[00:00:22] Bridget Scanlon: I am pleased to welcome David Maidment to the podcast. David is a professor emeritus at the Cockrell School of Engineering at UT Austin, where he taught since 1981, and he also served as Director for the Center of Water in the Environment for 14 years. His research focuses on surface water hydrology and in particular applying GIS to hydrology.
He was elected to the National Academy of Engineering in 2016. So today David I hope we can focus primarily on your work related to flooding in Texas and throughout the US. Thanks for joining me.
[00:01:02] David Maidment: Well, thank you Bridget. I really appreciate the opportunity to have this conversation.
[00:01:06] Bridget Scanlon: So David there's a lot going on related to flooding in Texas. So over the past year and maybe past decade, and I think we were all pretty devastated by the 4th of July flooding in Kerrville with the death toll of about 137 people, including 25 children at campsites. I read the testimony that you gave and listened to the testimony you gave to the legislature in Kerrville at the end of July 31.
And also read the op-ed you published in the Dallas Morning News on August 12th which was titled, “Texas is a leader in flood research, but more coordination is needed”. So I was wondering if you could expand on these topics and share your thoughts on them.
[00:01:54] David Maidment: Yeah, so thank you, Bridget. I appreciate the opportunity. I have, to say that I was really shocked by the flood that happened in July in Kerrville and other places here in Texas. And I was shocked for two reasons.
- The first was just the awful tragedy that existed itself and we had a gas explosion in a school in New London, Texas in 1937 that killed 295 teachers and children. And I think after that, this is the largest disaster that's happened in terms of loss of life in our state. And we had some hurricanes before that, but this is an awful disaster, and it could have been prevented. I mean, with better information, these people didn't have to die.
- And the second thing that really concerned me was that a lot of information has been produced over the last 10 years, and I didn't see that it had been used. I think we've got a last mile problem here where we've got technology behind the scenes, but the people who need to know about that simply don't know about it.
And I was moved to write this op-ed, which appeared in the Dallas Morning News. I'm generally a person who's not like you, Bridget, who gets out in the public. I just stay in the corner and do my work. But I felt like at some point you've just got to say, now, wait a minute. There's a point where you've got to stand up and be counted here.
And so that's why I wrote the op-ed for the Dallas Morning News, and I was certainly privileged to be able to testify to the legislature in Kerrville.
[00:03:19] Bridget Scanlon: Right. and you mentioned, that flooding in that region isn't unanticipated. I mean, it's in flash flood alley. But also that a lot of the pieces are there, but the coordination was missing. Forecasting, monitoring, mapping and modeling, all of these different things.
And in the Dallas Morning News oped, I think you suggested maybe we should have a unified flood intelligence system to address that last mile issue.
[00:03:46] David Maidment: Yeah, that's what we need is a distributed system. And Bridget, we've got some pretty strong things at the back end. The federal government has done a lot over the last 10 years to improve real time flood information. But what we need is the sort of outposts at the county level and at the state level where that information's being transmitted through to the local folks and also, stronger connections with local data. I mean, the federal system can only do so much, and there is an inherent delay between the time when a federal forecast gets issued and the time that it applies of about two hours. In other words, it just takes time to absorb information and process at the national level.
And the tragedy of the flooding in Kerrville was that it just, it happened so fast that the warning didn't get there in time. And that two-hour lag time is really a bit too much when we have flash flooding in the Texas Hill country.
[00:04:40] Bridget Scanlon: Right. And David, you started a group with Planet Texas at the University of Texas and along with the Texas Water Development Board called FLOG, Flood Organizing Group in 2021. And I attended the meeting that you had after the flooding event in July 4th. And it was interesting to hear the various perspectives that were provided during that meeting from the Corp of Engineers, US Geological Survey, Water Development Board and consultants. And one of the things that interested me was somebody mentioned that in Norfolk, Virginia, people have something in their transportation app like Waze to warn people about flooding.
And that's now based on flood map nowcast and, shows impacts on roads and water crossings and things like that. And, maybe something like that would be helpful because when I talk to different people, they say you really have to give people, tell people how they should respond and give them actionable information.
What are your thoughts about that?
