 It's one o'clock on a Monday afternoon, so you are watching Think Tech Hawaii Research in Manoa. I'm Pete McGinnis-Mark, and I'm your host today, and I'm delighted to say that we have a really interesting discussion planned for you. We'll be interviewing Matt Barbie, who is a researcher at the Coastal Studies Group at the University, and Matt is going to be telling us quite a lot about the changes in the Oahu coastline and potentially the impacts of sea level rise. So welcome Matt. It's a pleasure to have you here, and hopefully we're going to have a really interesting discussion. You've brought along a variety of slides, but even in our background we can see, for example, here we've got Cocoa Head and Cocoa Crater, and some shorelines where we've got some salt marshes, for example, and I understand at the University you and your group actually spend a lot of time working on how the coastline might be flooded, where we would expect to see some new marshes developing as sea level is rising. But this is a pretty new technique, and it obviously has many implications for people living here, not only on Oahu, of course, where we live, but around the Hawaiian Islands as well as on the mainland. So this is a really important topic as we're facing, say, changes in sea level due to global climate change, for example, as well as it has economic reasons that we should become interested because obviously people will be living along the coastline. So tell me a little bit about what do you do? So my position at the University is looking at research and research technologies that go into shoreline change analysis, sea level rise around the Hawaiian Islands that specifically impacts the coastline and low-lying areas. So most of the areas where we have all of our population development, or the vast majority of our population development, and we're looking at those impacts and the potential impacts that might happen under different sea level rise scenarios and erosion regimes. And so by shoreline, you don't just mean the Sandy Beach, presumably it's a little bit inland. Are we looking at, say, 10 meters or 100 meters or what? It kind of depends on the location and the configuration of the coastline. Most of our interest in our study actually goes into the larger coastal area. So the whole coastal plain, which in some areas, like on the west coast of Kauai, can go all the way two or three kilometers inland. And so anybody who's living along this coastal plain, for example, you should be paying attention, because Matt's got some interesting illustrations. But I think it's a value for our viewers first to get some idea of how you actually do this technique. And I believe you brought along a few images that we can take a look at. You're using a technique called LiDAR. Can you explain to us as we look at the first image here? So LiDAR is a light detection and ranging technique. It's in this case, it's aerial mounted. You can see the plane on the slide. And it collects a single point of elevation directly below the plane. And as the plane's flying, it collects approximately 30 million points per second, or sorry, 30,000 points per second as it flies along. And therefore, you can imagine, it collects upwards of a billion points in a single survey. Okay. And presumably we know where the plane is flying. Yes. We have good control on the plane. A lot of that post-processing or processing of the data goes actually on inside the instrument in the upper right. And it gives us a whole set of data, both immediately it gives us the elevation on the land and also in the near shore bathymetry, which means the ocean floor along the coastline. You can study the shallow water topography as well as the elevations on the dry land. Absolutely. And that becomes very important when you're trying to model waves and near shore processes that happen along the coastline. I understand. And waves, of course, may become more of a problem as sea level is rising, they might overtop parts of the coastline. Is that why you're trying to study what the shoreline is like? Yes. We have researchers in our group that actually model the waves as they develop and change over the near shore reef. And as sea level rises, the estimate is that that amount of energy that's available to be erosive increases because you have more water over the reef. Understood. All right. And you brought along an example of what the data set is like after. So tell the listeners or viewers what it is we're actually looking at here. Yes. So you're looking at a portion of the south coast of Oahu. This is near Eva Beach. And this is just an aerial photo that you could find in Google. But in this case, it's a satellite image. And the ocean's down to the bottom of the image. Correct. You can see the ocean. You can kind of see that it has different colors of blue and some of the darker colors are reef. And you can see a few waves captured in the image. And this is just essentially a regular aerial photograph. Correct. This is like what you would see if you looked out the window of a plane. Now your LiDAR system, I think, is shown in the next slide. And it's for exactly the same area. Correct. This is exactly the same area of Eva. And you can see that this is actually a hill shade of the elevation data. So you could see that the offshore, the blue area, is kind of rough. And that represents the roughness of the reef. And then you can see all the structures, the houses, trees, open fields, and roads. Now many of our viewers are probably familiar with the topographic map where you've got contours showing equal elevation. How does the hill shade surface model we're seeing here differ? Well, this is a surface model. So this is actually a complete picture of the elevation. You can imagine that contours are lines of equal elevation. So if you wanted to turn this into a contour map, it would look very complex. Because the resolution of this image is