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  1. Science and Technology
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  3. Technologically Speaking Podcast
  4. Season Three
  5. Episode 2: Secondary Perils of Flooding

Secondary Perils of Flooding

Technologically Speaking Ep 2 Season 3

In this episode, host Deepak Saini is joined by Dr. David Alexander, Senior Science Advisor for Resilience. Dr. Alexander explains the interconnected nature of global climate change, local weather patterns, and the constant challenge of shoring up our critical infrastructure to withstand it all. You’ll hear about advanced modeling, smart sensors, and next generation materials designed to mitigate the deadly risks of flooding and be able to explain exactly what a compound flooding event is. And you’ll discover Dr. Alexander’s personal connection to Manhattan Project scientist Dr. Robert Oppenheimer. 

Run time: 31:09
Release Date: November 8, 2023

Show Notes

Host: Deepak Saini, Media Strategist, Science and Technology Directorate, Department of Homeland Security

Guest: David Alexander, Senior Science Advisor for Resilience, Science and Technology Directorate, Department of Homeland Security

[00:00:00] David Alexander: So, we have a big flood event. It involves, you know, coastal, tidal, you know, riverine and flash flooding. Where is the community going to be affected? And what does that mean to that community?

[00:00:13] Dave: This is Technologically Speaking, the official podcast for the Department of Homeland Security Science and Technology Directorate, or S&T as we call it. Join us as we meet the science and technology experts on the frontlines, keeping America safe.

[00:00:26] Deepak: Welcome to this episode of Technologically Speaking. I'm your host, Dee Saini. Today, we're going to talk with our Senior Science Advisor for Resilience, Dr. David Alexander. Welcome.

[00:00:37] David Alexander: Thank you.

[00:00:38] Deepak: I'm so happy to have you here. We have so much to talk about. I’m really curious, David, when you were young, did you always want to be a scientist? Or did you have something else in mind?

[00:00:48] David Alexander: You know, my family has had deep roots within our community, where we call our home, which is in Aiken, South Carolina. Where, you know, we were involved heavily in, in terms of providing emergency support services. This is before the advent of 9 1 1, where we supplied, uh, ambulance services to the community. I had family members that were leaders in terms of the establishment of public safety and serving as the first chief of public safety in my hometown. And then at the same time, you know, my, my father and my godfather and very close friends of the family, were scientists.

[00:01:25] They were professors at the University of South Carolina. In some cases, they worked with Robert Oppenheimer and the, on the Manhattan Project and were involved in the Savannah River Site. So, I think a deep affinity towards, you know, science that can provide value to society.

[00:01:44] Deepak: You must have been privy to some very interesting conversations growing up. I feel like your title in a way is, what's the word I'm looking for? It's a little intimidating, right? So, you know, your title is Senior Science Advisor for Resilience, and I feel like that packs so much within it, right? So, how do you approach your position and kind of... Like, what does it entail? I feel like you have a hand in so many different things throughout the department.

[00:02:14] David Alexander: Yeah, so resilience, like you said, is a very broad term. It can mean a lot of things to different missions, different sectors of society, different aspects of the scientific community. I think when we look at resilience, we kind of step back and say, what are the core missions of the Department of Homeland Security? So that we can start to identify where there are tangible areas that we can advance science, create new technologies that can then drive innovation across those key stakeholders, missions, and operations.

[00:02:48] You know, so, for example, you know, we know a lot of our critical infrastructure, relies on and depends on concrete. So, where can we make advances in concrete to where we can reduce the risk of adverse effects from different types of stresses and shocks? Think of a stress as, you know, the road and the bridge is getting used every day by cars and automobiles and other traffic. So, there's a maintenance burden on that infrastructure. At the same time, you know, there could be a catastrophic event like a flood and earthquake that could create a shock against that infrastructure. How can we ensure that the materials we’re utilizing one, allow us to more effectively monitor and ensure the performance of that infrastructure and detect adverse conditions early? And two is, how can we provide additive materials or fillers to that infrastructure so that it makes it stronger, more elastic, more resistant to those types of shocks and stresses and reduce that risk, both from a maintenance as well as a threat perspective.

[00:04:04] Deepak: Yeah, it sounds like a multi-pronged approach to this. I know at S&T, we're doing quite a bit of work, especially to help extend the life of concrete dams in Kansas. Can you talk about that project?

[00:04:17] David Alexander: Yeah, and that's an extension of the initial landscape research we did on advanced materials and new composites, for concrete infrastructure, where we chose to look at a very complex use case for Homeland Security, particularly water concrete, infrastructure. Why? It's because water-based concrete infrastructure is typically exposed both at the surface and subsurface level, as well as it, it experiences conditions that are both emerged and submerged. And that makes it a challenge, right?

