Cyfoeth: The Natural Resources Wales Environment Podcast

5. Understanding and Analysing Flood Risk

October 16, 2023 Natural Resources Wales Season 2 Episode 5
5. Understanding and Analysing Flood Risk
Cyfoeth: The Natural Resources Wales Environment Podcast
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Cyfoeth: The Natural Resources Wales Environment Podcast
5. Understanding and Analysing Flood Risk
Oct 16, 2023 Season 2 Episode 5
Natural Resources Wales

In this series, you’ll hear from the different Natural Resources Wales teams who work together to reduce the risk of flooding to communities in Wales.

This will give you a 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 now and in the future.

·        Flood Risk Management Web Pages

·        Nature Based Solutions for Coastal Management

·         Shoreline Management Plans

·        National Flood Asset Database

·        Natural Resources Wales / Check flood warnings

·        Natural Resources Wales / Check river levels, rainfall and sea data

·        Natural Resources Wales / 5 day flood risk outlook

·        Natural Resources Wales / Check your flood risk on a map (Flood Risk Assessment Wales Map)

·        Natural Resources Wales / Flood Map for Planning / Development Advice Map

·        Natural Resources Wales / Jobs, apprenticeships and placements

If you have any questions or comments on anything covered in this podcast series, contact us at

Show Notes Transcript

In this series, you’ll hear from the different Natural Resources Wales teams who work together to reduce the risk of flooding to communities in Wales.

This will give you a 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 now and in the future.

·        Flood Risk Management Web Pages

·        Nature Based Solutions for Coastal Management

·         Shoreline Management Plans

·        National Flood Asset Database

·        Natural Resources Wales / Check flood warnings

·        Natural Resources Wales / Check river levels, rainfall and sea data

·        Natural Resources Wales / 5 day flood risk outlook

·        Natural Resources Wales / Check your flood risk on a map (Flood Risk Assessment Wales Map)

·        Natural Resources Wales / Flood Map for Planning / Development Advice Map

·        Natural Resources Wales / Jobs, apprenticeships and placements

If you have any questions or comments on anything covered in this podcast series, contact us at

Cerian: 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 will hear from the different teams who work together to reduce the risk of flooding to communities in Wales. This will give you 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 5 of the Natural Resources Wales Flood Risk Management mini-series. Today I’m joined by Mark Pugh who works in our national flood risk analysis group. Welcome Mark, and thanks so much for joining us! 

To start off, it would be really good to hear about your background. What did you study, how have you ended up in Flood Risk Management, and indeed in NRW?

Mark: Hi Cerian, I started off by studying building studies and then civil engineering in what is now called Glyndwr University in Wrexham in the early 90s. After graduating I decided to forget my studies and play in a band for a couple of years which unfortunately didn’t result in fame and fortune, so I ended up having to get a job! So my mum was the one who found a job vacancy in the paper for a technician for the National Rivers Authority, the predecessor organisation of Natural Resources Wales, and as I’d always loved geography and rivers, this sounded like an ideal job to me - although I very much thought of it as a bit of a stop-gap while the band took off and finally found our fame and fortune living it up as rock stars! 

Cerian: Of course yeah, that was Plan A.

Mark: So I really only expected to do this role for a short time while the band took off but actually, I found the job really interesting and it ended up not being the stop gap I had intended. So you know, needless to say, the band never made it in the big time and here I am now having just celebrated my 30-year (ouch!) anniversary in NRW and its predecessors. 

Cerian: Wow quite an achievement though – 30 years man and boy!

Mark: Yeah, 30 years in any organisation deserves a pat on the back. 

In that time, I’ve probably covered pretty much all facets of life in flood risk management from the bottom up – starting with the technician role in what we now call our operational teams and I worked my way through to Development and Flood Risk, looking at building in flood risk areas that sort of thing, Strategic Planning, Mapping and Modelling, Reservoirs and Assets and now finally find myself working in our Evidence, Policy, and Permitting national team as a principal advisor for our Flood Risk Analysis Group as we call it.