one meter versus the contour. One can see the roads, for example. Correct. You can see the roads. The individual structures and houses, trees can easily be resolved. And because these are digital data, you can process them further. Is that correct? Correct. Yes. And perhaps the next image would show us a little bit of how you can go, this clearly has been worth. So here we've identified the actual features, the structures and features. So the trees, the buildings, anything that we don't believe belongs in what we call a bare earth or part of the actual topography. It is a constructed surface. So all that's turned gray. I see. And so you have to compile this kind of data set before you make predictions on where the low points are along the shoreline. Correct. Yes. So to use this in our studies, we'd like to remove all these features. And you can do that in the next image. I think we can see this is, you call it a bare earth. What is the bare earth image? So that's what we call a processed digital elevation model that looks at or is an example of just the bare earth, the naked earth without any structures or features included. You've removed trees, buildings. Trees, buildings, mostly bridges as well, but you can see in this case that there needs some further processing. And this would be the starting point presumably for where you'd say this is a low point on the coastline. Exactly. This is where we might either get waves coming on shore or presumably water rising up through the ground as the aquifer. Yes. And in a lot of cases around Oahu, we've channelized our streams. And so those streams, those canals that enter the ocean actually become the perfect avenues for sea level rise in a dating farther back into the communities. And channelized means you've dug them out, we've lined them with concrete or just expanded them. So that's the pathway that the ocean would take is the path of least resistance. Absolutely. I understand. Okay. I wonder if we've got some examples. Let's take a look at one of the next slides. And so this is a little bit different. I think I recognize Magic Island and Alamoana Beach Park here, right? And so is this the kind of product which your group would actually be generating? Does this depend on the topography or is this something else which we're seeing here? So this one is actually a historical shoreline change map. And these are all available to the public on our website. We use this, this does not technically include the topography other than it is a representation of all of the historical shorelines, all of the historical positions of the shoreline as it changes through time. And then we develop statistics based on that. So this is a separate product that we generate. And our viewers may not be able to read, but I see at the top there 1927 is the first shoreline going all the way down to red in December 2005. So you've got almost a hundred years or so of where the shoreline was and you can observe how does it change? Yeah. You can track that through time. Okay. And I guess the changes, is that what those little blue and red bars are showing us? Yes. Blue bars are erosion and the blue bars are where we've predicted or where we've mapped that there is historical accretion or the seaward movement of the shoreline. All right. So collectively where you're studying the historical changes along the coastline and then you've got topographic data to show us what it is today, then you can combine those two and get a much better picture of what actually is projected to happen in the future. Is that correct? So in our group that's exactly the next step that's happening is an integration of this 3D topography and the 2D historical shoreline change and to trying to assess what is the potential for impacts in the future perhaps identifying an erosion hazard zone. And that is a good lead into the video which you brought which is actually providing us I believe for Waikiki projections going into the future. So if we could run the video and Matt just talk us through what we're seeing here. Sure. We're looking at sea level rise scenarios mapped onto Waikiki and a very high resolution surface model. And the buildings that are painted in red are impacted by mean high water today. That means they have points that are lower than mean high water today. And then each separate color is a one foot interval. So orange would be impacted by one foot of sea level rise. Yellow is impacted by two and green is impacted by three and then purple is impacted by four. Let's run it again. But this doesn't look very good for people who are living in Waikiki. What time frame are we thinking about here? So that's where there's a political nature to science and that time frame is a very political question. We're in the science of it and so the best scientific way is to see what these different scenarios actually three foot scenario matches up roughly with about 2100. So people live today probably won't see Waikiki flooded by three feet of water but the one foot elevation change do we know what the rate is of sea level rise? Is it? Oh yes. The rate of sea level rise today and that's you can go to the tide gauges today and actually see it. They have a separate website or a webpage just for sea level rise. And so we're seeing some of the buildings in the video potentially at risk are there things that people can do to sort of mitigate against that sea level rise. I would imagine that it's the basements or it's the roads. Is that the kind of thing we should be concerned about? Yes. We should be concerned about infrastructure, all of these important things that we take for granted roads, sewage, storm drains, everything that we have below the surface or at the surface. We should be concerned about them and we should be planning for change. Okay and this sort of planning for change we're just coming up to a break right now but I'm hoping in the second part of this show we can