Predicted Sea Level Rise

Dr. Patricia Manuel (00:16)

Over time, we’ve become sort of more attached to the sea for not only industrial and commercial reasons, but aesthetic reasons as well. And that draws us closer. So, all of those things combined makes you want to understand, me want to understand at least, you know, why? What does that mean? What does climate change impacts along the shore mean for that way of life? How can we improve the situation by perhaps learning to live more responsibly and sustainably along the shoreline? And when we really can’t move things or make a direct change on the material and the development that’s there, what do we need to do?

Dr. Timothy Webster (00:53)

Believe it or not, we are actually sinking. We’re on something called forebulge of that depressed crust. So, the idea of relative sea level rise takes into account global sea level rise, and the local adjustment of the crust. Unfortunately, for the sort of southern Maritimes, we are sinking, the crust is sinking at 10 to 15 centimeters per century. But of course, that compounds the problem of global sea level rise.

Rhys Waters (01:30)

Welcome to Beyond Research, a podcast brought to you by Research Nova Scotia.

Today we will be speaking with leading researchers who are helping us better understand, plan, and prepare for rising sea levels. Using the province of Nova Scotia as a case study, first, we explore coastal flood risk mapping and how it can help us gain a deeper understanding of how future scenarios will likely play out on our shorelines. Then, we look at the ways we can use this information to better plan and adapt to the world as it will be in the coming decades.

Nova Scotia and its 13,300 km of coastline and is home to many coastal communities. Of these communities, some are already facing the impacts of changing sea levels, storm surges and climate change firsthand. This episode explores how sea level rise has affected our province to date and proposes collaborative approaches we should consider implementing to mitigate the impacts on our communities, our industries, and our way of life.

So, what is sea level rise and why should the public pay attention? Simply put, sea level rise is the progressive rising of the ocean water level. And there are two types of sea level rise to consider. The first is global sea level rise, which as it sounds, provides global projections. The second, relative sea level rise, is regional in focus, and involves the relative position of the earth’s crust to the sea level. Relative sea level rise is of particular concern in the southern Maritimes, because believe it or not, we are sinking 10 to 15 centimeters per century. We must also account for extreme weather events. During these extreme events, factors such as high tides, full moon, strong winds, and low atmospheric pressure can lead to severe storm surges and wave runup. This gradual sinking, coupled with extreme weather events actually compound the problem of global sea level rise on Nova Scotia.

Dr. Tim Webster (03:31)

What we really need to think about is relative sea level rise and we see a very nice straight linear trend that shows us relative sea level has been rising since that early part of the 1900s at about a foot per century. Of course, the big question, though, is, how is sea level rise going to change? Is the rate of sea level rise globally going to accelerate as we heat up the climate more? And that, of course, is the million-dollar question that there is still some uncertainty. But, you know, I think the science is narrowing in and not too many people will dispute the idea of a one-meter global sea level rise by 2100, as an example.

Rhys Waters (04:19)

This is Dr. Tim Webster, lead research scientist with Nova Scotia Community College’s Applied Geomatics Research Group. The Applied Research Group is associated with the NSCC’s geomatics training facility, the Centre of Geographic Sciences. Dr. Webster’s research focus includes lidar and other high-resolution remote sensing and Geographic Information System techniques for mapping, monitoring, and modelling processes in the coastal zone, with an emphasis on flood risk and erosion.

With his team, Dr. Webster creates maps overlaid with sea level rise predictions, high tides, and storm surges numbers to show where flooding will occur. His work has helped model what sea level rise could look like across Nova Scotia.

Now, I use the word Geomatics, and if you are like me, you probably have no idea what that means. So, we are going to let Dr. Webster shed some light on his work.

Dr. Tim Webster (05:11)

So, geomatics is for those not familiar with that term, it’s basically the science of mapping. And we have really developed strong expertise in mapping high resolution elevation models. And we can do that both onshore and more recently offshore, with using lasers on aircraft, something known as LIDAR (light detection and ranging).

Rhys Waters (05:37)

LiDAR technology fires laser pulses at surfaces and maps them by measuring how long it takes for the light to bounce back. With that geographic information, Dr. Webster can create these predictive maps. You could wonder what practical application these maps can have for government or the public. So, Dr. Webster provides some insight.

Dr. Tim Webster (05:55)

Our field of study has been dealing with creating these high-resolution elevation models along the coastal zone, and then projecting sea level rise into the future of where areas could be inundated. So, what are vulnerable to say, a road being overtopped, and therefore affecting transportation and emergency services, or, you know, planners are using our maps to consider, you know, oh, we need to put in a new sewage treatment facility. Here’s the site we planned, but okay, in 100 years time, if sea level were to rise a meter, then we would see what is inundated. Oh, that that particular area will be inundated. Let’s find a new location to put the sewage treatment plant so we’re sure it’s going to be operational and not threatened as the years of its lifespan continue.

