Some stats from Sunday

Peter Kreft at the MetService has kindly provided us with some statistics from Sunday's heavy rain event. In the hour from 11am to noon, the weather station on Mana Island recorded a whopping 39.2mm of rain, with a maximum rate in the middle of the worst downpours of 2.4mm per minute - no wonder there was flooding! The water was falling out of the sky faster than it could run off!

There is some stormwater system upgrades included in the draft annual plan - http://www.pcc.govt.nz/News---Events/Public-Consultation/Annual-Plan-2011-12 so don't forget to have your say on whether there needs to be more done or not.

And also, if you are ever having problems with stormwater flooding on your property, please call the council - 04-237-5089 (24hrs) It's one of our performance measures to respond to the problem within an hour of notification, but we have to be told there's a problem first, and we can't read minds!

It got really wet!

It got a bit more than just wet! There were streets flooded all over town, over a metre deep in places. http://www.stuff.co.nz/national/4815041/Porirua-drivers-stranded-in-floods And the library & Pataka are going to be closed for several days as the carpets need to dry out - they had two inches of water through them, and the staff were all hard at work with wet vacs trying to suck up all the water before it started affecting the books. One of the things we saw a lot of yesterday was kids playing in the floodwater - http://www.stuff.co.nz/national/4815519/Playground-turns-into-pool-as-heavens-open This really isn't recommended as it's almost guaranteed to contaminated with sewage, and you wouldn't let your kids play in a septic tank would you?? There were also a report of a child falling down an open manhole where the cover had been blown off by the pressure of the water - fortunately someone was there to pull them out, but since it was completely underwater things could have gone badly wrong. Another complaint from people living near flooded intersections - don't drive through the floodwater! The waves created by vehicles passing through were washing into properties.

It's wet!

In case you haven't noticed we are experiencing some quite heavy rain! Ooh, and occassional thunder.

Please take extra care while driving, and watch out for surface flooding and slips!

Drop, cover & hold is the best advice

It's pretty much inevitable whenever there is a large earthquake somewhere in the world that an email will do the rounds about the so-called "Triangle of Life" as promoted by a man named Doug Copp.

The man himself is a fraud, and his theories have been discredited the world over, and are downright dangerous, so if you are guilty of forwarding that email to everyone you know, can you please also forward the links below - it will help save their lives.

This one is from the Ministry of Civil Defence & Emergency Management:

http://www.civildefence.govt.nz/earthquake_safety_advice-web.pdf?attredirects=0

And this links to an interesting dissection of the main points - http://www.earthquakecountry.info/dropcoverholdon/Petal_on_Copp.pdf

Drop, cover & hold is still the best advice.

Tsunami propagation - March 11 2011

Cancellation of National Tsunami Warning

Tsunami Warning cancelled:

According to scientific advice , no further tsunami threat exists for New Zealand coastlines as a result of the earthquake in Japan. Nonetheless minor fluctuation in sea level may continue for up to 48 hours and caution is required on beaches and in marine environments.

From update 19 - Tsunami Warning still in effect

The arrival of waves has been tracked by the tidal guages at the New Zealand coast. For locations in the North Island, tsunami waves of amplitudes up to 70 cm continue to be recorded. There have also been reports of significant tidal fluctuations. The Chatham Islands has recorded sea level changes in excess of 1 metre. Modelling of this event suggests that the amplitude of the waves should now begin to decrease. MCDEM and scientific advisors are closely monitoring the situation and will be reviewing the level of threat over the next couple of hours.

Highlights from update 18

The arrival of waves has been measured by tidal gauges at the New Zealand coast. At Raoul Island the first arrival was recorded at 0635 hours today and at North Cape at 0710 hours. Initial wave amplitudes were in the order of 15cm but with measurements of amplitudes of up to 60cm over the last six hours. There have been reports of some locations (such as harbours and bays) experiencing tidal surges and greater wave amplitudes (of up to 1 metre). Modelling indicated that the highest wave amplitudes were expected to occur until around 1300 hours today. There are suggestions that the amplitude of the waves is beginning to decrease in accordance with the forecast provided by the modelling for this event.

Highlights from update 16

The arrival of waves has been measured by tidal gauges at the New Zealand coast. At Raoul Island first arrival was recorded at 0635 hours today and at North Cape at 0710 hours. Additional arrival times have been detected for the North Island and Chatham Islands. Initial wave amplitudes were in the order of 15cm but with measurements of up to 40cm over the last four hours with some harbours reporting amplitudes of up to 50cm and tidal surges. Modelling indicates that the highest wave amplitudes are expected to occur in the period from now until around 1300 hours today. The pattern of wave arrival closely matches that forecast by the modelling that has been undertaken for this event.

Update 12

Summary

The Pacific Tsunami Warning Centre (PTWC) has issued a Tsunami Warning for New Zealand in response to the above earthquake. Confirmation has been received that a tsunami was generated. Wave heights of up to 4 metres have been measured in coastal Japan.

First arrivals have been measured by coastal gauges at the New Zealand coast. At Raoul Island Kermadecs first arrival was recorded at 0635 hours today and at North Cape at 0710 hours. Initial wave amplitudes are in the order of 15cm. It is important to note that higher wave amplitudes are expected to follow in the next few hours based on modelling.

The New Zealand Tsunami Expert Panel assessment is that there is a marine and minor land threat only for parts of the upper North Island coasts of New Zealand.

Based on real-time tsunami modelling and comparison with historical events, the interpretation is that a minor land threat (i.e. wave heights just over 1 m) now exists in Northland between Ahipara and the Karikari Peninsula as well as in the Bay of Islands and the Chatham Islands. A minor land threat means there is a small potential for impacts on beaches in these areas. A marine threat (i.e. threat to the coastal marine area and small boats) remains in place for the northern North Island from Kaipara to Ahipara and south of the Karikari Peninsula to Gisborne. Unusual tidal surges may be observed in other parts of the country.

As at time of issue of this update (#12), passage of the wave through the South Pacific has been observed. Wave heights observed in the Pacific islands confirm the current threat assessment for New Zealand.

The first wave to arrive to New Zealand was calculated to be in the area around North Cape at approximately 0623NZDT 12 March 2011. First arrival at North Cape indicates that actual arrival times may be up to an hour later than the modelled times published (previously).

A tsunami is a series of waves or surges and the first wave may arrive later and may not be the largest. The largest arrivals are anticipated from about 0800 NZDT and expected to last for several (at least five) hours. Tsunami activity such as unusual currents and changes in sea-level will continue for several hours after first arrivals. Tsunami wave heights cannot be accurately predicted and can vary significantly along a coast due to local effects.

Only messages issued by MCDEM represent the official warning status for New Zealand. Local civil defence authorities may supplement these messages by applying local threat assessments.

People in coastal areas should:

1. Stay off beaches

2. Stay out of the water (sea, rivers and estuaries, including boating activities)

3. Do not go sightseeing

4. Share this information with family, neighbours and friends

5. Listen to the radio and/or TV for updates

6. Follow instructions of your local Civil Defence authorities.

MCDEM and scientific advisors are closely monitoring the situation to determine the severity of the threat to New Zealand.

This warning has been issued to all local civil defence authorities, emergency services, other agencies and media.