actually think a bit more about change and how it might occur on various parts of Hawaii's shoreline but also perhaps we can talk a little bit more globally around Hawaii as well as around the rest of the world as well because this is clearly a problem where we're starting to see a lot of flooding along various coastlines. So let me just remind our viewers you are watching Think Tech Hawaii and this is research in Manoa. My guest today is Matt Barbie who is a researcher in the Coastal Studies Group at UH Manoa and I'm Pete McGinnis-Mark and we'll be returning in a few minutes time. Bye. I'm Ethan Allen, host of likeable science here on Think Tech Hawaii. Every Friday afternoon at 2 p.m. you'll have a chance to come and listen and learn from scientists around the world. Scientists who talk about their work in meaningful, easy to understand ways and they'll come to appreciate science as a wonderful way of thinking, way of knowing about the world. You'll learn interesting facts, interesting ideas, you'll be stimulated to think more. Please come join us every Friday afternoon at 2 p.m. here on Think Tech Hawaii for likeable science with me, your host Ethan Allen. Hi, I'm Cheryl Crozier-Garcia, I'm the host of Working Together on Think Tech Hawaii. It's a program where we discuss the impact of change on workers, employers and the economy. So join us every other Tuesday from 4 o'clock to 4.30, we're live in the studio on Working Together in Think Tech Hawaii. Take care, see you soon, bye. And welcome back, you're watching Think Tech Hawaii, I'm Pete McGinnis-Mark and this show is research in Manoa and today's guest is Matt Barby, who's a researcher at the Coastal Studies Group at the University. And we've been talking quite a bit about how you measure coastal changes here on Oahu. But Matt, during the break we had a brief discussion about how can you convince me that it's sea level rise as opposed to the ground subsiding because presumably it's all relative, right? Either the ocean comes up or the ground goes down. How do you tell the difference? Well, we have a whole network of tide gauges set up around the state at most major harbors. We also, so we can monitor the tidal and how the tide gauges themselves which are of course anchored to the island, how the islands are changing. And there definitely is, there is a spatial variability. There is a difference in the sea level. It's not all the same around the whole state. No, it's not. Can you give me an example? Where is it sinking as opposed to? Oh, we have Kauai High Harbor on the Big Island is a good example of where the uplift due to the mass of Mono Lua and Mauna Kea is actually pitching the tide gauge up and therefore they are not going to have to worry about sea level rise as much as areas of Hilo which are on the back side of that process and they're actually going to end up being in more danger. As a volcanologist, I've been out to Kapoho on the Big Island for example and quite often that the roads are flooded. So that's not due to sea level rise. That's due to ground subsidence. Correct. So there's, there definitely is there geologic processes that affect not just the whole state but individual islands and how sea level is going to impact the different islands and communities differently. But on Nahuahu or Kauai, presumably the older islands aren't subsiding as rapidly as they would be. Not as they would otherwise. No, but there are different areas in the world where you do not have to worry about sea level rise and other areas where you are going to experience sea level rise much sooner such as the Western. So it's complicated and then presumably sea level rise is a global phenomenon and it's not uniform across the entire planet. So if you're in the Maldives Islands or if you're in Holland, it will be different than here in Hawaii. Yes. Okay, okay. So we really need to see some specifics which is my cue. So let's take a look at one of the examples of the images which you brought in. I'm not quite sure this looks as if it's Kailua. Okay. And here we're seeing just part of the canal system around Kailua. And I see a lot of light blue areas. That presumably is where flooding might be taking place. Correct, yeah. So the areas that are blue are those that are being directly impacted by sea level. And so those are connected to the ocean. You can see a light blue area on the left side of the screen. Those are being impacted actually by wave inundation and some more changes in the coastal processes that are going on. This is the result of the channelization that you mentioned earlier before the break. Is that correct? The blue areas in the channel are definitely, I wouldn't say the flooding is due to the channelization, but it definitely lends itself to exacerbating a large problem. Okay, and let's take another look at a different example. Okay, and this seems to be what, Hawaii? Yeah, this is Hawaii, and you can see the neighborhood adjacent to the ocean right there where the green and the blue overlap. That's where our models show that the wave impacts in 2100 actually will then overtop the existing beach system and flood the back beach area in that neighborhood. So our viewers shouldn't panic. This is your projection for 2100, if the rates stay the same. If the rates stay, there are a lot of ifs in that statement. We have to make a lot of assumptions in order to. We don't want to be scare mongers in this. This is purely scientific data, and you're projecting if the rates stay the same for the next 80 years, this might be one of the consequences. And I'm guessing that the causeway has been broken because you took that out of your line. Yeah, that was part of that filtering and cleaning process. So although those types of structures lend themselves to hardening and might in the future become a type of mitigation effort. And I see that part of the highway to the lower right is actually flooded as well. Yeah, so