Rhys Waters (06:49)

This process of uniformly raising the sea level is called a bathtub model. However, it does not account for the underwater elevation levels, also known as near shore bathymetry, which is an important component to this process of storm surge and coastal flooding and erosion.

Dr. Tim Webster (07:04)

So, they are very accurate maps and I stand behind them and that water is going to get to the low spot given enough time, but what these maps don’t show you is the velocity of the water and so forth. In order to do that, we go to a more sophisticated modelling approach rather than a flat plane.

Rhys Waters (07:22)

This model is called hydrodynamic modelling. Using this, Dr. Webster and his team can simulate a storm surge on top of a predicted tide to calculate both the water level increases and changes, as well as the current velocity and where the currents are moving and how that area is going to flood.

The next big leap in their work is through the modelling of waves and wave run up. To achieve this, Dr. Webster uses something that is hard to say – topographic-bathymetric LiDAR, which is mounted in an aircraft and uses lasers to measure the precise elevation of the earth’s terrain across the land-sea boundary out to depths of about 15 meters on the Atlantic Ocean Side.
So, what pushed Dr. Webster to pursue this area of research?

Dr. Tim Webster (08:04)

Well, I’m a born and raised Bluenoser. My knowledge and love of the coastal zone, seeing the threats that are present today with storm surges, and of course will be exacerbated with climate change and sea level rise in the future is really what made us focus in and try to make sure we became as skilled as we could with making these types of predictions.

Rhys Waters (08:34)

International models supported by the United Nation’s Intergovernmental Panel on Climate Change predict global sea levels will rise between 29 centimetres and 110 centimetres by the end of this century. The urgency of our situation becomes much clearer and more immediate when we consider that Nova Scotia is sinking 10 to 15 centimeters per century. So, at a time that the ocean is getting higher, Nova Scotia is getting lower. This progressive sinking and extreme weather events combine to worsen the problem of global sea level rise on this province.

Considering the range of variables at play for how sea level rise could play out, some may wonder how Dr. Webster determines what water levels to use for his predictive models. His team’s approach has been to try and research and document historic storms as the basis for future modelling.

Dr. Tim Webster (09:23)

We call them benchmark storms, because of course, at the end of the day, this information through planners or other municipal officials is going to make it to the public. And, you know, there’s still skepticism there about you know, would my area really flood it hasn’t flooded while I’ve lived here. How am I convinced? So, our approach has always been when we go to an area to do a study like this would be to research when there was a benchmark storm, try to find any documentation we can about how far was the flooding inland? What was the extent what were the conditions, the damage, etc. And then of course, as we are modeling that, we try to duplicate that to see, you know, does our model show the similar extent and so forth.

Rhys Waters (10:10)

So, will we be able to fully halt the affects of sea level rise on our province going forward if we act now?

Dr. Tim Webster (10:16)

The best we can do is slow down Mother Nature, there’s no way we’re going to stop it, in my opinion. But we can slow it down, and perhaps, protect infrastructure for some more decades. And then, of course, if we have those maps, if we are going to build new infrastructure, we build it in a smarter place where it’s going to be less vulnerable for a longer period of time as these processes continue.

Rhys Waters (10:43)

With this topobathymetric LiDAR, Dr. Webster and his team have surveyed some areas, but he sees an opportunity for a systematic approach to coastal mapping everywhere in the province.

Dr. Tim Webster (10:54)

On the positive side, all three Maritime Provinces now have topographic lidar across their entire landmasses. So that the high-resolution elevation data exists in order to make these flood maps. So that’s a big step forward for us. But those other areas, more information on tide gauges, more information on the impacts of storms, and how far they flooded, advances in technology to be able to map the near shore bathymetry. Those are some of the things we’re really you know, excited about as part of our research program.

Rhys Waters (11:30)

Dr. Webster is deeply engaged in advancing the state of the art in geomatics. He is committed to pursuing the most technically advanced understanding of how sea level rise will interact with the coast in the decades to come.

Dr. Tim Webster (11:43)

It’s an important topic. It’s something we try to keep on top of the latest literature. And there’s better modeling could be done, better mapping could be done. So there’s lots of room for scientists in the future to continue on with this work when I’m long gone.

Rhys Waters (12:06)

So, now that we have a better understanding of how some of our leading researchers are gathering information and creating predictive modelling, how does this knowledge translate to action in our coastal communities?