Cerian: So you’ve done a bit of everything over the years then. To be fair, 30 years is a long time so no wonder you’ve tried lot of things, but it’s an interesting career path – rock star to flood risk management is not a career path that many people will have chosen I’m sure! Can you explain a little bit about what happens in the Flood Risk Analysis group and the teams within it? 

Mark: Yeah so I work with a small team of lead specialist advisors as they’re called, in a national team covering all of Wales, which represents a work area of what we call flood risk analysis and also development and flood risk. Flood Risk Analysis is the creation of flood risk evidence used by us in the business, and the outside world, to help with decision making when it comes to flood risk. Essentially what we do is model the flood risk from rivers, the sea, and small watercourses, then we map those areas of flood risk on our website for people to easily access and use to help inform their decisions around buying a house, building a house, or where areas might be unsuitable for development due to the level of flood risk being too high or inappropriate for that type of development. 

Cerian: So I’m just in the process of buying a house and I’ve used these maps to check that the house I’m buying is not in a flood risk area, so I can confirm, it is easy to access and easy to use and very useful. 

Mark: well done you, yes, we don’t want flood risk staff living in areas of flood risk housing, that doesn’t look very good.

Cerian: Not ideal no. I mean, nobody wants to be living there really because if you’ve got the choice, this is the point isn’t it, to inform people, to give them that choice to maybe look elsewhere and as you say to influence developers as well perhaps to build elsewhere. 

Mark: yeah absolutely, nice little segway there, the other part of it or the other hat that we wear in this team is around Development and Flood Risk, and that really is around providing advice to the development community about where is sensible or safe to develop new buildings whether that be for residential housing, or industrial units or everything in between. 

Another facet to that side of things is that we also have a responsibility for permitting activities in watercourses to make sure that any work that’s being undertaken in them doesn’t increase the flood risk. So typically that includes things like bridges, new bridges, walls, dams, and weirs. Any structure in the watercourse really that could change the flow in a way that could increase risk.

I think I should also point out that the whole work area that we represent as the national team, is also covered by our local operations teams so we have one team that’s based in the  North of Wales and they cover the north and the mid, then one team that’s based in South Wales which covers south east and south west and those guys deal with evidence creation at a more local level, local detail sort of modelling as opposed to the national scale  modelling that we do in our team. 

Cerian: Yeah, that makes sense.

Mark: So we have a small national team of about four or five people and then in each of the operational teams north and south there’s about 15 people who do the local detail work.  

Cerian: Yes, because they’ve got that local knowledge that somebody perhaps doing the national work wouldn’t necessarily have for those local areas, so it makes sense to split them up as well doesn’t it. 

Mark: It does yeah, and it’s important I think, for somebody who wants to talk locally about local flood risk they’re speaking to people who know the area well.

Cerian: Yeah, absolutely, yeah. Okay, so take us through that process then. How do we start? What’s the beginning of the process to identifying areas or communities that are at risk of flooding?

Mark: okay, so at a local level we build what we call hydraulic models, which give us a representation of where the water will go in the model – so you know, to simulate what happens when a river breaks its banks due to heavy rainfall or massively increased flows in the river. A hydraulic model is a simulation that is built in software, which represents a river channel and the surrounding land in the model and then we estimate flood flows using other software which is based on historic flood events, rainfall and river levels and then we apply these flows to the model.  

Cerian: Okay, quite techy!

Mark: Yeah absolutely it is. But you know, these things used to be done with physical models a long time ago so people would spend an age actually making models out of clay and sand and so on and then putting real water in to see where it would go. So this is a virtual simulation of that which is clearly more cost-effective and time-effective and you don’t need a massive garage to build a pretend river in. 

Cerian: Yeah, probably a bit more sensible I suppose in this day and age to be able to make use of that technology and as you say, it’s going to be quicker, more efficient overall and I guess you can cover bigger areas too because the time it would  have taken to make one of these clay models or something you know, even for a small river or a small area if you then wanted to do say a whole catchment or something that’s going to be potentially months of work there that I guess can be done on a computer system pretty quickly. 