[00:04:52] We just chose water infrastructure as our use case and dams and levees as a key area to test and innovate these technologies and advance the science because it posed such a complex, but very targeted opportunity for Homeland Security, given that there are tens of thousands of dams, levees, across the country at varying degrees of age.

[00:05:17] Deepak: I'd like for you to touch on the material we're looking at. I find it fascinating and innovative: fiber-reinforced polymers. Is this kind of a new type of compound or is this something that's kind of being used in other cases, but we think it makes sense in this situation?

[00:05:34] David Alexander: So, there are a lot of different types of, of additive materials that the science community, as well as the engineering and construction community has explored with concrete. We were looking specifically at fiber-reinforced polymer innovations particularly because we thought they had significant applicability to concrete dams and levees or water infrastructure in some of the conditions and factors that they face, whether it's cracking, whether it's erosion or other issues that are more daily versus a breach, which may be more catastrophic caused by some seismic or flood event.

[00:06:14] You know, but essentially you could think of fiber-reinforced polymers as composite materials that consist of two or more different constituent materials. In this case, it's oftentimes carbon or glass fiber that's embedded in an epoxy matrix. So, when you create concrete, you essentially concrete is an epoxy that then dries, right? That's why you need your concrete to curate. You can't just, you know, put it out on the ground and then start walking on it right away. Um, it has to curate.

[00:06:44] Deepak: Yeah, they're building houses across the street from me, so I'm watching that process as we speak.

[00:06:50] David Alexander: Yeah. And the added benefits are, is that, you know, these fiber-reinforced polymers provide a material basis both tough, lightweight. Very strong. It has some elasticity, meaning it can flex based on changes and conditions. So, it has some interesting structural properties that then allow us to exploit those structural properties in a couple ways.

[00:07:13] One is, as I mentioned earlier, is it can provide us an ability to sense potential disruptions or stresses or potential issues with failure of that infrastructure, because we can sense changes in the electrical signals from those properties that have been embedded in that concrete infrastructure. At the same time, the concrete, these polymers, because they're made of similar type chemistry as the concrete that we're adding these materials to, they tend to have a high success rate and a high bonding potential with the concrete material itself. So, it, so invariably that then means that it strengthens and reinforce the structural properties and characteristics of the concrete itself that can also create some self-healing, as well as elasticity within the material.

[00:08:12] Deepak: When you're trying to analyze visually the deterioration that's happening, does machine learning ever come into play to help speed that up or maximize that effort for you?

[00:08:23] David Alexander: Absolutely. So, what happens is that you have these new materials that you've embedded. They give you new potential distance and earlier detect when an anomaly or stress is happening on that structure. It can give you maybe some potential for it to respond to those stresses by adapting its bonds to the concrete, but at the same time, because we get that early signal that a stress may be occurring, it allows us to exploit new technologies and innovations like AI paired with new sensors, like drones, so that we can capture images, right?

[00:08:58] Because, there could be a surface, in, in concrete infrastructure that has a surface component; we can observe those conditions through more persistent imaging, and then use the AI to learn and understand how the physical appearance or representation of the infrastructure is changing as we're receiving signals from those additive materials. And you could then eventually use similar approaches for the subsurface or submerged components of the concrete. You just may not use a, optical sensor. You may use a different type of sensor, like sonar or other imaging that is more appropriate for underwater conditions.

[00:09:42] Deepak: I feel like that also helps you spot problems with the infrastructure in advance versus maybe decades ago. You wouldn't really realize what was happening until you saw a crack in the system.

[00:09:54] David Alexander: You waited until a breach occurred or was about to occur because someone witnessed or observed a crack or failure within the system, or you had to routinely, either through a standard maintenance regime, send out physical inspectors and/or you may expedite physical inspection because, an event is imminent. Like, for example, you're anticipating a high precipitation event or flooding, and so you send out inspectors immediately following the event to assess the performance and the integrity of the infrastructure. So, pairing new technologies with new drones and UAVs and AI with additive materials, really creates an ensemble – a suite of solutions to really help the construction and engineering and the critical infrastructure protection community to better manage these assets going forward and not necessarily extend their life, but strengthen, and increase the resilience of that infrastructure during its planned life.

[00:10:58] Deepak: Yeah, that's a really good point. I would love for you to talk a little bit about what we're doing to address compound flooding events. First off, though, what even is that? What is a compound flooding event?

