Hurricane vs. Tiny Houses

[00:00] By the end of this video, one of  these buildings will be knocked   because there’s a lot we still don’t understand  about hurricanes and their effects on buildings.

[00:14] In September 2022, Hurricane Ian tore  across the Caribbean and southeastern U.S.,   Carolinas. It was one of the strongest  and deadliest storms in modern history.  

[00:28] We often think of hurricanes in terms of wind  and rain. But in coastal areas, it’s the surge   of seawater driven inland by the storm that causes  the most catastrophic damage. Homes and buildings  

[00:41] didn’t just get wet. Many were obliterated,  swept from their foundations entirely. But unlike many storms of the past, Ian came  with data, and lots of it. Today’s tools for   collecting and analyzing information mean that  even tragic disasters can lead to really important  

[00:58] insights into how we can build safer and smarter  in the future. After Hurricane Ian, FEMA analyzed   more than a thousand flood claims, and what they  found about building performance was remarkable. To dig deeper, I’m here at O.H. Hinsdale  Wave Research Labratory at Oregon State  

[01:14] University. A team of engineers is running  a one-of-a-kind experiment to simulate storm   surge and study how buildings actually respond.  They invited me here to see it firsthand and   share what they're learning with you. I’m  Grady, and this is Practical Engineering.

[01:39] Everyone knows hurricanes are destructive,  but storm surge often gets underestimated,   not just by the public, but policymakers and planners too. We see footage of roofs ripped  off and trees snapping like twigs. But just a few  

[01:56] feet of storm surge can cause even greater  damage. And waves amplify the destruction. If you’ve spent time in coastal areas, you’ve  probably seen homes raised on stilts. Since   the early 2000s, this has become one  of the most common construction types  

[02:12] in flood-prone coastal zones. The concept is  straightforward: move the living space above   the reach of storm surge. If a hurricane  hits, the lower area used for parking,   storage, or access might flood, but the  critical parts of the building stay dry.  

[02:26] All the devastating power of the waves flows  through and around the stilts instead of slamming   into walls and destroying the structure. It  turns out this idea is remarkably effective. After Hurricane Ian, FEMA found that flood  insurance claims for elevated structures in  

[02:42] Fort Myers averaged about one-third the cost  of claims for non-elevated buildings. That’s   a staggering difference in performance. But zoom  in, and things get more complicated. On one hand,  

[02:54] this is pretty obvious stuff. You don’t need  a massive wave laboratory to figure out that   elevated structures survive storm surge much  better than buildings at grade. But if you look   at footage from Hurricane Ian, it paints a more  nuanced picture, because some elevated buildings  

[03:10] didn’t fare well at all. They weren’t all high  enough to avoid the surge. And that gets to one of   the most difficult questions in the entire field  of hurricane engineering: Needless to say, it is expensive to lose your  home in a storm. The conundrum is that it’s also  

[03:28] expensive to build your home in such a way  that it can withstand one. If it were easy,   every building in Fort Myers would be a  hundred feet above sea level. But the reality   is that elevating a structure adds significant  upfront cost, and the higher you go, the higher  

[03:44] that expense climbs. It’s not just a cost for  homeowners but also something that’s passed down   to renters. Shifting the actual housing upwards  shifts the affordability of housing downward for  

[03:56] everyone. And because major hurricanes are  relatively rare events, the return on that   investment comes with a lot of uncertainty, with  benefits that are invisible most of the time. That’s one of the biggest challenges for  engineers and officials. In theory, you can  

[04:11] design a structure that withstands anything. But  in practice, no one’s building hurricane bunkers   as homes. Codes and policies have to balance  safety with economic viability and long-term  

[04:23] risks with the upfront cost of resilience. Local  governments want robust, resilient development,   but they also need development to happen in the  first place. Overly strict codes can scare off  

[04:35] builders or price out developers. And while the  National Flood Insurance Program might prefer   fewer claims, stricter floodplain regulations also  come with tradeoffs: reduced property tax revenue,  

[04:47] limited housing supply, and the burden  of compliance placed on individuals. but when you multiply them out along developed  coastlines, the implications of each extra foot  

