rates to allow for the lower values that would necessarily result from predictions of flooding or erosion. The answer from the councils is “No!”. In fact councils claim values are increasing “because Mangawhai is a desirable coastal community close to Auckland”.

Land that will be eroded away or under water in 100 years is “desirable”? How can that be?

Well, perhaps this is part of the reason. Local ports have been keeping tidal records for decades. You can access these records at a global data base run by the Permanent Service for Mean Sea Level. They have data for Marsden Point, just north of Mangawhai. Here is the chart the data produces.

The last data point on the chart is for 2019. Check the vertical axis for the movement in sea level. Over the last 30 years it has only varied between 1 and 2 millimetres. That’s less than half the height of the font used to write this post.

The level trended down from 2000 to 2010. The level in 2019 is lower than many past data points. For a more stark understanding of how little movement there really is, here’s a chart with a one metre (1000mm) vertical axis.

How can such a small degree of variation be a reason to devalue so many properties and scare the hell out of a large sector of the population?

Don’t forget the sea level is affected by such factors as heat, cold, rain, wind, soil erosion, tectonic plate shift and the magnetic pull of the moon (including normal tide movement). Its hard to believe the minimal degree of variation displayed in the chart could be realistically tied to the doom laden threat of climate change. In fact it amounts to not much more than the expected margin of error.

Whatever, if the Marsden Point chart is accurate, how can there be a threat of sea level rise as predicted? Something stinks about this whole scenario. What a shame newspapers don’t hold the powerful to account as they should.

The people who produced this report, which is causing understandable panic to so many Northland property owners, should clearly face a hell of a lot more scrutiny than they have had to face so far.

Or maybe we all know its just politically driven hogwash anyway.

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