Mark: Yeah absolutely, some of the models that we’ve build cover the whole of Wales so water maps, so zero chance that you could build to scale a model of Wales and apply water to it to see where it goes. So this is all based on fundamental physics and geography topology and so on. We’ve probably got about 40/50 years of science behind this in terms of where we’re at with modelling right now so the outputs from them are really good, they do calibrate really well with observed events when we have a flood. 

So what happens then is that the model chugs away and calculates the depth, velocity and direction of flood waters and gives an indication of it leaving the river and which direction it goes in. then we can use that to study the impacts of the flooding on the built and the natural environment. We build these models using topographical surveys, so in the old days we’d be going out with levels, flood lights and so on, spending days or weeks just doing cross sections of river channels and flood plains, but these days we tend to use a lot more what we call remote sensing information, and that covers really airborne and satellite imagery using 3D topographic images of land, so it’s a lot more time-effective, cost-effective.

Cerian: So again it’s technology helping out really isn’t it? And making use of that.

Mark: Yeah it’s a facet of the job really, trying to keep up with what’s going on in the outside world in innovations and so on, to try and use ever-better, more accurate ways of creating models representing risk.

So from that point on, we use a combination of local detailed model building, sometimes with more traditional methods such as topographical surveying, and then we merge that with a national model built for Wales which we call FRAW – and that’s an acronym for Flood Risk Assessment Wales. This has been a large multi-year project which started in 2017 I think, the data was all developed by 2019 and since then we have conducted a series of projects to display that information on our website and then to work out how to keep it as current as we can, given our resources in NRW and how to accept challenges on it and so on and to incorporate new information so it’s been a multi-year project and it’s been multiple projects within it, we should have really called it a programme really, but what it’s given us is an all-Wales view of flood risk and it helps us to produce therefore a consistent data set.

Cerian: That link to the FRAW flood risk assessment maps we’ll put in the show notes so that people can go and have a look and they can try it for themselves, because you can pop your postcode in and then it will pull up your flood risk chances or risks on there, so yeah, we’ll add that to the show notes so people can have a play around.

Mark: Yeah you picked up on a good point there, most of what we do or what we’ve historically done has led to producing maps on the website but we found from talking to customer groups that maps aren’t easily understandable for the target audience that we’re going for for a lot of this so we developed a little app which sits in front of the maps which allows you to put your postcode in ad then it gives you a textual report of your flood risk. You’ve always still got the option to go and have a look at a map through the app into the map if you really want to look at it in a lot more detail but when we put that app in it soaked up about 90% of the web traffic that we had to our maps so it shows there was a demand for people to just get flood risk information in a very simplified way and a very targeted way.

Cerian: Having used it myself recently it is easy, and it is simplified. I mean, I’m not brilliant at reading maps and things so I think to be honest a map would have probably been less helpful for me and I think it’s good the option is there for other people who want to delve into it as you say, but for me reading that quite brief and simplified explanation of that flood risk was really helpful. 

Mark: Good, glad to hear it.

Cerian: It’s a good addition I think. So once we’ve created these models and these maps, what do we do with that information? And what technologies do we use? 

Mark: All of the models that we build locally are then combined with the national model that we’ve built, and we produce those outputs as maps on our website. Collectively they’re known as the Wales Flood Risk maps, and we update them every 6 months with new local model information. We use industry standard 2 Dimensional modelling software combined with techniques to estimate flood flows. They use the latest hydrology information along with information about any Flood Risk Management assets – belonging to ourselves and other risk management authorities – like culverts, dams, weirs, embankments that sort of thing,  those give us an idea of how the risk is mitigated by those structures. 

Cerian: Because that’s important as well isn’t it, you know, you’ve spend lots of time and money and we build these defences of different types as you mentioned, but obviously they will then help – hopefully that’s the plan – to reduce that risk of flooding, so the maps will need to take that into account won’t they.