[00:05:45] David Maidment: Oh yeah. I mean that's been a motivation for what I've been doing for many years, Bridget, and absolutely we should have real time flood information in vehicles. I mean, there should, we have navigation systems now that warn us and redirect us when we've got congested traffic. I mean, why can't we have flood information that gets into the navigation systems that we use that redirects the vehicle, offers you an alternative path if there's a flood, and I think we will.
It's just a question of time and it's translating. It's another one of these last mile problems, right? You can have a central system that forecasts flood mapping and one of the really good parts of this picture is that as of September of this year, the National Weather Service will have completed real time flood inundation mapping for the whole country.
And, that's a huge lift it's taken to do that. It's the first time that flood mapping was ever completed for the whole United States. And this is in real time as well, which makes it even harder to do. So the backend is actually pretty strong. The question now is how to move that information from where it's being created, into the places where it's needed.
[00:06:54] Bridget Scanlon: Right, and during the FLOG meeting they mentioned the Waze app, and getting that information, and I think, the flooding that San Antonio experienced last summer, where people, 10 or 11 people were killed on the highway, system like that could really have helped them realize that they should not have been going in that direction.
[00:07:14] David Maidment: Yes, I looked into that pretty carefully and we've built a road elevation model for Texas that, measures the elevation of the road system on 470,000 miles of roads, including all the residential streets and the collector roads. And I checked in that particular instance that the place where the cars were washed off was on the access road for Loop 410.
And sure enough, our road elevation model showed there was a dip there at the place where the water came across the road. And that was done with the state's LIDAR data. There's about, in that area, 85,000 points, LIDAR points per mile. So we know really accurately now how high the elevation of the road system is.
And that's an important piece for being able to get flood security on the roads. I mean, up to that point, it had the elevation of the road system and the bridge system of the state had not been quantified. We only had the x and y, we didn't have the z. So part of the research that we've done at the University of Texas at Austin is to add a z value to all the road and bridge system of the state.
[00:08:17] Bridget Scanlon: Well, that's great. And since the July 4th flooding last summer there has been a lot of activity going on. Texas Tech has been working on developing an expanded meteorological network. Brian Hirth at Texas Tech University and Brian Ancell and a radar system expanded the soil moisture network and I think that was part of the Senate Bill 5 with about $24 million to Texas Tech.
You visited there recently. David, and what are your thoughts on this expanded network at Texas Tech?
[00:08:52] David Maidment: I'm impressed. Bridget, I mean, they've put a lot of energy into building an operational system for weather forecasting for other reasons. The work at Texas Tech is being done by the National Wind Institute there, so they've got a long history of working with meteorological phenomena and putting out measurement systems. So they've expanded the west Texas mesonet which is a network of weather stations into the Texas Hill country now with additional stations. And they're going to put in three new radars to densify rainfall measurement and also make a weather forecasting system that has one kilometer cells for the computation for Texas.
And instead of three kilometer cells, which are the standard and the National Weather Service showed that they have a densified weather forecasting system as well, which they move around the country when their severe storms, but it was not deployed in Texas during the July 4th flooding. And if it had been the center of the storm over the South fork of the Guadalupe River was calculated correctly with the densified model that the weather service had when they did it in retrospect, but it wasn't really run live. So that's an impressive effort and I admire the capacity of Texas Tech to build and operate an operational system.
They call it the Texas Weather Prediction and Measurement System, I think. And having, tried to build and operate technical systems at the university, I've deferred to commercial partners to do that because just maintaining things inside an academic environment, it's pretty hard to do.
[00:10:31] Bridget Scanlon: Right. We're not great at the operational aspects, are we? Well, I mean, you're relying a lot on students and everything who come and go and postdocs and PhD, so it's difficult, but we also spoke with them, Brian Hirth and Brian Ancell. In addition to the radar system and the 40 stations that they're proposing for the Hill Country.
And they will provide the data at one minute intervals up to five minutes. So this will really expand the information on the meteorological aspects of flooding. And then I think Brian Ancell is going to provide a hundred ensembles of models of what could happen, real time. and so, this should cover all of the different and give us a probabilistic view of what could happen during a flood event.
So I think that's extremely impressive with all the computing power that we have now and everything I think that would be very helpful.