Dr. Patricia Manuel (12:16)

In coastal regions, we have been building right up to the shoreline pretty well, our activities are right along the shore, our roads, our infrastructure, you just have to go into any coastal region, like here in Atlantic, Canada, and on the west coast of Canada, for sure. And we have a history here, of course, you know, of settlement that has been tied to the shoreline. So, that infrastructure that’s in place is now at risk of being impacted by the rising sea level as well as when we have storms, the storm waves and the storm surge will be pushing further inland as the sea moves the sea line, the coastline, the tide line moves further inland, so then our infrastructure becomes impacted. And that impacts our economies, and our health and safety.

Rhys Waters (13:09)

This is Dr. Patricia Manuel, a professor in the School of Planning at Dalhousie University. Dr. Manuel conducts research in environmental planning with a focus on climate change adaptation planning, wetlands interpretation and management, and watershed planning and management. She also researches community planning and design and health. Her recent work has focused on climate change impacts along the coast and the vulnerability of coastal populations and communities to sea level rise and coastal flooding.

Dr. Patricia Manuel (13:38)

By and large, some communities along our coasts are experiencing a lot more coastal erosion more frequently and to a greater degree than what they were experiencing previously. So, they’re seeing land being sloughed away from in front of their roads in front of their houses.

So how do we deal with that? There are engineering approaches that one can use that communities and governments and individuals can use to address this. And there are also land use planning approaches, and there’s behavioral change.

Rhys Waters (14:07)

The pursuit of fully understanding sea level rise and how to go about addressing it remains a difficult, nuanced debate, with clear trade-offs to be made. With the knowledge we gain from modelling such as Dr. Webster’s coastal flood risk mapping, and the complexity and range of solutions for how to address it, which Dr. Manuel discusses, we are provided with the tools to better prepare, but there is still no single solution. And as the sense of urgency continues to grow, we must keep exploring these evidence-based solutions and having these tough discussions on how we will make an effective effort to prepare our province for generations to come.

Dr. Patricia Manuel (14:42)

When you live along the coastline, you’re always seeing impacts of coastal processes, but people are beginning to perceive them as being more frequent, more aggressive. That hopefully will lead us to more action because people are recognizing that now we really do have to do something.

Rhys Waters (15:01)

With this sea level rise and erosion that we are continuing to face on our shorelines comes another problem – Our natural coast and its natural defenses are left little to no room to retreat further inland in areas with direct coastal infrastructure.

Dr. Patricia Manuel (15:13)

That’s a problem because, wetlands for example, can adapt over time to sea level rise if you have a reasonably gentle slope and nothing blocking their way from moving inland to sea level rises, then they can adapt. But where you’re blocking their retreat, if you will, inland and keeping up with sea level rise, you risk the flooding of wetlands, the loss of this really, really important natural system.

Rhys Waters (15:46)

There are many available approaches to mitigate these impacts of rising sea levels, erosion and storm surges before being faced with the hard reality of having to retreat our infrastructure further inland.
A common response to erosion has been to use large boulders or structures to protect the shoreline from being eaten away any faster than we can accommodate. There are other approaches, such as seawalls that can dampen the effect of flooding on our coasts.

Dr. Patricia Manuel (16:11)

Those are not necessarily going to be the things we want to keep doing because it’s disruptive to the shoreline itself creates its own problems for neighbors down shore, and it’s very harmful in many cases to the to the ecology of the shoreline.

Rhys Waters (16:26)

In place of these solutions that are expensive to repair and harmful on the local environment, Dr. Manuel proposes using more natural processes, also known as nature based solutions or nature-based approaches.

Dr. Patricia Manuel (16:39)

Where we used to drain wetlands and infill that site and put in new land, now we’re looking at reinstalling or encouraging wetlands to grow in front of the shoreline again, or reintroducing them where they used to be, or knowing that, you know, if you give them the chance to grow there, they would with a little bit of help in those wetlands, salt marshes, for instance, that they have the effect of being a first line of defense against energy at the shore.

I think we need to have a lot more examples of these approaches that show less reliance on engineering, you know, physical engineering, hard engineering approaches and looking more to nature to help address the problem. I think, as individual property owners and as government property owners, we need to start looking at where we’re allowing development to occur along the shore.

Rhys Waters (17:32)

To address this need for development control, the Nova Scotia government has established the Coastal Protection Act, which helps protect natural ecosystems by enacting clear rules that will ensure new construction is built in places safer from sea level rise and coastal flooding.

When we look at places that are leading the way in fortifying their coasts with nature-based solutions, Dr. Manuel points to Mahone Bay.

Dr. Patricia Manuel (17:56)

The town of Mahone Bay, for example, is one place that’s already starting now to do an installation of we call them living shorelines in their in their home harbor. So that is an example Mahone Bay has been showcased in some cases as being quite progressive, and in trying something different. I mean, they’ve got this incredible historic waterfront that they do need to protect, so they know that there’s something that they have to try, that’s different, and this will not only address some of that energy that at the shoreline, but it’s also going to provide habitat.