Mark: They do yeah, so for any more modern structures that are built to manage flood risk, there will have been some modelling that’s gone along with it to basically estimate the effect of the structure on flood flows and we can use that information to plug back into the models to show the benefits of those structures, which is what this is all about really. Where it gets a lot harder is smaller structures and structures that don’t have any model information with them, and indeed older land features and things that have been built along time ago and nobody is sure what effect they are having but they are having some effect. That takes a lot longer to work out the effect of and incorporate it into the maps. So it’s not as easy as I’m making it sound and it’s a very complicated science with things that range from very small watercourse or small drain right up to massive structures that are almost like dams so and everything in between and you’ve got to try and model those and show the effects of them, which is what we do, but, you know, there’s tens of thousands of structures that have an effect on flood risk across Wales and we don’t have them all mapped and I dare say that we probably won’t because that’s a never-ending task, but the main ones, yes, we do.

So after we’ve done all that we map all the outputs of those local and national models using something called GIS which stands for Geographic Information Systems and the outputs are displayed onto our website where those maps are freely available to members of the public to view and explore.

Cerian: So the GIS is a map then, is it?

Mark: GIS is the tool, so yeah, Geographic Information System

Cerian: And it produces maps? 

Mark: It’s a bit like, how’s the best way to describe it? So in the old days you’d sit down at a drawing board with a pen and you would draw by hand maps and engineering drawings and so on, so this is an electronic way of doing that really so it pulls maps in and allows you to do very clever things with maps with a lot of data analysis and so on so it’s kind of like the bed rock on which we build all of our mapping products on. 

So as I mentioned, there’s really quite a high level of complexity to all of this work. We have around £20m pounds worth of river models that we’ve built over the years at a local level. So that’s all inputted that into the FRAW - Flood Risk Assessment Wales – system / process and that in itself is around 16 terabytes of model outputs.  

Cerian: That sounds like a lot!

Mark: Yeah so there’s a good chunk of information there between the local models and then there’s the national FRAW model as well. 

Cerian: Yeah I’m just thinking of my phone memory is in gigabytes, terabytes is even bigger so it’s a lot isn’t it. There’s clearly a lot of data on there.

Mark: Yeah and I think the other point as well is that it carries on growing year on year as well because there’s never a period where you go ‘that’s it, we know everything about flood risk for Wales, we’ll stop modelling.

Cerian: Yeah it’s an ever-changing picture really isn’t it.

Mark: Yep, we’re forever producing models for areas that don’t have models previously or updating old ones with new hydrology and so on, and techniques change, tools change and so you’ve got to keep on top of it and therefore it’s an ever-expanding model base. 

I think, because of this, because it’s so complex, the whole process itself is very complex, we’ve developed a partnership working arrangement with our supplier, and they help us work through surveying, creating models, through to constructing FRAW information and then we display it or use it in our mapping systems on our website. 

Cerian: There’s a lot of work that goes into it behind the scenes before it even becomes a map that’s easy to read on the website.

Mark: Yeah, it’s easy to perhaps look at the website and just think ‘somebody’s just drawn and outline and coloured it in’ and that’s the flood risk, and that’s probably what used to be done 20 30 40 years ago but now everything you see on our website is created from data and technology from models so we’ve got some consistency there because in the old days people would just go out after a flood, draw the outline, colour it in and say ‘there’s the area that flooded’ but in order to estimate where it could flood in future there wasn’t really an awful lot of science that would help them do that so what we’re doing is the consistent scientific way using approved models that the whole industry uses so yeah, there’s some consistency there and sound physics and science that underpin it all.

Moving on from that, one of the key outputs that we generate from the whole FRAW process, which isn’t just maps, there are tools as well that fall out of the processes we’ve developed. One of them is called the Communities at Risk Register, that uses all of the evidence that’s been gathered to date and it helps give us a prioritisation ranking for all communities across Wales that are at risk from flooding. 

Cerian: Okay, so you’ve got sort of the highest risk communities ranked all the way down to the lowest risk then?

Mark: Yeah it’s a clever piece of GIS analysis which allows us to look at the numbers of properties, numbers of people and so on that are at risk of flooding in a particular community, so each community across Wales is given a geographical area, so Wales is split up in to areas of communities if you like, and we cross-reference that against flood risk and then we’re able then to count properties plus a number of other factors and any mitigation where they receive flood warning schemes, that sort of thing, and give them a number of rankings really, but what it does is, it allows us and other decision-makers to address our limited resources to the areas with highest flood risk first, if that makes sense?