[00:11:28] David Maidment: Yeah, the challenge for us is okay, so now we have a hundred rainfall scenarios. We have to convert that into a hundred flow scenarios and a hundred flood map scenarios, and we have to do that really fast. In other words if that can be done in five or six minutes, perhaps 10 at the outside, right?
So now we're talking about a hydrological calculation that normally takes a period of time, has to be a hundred times, and it has been done a hundred times in five or 10 minutes at most. And that's a huge challenge. I've decided that there's a new field emerging that I'm calling real time flood engineering.
Has to adapt itself to not simply being accurate, but to be accurate, reliable and timely. And those, the reliable and timely parts of that put you in a box. You don't have time to spend hours and hours ensuring that what you're doing is accurate. And you have to build it into a system that's always there, it cannot fall down.
You, can't have some, oh my gosh, now the operating system wasn't working. No, it's got to be completely reliable. And so that means we have to adapt a lot. And our state spent over a hundred million dollars on engineering scale, hydrology and hydraulic models as part of the base level engineering program that the Texas Water Development Board has operated and other projects as well.
Well over a hundred million dollars. But all of that technology is not designed to be executed at the speed that this particular application requires. So that means there's a big challenge here to translate the results of all that put it into forms that can be executed approximately what the more complicated model would provide, but can be executed in seconds, not in minutes or hours.
So that's a real challenge and I think a science challenge that we in the academic sector can contribute to.
[00:13:33] Bridget Scanlon: Right. and you mentioned David, that the National Weather Service has this warn on forecast system that didn't deploy for the Hill Country. And that would have really helped us, but now with this expanded meteorologic network Texas would be able to have that in Texas for any of these proposed floods.
[00:13:53] David Maidment: Yes. And what's happening also is that local communities have decided they need to have their own flood warning systems too. Like Kerrville itself is building its own flood warning system. So you've got a federal system, you have to some degree a state system now being built and local systems, all three operating.
So, and now we've got, oh, we want to have somebody in their vehicle gets notified. Well, okay, notified by whom from where, and how do you combine all that together so that citizens and the first response community can get the best information available at any particular location.
[00:14:27] Bridget Scanlon: Right, and, you highlight the trade-offs between accuracy, timeliness, and reliability. And so we might not get extremely accurate results, but we have to provide it in a timely manner and have it at the most reliable that we can get within that timeframe. So these are trade-offs we're going to have to manage in the future. I think.
[00:14:47] David Maidment: Another thing that's happening is that there's going to be a lot more gauging put in as a consequence of this flood. And that's part of what the Texas Water Development Board's funding is intended to support. And I think that a part of this real time flood engineering is a stronger reliance on real time data.
In other words, checking mathematics in it, but checking with real time observations and doing that quickly. In other words, the data assimilation, real time data assimilation is a really critical piece of this real time picture. And that we can't rely on sort of abstract science to think our way through things you have to acknowledge the potential for error and correct the forecast with real time data.
And that's going to be a more reliable result than trying to just do a gargantuan model.
[00:15:39] Bridget Scanlon: Right, and David, you have been heavily involved with flooding for over a decade, and when we chatted recently, you mentioned that one of the things that motivated you was the death of a Senior Deputy Jessica Hollis, Travis County Sheriff's Office, who lost her life at a low water crossing on September 18th, 2014.
And she was only 35 years old, had a family and everything, and she lived somewhere near where you were living. And so, then you got involved with the tech start and monitoring systems on bridges and stuff like that. Maybe you can expand on that a little bit. David.
[00:16:20] David Maidment: Yeah, so I was at that time just starting on the work that later led to the National Water Model here at the University of Texas. And I didn't know Jessica Hollis personally, but I heard the news of the tragedy of her death. And it was in Western Travis County, which is where I live. And so I thought to myself I need to go and see what happened here.
And in particular, if this model that we were then starting to create would the stream that washed her away be in the model? In other words, was her calamity forecastable. And I went out there and found the stream and I looked on the map of the data that we were working with. Sure enough, there it is.
It's called Bear Creek. And so, yeah, that meant that if we could have built a, or could have had available that forecasting model, that particular situation could have been anticipated. And she had a son and she was 35, as you mentioned. And at that time I had two daughters, 34 and 36 each with a son.
