Midnight Collective: Kapiti Flood Emergency II

Welcome to the Midnight Collective Broadsheet 77

Actively supporting NZ’s endangered wetland birds

Life returns to the Wharemauku - young black shag in the lower reaches

We have been out taking the measure in the aftermath of our recent storm and it seems we have had been fortunate; at least here in Raumati Beach. Houses were abandoned but water has entered few even while making a dog’s breakfast of the gardens.

Flooded dwelling flood level visible on fence

Then there’s slippage along the banks.

Typical stopbank slippage along Wharemauku

Meanwhile a large boulder from further up the Wharemauku has been shipped 2 kilometres out towards the sea. It’s always a surprise to see how water can move such seemingly immovable objects when it gets as high as this.

Large boulder stranded after flood - lower reaches

It’s left a mess of course, but a front end loader has cleared the track while the fire brigade have been busy pumping out water from low lying sections. There’s nothing like a crisis to bring a community together, so long as it doesn't last too long.

Undermined toetoe in lower reaches

Meanwhile it’s interesting what can be learnt from an emergency like this. The flood stopbanks on the Wharemauku are the result, not of precisely engineered expertise but the more halting process of learning from experience. As each flood has breached or topped a section of the bank, at least from the 1920’s when this area was first surveyed, remedial work has then raised or extended it. This may indicate that these floods are getting more destructive, (the result of deforestation), but also that each flood has its own unique character.

Another issue is centred on the Met Service and how we measure rainfall. A reasonably large but not troublesome storm will drop around 70 mls, though the damage a flood can do is dependent as much on the speed with which the rain falls, as on the volume of water. Then it's significantly worse if coincident with a high tide. Interpreting longer term weather trends is notoriously difficult which is why anti-global warming nutters still get so much air time, but there’s a growing consensus along this western coast, that we are getting more of these extreme weather events, (which are glammed up in the media as weather bombs.)

Another issue centres on the reliability of the Met readings posted in the media. There is a pretty vocal response in summer (and isn’t this true of every community across the planet!), when people think the reported Met temperature for the day is too low. Everyone has an opinion and someone is always rising up onto their hackles because they disagree with the TV. It’s taken as a personal affront on behalf of the community.

The Met's weather girls (they all used to be male), take their reading from one site quite close to here, at the airport. Yet how accurate a picture of a rain storm can you get from a reading on just one site. The important readings for a flood like this should be from up in the Tararua foothills, so this might potentially mislead about the likelihood and progress of a major flood.

Still munted after all these weeks -NIWA polution monitor on the Wharemauku

Here we have a case in point because when we posted our first flood review (around 2 in the afternoon), the Met readings were around 90mls, which had climbed to 115 by morning. Ross Waterhouse however keeps an eye on his own gauge over in Waikanae which is 8 km due north as the tui flies (We don’t have crows out here). His reading over the same period came in at 152mls.