Cerian: Yeah that makes sense. It seems a fairly sensible way forward.

Mark: I suppose the key thing to point out here is that it’s an impossible task to try and reduce the flood risk to every community across Wales isn’t something that we can probably do with the resources that are available to be brutally honest, so hard decisions have to be made about where the money is spent and this sort of tool helps us make those decisions based on priority which is transparent, understandable and logical. 

Cerian: Yeah I guess climate change will place into that too because it’s obviously having impacts for all of Wales and the UK and the world, so it’s a massive issue for everyone. What impacts do you think it will have on this work, and what changes you think you might need to implement as a result of that?  

Mark: Yeah, climate change clearly is a massive issue and I think we’re really only starting to think what we can do with what we have, with the evidence that we have, how can we start to show it to help people make better decisions around areas that are going to suffer from increased flood risk as a result of climate change increase so from an evidence perspective we’ve already modelled and mapped different climate change scenarios and that also gives us the data that we use as a business to start thinking about future risks and where they might be. We know that with climate change we’ll see more communities at an increased risk of flooding from seas and rivers. We’re already seeing the impacts of increased rainfall raising those river levels, but it’s also likely to increase surface water flooding, and again, we’re already seeing that happening. That’s probably evidenced by the increasing numbers of properties that suffer from small watercourse and surface water flooding in recent storm events.

I guess for me, the first step in tackling climate change is making people aware of how things are going to change. Once you’ve got the awareness in the general public about the increasing risks of flooding for example, then you can start to work with communities to be better prepared and more resilient. 

Cerian: Yes absolutely, knowing is the first step isn’t it, knowing that there is a risk there.

Mark: An important step in raising that awareness is the flood risk map for planning which we published earlier this year, which is one of the maps that we show within the umbrella term Wales flood maps. This map shows climate change on our flood risk maps for the first time and is really aimed at helping people make informed decisions about where to build - or not to build - and takes into account the next 100 years worth of climate change data. We’re aiming to release more climate change information over the next couple of years, but we’re going to have to continually monitor the best estimates of climate change over the coming decades and reflect them in the evidence that we publish to the outside world. 

Cerian: I mean I guess you can put those projections on there but because it’s a changing picture those projections will change too so I can understand why you’d need to continually monitor it because it will be a changing thing, won’t it.

Mark: It will do, and I think climate change as a science is reviewed every five or six years through a national climate change risk assessment that the UK Government does and we take outputs from that to help us model and then map the effects of that climate change and that changes every few years, so I think that’s really a reflection on how well we as a society are doing at reducing carbon going into the atmosphere because that’s clearly having an impact on temperature that increases rainfall and sea levels and therefore increases the flood risk from the sea to more watercourses. So you can foresee that every five years or so we may have to get into the routine of remodelling new outputs of new climate change assessments and then re-publishing those to let people see what the effects of the latest thinking is and how well we’re doing.

Cerian: Yeah, and as we get more evidence about climate change that will continue to change the outputs that we are then releasing to the public to see how it’s going to have those impacts, so I think it sounds like the flood for planning are an important tool as well. How are they used and who uses them?  

Mark: Yeah, one of the key mapping products that’s come out of the Wales Flood Maps is the flood map for planning which is the mapping tool that supports TAN15. TAN15 stands for Technical Advice Note 15 and that’s a planning guidance tool created by Welsh Government around developing in areas that are at risk of flooding. In a nutshell, the way that it’s used is that planners and developers look at the map to be better informed of the highest flood risk areas. That provides them with the evidence needed to avoid building in those highest-risk areas and look instead at either building elsewhere in lower risk areas or using the land for lower risk developments like greenspaces and parkland, where the risk to life would be far smaller than if residential properties, houses were built on the land. The idea is that the guidance in TAN15 combined with the flood map for planning should help to steer developers away from building in unsuitable, high-risk areas. It’s predominantly used by planners and the development community, their consultants and so on.

Cerian: You mentioned there about the importance of steering development away from flood risk areas. What would be the consequences if building does happen in those areas?