[00:11:10] David Alexander: Yeah, I mean, so there's a lot of different ways to look at a compound flooding event, traditionally and probably the most common in discourse is recognizing that, flooding can come from a lot of different vectors. So there could be that, you know, there's a hurricane that is now coming in, onto the coast. At the same time, that hurricane is a heavy precipitation event that is not just causing coastal surge, that's creating, you know, coastal wave erosion and tidal erosion, but at the same time, it's creating inland flooding conditions because of the amount of rainfall that it's, that is, that is precipitating inland, you know, and those converge.

[00:11:51] Now, on top of that, you get what we call new, a new emergent risk called, pluvial flooding, which is essentially ponding, but don't think of a pond in terms of a small lake. Think of ponding as when you go to a parking lot, a big parking lot in one of the retail stores, and there's a heavy rainfall event, you notice that there are pools of water, that, that are left behind. So, pluvial flooding is, uh, result of essentially flash flooding. Where we've, transformed the environment in ways that now it's more susceptible to heavy precipitation, not because it's a river, but because it's an area that now is impervious, meaning that the water has nowhere to go, and the stormwater system may not be able to absorb the amount, the volume of water that is occurring during the event.

[00:12:45] And so it cascades over the surface as what people recognize as flash flooding. And collectively, those different types of flooding come together around major events, whether it's a tropical event like I noted with a hurricane that's coming on coast, or it could be that it's a heavy precipitation event that's occurring inland, that is also affecting, you know, lakes and rivers and other, other infrastructure. And then you get what has been often considered by the insurance industry as secondary perils of flooding. That are now recognized as aspects of a compound flood event. And these would go with the example of, you've had heavy precipitation flooding, getting a river that's overflowing its banks, you're getting flash flooding that's occurring in areas that are heavily built and impervious surfaces. You may be experiencing tidal or coastal flooding, and on top of that, you're now experiencing mudslides because the heavy precipitation rainfall has caused erosion along the hill slopes. And now mud is sliding down those hill slopes and creating what we call a secondary peril.

[00:14:01] Deepak: You know, listening to you describe all this made me realize, I've been through compound flooding events multiple times. When I was a reporter in New Orleans for ABC affiliate there, WGNO, I covered many hurricanes. And what's unique about New Orleans is, so a lot of times it would have me do live reports from Lake Pontchartrain, right? And so, the lake spills into the Gulf. And then we also have the Mississippi River, so anytime we would have a hurricane and all three of those bodies of water would start to swell and overflow into one another. So yeah, this just brought back so many visuals for me.

[00:14:38] David Alexander: Yeah, so just throw on the fact that you've now had a heavy precipitation event that's caused overflow and an increased volume of water within the river system and that is putting additional stress on the dams and levees that are controlling that riverine system. Those, dams, or levees may be old, aged and, you know, and not maintained enough to absorb that stress and now they fail. So, now you get a flooding triggered by a failure of the infrastructure, not because of just, of the fact that you have an increased rate of rainfall.

[00:15:14] Deepak: Yeah, that's a good point. Speaking of the South, so obviously earlier we talked about your, you know, your long generational history in South Carolina and just expanding this to the Carolinas in general. It seems like we've got quite a few, you know, big ticket items there that you're working on. Can you dive into the community flood resilient support system that S&T developed in Charleston?

[00:15:39] David Alexander: Yeah, that's a new solution that we've been working with our partners within the Deltares Lab within the U.S. Deltares is a Dutch-affiliate laboratory, so this is an opportunity for us to have international, not just a domestic, collaboration on a major risk area, in this case, flooding. We chose Charleston, as an initial use case because as I noted, you know, it experiences, all those types of flood conditions: tidal, coastal, riverine, flash flooding, and Charleston is also experiencing a new form of tidal flooding as a result of climate change where whenever it has king tides, and king tides are essentially the tides where it's the highest rise of the tide during the title cycle, because of the increase in sea level rise. And now, parts of Charleston during king tides are flooding regularly, whereas previously did not. So, they're experiencing a variety of types of flood conditions, whether they're driven by heavy rainfall or not, and it posed an interesting use case for us, and they were also interested in working with us because they were making a big push to do community-wide resilience planning.

[00:16:54] Now, you mentioned the, the tool, you say Community Flood Resilient Support System. We've rebranded to make it a little bit more user-friendly. We called it Flood Adapt, and the intent of the tool was to say, not just create another flood modeling tool, it was really to go towards what I, what we call, we're not just interested in knowing and understanding the what and the where. We're interested in understanding the so what, and then what do we do about it? And so Flood Adapt is really getting at those last two questions of, hey, we got all these great modeling capabilities out there that include future forecasting and around changes in sea level rise. That is a key driver along the coast. As well as other future casting models of different aspects of flooding.