[05:01] of elevation are monumental. So what you  end up with is a delicate balancing act,   shaped by competing priorities, enormous  uncertainty, and billions of dollars on the line.   Changing building codes or policies requires  buy-in from a broad array of stakeholders,  

[05:17] But there’s one more thing that makes this  even more complicated. Of course, “stuff   getting wet” is a problem with storm surge, but  it’s more than just typical flood damage you’re  

[05:30] dealing with when it comes to hurricanes. In a  sense, the surge is a rise in sea level itself,   and once your home is essentially IN the ocean,  that brings wave action into play. Forces  

[05:42] intensify. Structural systems are tested in ways  that ordinary flood damage doesn’t account for. You can see why this idea of elevating structures  is one of those engineering concepts that seems  

[05:54] obvious on the surface, but gets way more  complicated when you start looking into   the details. And that’s why we’re here. Computer  models are limited in their capabilities. And you   can’t just call up an actual hurricane to knock  over a test structure (and even if you could,  

[06:08] it would probably violate the ethics rules).  So we go to the next best thing: the wave lab. The OH Hinsdale Wave Research Laboratory is one  of the largest facilities of its kind in the  

[06:21] world. Since the 1970s, this lab has supported  cutting-edge research into coastal engineering   challenges like sediment movement, tsunami  behavior, and wave-structure interactions.  

[06:33] It actually has two major test beds. This  is the Large Wave Flume. It’s used for all   kinds of hydraulic experiments related to waves,  coastal structures, and erosion. It’s basically   a super-sized version of the flume I use in  a lot of my garage demos. It can do a lot,  

[06:48] but it has a limitation in that it’s inherently  two-dimensional. Flow can really only move in the   direction of the flume. That’s why the lab  also has this: the Directional Wave Basin.

[07:00] Think of it as a wave pool turned up to eleven.  This enormous tank uses dozens of piston-driven   paddles, each with independent control, to  generate complex, multi-directional waves.  

[07:12] You can create a single tsunami-like pulse or dial  in irregular wave trains to match the chaotic sea   states found in real hurricanes. This facility  is utilized in large-scale research projects on  

[07:24] wave hydrodynamics, floating structures, and  devices that harness wave energy to generate   electricity. But, of course, it can also  test coastal structures, like these houses.

[07:36] Dr. Dan Cox is a Coastal Engineer and Civil  Engineering Professor at Oregon State.   He explained to me why they chose  the basin for this experiment. “The nice thing about the basin is, you  can look at kind of a full 3-D picture, rather  

[07:53] than just a slice. And I think for this set of  tests, we really wanted to do an entire house, not   just a wall, you know, a bit of the foundation.  And that’s why we chose the basin for this one.”

[08:05] The research team has spent months building  two incredibly detailed model homes,   each one a near-perfect one-third scale replica of  a real coastal house. Each foot is equivalent to  

[08:17] three feet in real life. And the only difference  (besides color) between them is elevation. The   green model is a foot or 30 centimeters higher  up than the orange one. That corresponds to 3  

[08:29] feet in the real world or roughly one meter. In  every other way, both structures are identical.   They’ve got interior walls, windows, framing  details, everything. At this scale, that means I’m   about the size of an 18-foot-tall civil engineer…  which is actually something I’ve had dreams about.

[08:46] One-third scale is still just a model.  But this is not a toy experiment. The   researchers have carefully accounted  for all the physics involved. The wave periods and velocities have been adjusted  to simulate full-scale conditions, and the  

[09:02] structures have reduced stiffness to reflect  the relative rigidity of real-world buildings.   It’s all about maintaining dynamic similarity,  a fancy term for making sure the test results  

[09:14] actually mean something when translated back  to full size. And that’s a tough thing to do: “On the structure side, it’s a lot more difficult  to scale the structural behavior. So, for example,  

[09:27] when we’re doing computer simulations, the  simulations are primarily at scale - trying to   get that difference in shaking. The forces can  generally be scaled up as well, so we kind of   know what the forces are. But I think the mode of  failure - like how this structure failed - I’m not  

[09:46] sure so much as like a quantitative scaling. It’s  a little bit more like qualitatively, this is what   we would expect to happen under these conditions.” small and build gradually, both in height and  frequency, simulating the approach of a storm.  

