Cerian Gingell: Hi there and welcome to the Natural Resources Wales podcast mini-series on Flood Risk Management. My name is Cerian Gingell and I work here at Natural Resources Wales. In this series you’ll hear from the teams who work together to reduce the risk of flooding to communities in Wales,
This will give a really good overview of what flood risk is, what we’re doing to manage it in Wales and what impact the climate emergency is having on flood risk in Wales, both now and in the future.
Hello and welcome to episode 7 of the Natural Resources Wales Flood Risk Management mini-series! Today I’m joined by Samantha Mitchell and Nia Crayford who both work in our national Flood Forecasting team. Welcome both, and thanks so much for joining us!
I wonder if we can start by finding out a little bit about you and your background. Did you study specifically with joining NRW in mind? Or was it more of an evolution to find yourselves in the roles you have today?
Nia Crayford: I did a Geography degree at university, and yes, I wanted to work for NRW. I kept an eye on the job vacancies. Initially I started in the Facilities team working on reception in one of the Cardiff offices, and then in a few months when a job came up in the team, I moved to Flood Forecasting. I’ve now been in the team now for 6 years and I work on the systems, the duty rota and the operational procedures.
Samantha Mitchell: My degree was in Environmental Science, and after graduating in 1999 I started work for Environment Agency Wales which was eventually merged with the other environmental organisations to become NRW in 2013. So, I started in the Hydrometry team for the first couple of years, then I moved to the Hydrology team for about 6 years, and now I’ve been working in Flood Forecasting for the last 14 or 15 years. So, I’m responsible for all the river forecasting models which is how we monitor and predict possible flooding from rivers here in Wales.
CG: Wow, ok, so we’ve heard a little bit of how you both came to work in the flood forecasting team here in NRW, could you explain a little bit what the team actually does?
NC: Yes of course! Our team is responsible for running and maintaining the operational forecasting service for potential flooding in Wales. This is a 24/7 service that helps our colleagues in other teams in NRW to issue Flood Alerts and Flood Warnings across Wales when there is a risk of flooding this is to help the public prepare and take action if necessary. To do this we use computer models that we run in real time during times of heavy rain or high tides for example, and this helps to predict which areas might flood due to high river levels and/or sea levels. So, there are 10 of us in total in the team at the moment, and our work is split into three main areas – so this covers rivers, coasts and also the computer systems that are needed for our work.
CG: Ah, ok thanks. So, not a huge team either so just 10 of you really doing all this nationally,
NC: Yeah
CG: So how do you do these forecasts then, how do you forecast flooding for example?
SM: We use a variety of models and specialist computer software to predict river or tide levels and that can be anywhere from an hour in advance to about 5 days in advance. So, for our river models we use data from NRWs observed river level network – this is the data we get from our Hydrometry and Telemetry colleagues that you’ll have heard about in a previous podcast. We also use forecast rainfall data from the Met Office. So that’s essentially the numbers behind the blobs of rain that you see on TV in the weather forecast. And then for our coastal models we use forecast tide data, we use observational data from wave buoys and wind stations and we also use forecast wind and wave data from the Met Office as well.
CG: OK, you’ve said that you use some of the data from the Met Office Where do you get these models? Do you create them or develop them yourselves?
SM: Yes, we do, so we use data from large weather events that have happened in the past such as Storm Ciara and Storm Dennis back in 2020 for example. So, we create the models and we run them to see how the results compare with what we know happened during those big events, and then we tweak the model parameters until we get the closest match to the observed river levels. This is part of what I am responsible for on the river side of things, along with Rachel and Sian in the team. Neil in our team does the exact same thing for the coastal models. And after the models have been developed, they are passed to Christopher, Nia and Lisa who then configure them into the right files and formats to be used by our forecasting system. Once the models are live, we constantly monitor their performance, and s we’ll often go back and recalibrate them after events if we think they are not performing as well as they should so we’re constantly trying to improve the quality and accuracy of our forecasting
CG: So, tweaking them a little bit to make sure they’re spot on.
SM: Yes
NC: Then I’ll just come in a bit about the system we use. That’s called FEWS, which stands for Flood Early Warning System. The FEWS system is used widely in lots of other countries across the world. Our current version of FEWS we went live in 2016 and was the first time anywhere in the world that FEWS had been run remotely in the cloud rather than on dedicated local servers. So, this makes it just a lot more resilient system really. FEWS contains all the model files that have been configured and it also continuously receives the observed data from the monitoring stations that our hydrometry and telemetry colleagues are responsible for and also forecasts from the Met Office every 15 minutes, so it’s always got the most up to date forecasts ready whenever they’re needed. It’s a very flexible system and we can run forecasts manually as and when needed or we can set them up to run automatically in advance of heavy rainfall. The forecasts then are sent to the Forecast Web Service, and this is an internal website where NRW staff can view the forecasts to help decide whether they need to issue any warnings or alerts and you’ll hear more about that part of the work in the next episode on flood warning and informing. So FEWS is critical to us in delivering the operational forecasting service for Wales
CG: OK, it sounds very technical! How do all these technical elements come together when we have bad weather?
