Hurricane vs. Tiny Houses

0:00 By the end of this video, one of these buildings will be knocked down

0:04 by the force of a simulated storm surge, because there’s a lot we still don’t

0:09 understand about hurricanes and their effects on buildings.

0:14 In September 2022, Hurricane Ian tore

0:17 across the Caribbean and southeastern U.S.,

0:20 leaving a trail of devastation from Cuba to the Carolinas.

0:23 It was one of the strongest and deadliest storms in modern history.

0:28 We often think of hurricanes in terms of wind and rain.

0:32 But in coastal areas, it’s the surge of seawater driven inland

0:36 by the storm that causes the most catastrophic damage.

0:39 Homes and buildings didn’t just get wet.

0:42 Many were obliterated, swept from their foundations entirely.

0:46 But unlike many storms of the past, Ian came with data, and lots of it.

0:51 Today’s tools for collecting and analyzing information

0:53 mean that even tragic disasters can lead

0:56 to really important insights into how we

0:59 can build safer and smarter in the future.

1:02 After Hurricane Ian, FEMA analyzed more than a thousand flood claims,

1:06 and what they found about building performance was remarkable.

1:09 To dig deeper, I’m here at O.H.

1:12 Hinsdale Wave Research Labratory at Oregon State University.

1:15 A team of engineers is running a one-of-a-kind experiment

1:18 to simulate storm surge and study how buildings actually respond.

1:22 They invited me here to see it

1:24 firsthand and share what they're learning with you.

1:27 I’m Grady, and this is Practical Engineering.

1:39 Everyone knows hurricanes are destructive,

1:41 but storm surge often gets underestimated,

1:44 not just by the public, but policymakers and planners too.

1:48 The damage from high winds is visually dramatic.

1:51 We see footage of roofs ripped off and trees snapping like twigs.

1:55 But just a few feet of storm surge can cause even greater damage.

2:00 And waves amplify the destruction.

2:03 If you’ve spent time in coastal areas,

2:05 you’ve probably seen homes raised on stilts.

2:07 Since the early 2000s, this has become one of the most

2:11 common construction types in flood-prone coastal zones.

2:13 The concept is straightforward:

2:15 move the living space above the reach of storm surge.

2:18 If a hurricane hits, the lower area used for parking, storage,

2:22 or access might flood, but the critical parts of the building stay dry.

2:26 All the devastating power of the waves flows through and around

2:30 the stilts instead of slamming into walls and destroying the structure.

2:34 It turns out this idea is remarkably effective.

2:37 After Hurricane Ian,

2:38 FEMA found that flood insurance claims for elevated structures in Fort

2:42 Myers averaged about one-third the cost of claims for non-elevated buildings.

2:47 That’s a staggering difference in performance.

2:50 But zoom in, and things get more complicated.

2:53 On one hand, this is pretty obvious stuff.

2:56 You don’t need a massive wave laboratory to figure out

2:58 that elevated structures survive storm surge

3:01 much better than buildings at grade.

3:03 But if you look at footage from Hurricane Ian, it paints a more nuanced picture,

3:09 because some elevated buildings didn’t fare well at all.

3:12 They weren’t all high enough to avoid the surge.

3:14 And that gets to one of the most

3:17 difficult questions in the entire field of hurricane engineering:

3:21 how tall is tall enough?

3:23 Needless to say, it is expensive to lose your home in a storm.

3:27 The conundrum is that it’s also expensive to build

3:29 your home in such a way that it can withstand one.

3:32 If it were easy, every building in Fort

3:35 Myers would be a hundred feet above sea level.

3:37 But the reality is that elevating a structure adds significant upfront cost,

3:41 and the higher you go, the higher that expense climbs.

3:45 It’s not just a cost for homeowners

3:47 but also something that’s passed down to renters.

3:50 Shifting the actual housing upwards shifts

3:53 the affordability of housing downward for everyone.

3:56 And because major hurricanes are relatively rare events,

3:59 the return on that investment comes with a lot of uncertainty,

4:04 with benefits that are invisible most of the time.

4:07 That’s one of the biggest challenges for engineers and officials.

4:10 In theory, you can design a structure that withstands anything.

4:13 But in practice, no one’s building hurricane bunkers as homes.

4:17 Codes and policies have to balance safety with economic

4:21 viability and long-term risks with the upfront cost of resilience.

4:26 Local governments want robust, resilient development,

4:29 but they also need development to happen in the first place.

4:33 Overly strict codes can scare off builders or price out developers.

4:37 And while the National Flood Insurance Program might prefer fewer claims,

4:41 stricter floodplain regulations also come with tradeoffs:

4:45 reduced property tax revenue, limited housing supply,

4:48 and the burden of compliance placed on individuals.