[10:05] The goal is to observe how both buildings  respond as conditions get worse and worse.  It’s mesmerizing to watch: the wave generators  churn, sending pulse after pulse across the basin.  

[10:17] Within seconds, the models are surrounded  by rolling water, with each wave slapping   against walls, flowing around supports, and  rebounding off the basin walls and shoreline.  Even now, researchers at the lab are measuring the  behavior of the structures.

[10:35] you’ll notice targets for highly specialized  cameras and lidar to carefully monitor the   behavior of each structure. Sensors  placed throughout the experiment are   recording everything—wave height, velocity,  pressure on the structure, accelerations,  

[10:50] and even internal motion. The goal is to build a  detailed, physics-based understanding of how each   building absorbs and transfers energy from the storm surge. For one, this expensive and elaborate test is just  two buildings. And there are a lot more types of  

[11:09] houses in the world than that. So this data can  be used to calibrate and validate computer models,   making it easier for engineers to get  reliable answers to questions without   having to build scale buildings and put  them through huge model tests like this.

[11:23] And some of those questions are big  ones. When you’re looking at options   for large-scale flood infrastructure, a  major part of the process is estimating   the differences in damage and loss  of life between alternatives. Again,  

[11:37] we can’t build infrastructure, call down  a hurricane, and test it out in real life,   then revise accordingly. Even engineers shouldn’t  have THAT kind of power. So we have to be able to   make predictions about how any proposal will work  out. It’s educated guessing, essentially. But the  

[11:54] better we understand the connections between  all the variables (wave height, surge level,   building elevation, movement, and damage),  the more educated those guesses become. “I would say the physical model  is closer to the real world.

[12:08] It's the best, in a numerical simulation, it's kind of the best we think we can do. always looks really cool. But there’s really  - you have to verify it. You really have to  

[12:22] show that it’s correct, not just looks cool.  And I think when we get to the laboratory,   like we’re seeing during this test, like  okay, it’s not as simple as we think.   So there’s a lot more complexity, I  think, inherent in a physical model.”

[12:38] That’s why even though these tests seem  pretty straightforward at first, they can   have a profound impact on how we allocate public  funds, regulate floodplains, and ultimately,   keep people safe. You probably wouldn’t buy  a car without giving it a test drive first;  

[12:53] it’s too big a financial decision to take a  risk. Imagine changing the building code or   floodplain regulations without good data to back  it up. We necessarily make high-stakes decisions  

[13:05] about how to manage flooding in the face of  equally enormous uncertainties. So, you can   see why information like this would give more  confidence to engineers and regulators to write   building codes and improve floodplain regulations,  knowing those decisions are grounded in truth.

[13:22] But it’s not just about the data. You might have  noticed that these houses aren’t just bare minimum   structures. The team has added details like  roofing, window frames, and colorful paint jobs   to make them look like real buildings, even though  they don’t really affect the final results. That’s  

[13:38] because this test is also a communication  tool. Most people aren’t going to read the   academic papers that get published as a result  of this study, but this footage tells a story.

[13:50] You don’t need data to understand which of  these two structures you’d want to live in   when a hurricane comes. And the more  people who take storm surge seriously,   the better the outcomes we can  expect when a big storm arrives.

[14:03] Each set of waves is programmed into the  machine to simulate the variability of a storm,   with the upper limit of wave  amplitude increasing from one   set to the next. After four sets of  waves (delivered in about an hour),  

[14:16] they raise the level in the basin using this  massive bathtub faucet and repeat the process.   It was actually pretty surprising how well  both models were holding up for a while there. It’s hard to communicate in a video  just how awe-inspiring it is when  

[14:30] the directional wave basin starts  really churning. And eventually,   a particularly violent wave comes crashing into  the lower house, and we see our first damage.  

[14:42] You can see the wall underneath the window give  way, and now waves start penetrating into the   interior of the structure. In a real house,  this would already be catastrophic damage. But of course, they don’t stop at the first  sign of damage, and the team keeps hammering  

[14:57] the models with more intense waves. Over the  course of the experiment, the sea conditions   just keep getting worse and worse, and  the damage to the orange house does too.   More and more of the first story of  the lower house is swept away.