And her death affected me very greatly. And it still does. and I can't really explain why. I just can't, but it's, it gets me up in the morning. I just think, that son isn't going to have a mother for the rest of his life. And I had a cousin who lost his mother when she was young. She was 36 and she died of breast cancer. And he has never gotten over it, and even now, this is 60 years later, he's never gotten over that. And, it is easy to talk about so many people die and tragedies and floods and all that, but every death is a is a tragedy all by itself. And that particular one just struck me in a very personal way, and it still does.
And I recently reconnected with the Travis County Sheriff's Office and we are now working with them in particular to focus on how to get information into the deputy's vehicles. Two Travis County sheriff's vehicles were washed away in the July flooding. Fortunately, the officers got out, they rescued themselves, but the same thing nearly replicated itself in the July flooding and two first responders in other counties were killed.
And that's a big deal, not just somebody dying, but a first responder dying because they're putting their lives on the line when they go to work. The death of Jessica Hollis has always motivated me and it still does. And we are not there yet, which is, after she died in 2014.
Right, it's 2026. We're 12 years in, so, okay. Part of my motivation is by golly, what's the shortest path to fixing that problem and how can we get it done?
[00:18:58] Bridget Scanlon: Right, well, I mean, you have been working very closely with the Texas Department of Transportation building this bridge monitoring network to give you stage level height of the rivers and also the velocity. And that's an incredible program. David, maybe you want to describe that a little bit.
[00:19:17] David Maidment: Sure, so, after we developed the prototype of the National Water Model in 2015, I came back and said, we're densifying the forecasting here. All across the state, there's going to be 100,000 miles of roads and bridges that are forecast from the national or what later became the national water model.
How about we put in some more measurement systems? I mean, Texas has 25,000 span bridges over water. It's twice the number of the next state. And there's your measurement network. So they said, okay. And so we started off with a small project, but we started with this 20 radar gauges and these measure water level and also surface velocity.
And that means you can get an estimate of discharge right away. You don't have to wait for a couple of years to get a rating curve developed. Because if you've got a surface velocity, you can get a ratio of that to get the average velocity in the cross section. And if you survey the cross section, then you get the discharge right away as soon as the instrument gets put in.
And so, eventually we got another project and that number from 20 was expanded to 80 gauges, and that's the largest network of radar stream flow measurements in the country. And we had one of our gauges installed on the Guadalupe River at Comfort, which was downstream of Kerrville on during the July 4th flooding.
And there was just a remarkable signal that came out of that at nine o'clock in the morning. The velocity was two feet per second at 10 minutes after nine, it was 14 feet per second, and it was just boom. And the flash flood was coming and sent a velocity wave ahead of itself– a shockwave– and then after the water started rising.
But it was really interesting that the two things being measured. The velocity and the water surface elevation had a life of their own, but that was completely different. And when we use rating curves, what we do is we assume that the velocity and the level rise in sync with one another, which is true when the flow is rising and falling slowly.
But if the water's rising quickly, you've got a whole different pattern of behavior between the water level and the velocity. And that gauge is good for revealing that.
[00:21:28] Bridget Scanlon: And so, I mean there are a number of advantages to these gauges. David, I mean, we're accustomed to the US Geological Survey Buckingham Palace version of the gauges, the gold standards. But I mean, we also getting back to your trade-offs, between timely and reliable and distributed network.
So expanding the network with these gauges, which are not as expensive as the traditional USGS gauges, but also that velocity pulse, was about an hour ahead of the stage height increase of about 35 feet at Comfort. So it could have given you an early warning of the forthcoming flood.
And then of course all of the LIDAR data that we have now helps construct these detailed stream cross sections to improve this data. So I think you titled it Flood Assessment System for TxDOT (FAST)
[00:22:21] David Maidment: Yes, that's correct.
[00:22:21] Bridget Scanlon: Yeah.
[00:22:22] David Maidment: That's right. So that's a, that's an internal system for TxDOT that helps them to anticipate the flooding of roads and bridges. And the part of the reason that I started the Flog Flood Inundation Mapping group that you mentioned earlier, the flood inundation mapping subcommittee of the FLOG program, was to interact with the federal government, with the National Water Center in Alabama so that we would know what they're doing and they would know what we are doing.