NC: So, as soon as we get a heads up that bad weather is forecast, for example large storms like you’ve probably heard of Dennis or Ciara a few years ago, whoever is on duty at the time will start preparing. So, this usually involves liaising with the Met Office, running different scenarios through our models to get a range of possible outcomes, putting shift rotas together to make sure we have that crucial 24/7 response, and also briefing the rest of NRW.
There is also a 5-day flood risk outlook available to the public on the NRW website that we help determine the risk for as well.
So, once the event, or storm, starts, we usually open the National Incident Room in Cardiff. We then have 2 people actively monitoring and forecasting at the same time usually on 8-hour shifts, so maybe we’ll be covering different parts of Wales, or one might cover the rivers, and one might cover the coasts, depending on what is needed at the time the type of event we’re dealing with.
So, we usually run the forecasts every half an hour. We then relay that forecast information to other duty officers in different teams so they can start thinking about issuing the flood alerts and warnings to the public. Then, after the event, we analyse the performance of the models to see how well they did and if any need to be recalibrated at all. We also sometimes help compile statistics from the event, so for example where the highest rainfall totals were, or whether we've reached any new rainfall or river level records. All of this helps us to gather more data to use in future for more events and weather we have coming next.
CG: Yeah, there’s a lot going on isn’t there and working with other teams as well, it’s all very sort of cross functional I suppose? isn’t it?
NC: Definitely
CG: Are there any challenges when it comes to flood forecasting in Wales?
SM: There’s lots of challenges in Wales! Wales has a very long coastline for starters, we’ve got over 800 miles of it so there is lots of potential impacts from tides. And then the Severn Estuary has got the 2nd highest tidal range in the world, it’s about 14m so that’s really challenging to model and forecast. I think the highest is in Canada, the Bay of Fundy so we’re second only to Canada.
CG: Impressive
SM: Yeah,very impressive. And we also get a lot of large waves, particularly around Pembrokeshire and Cardigan Bay – these are the swell waves that cross the Atlantic and they’re really great for surfers, but they’re really quite tricky to forecast.
And then inland, most of Wales is very mountainous, and mountains cause more rainfall as air moves up and over the mountains and that causes more rainfall but it’s really difficult to forecast how much more rainfall there will be. And then the mountains can cause another problem because they can block the beams of the weather radars, so in many parts of Wales it’s hard to get reliable data on how much rain is actually falling, how fast, and in which direction the clouds are moving because the radars just can’t see past the mountains
And also Wales has lots of small, steep river catchments with a lot of impermeable rocks underneath, which means that when the water falls onto the land the water goes straight into the rivers so they rise really quickly in response to rainfall, and this doesn’t give us much time to forecast what may happen or for anyone to take action.
CG: That sounds like a lot of complicated elements working against you there! We know that climate change is having an impact already and it’s probably one that is likely to continue to cause further problems in future. Have you noticed any effects of climate change on your work already?
NC: Erm yes, I think across the team and probably lots of other teams havedefinitely noticed it. It’s having an impact on our work, in particular the duty role which is what we have in place to ensure that we have people on call 24/7 to respond to lots of different types of environmental incidents in Wales.
In the last few years, we have seen a lot of records being broken for highest river levels, across all parts of Wales. So, for example, Storm Callum in October 2018 that broke records for a lot of South-West Wales river level monitoring stations. Then in February 2020, Storm Ciara broke records across the North of Wales and just a week later we had Storm Dennis which broke records across South-East Wales.
Some of the stations recording these highest levels have been in place for 50-60 years or more so these record-breaking levels are really quite significant. I think we’ve also started to notice an increase in the number of named storms and larger events in general during the winter months So last year in February 2022 we had 3 named storms in the space of a week. The last of these, Franklin, again broke long standing river levels on the Severn and the Vyrnwy in mid Wales. So, it’s definitely become busier when we are on duty. We have to call on the assistant duty officer to help out a lot more often now, and just recently we’ve increased the number of duty officers on our rota so that we can better cope with the increase in the workload when we do get those bad events
And also these extreme weather events also has an impact on our day job which always has to take a back seat when we have these really large events, because everybody is being called in to help and assist everybody because we are also on shift rotas.
So, we also then after those big events we have more work after the events to keep on top of all the analysis and reporting work that helps to continually improve our systems and forecasting.
CG: Which is obviously important to keep it accurate as well Do you see the service developing in the future in order to tackle things like climate change?