[15:12] Waves  flow through the structure and knock out  portions of the wall on the beach side,   and everybody in the room fills with  eager anticipation of a total failure. And then, something I didn’t quite expect  happened. The model seemed to almost stabilize.  

[15:27] The walls of the front and back of the structure  were so totally obliterated that the first floor   almost began to act like another level of stilts!  Despite the first floor being utterly wrecked,   the second story remained more or less fine for  quite a while, even as the waves got stronger.

[15:43] Dan told us about a test at half this  scale (one sixth of real life scale)   that had shown similar progressive damage,  but that led to collapse much earlier on: “In the previous study, we started to see  the deterioration and then very quickly,  

[15:59] well we'll see that again at  larger scale, but we didn't.” That’s one of the cool things about moving up  in scale and realism: you learn things that   aren’t always expected. If we had cameras  on every structure during Hurricane Ian,  

[16:15] we likely would have seen similar results -  damages from storms rarely follow a linear,   progressive trend. It comes in fits and  starts. For a while, it seemed like it   might be the end of the experiment, since the  stronger waves weren’t causing more damage.

[16:30] “…It was a tough problem, and I thought I  knew the answer, and it turns out I didn’t.   Little bit tough to swallow, but it also kind of  highlights to me, like, okay this is a challenge.   This is a hard problem. So for me, you know,  I’m trying to put a positive spin on it, but  

[16:45] I feel like that’s a success right there. To say  hey, this is more complicated than we thought.” Of course, everyone watching (including me)  and those participating in the experiment   were hoping for that final blow that would  knock the whole thing over so they could get  

[17:00] the full range of data needed from safe  to damaged to destroyed. And eventually, the moment came.

[17:12] The waves finally  won, and the lower house collapsed. "Holy moly!"

[17:31] What’s probably more interesting  than that is the condition of the   other house. Take a look at that. Almost no  damage whatsoever. This building sat in the   exact same conditions as the other house  and took almost no damage. And in a way,  

[17:47] that’s kind of remarkable. Because there really  wasn’t that big of a difference between the   two. I said it’s expensive to elevate a  structure, but the marginal cost between   the green and orange models is almost negligible  compared to the overall value of the structures.

[18:04] “In talking to people about flood risk,  you know, we talk about the 100-year,   500-year. And I think there’s a misperception  that the 500-year is like 5 times bigger,  

[18:16] 5 times worse, I have to elevate 5 times  greater. And I think just trying to show   people it doesn’t take much. Like, there was not  much of a difference in elevation between those   two buildings. The one on the right is toast.  The one on the left had a little bit of damage,  

[18:33] but hardly any, and that was only after we  really tried to... The researchers will be studying the data from  this experiment for years to come. But the   story's pretty clear. Same surge, same  waves. A little difference in elevation  

[18:48] can make a huge difference to a structure  when it comes to surviving a hurricane. You might be watching these buildings get knocked  about and thinking: “We don’t need more resilient   structures in the floodplain; we just need  them to not be there in the first place.”  

[19:02] And in many ways, you’d be totally right.  Often, the most economical way to reduce   flood damage is to avoid building in flood prone  areas, or if development has already happened,  

[19:14] simply to buy out property, tear it down, and  leave the land empty as a buffer. But where’s the   line between flood-prone and not, especially when  it comes to rare events like hurricanes, where the   probabilities of occurring in a year are in the  range of 1-in-100 or 1-in-500? And if there’s  

[19:31] not a bright line between at-risk of flooding  and not, what’s appropriate for the fringe? The truth is that there is no catch-all solution  to flooding. We need options to accommodate the  

[19:44] vast array of situations where development  occurs, whether those areas are flood-prone,   flood-free, or, most importantly, somewhere  in the middle. And not just options, but also   the data to determine which of them is truly the  best path forward. Engineering is a balancing act;  

[20:02] we need structures that are both strong and  safe, but also affordable, easy to occupy,   and maybe even architecturally pleasing.  Using knowledge gained from tests like   this helps us get a clearer definition of  the edges of the problem we’re solving.

[20:18] Huge thanks to Dr. Dan Cox and his team of  researchers for inviting us to see this happen.   I love talking about the engineering of the built  world that often goes unseen like this test. I  

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