← Natural hazards field trip videos
Tsunami hazards: know the signs, stay safe
Andrew
Kia ora koutou. Ko Andrew tōku ingoa. And here we are in Te Moana-a-Toitehuatahi | The Bay of Plenty. And we're going to meet experts to learn more about Earth's dynamic natural processes, and how they can be a hazard for us here in Aotearoa. But also, how we can reduce, get ready for, respond to, and recover from their impacts.
Let's go and find out more.
We've come to Ōmanu Beach. We've got Mount Maunganui up there. And Pāpāmoa down that way. Ōmanu Beach. This is Tane. Tane's with the emergency management team at Tauranga City Council.
The sun is shining; the surf's up. I hate to mention it, but we need to think about tsunami and the impacts of tsunami – what we need to do in a tsunami.
Tane, tell us, first of all, briefly: What's a tsunami? How are they caused?
Tane
So a tsunami, basically is, it's a giant big wave. So it happens when there's a displacement of water. So that could happen from either an underwater earthquake or sometimes even underwater volcanoes.
Andrew
Right. And maybe, coastal earthquakes as well?
Tane
Yeah. So, they mainly happen on our subduction fault lines.
Andrew
Okay. Yeah. So we've been learning a lot about those sorts of processes.
How do we know that there's a tsunami on its way? What are some of the warning signs?
Tane
So for us here on the beach, it's that earthquake. So if you feel that long or strong earthquake, that is a telling sign that we need to get away from the beach.
Andrew
Okay. So when you say, 'long and strong', what are we talking here?
Tane
Yeah. So if you feel it for over around 45 seconds or if it knocks you around a little bit, those are the kind of telling signs that we take.
Andrew
Okay. So, if we feel something like that – we're at the beach, hopefully it's not going to happen anytime soon – what do we do?
Tane
So first of all, when we feel that earthquake, we want to drop, cover, and hold. We need to stay safe during that initial earthquake. And then straight away afterwards, we want to head away from the beach. So we want to either get up to higher ground or if that's not close, as far inland as we can.
Andrew
Okay. So here at Pāpāmoa, or Mount Maunganui, or Ōmanu Beach, where are we going to go? And how do we know where we're going?
Tane
Yep. So, there's tsunami signs all along the coast here. So these kind of take you to your signs. But for these types of areas, if when you're at home, we really want people to know their route. So that is about knowing where to go. So practising those types of things as well.
Andrew
So yeah it's all about getting ready, isn't it? So I guess if I'm a visitor here, I should be looking at the signs, getting that knowledge, knowing what to do if that happens. And then it's that message – if it's long or strong, get gone! And you're getting gone to higher ground.
Tane
Exactly. Yeah.
Andrew
Oh well, that's brilliant. But a lovely day, otherwise.
Tane
Exactly.
Andrew
But it's always good to just have these plans in the back of our minds.
Tane
And we hope it never happens. But we do need to have these kind of plans and discussions before it really does happen. So yeah.
Andrew
Yeah. Kia ora Tane.
Tane
Thank you.
Grab bags and smart planning: preparing for hazard impacts
Andrew
We've come into the surf lifesaving club here at Ōmanu Bay.
Now, Tane, we've learned a lot about the impacts of Earth's natural processes. And we've learned a little bit about some of the things that we need to think about doing. But from an emergency management perspective at Tauranga city, what are some of the key things that we need to think about doing today?
Tane
Yeah. So there's a few things that we really kind of push. So the main thing for us is kind of having that plan in place. And for people that's kind of having... we recommend three days' worth of resources, kind of, to have kind of stocked up as ready. Because when these events happen, like, sometimes we know that we could be isolated from everyone else for up to three days.
So just having those kind of basic amenities and stuff.
Andrew
So, food and water.
Tane
Yeah. Exactly. So food, water. And for some people that's medication as well and stuff like that, because yeah we don't know what could happen.
Andrew
So you could be stuck at home. So you might have your water cut off. You might have no power. No internet, heaven forbid. And those sorts of things.
So what are the sorts of things we're going to need to keep on hand in case of that?
Tane
Yeah, so of the no power – for a lot of people that means no cooking as well. So it's having, kind of, options like gas for cooking like that.
Andrew
Gas cooker.
Tane
So you might have to bring the old camping supplies out or something like that. And if its no phone, no internet, like you said – the end of the world. But it's having those other communications. So that could be a radio. So you could connect with other people in different ways.
Andrew
And making sure you've got some batteries.
Tane
Yeah.
Andrew
And I guess if no power, a torch. And again, spare batteries is going to come in handy as well.
Tane
Yeah. So you've got to have a plan for when you're at home, but you've also got to have a plan when you're at school or if you're at work as well. So all these plans are different and they're going to be for the different scenarios. So when you're at school, that plan is going to be different to those other plans. And everyone is going to have different plans. Their household plan is going to be different to somebody else's.