4:52 These decisions might seem kind of trivial at the scale of a single structure,

4:55 but when you multiply them out along developed coastlines,

4:58 the implications of each extra foot of elevation are monumental.

5:02 So what you end up with is a delicate balancing act,

5:05 shaped by competing priorities, enormous uncertainty,

5:08 and billions of dollars on the line.

5:11 Changing building codes or policies requires

5:14 buy-in from a broad array of stakeholders,

5:17 and that kind of consensus demands reliable data.

5:20 But there’s one more thing that makes this even more complicated.

5:24 Of course, “stuff getting wet” is a problem with storm surge,

5:27 but it’s more than just typical flood damage

5:30 you’re dealing with when it comes to hurricanes.

5:32 In a sense, the surge is a rise in sea level itself,

5:36 and once your home is essentially IN the ocean,

5:39 that brings wave action into play.

5:41 Forces intensify.

5:42 Structural systems are tested in ways

5:45 that ordinary flood damage doesn’t account for.

5:48 You can see why this idea of elevating structures is

5:51 one of those engineering concepts that seems obvious on the surface,

5:55 but gets way more complicated when you start looking into the details.

5:59 And that’s why we’re here.

6:00 Computer models are limited in their capabilities.

6:03 And you can’t just call up an actual hurricane

6:05 to knock over a test structure (and even if you could,

6:08 it would probably violate the ethics rules).

6:10 So we go to the next best thing: the wave lab.

6:15 The OH Hinsdale Wave Research Laboratory is one

6:18 of the largest facilities of its kind in the world.

6:21 Since the 1970s, this lab has supported cutting-edge

6:25 research into coastal engineering challenges like sediment movement,

6:29 tsunami behavior, and wave-structure interactions.

6:33 It actually has two major test beds.

6:35 This is the Large Wave Flume.

6:37 It’s used for all kinds of hydraulic experiments related to waves,

6:41 coastal structures, and erosion.

6:42 It’s basically a super-sized version of the flume

6:45 I use in a lot of my garage demos.

6:47 It can do a lot, but it

6:49 has a limitation in that it’s inherently two-dimensional.

6:51 Flow can really only move in the direction of the flume.

6:55 That’s why the lab also has this: the Directional Wave Basin.

7:00 Think of it as a wave pool turned up to eleven.

7:04 This enormous tank uses dozens of piston-driven paddles,

7:07 each with independent control, to generate complex, multi-directional waves.

7:12 You can create a single tsunami-like pulse or dial in irregular

7:16 wave trains to match the chaotic sea states found in real hurricanes.

7:21 This facility is utilized in large-scale

7:23 research projects on wave hydrodynamics, floating structures,

7:26 and devices that harness wave energy to generate electricity.

7:31 But, of course, it can also test coastal structures, like these houses.

7:36 Dr.

7:36 Dan Cox is a Coastal Engineer and Civil Engineering Professor at Oregon State.

7:41 He explained to me why they chose the basin for this experiment.

7:45 “The nice thing about the basin is,

7:48 you can look at kind of a full 3-D picture, rather than just a slice.

7:54 And I think for this set of tests, we really wanted to do an entire house,

7:59 not just a wall, you know, a bit of the foundation.

8:02 And that’s why we chose the basin for this one.”

8:05 The research team has spent months building two incredibly detailed model homes,

8:10 each one a near-perfect one-third scale replica of a real coastal house.

8:15 Each foot is equivalent to three feet in real life.

8:19 And the only difference (besides color) between them is elevation.

8:22 The green model is a foot or 30 centimeters higher up than the orange one.

8:27 That corresponds to 3 feet in the real world or roughly one meter.

8:32 In every other way, both structures are identical.

8:35 They’ve got interior walls, windows, framing details, everything.

8:38 At this scale, that means I’m about the size of an 18-foot-tall

8:43 civil engineer… which is actually something I’ve had dreams about.

8:46 One-third scale is still just a model.

8:49 But this is not a toy experiment.

8:51 The researchers have carefully accounted for all the physics involved.

8:57 The wave periods and velocities have

8:59 been adjusted to simulate full-scale conditions,

9:01 and the structures have reduced stiffness

9:04 to reflect the relative rigidity of real-world buildings.

9:08 It’s all about maintaining dynamic similarity,

9:10 a fancy term for making sure the test results

9:14 actually mean something when translated back to full size.

9:17 And that’s a tough thing to do: “On the structure side,

9:21 it’s a lot more difficult to scale the structural behavior.

9:25 So, for example, when we’re doing computer simulations,

9:28 the simulations are primarily at scale-

9:31 trying to get that difference in shaking.

9:33 The forces can generally be scaled up as well,

9:36 so we kind of know what the forces are.

9:39 But I think the mode of failure- like how this structure

9:44 failed- I’m not sure so much as like a quantitative scaling.