And what has happened over the past 10 years is that a national system has developed with the flood mapping where Texas has more or less been the prototyping piece ahead of time. So you mentioned the road and bridge flooding work we've done with the National Weather Service now has its own internal road and bridge flooding system for the whole country.
So it's not just a question of, what happens here in Texas. It's a question of what happens all across the country. And I'm really proud about the fact that we've been able to serve as a prototyping system within the state for a national system that was being built in parallel.
[00:23:27] Bridget Scanlon: Yeah, and you've mentioned frequently this national water model, David, and you were a key driver of this way early on to provide water forecasts like weather forecast. Everybody's familiar with the weather forecast and get it in the news and, complain all the time when it's wrong and. But, so, this water forecasting and the prototyping you developed at UT it sort of reminds me of the mantra they have at UT, What happens here– What is the mantra? What happens here–
[00:23:55] David Maidment: What happens here changes the world, yeah.
[00:23:57] Bridget Scanlon: I was thinking that's what it was, but I wasn't positive. So maybe you can describe, how you were involved with the National Water Model from early on and what you guys did and and the iterative process that you went through to ultimately end up with what we have now in the National Water Model.
[00:24:16] David Maidment: So I first heard about this this National Water Center in 2014. I was actually, I was in going to Washington for another reason, and I went over to the National Weather Service to give a lecture and they said "Oh well, we're busy, we're building a national water center." And I said, "What?" I've never heard of this. Right. And the center's being built in Tuscaloosa, Alabama, and why Tuscaloosa it's the hometown of Senator Richard Shelby, who's a very powerful Republican senator. And they had a tornado there in 2011 that tore through Tuscaloosa. It killed about 50 people, including six at the campus of the University of Alabama.
And the senator said, look, we better do better than this. And the National Weather Service said, look, we've already got a storm center in Norman, Oklahoma. And so they proposed doing water instead, and that's why the center is in Alabama. Anyway, they had the opening meeting of that center and I thought, I have got to be there in person.
Well, they invited me to be a speaker and I thought, I've got to be there in person. I can't just sort of mail this in, with a virtual presentation. And so I went down to Tuscaloosa and they've got a, the building, it's a beautiful building, and somebody said at the meeting what's the footprint of this building and how many people does this hold?
And they said, well, 200. And they said, how many are you going to have a year from now? Somebody said, maybe 50. And there was kind of an embarrassed silence in the room, like, oops we've got this big building but we can't fill it up. So I thought to myself, well, you could regard that as a problem or you could regard that as an opportunity.
And so that night I wrote the Director of the National Water Center a long email and said, how about you bring in the academic community and we'll prototype a new national flood forecasting system atmosphere of the oceans, coast to coast, high spatial resolution near real time in one year. And we'll just blast it out and bring in students from around the country and from the University of Alabama and have what I called a hackathon at the time to research to improve the quality of this model. And I put at the end of this message, look, if you think this is too crazy, just put it in the garbage can and I'm not going to be personally insulted. But that's not what happened. They had all their management in Alabama and the Director put this message up on the big board and went through it and said, this is the kind of thing we can do now that we've got a national water center that we couldn't do before.
And about a week later, I got a thumbs up. Okay, go for it. So that set off a prototyping effort that we did here in Austin at the Texas Advanced Computing Center. And I have to say that the work of Dave Gochis shared at, NCAR and the WRF-Hydro system that he had developed there was really instrumental in what we had done and also of Cedric David, who was a PhD student of mine, who developed a routing model for the river network of the country.
We put those two things together here in Austin with GIS to convert weather information on square cells into hydrology information on catchments. And we succeeded. And by November we had a model that ran across the country, but it was really slow. And by February we had a model that ran across the country in 10 minutes, one calculation for the whole country coast to coast.
And just the routing part, not the service hydrology part, but just the river routing took 10 minutes for the whole country. It was the Muskingum method actually. And that was crucial. That set off a few waves in Washington. Okay, we started in July, by the following February, we had something that worked for the whole country. And we ran that in the summer of 2015 for three months, June, July, and August here at UT at the Texas Advanced Computing Center.