Andrew
It's probably a good idea to have a conversation, isn't it?
Tane
Yeah. So that's the main thing – it's going home and it's having a kōrero with your whānau. Do we have a plan? Are we ready for when this actually happens? And if they're not, there is so many resources online. So the Get Ready website page, they've got so much stuff just to easily make plans and have those things ready.
Andrew
Awesome. So a good idea to go and check that out! And even if you've got an old plan, review it, because things change.
Tane
Yeah. So this is the perfect thing. So you can see this one here – this is a pre-made up one. So it's just got all the basic things. I'll go into it shortly. But everyone's grab-and-go bag is going to be different. So it doesn't need to be this kind of made up one. This could be an old bag – just some stuff ready to go.
Because when these emergencies happen and we do need to go, it is a lot easier if you've got something to pick up and get straight away. Because you would have be talking about these hazards earlier. Sometimes we don't have that much time, and time is of the essence, and we do need to go quite quickly.
Andrew
Perfect. And you were saying... so this is one you can buy pre-made, but you can make your own ones up. So what have you got in here that you would take with you for instance?
Tane
So I'll open it up. It's just the main things right. So you've got your water bottle. We've got a first aid kit here.
We've got food as well – this is just a bar. But you want food that can kind of last as well – so long-lasting food.
Andrew
Non-perishables.
Tane
All we've got here. We've got a blanket, a torch here, and then a pack of cards. Because when we do go, we might be stuck in these places for a little while, so...
Andrew
Yeah. We'll see, this is good if you've got younger brothers and sisters that might get bored, you've got to keep them occupied.
Tane
And that's another thing, everyone's grab-and-go bag is going to be completely different. So a young kid, they might not have their own. But if you're a parent, your grab-and-go bag might want to have some toys to keep that kid occupied.
Or if you're elderly and you've got specific medication you want to take, that medication might need to be in your grab-and-go bag because that's an important thing in your life.
Andrew
Yeah, that's right. And I see in here, so this one's a torch and radio.
Tane
Yeah. So that's again very important. That takes up that comment earlier about that radio – getting in contact with other people. So that's your torch. It's a kind of double-edged sword there.
Andrew
This one's good too because you, it's like it's self-charging.
Tane
Takes your battery problem as well.
Andrew
Yeah. And even in here, you've got masks for in the event of volcanic hazards – ashfall.
Tane
Yeah.
Andrew
Yeah. So that's awesome. Some really key things to think about. Things to think about if you're stuck at home. Things to think about if you have to leave suddenly.
Tane
No worries. Thank you.
Volcano monitoring, impacts, and preparedness
Andrew
Well, right now we are at a place called Kōhī Point in Whakatāne.
And, ko Craig tēnei. Craig is a volcano geophysicist for GNS Science. And we've got the right man for the job to talk about volcanoes. And from this vantage point, Craig, we can see quite a few volcanoes – some that are a bit more active today than others.
Tell us about some of those volcanoes we can see from here.
Craig
Yeah. So I guess behind me we've got some of the oldest as well as some of the youngest volcanoes in New Zealand. We've got Pūtauaki. In behind that we've got, Mount Tarawera. Both of those have erupted within the last 100 or several thousand years. Further round, behind these hills, behind that have some of the oldest volcanoes, which are up to about half a million years old.
And then offshore, we've got Moutohorā – erupted tens of thousands of years ago. And then further away, there's Whakaari, which is of course, erupting nearly all the time.
Andrew
So thinking about all those past eruptions, and some more recent than others, such as the 2019 Whakaari eruption, what are some of those impacts that we can expect from future eruptions?
Craig
Yeah, I guess volcanoes have a range of impacts they can have. The most common one is probably ashfall. That's where we might have the ash go up into the air and it blows generally downwind.
So the impact for that is if you happen to live downwind, the ash can land on your roof. Could land on your farm. You know, the animals, not happy eating ash, and it can get into your water supply.
So the main impact is mostly around ashfall. As you get further away from the volcano, the impacts generally become less. So it really depends on quite a few factors – where you are in relation to the volcano, which way the wind is blowing at the time.
Andrew
And the size of the eruption, right?
Craig
Yeah, of course.
Andrew
So obviously big eruptions are going to have a bigger impact.
But even minor eruptions can stop planes.
Craig
Yeah. That's right. So we saw just a few weeks ago from Whakaari – it's 50km offshore here; small ash eruptions. But even with that, flights around Tauranga had to be delayed for a few days while that was going on.
Andrew
So we can see Whakaari now and it's... is that just a steam plume is it?