that looks like it's the harbor area and the small boat harbor there. And so that area is low lying and might be in a dead end by waves. Let's take a look at another example. Oh, and this is just mentioned that you might be losing a road system. Yes, well, these are if we're this is the historical shoreline change rates for that portion of the Oahu coastline. And that's based on the historical shoreline positions. So in the past, we've had a shoreline that was significantly more seaworth than it is today. And this kind of just approximates that. And that's presumably one of the things I see when I go up to Kahuku to get some spicy shrimp. Is that the coastal road seems to that the rebuilding parts of that coastal road? Is that a risk or is that something which is it the sea level rise? Or is it that you're voting away to the beach material? All of the above. Well, in that case, the current sea level is rising. However, it's not rising at the projected rates that we're going to be seeing in the future. It's rising approximately six millimeters per year or per decade. Sorry. And that type of sea level rise is not what we're mapping here. We're mapping a potential scenario based on some global models being run. But all of your observations must be incredibly important. You know, if you were to step away from just the scientific data and anybody who's living here on Oahu around the state of Hawaii, how do they get to know about where the safer place is to build a house along the shoreline? Or what are the different agencies like NOAA doing to help us prepare this? Because it's going to happen, correct? Whether it's 2100 or 2200 whenever, this is potentially a very serious issue the state's going to have to face, isn't it? Yes, and the state is facing it and they are some of these products that we developed for them. And these are perfect planning materials. You don't plan for the most average, most occurring event in your life. You plan for those unexpected ones, for those ones you don't plan, that you didn't realize were going to happen. So we plan at like a 95% confidence interval, which means that's going to happen maybe 5% of the time. And that's what you want to build, or that's how you want to plan or generally want to plan when you're talking about infrastructure or you're talking about these large works where whole populations will be impacted by the ability to access and access. So in those illustrations where you had areas of flooding, they may not be, but we're not going to be like Venice. It might be that at high tides, we might have flooding for a few hours, several times a month or something. Is that what you would expect? That is what we kind of expect. I think, I mean, currently today we have our sea level at the tide stations is about six centimeters above the normal. And that's not sea level rise. That's an episodic event that we don't know how long it's going to last. But it's sort of a preview of what six centimeters of sea level rise will look like in the future. That kind of frequency, that flood frequency, will increase through time. And soon you'll then get to this point where you say, we have experienced one foot of sea level rise, but you'll get previews of it before that. OK, but this is a wonderful example. Viewers who are watching us live will realize we're just two days past Earth Day this year and the March for Science, for example. This must be a wonderful demonstration of how, say, the university research group doing basic studies, either with your LiDAR or studying shoreline change, producing information that has direct relevance to everybody's lives, whether you're trying to buy a condo in Kakaako or you want to drive around to Turtle Bay. This kind of dialogue, which it sounds you've established with the agencies, is really important. Science matters, for example, right? Yeah, I derive a lot of value from my job. And which agencies? You mentioned NOAA, correct? Is that the main group you work with? We work with federal agencies like NOAA and USGS, and then we work with local agencies like the Department of Land and Natural Resources and Department of Transportation, if asked, and facilities and management. And hopefully they build your recommendations into their plan for 2050 or plan for 2020 or whatever it is. Yeah, it's a process. I think, you know, when people first see these numbers and they see the potential impact with these scenarios, it's easy to shut off because it's kind of scary. But making people first aware so that they have a frame of reference when they see more frequent flooding, they can actually start to understand, well, this is what we knew this would happen. Very good. But what would you do next? Where do you go in terms of the discipline of coastal studies here on NOAA? What factors do we need to further investigate? One is, I think, identifying those sections of coastline that we want to preserve as beaches. Beaches are going to be more and more scarce commodity as they start moving more landward and intersect with hard shoreline, either privately owned or valuable infrastructure. And so there should be a program set up that actually identifies these sections of coastline we want to save for our Kiki, for our generation. But this is just a wonderful demonstration of how research at the university has practical significance for our community as well as perhaps extending out to the rest of the globe. So it's really important stuff. Well, we're getting to the end of the show, Matt. So, you know, I just want to thank you for bringing some of this material. It's been a pleasure to have you on the show. Let me just remind the viewers that you've been watching Think Tech Hawaii research in NOAA. And I'm Pete McGinnis-Mark, and my guest today has been Matt Barbie. Thank you for watching. And please join us again next Monday at one o'clock, Hawaiian Standard Time for Think Tech Hawaii. Goodbye for now.