Continuously, we had forecasting coming from UCAR, the high-resolution rapid refresh forecast, and we ran like a prototype national water model forecasting system for three months so the students could work with the data at the first summer institute. And that summer Institute now has run annually ever since, and more than 250 graduate students have gone to Alabama and they spend seven weeks working on research projects to improve the quality of the National water model.
So, yeah, after the first summer institute, the model was taken back into to NCAR and the National Weather Service itself, and they started running it operationally in August of 2016. So that's, yeah, that's water forecast everywhere all the time, just like weather. And that's a transformative change.
When I was talking with this group in Alabama, I thought, I got the slide from the National Science Board and there's the definition of transformative research and what is transformative research. So the very first slide of that presentation was the definition from the National Science Board of what is transformative research.
And it leads to a paradigm change and all that fundamental shift in approach. And I put at the end can we move from evolutionary change to transformative change? And I put that as a question mark. But I think 10 years later you can look back and say, yep, that happened. that was a blast off point.
Kind of a moonshot point where hydrology became national in scope. We have always been a bottom up field in hydrology. We've always had our small watersheds and we've studied the heck out of them and weather there's always been a top down thing. Right. And what we succeeded in doing when building the national water model was showing that the two things could merge.
Could go together that the bottom up and top down could be connected with the bottom up. And you could do that at scale for the whole country and well, for the whole continental United States at that time. Later it's been extended to the Marianas Islands and Puerto Rico and Alaska and Hawaii and so on.
But yeah I'm– that's a big turning point for hydrology in this country. And it inspired a research program called the Cooperative Institute for Research to Operations in Hydrology, which is a substantial effort now. There's over a hundred faculty members involved in that research project.
And so it's a huge effort, the largest research project that we have in hydrology for the country by far actually.
[00:30:29] Bridget Scanlon: Yeah, it's amazing. And, David, when you suggested doing all of this, I mean, you really were putting your reputation on the line, I can imagine you must have had some sleepless nights, can I pull this off and, but I mean, you mentioned that academics can take those risks, but maybe organizations that may be more difficult for them, and so maybe that's identifying the role of academia in this process.
[00:30:51] David Maidment: Oh, it was, no, well it was scary, Bridget, I mean... I took a huge professional risk, right? I could have ended up looking like a real idiot. And, I remember it was May of '14, was when that first meeting happened. And in the summer I was in Washington meeting with the weather service people about how we were actually going to do this.
And I remember thinking, I'm walking across Niagara Falls on a tight rope and the water's rushing by underneath, and there is no safety net. I'm up here on the wire. Right? This was, it was a scary moment. And another thing that made it really hard was is how do you box in the problem? I mean, so now you've got a hundred things connected to a hundred things, right?
How do you deal, how do you deal with groundwater, for example, was one of the questions I worried about a lot. And eventually I reached the conclusion, you can't deal with everything, can we just put off groundwater for a while and we'll just deal with this surface flow problem. And, I divided the problem into five boxes, which was what I now call the geofabric, which is the GIS foundation.
Then the hydrology, then the hydraulics, and then the impact assessment on roads and bridges and other things. And then the services framework that's needed to transmit the information out of from where you produce it to where it's needed. And even that framework, which doesn't sound very complicated, took me five months to figure out.
And, but when I got to that point, I realized, okay, this, now I've just got my hydrology box or my hydraulics box or whatever. And it was at that time that I thought we have to translate flow into water depth or water surface elevation. And the sort of, the obvious way to do that is to use rating curves.
And I remember talking to a person from the US Geological Survey and saying. We're going to have rating curves for the whole country. And she just started laughing. She was laughing so hard, she almost fell over. I still remember exactly where we were when that happened. But now, yep, just rating curves across the whole country and nobody even questions it anymore. It's like, it's just baked into the the wallpaper. And you may say, and I remember thinking at the time, rating curves, surely we can do better than that. but the reality is that if you're going to do something in real time, you have to be simple.
You can't afford all the complications that doing things in a really precise way would require. And so that's how the National Flood Inundation mapping system works. It works on rating curves where you've got– just how the flow comes along and then, you know how deep it is, there's a connecting function there.