[00:17:47] We could pull those together. We could then start to analyze what are the societal impacts of a variety of different types of flood events occurring in Charleston? Who and what and where would those effects be experienced, which gets to the so what. So, we have a big flood event. It involves, you know, coastal, tidal, you know, riverine and flash flooding. Where is the community going to be affected? And what does that mean to that community? What's the so what about it? And then once we were able to produce that picture, then we went the next step and said, okay, now that you understand where and the variation of flood risk across your community, and how it's going to impact those communities, what can you do about it? That gets to including intervention modeling within the tool. Um, so a community to go in and say, hey, this area is a historic area. So, there's limits in terms of what we can do because we can't change, we don't want to lose our cultural heritage in this area.

[00:18:54] So what are the intervention options we could deploy, that would still  reduce the flood risk and improve their flood resilience in that area and not disrupt the cultural heritage of that part of the community? Another area, may say, hey, these are new neighborhoods, and we don't have the latest building codes deployed in that part of our community. Maybe we should implement new building codes that, that included what we call a three-foot freeboard, meaning you have to build three foot above the base flood elevation, and then we could implement a retrofit program in that area for any existing structures so that we could bring them up to that building code. And what would the cost be? Um, for that action. In another area of the community, they may choose that it's more appropriate to deploy nature-based solutions. So, they may want to put in mangroves or marshes, marsh barriers, or sand dunes… other nature-based options that help absorb and address, you know, antecedent, as well as precipitous flood, flood conditions. So, so Flood Adapt starts to provide them, you know, that holistic approach. And then model out, what not only the appropriate actions would potentially be for our community, but what would the likely benefits from those actions achieve.

[00:20:17] Deepak: Yeah, no, that's all really fascinating too. I mean, we we’re working on a lot of manmade products, but also it's important for like the natural barriers that we can restrengthen as well along our coastlines, especially along the Southern states that, like you said, just have such rich, beautiful, historic culture that we don't want to lose. I would like to talk quickly about. Yeah. The low-cost internet-of-things flood sensors in Charlotte, North Carolina. Can you just explain how they work and their benefit?

[00:20:48] David Alexander: Yeah, so, what I referenced in the discussion around additive and advanced material science, I noted that there this need to have sensing capabilities. Um, so that we get early warning and indication of an issue occurring so that we can appropriately respond, mitigate, and address those issues. In this case, uh, you reference our internet-of-things flood sensors, and those are low-cost, devices that we can deploy in a variety of scenarios within a community that will detect flood conditions, and essentially expand the community's flood warning, sensing network so that, you know, they can one: implement more efficient protective measures, two, use that data to drive their investments in mitigation, meaning where do they need to do capital improvements to reduce red flood risk.

[00:21:45] Because those flood sensors are detecting and providing them empirical data, to substantiate that there is a risk there and what that risk is. Uh, and then third, is that it provides a way to send out warnings to different sectors of the community, that flood conditions are occurring. You need to avoid that area or take appropriate, protective measures. In this case, our first initial deployment and operational test of those sensors within Charlotte, North Carolina, and we work with their stormwater management services division that also managed their flood information and notification system and look to deploy the IoT flood sensors in locations where they lacked coverage.

[00:22:33] They had only about 15 sensors, stream gauges within the entire metro area of Charlotte, Mecklenburg. And so, there were significant gaps in coverage in terms of being able to detect flood conditions and then model those flood conditions. And so, we worked with them to fill those gaps by deploying sensors within those areas and then integrating it within their stormwater management operations, so that they could digest the data, they could react to the data, and they can use it to inform their investments.

[00:23:09] Deepak: You know, I'm really liking that we're talking about all these specific examples at the micro level. I just want to zoom out really quickly department wide. You know, you're like I said earlier, you are involved in so much, right? Secretary Mayorkas announced a climate change action group a couple of years ago. You're involved there. You're involved with the White House National Climate Task Force. Earlier this year, in February, we became a member of the United States Global Change Research Program. And this fall, we're releasing a comprehensive report on climate change, which is called National Climate Assessment 5. Can you just talk about… how do you tackle all of this, the importance of all of this, and how it's helping move the needle forward for the country?

[00:23:57] David Alexander: By joining USGCRP, it gave us a sounding board to communicate to those other science agencies… hear the operational needs of the department, and better explain how climate change is affecting those operations, so that we could influence and inform the research that is going on across those agencies so that it is easier to transition and make it more applicable to the Homeland Security Enterprise. And that, therefore, then it's not just an army of one. It's not just DHS trying to act on its own.