SM: Yes definitely. So firstly, we’d like to increase the number of river forecasting locations and cover more catchments. At the moment we’ve got about 117 river forecast locations across about 30 catchments, which sounds like a lot a lot, but we that still means we don’t forecast for every location that we issue warnings for in Wales and we’d like to.
So, over the next 5-10 years we’ve got a plan want to increase that forecasting to 100% coverage And I think that’ll take us up to take us up to about 215 river forecast locations across 43 catchments. Yeah, it’s a lot
CG: It is a lot, it’s practically double, isn’t it?
SM: Yeah, pretty much, yeah, so a lot of work to be done there.
On the coastal side, we ‘ve got, I think, 87 coastal forecast locations and that is actually 100% coverage at the moment, so we are not planning to necessarily expand on the coastal side, there may be the odd location but we haven’t got many big plans to increase coverage but we have got big plans to improve the actual forecasts themselves in the existing locations.
So for example there’s a lot of work going on at the moment to refine the beach profiles and the flood defence profiles held within the models to try and model that more accurately and also to try and validate the forecast results for the coastal forecasts with observed data so we can see if when we issue the alerts or warnings if they’ve been set at the right levels or if they need tweaking.
And then more generally on both sort of coastal and river we’ll also continue working with the Met Office to try to improve the weather forecasts themselves , so that in turn would in turn increase the lead time for issuing alerts and warnings, hopefully. So, there’s a plan to move to probabilistic forecasting,
At the moment we just use 1 Met Office forecast input into our models so we get one river forecast or coastal forecast output like we do now but the Met Office has already moved to probabilistic forecasts years ago so this is where they’ve got their massive big super computers and they run up to 24 slightly different forecasts so they produce a whole range of outputs, so this is how come they can then say we think there’s a 60 percent chance of rainfall occurring today in mid Wales or wherever. That’s where that probabilistic percentage comes from.
So we want to try and do the same thing with our coastal and river forecasts, so we take 24 forecast input and then we’ll get 24 forecast outputs and then this will help us then to determine likelihood of different scenarios occurring more easily, so hopefully that will then help us make more informed decisions about whether or not we issue warnings and in what sort of time frames
CG: Yeah, and hopefully it helps with that accuracy as well It sounds like there’s lots of drive and ambition in the team to do more and to constantly improve, not only to keep up with climate change, but also, I guess o continually offer a better service. I would think that means you must love what you do? So, what's the best part of your job - what do you enjoy the most?
NC: It’s a great job but it’s also just a really interesting job to do and it’s great to work as part of a team where everybody does something a little bit different and they each contribute a different element to the service. So, I really like receiving the models that have been developed by Sam and the others, then we configure them onto the system as part of my day job, and then also getting to see those models being used by myself and all the other duty officers as well in real-time when they’re needed during those big events and bad weather events. It’s just great to see how the platform and the difference they make in ensuring the public are aware of what might happen whilst also giving them as much time as possible to prepare and take any action that may be needed to protect their homes from flooding and such
CG: Yeah, and I guess you get to see both ends of it, you get to see the part where you’re preparing and then you also get to experience it on the duty side of it and at the other end so you get to see the full spectrum as well which must be interesting
NC: Tiring when we’re on duty but… (laughs)
SM: I agree completely, this is going to sound really cheesy now, but the best bit for me is knowing our work makes a difference - we help in that process of getting flood warnings out earlier to people at risk of flooding, so they’ve got more time to take action to protect their homes and their livelihoods. Given the challenges of forecasting in Wales we don’t always have much time, but it’s when it does all come together it’s really rewarding.
So, for example, back in 2012 there was a very large storm that was forecast to affect St Asaph in North-East Wales overnight, but our forecasts in the morning meant that the local councils decided to set up evacuation centres in the afternoon, and then the evacuations themselves took place about 9 o’clock in the evening. If we hadn’t had any forecasts, we wouldn't have even known that evacuation would be needed until about 3 o’clock in the morning, so the centres may not even have been ready.
And also, it would have been much more difficult and distressing to wake people up to evacuate them in the middle of the night, and there’s a good chance they wouldn’t have been able to evacuate everyone in time. But in that event because we have really good forecasts in the morning available for St Asaph beforehand meant everyone had plenty of time to plan and prepare throughout the day
CG: Which is just really important isn’t it, isn’t it? And so, rewarding to know that you’re making a real difference to people as well
Thank you both for giving your time up to talk to me today. It’s been really interesting to hear all about the work that you do and the way you help communities in Wales prepare for possible flooding and to hear what a difference that makes in real life like in St Asaph back in 2012. It’s been really interesting. Thank you both
I hope you’ve enjoyed today’s episode, if you have any comments or questions, you can contact us by Facebook, twitter or Instagram or by the email address– which you can find in the show notes. You’ll also find links to our flood risk management pages where you can view some of the things that we talked about here today.
Thanks for listening!