[00:33:29] Bridget Scanlon: Right, yeah, and you're right. I mean, traditionally we've been so caught up in having the most accurate results. And we really haven't been pushed possibly in the past for timely data and things like that. But now there's more demand for that. And I think the HAND program, height above nearest drainage approximation then to determine the flood depth and the flood extent. That was a very valuable for the flood inundation mapping. And of course, the increasing reliability of digital elevation models and all of that, and more information on stream, channel geometry, all of those things come together. So a lot of things are advancing, and you were able to take advantage of those and then develop this.
[00:34:12] David Maidment: Yeah, well it was, there's an interesting story behind that because after we finished the Summer Institute in 15, I was teaching a GIS and water resources class here jointly was David Tarboton at Utah State University. And what had become apparent was that in my original message to the National Weather Service, I had said, oh, we'll have forecasting inundation mapping, blah, blah, blah.
And I was sort of very effusive in my ambitions, but it turned out the mapping part was much harder than forecasting the flow, but the forecasting, the flow is a hydrology problem. And to a certain degree, I was confident that we could carry this off because we'd done a lot of work on it ahead of time.
And we started doing this flow routing on a network, on a large-scale network in 2006. I mean, it wasn't like in 2014 we were starting from scratch. But the mapping part was difficult because there was no precedent for, mapping hundreds of thousands of miles of rivers. And so I was talking with David about it, and there was an image in my mind.
I wrote a hydrology textbook in the 1980s with Ven Te Chow and Larry Mays. And in that there was a river channel represented as a stream tube and it had gravity forces and friction force and pressure force and all that. And I worried about that stream tube for about five years because we have continuity, momentum, and energy. Okay, we've got three principles, but we've only got two equations.
We have a continuity equation, we have a dynamic equation, right? So how did three principles get boiled down to two equations? That worried me. And finally I reached the conclusion that force through time is momentum and force through distance is work and energy. And so that's why if you've got a dynamic equation which deals with force, actually three principles converged to two.
But I spent a long time when I was young worrying about things like that, and that image of that stream tube just stuck in my mind. And then traditionally, we always did stream hydraulics with cross-section in the vertical. So I said, well, why can't we do it the other way? Why can't we go, along the stream itself rather than vertical?
And so if you have a stream tube and then you just fill it up a bit more and the water spreads out a little bit more, you've got a volume. And if you divide the volume by the length of the reach, then you've got a cross-sectional area. And if you've got the wetted surface of the channel and you divide that by the length, then you've got a wetted perimeter.
Okay, there we go. So now we've got area and where the perimeter, which are the two geometrical characteristics that we need for calculating Manning’s equation. If we can then have a resistance and a slope, okay, we've got what we need here to calculate a rating curve. And so that was the concept, right?
Just have a stream tube and it fills up progressively with depth. We increased the depth one foot at a time. Now look, this is an incredibly simplified model, but it is as simple as you can get because you're assuming uniform flow conditions, the depth is the same all along the reach and the discharge is the same all along the reach.
Well, we know that's not true, but by making that simplifying assumption, we were able to then compute a flood inundation map library by doing this, the slicing business up the stream, which is what the HAND nearest drainage method does. And do that for the whole country. And we produced by that mechanism a relative elevation model of the United States.
So the regular digital elevation model measures how high you are above the geodetic datum and the relative elevation measures every point in the landscape, how high it is above the stream to which its drainage flows, and we did that for the whole country. And Yan Liuat the University of Illinois was the one who actually did the computations.
And David Tarboton’s TauDEM system had a function in it that measured from the point in the landscape to the point in the stream, what's the vertical drop? He could do some other things too, but that was the only one we used. And Yan was the one, they had a GIS supercomputer at the University of Illinois and they had all the national elevation data set in one place.
And we had David Tarboton’s have the system parallelized and Yan Liu was able to do a mass computation for the whole country. And, in the end, he was able to analyze the whole continental United States in a single day. He calculated that function relative elevation of the country in a single day at the University of Illinois.
And so we, we showed the first version of that in 2016, and the national deployment of that system in real time by the National Weather Service, is going to be finished this year in September of 2026. So it's taken 10 years to translate the first example of a research prototype into a deployed system across the country.