Mark: It’s really important to try and influence developers away from building on land that is at risk of flooding because flooding is so devastating when it happens. A lot of flooding occurs in areas where building took place before people understood the risk of building there, before the evidence existed to try and steer development away those flood risk areas but then when a flood does happen there, it really shocks and devastates the community. 

From experience, it takes about a year to get back into a property that’s been flooded so as well as being hugely expensive to carry out all the necessary work and repairs to a house damaged by flooding, you’ve also got that trauma of having to leave your home and all your possessions, losing your possessions in a lot of cases, - not to mention that flooding is really really dangerous, literally life threatening. Unfortunately people have died in the past years from flooding. At the moment, we currently estimate around 245,000 properties are at risk of flooding from rivers, the sea and surface water in Wales, which roughly translates to around 1 in 8 of all Welsh properties.

Cerian: And that’s why it’s so important isn’t it that we are looking at ways of reducing that risk to those people.

Mark: Absolutely, first hand I’ve seen devastating impacts of flooding on individuals and communities. There’s the physical trauma of losing all your possessions and being out of your house for a long period of time, but we’re only just beginning to understand the long-term mental health impacts on people that have been affected by flooding events, which we know do have a lasting impact. So I guess, putting everything I’ve just described into context that’s why for me, the work that we do in this particular field makes a difference, and where it does make a difference that’s satisfying where we’re advising developers to avoid building in areas of flood risk, that’s why it’s really important. We really want to avoid people having to go through the trauma of being flooded if at all possible. 

Cerian: It certainly sounds like you’ve had 30 years in this flood risk management arena and it sounds like a really worthy career, doing important work that is hopefully making a difference for people in Wales. What’s your favourite part of the job?

Mark: Thanks for saying that, good it hear it hasn’t been a 30 year mistake.

Cerian: It does sound like you’re doing important work and have done in all the different teams that you’ve worked in and that’s got to be rewarding I’d have thought.

Mark: It’s quite hidden what we do and people only see the end of it so you can say it’s just producing a map, but it’s a lot more than that. For me, it’s around seeing the results of all of the work that we do when it’s published on the website and there’s a real-world output that the public have access to, so that’s really satisfying. I can then point to something on the website and show people that this is what we do and then explain the process of how we get there, and how it’s used, and how it stops certain things happening.  And of course, ultimately, the knowledge that if we do it right and people listen to what we’re saying, then we’re going to save people the trauma of being flooded in the future. As I said earlier, that’s things that I’ve experienced first-hand by being out on the ground during flood events and seeing the impacts flooding has on communities both during and after the event as well which takes a long time to come down from. That’s not the right word but it stays with people in the community for an awful long time. I’ve seen first-hand how distressing flooding can be and it’s not really something I want to see again so if I can play any part in avoiding that for the future, and future generations, then I think that’s something to be proud of. 

I guess the other thing, is talking about the people we work with. I like to think we’re a quite similar set of people in terms of why we’re doing these jobs. I don’t think everyone started off playing in a band, but we’ve all ended up doing these things and we’re all quite like-minded people. The people we work with make it as much as anything because we have that like mindedness and that common goal and ultimately it comes down to being part of a community of professionals dealing with flood risk management, whether in the teams we work in or the wider organisation or partner organisations like the local authorities and so on, we are trying to work to one aim here. The footnote is I’ve always been a bit of a geek really, who enjoys using computers and this job has allowed me to do that and so this job, previous roles, GIS modelling, so on, it’s all helped me utilise that interest in technology that I have and bring it in to the professional environment as well.


Cerian: So you don’t miss the rockstar lifestyle too much then?

Mark: Well, I still dabble in the outside world. 

Cerian: Thank you Mark, for giving up your time to talk to me today. It’s been really interesting to hear all about the work that you’re doing that’s helping communities in Wales do to help communities in Wales prepare for possible flooding and hearing what a difference that makes in real life. 

Mark: No problem.

Cerian: I hope you’ve enjoyed this episode, if you have any comments or questions, you can contact us on Facebook, Twitter or Instagram or by the email address that you can find in the show notes. – 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 we’ve talked about here today.

Thanks for listening!