Rhys Waters (18:32)

Dr. Patricia Manuel points to examples of innovative coastal adaptation work in Nova Scotia, like that of her colleagues at TransCoastal Adaptation Centre for Nature Based Solutions at Saint Mary’s University, which is under the direction of Dr. Danika van Proosdij. Researchers and practitioners with TransCoastal are helping build climate resilient coastal communities and ecosystems by protecting, enhancing, and restoring natural processes. TransCoastal is advancing work in coastal adaptation of dykelands through dykeland realignment, for example.

Dr. Patricia Manuel (19:05)

What that’s involving is understanding where is it that we can actually find opportunity to reintroduce natural wetlands while also protecting dike infrastructure. What can we do to ensure that the dikes that we have are going to be effective in the future? Do we have some choices to make on areas which need more attention than others? What’s the risk to the property, the land behind the dikes, whether it’s agriculture or in some cases, there are even communities behind these dikes. And Investigating that.

Rhys Waters (19:44)

Another process the TransCoastal Adaptations Centre focuses on is managed dike realignment. This process is a combination of engineering and natural approaches that involves moving dikes back from its current location more inland, as well as shortening the dikes in some cases. In doing so, they decrease the amount of dike that needs to be rebuilt needs maintenance in the future, all while making sure they’re protecting the valuable land behind it. This solution also provides other benefits to the local ecosystem.

Dr. Patricia Manuel (20:13)

In front of the dike you have a space now for wetland to return to that estuary, right. So, these are areas that were drained in the past, wetlands used to be there and now they’re reintroducing the wetland. The wetland provides renewed habitat, of course, but the other thing it does is it protects the dike.

Rhys Waters (20:33)

In the more severe cases, proposed adjustments, such as moving infrastructure further inland, are understandably challenging for many people to accept. Even if they are accepted, in some cases, it is simply economically infeasible. That being said, whether we make the necessary compromises or not, the sea level will continue to push further up our coasts.

Dr. Patricia Manuel (20:55)

No one wants to say, don’t be up the coast. I mean, that’s coastal islands and peninsulas or coastal, and that’s what we define ourselves by the ocean and our relationship to it. So, it’s really important to be able to have that connection and keep it that way. But we need to keep the spaces that coastal, marine and coastal industries need for access to the shore, we don’t want to be encroaching on those if we can avoid it. And then for those other uses that don’t need to be so close, let’s move back a bit. Some places may need to think about moving their communities or certain areas back entirely. But here in the Atlantic region as other places in the world, we’re experiencing faster rates of sea level rise. And so, when things are happening more quickly, we’ve learned to adapt at a particular rate. And now we’re going to have to adapt a lot more quickly to accommodate that change.

Rhys Waters (21:53)

The expectation of a one-meter global sea level rise by 2100 is widely accepted by the scientific community. This coupled with the fact that the parts of the world are slowly sinking paints a stark picture for our future if this goes unchecked. It may not be possible to fully halt a force as strong as the sea encroaching on our coasts, but with the help of experts like Dr. Manuel and Dr. Webster, we continue to gain a deeper understanding of where we can make a tangible impact and where we may need to consider conceding some land for the wellbeing and longevity of our coastal communities. It will require strategic, evidence-based approaches from government, industry, and the public to collectively ensure that our communities prosper for generations to come.

In issues as nuanced as sea level rise, we may not all agree on a single approach, but by continuing to research, explore and implement solutions and further the debate, we better position ourselves going forward. Living on and near the coastline is deeply rooted in who we are as a people, and we must carefully navigate how we maintain this identity while coming to terms with the changing landscape of our future.

Dr. Timothy Webster: (23:00)

I imagine most Nova Scotians have driven along some of the road network, and, you know, kind of look off to the side past that railing and think, “whoa, if you ever went over here, you would be in trouble”. And of course, that infrastructure is at risk as we move forward with sea level rise. I don’t think we really have a good handle on how much of that there is and what the assets are that are at risk. So, to do that, we need to map it first, then we can start thinking about mitigation and adaptation.

Dr. Patricia Manuel: (23:33)

It’s really about you know, trying to figure out how to ensure that moving into the future we’re doing, we’re living on the coast in a sustainable way by it’s still able to enjoy it still able to draw the benefits from it for our culture and our society and economy. It’s also a case of, multi generational responsibility. I’m, I mean, I’m here now. And I have some experience and expertise in the area. And if I can lend that to improving the future for our, future generations and our children and their children, then I want to be a part of that too.

Rhys Waters (24:13)

Thank you for listening to Beyond Research brought to you by Research Nova Scotia. We wanted to say a special thanks to Dr. Patricia Campbell and Dr. Timothy Webster. To learn more about the research heard on this podcast visit researchns.ca/beyondresearch.

I’m Rhys Waters and I’ll see you next time.