[00:24:33] You know, like I said, you know, it's important for us to get out and communicate and educate, you know, there is a scientific communications aspect to our job to see your science advisors, you know, we, we shouldn't just be the smart people in the room behind the door, we need to get out in front and explain to people, here's what we know and how we know it, and what it means to you.

[00:24:57] Deepak: Yeah, no, that makes a lot of sense. I mean, as technology is rapidly expanding, as our threats are growing, you know, all of these different agencies have different and overlapping expertise, right? So, we all have to be in the same room and approach these together, for sure. I really do appreciate the fact that DHS also has climate resilience prize competitions. You know, there's a Cooling Solutions Challenge. There's a Civic Innovation Challenge, as well. Uh, why is it important for us to engage with academia and industry with challenges and solutions like these?

[00:25:33] David Alexander: So I think there's two, rationales and explanations for the approaches we take. The first is recognizing that there's a lot of technology that's already out in, in, the private sector and industry. And so there's an opportunity for us to challenge industry by better articulating what our issues are, what our gaps are…better explain the problems that we're trying to address. And then enabling them to compete, basically submit solutions that they think meet and close those gaps. And a prize challenge is a great way to do that. We can target a discreet problem. Uh, we can then open it up for any innovator, whether it's a small business, or it's a scientist in a university… or it’s just somebody sitting around and is very smart in their living room and has come up with a great idea and how to pull it off. And then their other aspect is recognizing that a lot of Homeland Security's goals will only be achieved by strong relationships with the state, local, tribal, territorial, and community organizations that support us and we support. As that will then uplift and build up national resilience. And it also provides us a pathway to ensure that the solutions and the technology and the science we're invested in is fit for purpose, and is adding value in addressing challenges that society at large faces.

[00:27:06] And we do that through something like the Civic Innovation Challenge, which is a partnership with the National Science Foundation, NSF and Department of Energy, DOE. And then, of course, this year, U.S. Department of Agriculture is starting to participate in that effort. And that is by pursuing a participatory research model, where we're inviting researchers to partner with local communities. And communities determined liberally. And a technology provider and really work on solving a problem within 18 months that can be deployed in that community and show value. And that's really what CIVIC is about. It's really about working hand in hand with our communities to advance the science, but also ensure the technology is fit for use.

[00:28:02] Deepak: Speaking of advancing the science, what advice would you give for the future David Alexanders or Davina Alexanders of the world that are, you know, still young, maybe trying to figure out life… what would you tell them?

[00:28:16] David Alexander: So I think if you're talking to the K through 12, I think it's, you know, hey, join a club, join a science club. Pursue extracurricular study programs. Get involved. Because that's how you'll, you'll help yourself identify what areas are most interesting for you. And really, it'll, shape your future. For more of the college, higher education level. It's, you know, apply for internships, look at co-op opportunities. Do volunteer work with groups that, you know, are involved in things that you're interested in. And that might also help you to target where, what direction you want to go in your academic career, and what topic you may want to pursue for your master's degree or your dissertation. Or it may open up an opportunity for a job that you didn't anticipate, because you've engaged. Um, so get out there and, you know, and don't just stay in the lab.

[00:29:12] Deepak: Yeah. It's all about the journey, right? Some of life's biggest career blessings are sometimes unexpected. I am curious to know though, I feel like you have such an important role that carries so much weight. What do you do to de stress? Do you have any hobbies unrelated to your job?

[00:29:30] David Alexander: Uh, yeah, I mean, of course most scientists are avid readers, but yeah, I do enjoy traveling and, I do have a nascent photography interest, partly because my father at one time, in his first career, was a photojournalist. Um, so I, I do like to do photography on the side. More the nature of photography, but it's a good way to decompress. Uh, and if you pair it with traveling and, and getting out and seeing places, it just gives a way to, to preserve your memories.

[00:30:03] Deepak: Yeah, I agree with you, David. I do photography on the side as a hobby. I've actually been hired to do like weddings, engagements, you know, like family portraits and things like that. And I always find that it's a huge de-stressor for me because it's such a, creative way to visually showcase to other people how you see the world or how you see them within a frame. So, I see what you're saying. Definitely. I definitely find photography very therapeutic…David Alexander, S&T Senior Science Advisor for Resilience. This has been such a great conversation and I've learned so much from you. You're a huge asset to S&T and the department and, you know, we can all collectively say we're proud of the work that you do. Thank you so much for being on.

[00:30:47] David Alexander: Thank you.

[00:30:48] Dave: Thank you for listening to Technologically Speaking. To learn more about what you've heard in this episode, check out the show notes on our website, and follow us on Apple and Google Podcasts, and on social media @DHSSciTech. DHS SCI TE CH. Bye!

Last Updated: 04/01/2024
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