9:49 It’s a little bit more like qualitatively,

9:52 this is what we would expect to happen under these conditions.”

9:57 The experimental design has the waves start small and build gradually,

10:00 both in height and frequency, simulating the approach of a storm.

10:05 The goal is to observe how both

10:07 buildings respond as conditions get worse and worse.

10:10 It’s mesmerizing to watch: the wave generators churn,

10:14 sending pulse after pulse across the basin.

10:17 Within seconds, the models are surrounded by rolling water,

10:20 with each wave slapping against walls,

10:23 flowing around supports, and rebounding off the basin walls and shoreline.

10:27 Even now, researchers at the lab are measuring the behavior of the structures.

10:35 If you look carefully,

10:36 you’ll notice targets for highly specialized cameras and lidar

10:39 to carefully monitor the behavior of each structure.

10:43 Sensors placed throughout the experiment are recording everything—wave height,

10:46 velocity, pressure on the structure, accelerations, and even internal motion.

10:51 The goal is to build a detailed,

10:54 physics-based understanding of how each building absorbs

10:57 and transfers energy from the storm surge.

11:00 And that data is incredibly valuable.

11:03 For one, this expensive and elaborate test is just two buildings.

11:06 And there are a lot more types of houses in the world than that.

11:11 So this data can be used to calibrate and validate computer models,

11:15 making it easier for engineers to get

11:17 reliable answers to questions without having

11:19 to build scale buildings and put them through huge model tests like this.

11:23 And some of those questions are big ones.

11:26 When you’re looking at options for large-scale flood infrastructure,

11:29 a major part of the process is estimating

11:32 the differences in damage and loss of life between alternatives.

11:36 Again, we can’t build infrastructure, call down a hurricane,

11:39 and test it out in real life, then revise accordingly.

11:43 Even engineers shouldn’t have THAT kind of power.

11:45 So we have to be able to make predictions about how any proposal will work out.

11:51 It’s educated guessing, essentially.

11:53 But the better we understand the connections

11:56 between all the variables (wave height,

11:58 surge level, building elevation, movement, and damage),

12:02 the more educated those guesses become.

12:04 “I would say the physical model is closer to the real world.

12:08 It's the best, in a numerical simulation,

12:10 it's kind of the best we think we can do.

12:14 But- And it always looks pretty, always looks really cool.

12:17 But there’s really- you have to verify it.

12:20 You really have to show that it’s correct, not just looks cool.

12:24 And I think when we get to the laboratory,

12:28 like we’re seeing during this test, like okay, it’s not as simple as we think.

12:32 So there’s a lot more complexity, I think,

12:35 inherent in a physical model.” That’s why even

12:39 though these tests seem pretty straightforward at first,

12:41 they can have a profound impact on how we allocate public funds,

12:46 regulate floodplains, and ultimately, keep people safe.

12:49 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.

12:56 Imagine changing the building code or floodplain

12:59 regulations without good data to back it up.

13:03 We necessarily make high-stakes decisions about how to manage

13:06 flooding in the face of equally enormous uncertainties.

13:09 So, you can see why information like this would give more confidence

13:14 to engineers and regulators to write

13:16 building codes and improve floodplain regulations,

13:19 knowing those decisions are grounded in truth.

13:22 But it’s not just about the data.

13:24 You might have noticed that these houses aren’t just bare minimum structures.

13:28 The team has added details like roofing, window frames,

13:31 and colorful paint jobs to make them look like real buildings,

13:35 even though they don’t really affect the final results.

13:38 That’s because this test is also a communication tool.

13:41 Most people aren’t going to read the academic papers

13:44 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

13:52 structures you’d want to live in when a hurricane comes.

13:55 And the more people who take storm surge seriously,

13:59 the better the outcomes we can expect when a big storm arrives.

14:03 Each set of waves is programmed into the machine

14:06 to simulate the variability of a storm,

14:08 with the upper limit of wave amplitude increasing from one set to the next.

14:13 After four sets of waves (delivered in about an hour),

14:16 they raise the level in the basin using

14:19 this massive bathtub faucet and repeat the process.

14:21 It was actually pretty surprising how well both

14:24 models were holding up for a while there.

14:26 It’s hard to communicate in a video just how awe-inspiring

14:29 it is when the directional wave basin starts really churning.

14:33 And eventually, a particularly violent wave comes crashing into the lower house,

14:38 and we see our first damage.

14:42 You can see the wall underneath the window give way,

14:45 and now waves start penetrating into the interior of the structure.

14:49 In a real house, this would already be catastrophic damage.

14:52 But of course, they don’t stop at the first sign of damage,

14:55 and the team keeps hammering the models with more intense waves.

14:59 Over the course of the experiment,

15:01 the sea conditions just keep getting worse and worse,

15:03 and the damage to the orange house does too.