Craig
Yeah. So that's mostly water vapour coming out of the vent there. Just rises up into the atmosphere, kind of like a cumulus cloud. But when it erupts that goes darker, and that's when it's got the ash in it. And that's when we start paying more attention as to where that's going.
Andrew
Well, speaking of paying attention, as scientists, you guys monitor these sorts of processes, don't you? And stationed not far from here, for instance, monitoring Whakaari.
Craig
Yeah, that's right. So there's several ways we monitor the volcanoes. Mostly we use seismic stations that record earthquakes and ground shaking. And generally what we look out for is an increase in those around a volcanic area before an eruption.
We also use really sensitive GPS stations that can monitor how the ground's moving – as the magma goes in and out, it bulges out a little bit. And we also use a lot of satellite monitoring, looking at things like the gas coming out. We can determine how much ash is in the ash plume, which is again really useful for the aviation to help with the planes avoiding it.
Andrew
And then you give an alert level rating, don't you, based on that information?
Craig
Yeah. That's right. So in New Zealand, we've got our volcanic alert level system. It's got six levels. Zero is basically nothing happening. One and two are various levels of unrest – so small amounts to moderate to high amounts. And then levels three, four and five are kind of small, medium and large eruptions.
Andrew
And at some of those monitoring stations, you've also got, real-time cameras. And you can go onto the GNS website and have a look at that live shot.
Craig
Yeah, exactly. So the cameras are really useful. We've got them around all our volcanoes. We can see every minute, what's going on. We get reports of activity. We can quickly look at those, see if there's a big cloud.
We can try and determine if it's just a steam cloud or if there's ash in it. And then we have procedures we can go through to tell people about what they need to know, to, you know, help prepare – help to avoid those processes.
Andrew
So in terms of getting ready, I guess, it's getting ready for those impacts we discussed earlier, like ash. That sort of thing?
Craig
Yeah. So there's some basic precautions people can take, I guess. In background times, you know, a really simple one would be – if you collect rainwater off your roof for drinking, knowing how to disconnect your spouting, so that the ash that gets on your roof, you can just disconnect your spouting and it doesn't contaminate your water supply.
We work with a lot of the regional local councils for them to understand what the volcanic hazards could be, how they might need to manage the roads or their other infrastructure, so that people can continue to get around safely.
Andrew
Well it's fascinating! Thanks so much, Craig.
And other than that, I guess we just enjoy the view on such a stunning day like this. But really fascinating just to hear a bit about the geology of the area, and knowing that some of these parts that we're looking at are actually old volcanoes.
It's fascinating stuff. Kia ora.
Craig
Thank you.
Shaken earth: faults, quakes, and readiness
Andrew
Right now we're in Edgecumbe. You can see behind us, Pūtauaki, the volcano. Ko Graham tēnei. Graham is lead scientist for hazard at risk at GNS Science.
Graham, why have you brought us here? We're in the middle of a farm, next to a kiwifruit orchard. What's significant about this place?
Graham
Well, this is one of the few places in Aotearoa where we can stand on the rupture of a fault line that's had an earthquake in living memory.
We're standing on the trace of the Edgecumbe fault that ruptured in 1987.
Andrew
So what is it that you can see here? And I think I might know, but tell us what we can see here that makes it obvious to you, and others watching, that this is a fault line?
Graham
On the day before the earthquake in 1987, the ground to your right was up at the same level as the kiwifruit orchard back here to the left.
And then all of a sudden, in a matter of seconds, this whole landscape to this side dropped down a couple of metres in an extensional earthquake. And it was a magnitude 6.5 that shook the entire region.
Andrew
A lot of forces at play to do that sort of level of shift.
Graham
Yeah, huge forces and huge impacts.
So it immediately ruptured this road, put a two metre step in this road, broke the services under it – couldn't drive across it. It buckled railway lines throughout the region from all of the shaking. It caused damage in the plants nearby here in Edgecumbe. At the electrical yard here it caused transformers to shift off their foundations. Weak buildings were badly damaged and collapsed nearby from the earthquake.
And that's typical from large earthquakes throughout the country.
Andrew
But these forces have been going on for quite some time?
Graham
These forces are completely natural for Aotearoa. The only reason that Aotearoa is even above the ocean is because this part of our Te Riu-a-Māui continent, which is normally under the water, is on the plate boundary between the Pacific and the Australian faults. And it's being thrust up out of the water, and erupted out of the water, creating the beautiful landscape and the beautiful agricultural lands we've got.
But it also creates these awesome natural forces.
Andrew
So the natural forces causing dropping of the land, if that keeps going, like, is that going to have any impact for things like flooding events?
Graham
Well, it's interesting you picked that up because the flattest areas around Aotearoa are places where fault lines have dropped the landscape down, allowing rivers to come in and create floodplains, or they're at the coast.