15:07 More and more of the first story of the lower house is swept away.

15:12 Waves flow through the structure and knock out

15:14 portions of the wall on the beach side,

15:16 and everybody in the room fills with eager anticipation of a total failure.

15:21 And then, something I didn’t quite expect happened.

15:24 The model seemed to almost stabilize.

15:27 The walls of the front and back of the structure were so totally

15:30 obliterated that the first floor almost began

15:33 to act like another level of stilts!

15:35 Despite the first floor being utterly wrecked,

15:38 the second story remained more or less fine for quite a while,

15:42 even as the waves got stronger.

15:43 Dan told us about a test at half this scale (one

15:46 sixth of real life scale) that had shown similar progressive damage,

15:50 but that led to collapse much earlier on: “In the previous study,

15:55 we started to see the deterioration and then very quickly,

15:59 rapidly, the entire building destroyed and I thought,

16:02 okay, well we'll see that again at larger scale,

16:04 but we didn't.” That’s one of the cool

16:06 things about moving up in scale and realism:

16:09 you learn things that aren’t always expected.

16:11 If we had cameras on every structure during Hurricane Ian,

16:15 we likely would have seen similar results- damages

16:18 from storms rarely follow a linear, progressive trend.

16:21 It comes in fits and starts.

16:23 For a while, it seemed like it might be the end of the experiment,

16:28 since the stronger waves weren’t causing more damage.

16:30 “…It was a tough problem, and I thought I knew the answer,

16:34 and it turns out I didn’t.

16:36 Little bit tough to swallow, but it also kind of highlights to me,

16:39 like, okay this is a challenge.

16:40 This is a hard problem.

16:41 So for me, you know, I’m trying to put a positive spin on it,

16:45 but I feel like that’s a success right there.

16:48 To say hey, this is more complicated than we thought.” Of course,

16:52 everyone watching (including me) and those participating in the experiment

16:56 were hoping for that final blow that would knock

16:58 the whole thing over so they could get the full

17:01 range of data needed from safe to damaged to destroyed.

17:07 And eventually, the moment came.

17:12 The waves finally won, and the lower house collapsed.

17:16 "Holy moly!" What’s probably more interesting than

17:33 that is the condition of the other house.

17:36 Take a look at that.

17:38 Almost no damage whatsoever.

17:40 This building sat in the exact same conditions

17:43 as the other house and took almost no damage.

17:46 And in a way, that’s kind of remarkable.

17:48 Because there really wasn’t that big of a difference between the two.

17:52 I said it’s expensive to elevate a structure,

17:55 but the marginal cost between the green and orange models

17:59 is almost negligible compared to the overall value of the structures.

18:04 “In talking to people about flood risk,

18:06 you know, we talk about the 100-year, 500-year.

18:09 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.

18:19 And I think just trying to show people it doesn’t take much.

18:22 Like, there was not much of a difference

18:25 in elevation between those two buildings.

18:27 The one on the right is toast.

18:29 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...

18:37 take the other one out.” The researchers will be

18:39 studying the data from this experiment for years to come.

18:42 But the story's pretty clear.

18:44 Same surge, same waves.

18:46 A little difference in elevation can make a huge difference

18:50 to a structure when it comes to surviving a hurricane.

18:53 You might be watching these buildings get knocked about and thinking:

18:57 “We don’t need more resilient structures in the floodplain;

18:59 we just need them to not be there in the first place.” And in many ways,

19:04 you’d be totally right.

19:05 Often, the most economical way to reduce flood

19:08 damage is to avoid building in flood prone areas,

19:11 or if development has already happened, simply to buy out property,

19:15 tear it down, and leave the land empty as a buffer.

19:19 But where’s the line between flood-prone and not,

19:22 especially when it comes to rare events like hurricanes,

19:25 where the probabilities of occurring in a year

19:27 are in the range of 1-in-100 or 1-in-500?

19:30 And if there’s not a bright line between at-risk of flooding and not,

19:35 what’s appropriate for the fringe?

19:38 The truth is that there is no catch-all solution to flooding.

19:41 We need options to accommodate the vast

19:44 array of situations where development occurs,

19:47 whether those areas are flood-prone, flood-free,

19:49 or, most importantly, somewhere in the middle.

19:52 And not just options,

19:53 but also the data to determine which of them is truly the best path forward.

19:59 Engineering is a balancing act;

20:02 we need structures that are both strong and safe,

20:06 but also affordable, easy to occupy, and maybe even architecturally pleasing.

20:10 Using knowledge gained from tests like this helps us get

20:14 a clearer definition of the edges of the problem we’re solving.

20:18 Huge thanks to Dr.

20:19 Dan Cox and his team of researchers for inviting us to see this happen.

20:27 I love talking about the engineering of the built

20:30 world that often goes unseen like this test.

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