And right here we're at a spot where volcanic landscapes have been faulted, allowing rivers to come in. And the Rangitāiki River floodplain here. And, right just over there, we've got coastline as well. So with this flat land, we also have the potential for flooding.
Andrew
And there was a flood here too. So was it 2017, you said? Edgecumbe had a really big flood.
Graham
Yeah. And in a way, it's a coincidence – 30 years after the earthquake. But it's all because of these dramatic natural processes. So Edgecumbe, over here in the distance, is on a flat floodplain. And actually, in some areas below sea level here, it's going down because of these earthquakes. And the town's protected by stopbanks. But they had a stopbank failure and a major flood in 2017.
Andrew
So Graham, all these natural forces at play, creating the amazing country that we live in – spectacular views and what not – but what do we do to reduce the impacts for us living here and get ready for future events?
Graham
Well, these natural processes become hazards. And they cause damage and they can be dangerous if we live in certain places or in certain ways. So reduction is really the main avenue to avoid that in the first place – thinking about where we choose to live and build. There are some risks with being on fault plains or on fault lines – you want to be away from them!
And then for earthquakes, thinking about how you build. So making sure we're building away from fault lines and we're building strong buildings, with light roofs that don't have old chimneys, or we've taken the old chimneys off of them. That we're on good foundations that we're tied to. And that inside the house, all of the things that could fall off have been fixed so they can't fall onto us.
Andrew
Yeah. Well, hey, awesome to be here!
You know, obviously, a traumatic experience, a terrifying experience to be in an earthquake like that, but fascinating at the same time – to see those forces at play, land dropping and, you know, just generally creating this landscape.
But thanks Graham. It's awesome.
Graham
Kia ora.
Andrew
Kia ora.
Know your slope: understanding landslides
Andrew
Graham’s brought us to Matatā. But you were saying Graham, it doesn't really matter where you go in the Bay of Plenty, you're going to come across all of those natural processes. This, as you say, is a natural laboratory for natural processes.
Graham
Yeah. The Bay of Plenty is fantastic for seeing all of the processes that have shaped Aotearoa, in one place.
You've got volcanoes inland, volcanoes offshore. You've got, faulting, bringing the land up. Major rivers, creating floodplains. And then we're at the coast – so we've got coastal processes and we've got tsunamis. So the full gamut.
Andrew
Yeah. And interestingly, you were saying, top of the list – you wouldn't think so – that causes the most damage and costs the most amount of money, is landslides; debris flows.
Graham
Yeah. That's right. It's kind of the under-recognised process. Landslides have killed more people over written, recorded history since the 1700s – more than 1500 fatalities from landslides. And they're the most claimed for, insurance claim for, natural hazard process.
Andrew
Yeah, well. Insurance is an interesting thing. Tell us quickly what insurance is and why we need it for natural processes.
Graham
It's really important to understand why you might get insurance. And that's paying a bit of money every year for coverage, for the unlikely case when a natural disaster occurs, so that you can get paid back for your house. And make sure you've got the right amount of insurance cover to really cover the full value of your house.
We're really fortunate to have the Natural Hazards Commission, which is organising the natural process insurance, as long as you've got standard house and contents – but house insurance – for your property. And it covers all of those natural processes, or many of those natural processes, which we talked about.
Andrew
Okay. So, coming back to that landslide – tell us a little bit about what causes those.
Graham
So, landslides are... they're everywhere in New Zealand. And they're caused by steep land.
So, knowing your slope is the first thing there. If you're close to steep land – you're either on steep land, at the top of it, or at the bottom of it – you may be at risk of landsliding. And the landslides themselves have two main causes – either earthquakes, so that steep land gets shaken and fails, or heavy rainfall and groundwater processes. And if you had heavy rain, and then you have an earthquake, that might be, you know, a double effect.
Andrew
Yeah. And you can see the coast is just over there. But right here, you can see that land goes really steep.
Graham
That's right. So here at Matatā – this beautiful landscape – the fault lines are raising these hills up out of the ocean, basically giving this lovely landscape.
But they're quite high – higher than the country around. They're made from reasonably soft volcanic rocks. And in 2005, there was a weather bomb of severe rain that suddenly hit here. And it caused what we call debris flows – a type of landslide that came out of catchments here, especially out behind here. And they're actually, they're quite destructive. They damaged and moved houses with lots of boulders in them.
Sometimes we think of those wetter landslides as being floods, but they're not, they're still more like wet concrete. And that can be really destructive.
Andrew
Well, that's great advice. Fascinating stuff. Once again, the forces of nature. But, you know, it's about being ready to respond to those.
Graham
That's right. Thinking about where you're living, how you're building. And then also being prepared for that, you know, unlikely but possible disaster.
Andrew
We'll talk more about preparedness in a little while. But yeah, another great kōrero. Kia ora, Graham.
Graham
Kia ora.