[00:39:19] Bridget Scanlon: Yeah, it takes a long time, but it's great to see it happening and, you have worked with the Texas Water Development Board a lot and you mentioned, their, flood planning program and the base level engineering, and I guess that they purchased the Fathom data set for Texas based on the LIS flood and doing all of this data developing a floodplain quilt for the state.
So this is all extremely helpful, I think in advancing planning at the state level.
[00:39:47] David Maidment: Yeah, it's safe. So what happened with that was so when we were working on HAND I had a PhD student working on that, Xing Zheng And we had a paper at AGU in Washington there, the AGU annual meeting, I guess it was still held in Washington at that time– and maybe it was in San Francisco, I don't remember.
Anyway, it was at AGU and the next poster was a student of Paul Bates from Bristol. And so, Paul was there and I said, "Hey, Paul, why don't you come to Texas? I'll cover your expenses." And that was 2018 or something, before COVID, and so he came and gave a lecture about his work with the LIS flood.
And so some people from the Texas Water Development Board or Saul from the TxDOT actually came to hear that, and later he became the Director of flood science of the Texas Water Development Board, and that's how the connection was made with the Fathom and Bristol. And the LIS flood was used to fill in the gaps of flood risk information for the state where the FEMA process had not been applied.
And they produced the three meter seamless digital elevation model for Texas as a part of that, which was certainly very helpful. And we used that and we continue to use that for all of the work that we've done since then. So that was, that, particular effort, which was designed to support flood mitigation and, long-term flood planning rather than real time response was instrumental in helping our work in real time response because it knitted together all the elevation data into a single seamless model, which was really important.
[00:41:23] Bridget Scanlon: Right, and I guess Paul was elected to the National Academy of Engineering this year, so.
[00:41:28] David Maidment: He was, and he's a fellow of the Royal Society in England, now.
[00:41:32] Bridget Scanlon: Right, right. David, we talked a lot about operational stuff, and you spent some time in the State Operations Center for hurricane Harvey, and I guess maybe you had PTSD after that or?
[00:41:46] David Maidment: It was, that was a tough experience, Bridget, I say it's the 10 most pressured days of my life and the pressure on– And that was an enormous disaster, right? And I was working with the Texas Division of Emergency Management at that time on a research project. Actually, it was HAND, I mean, the thing that we did for HAND was funded by the Texas Division of Emergency Management.
And so I was there before the hurricane came ashore, and I was listening to the weather briefings and we were running a prototype of the national water model, then. Well, actually the first operational system was working and we also collected all the address points for Texas.
So every place where you can get emergency response services dispatch has a point. The emergency dispatchers know you go to that point and there's, we ran around the whole state, collected up all the address points. There's more than 9 million of them. And then we did a calculation and when the flood map happens, how many of these points get flooded?
And in that region around Houston, the calculator showed 238,000 points being flooded. And the next one, which was south of Austin, was going to have 20,000 points flooded. So I knew before the hurricane even got to the coast that Houston is going to get creamed. And I remember standing in the state operations center, it was seven o'clock on a Friday night, August the 25th, 2017.
I'll never forget it. And listening to the briefing about the hurricane force winds that were happening in Corpus Christi. And they had a map on the wall, and there's a little dot up on the right-hand side of that map that said Houston, which is 165 miles northeast of Corpus Christi. And I had this voice in my mind that said, Houston.
Houston. Houston. Yeah, I get it. I mean, the hurricane force winds and Corpus Christi were bad. And my wife and I had a condo there, which got essentially destroyed in the hurricane. So I was personally impacted by it. But the real tragedy was in Houston. I mean, that's where the real impact was. It was the rain that happened after the hurricane came to shore that caused all the flooding that devastated the Southeast Texas.
So that place [State Operations Center] is two floors underground. I mean it's, designed to survive any kind of a disaster. And there were hundreds of aircraft, thousands of vehicles, and tens of thousands of people being directed from that place. And the pressure was just absolutely enormous. and people would walk past you and they don't even recognize you're there.
they're not even conscious of the fact that you're present. They're so preoccupied with what they're doing –
[00:44:24] Bridget Scanlon: Yeah, and I think you mentioned, David, your experience there and the late Gordon Wells lived at the state operations center for many hurricanes and was a huge resource that you have data coming at you from all angles, and that the planning has to be done way ahead of time and you can't wait until the catastrophe to start planning.
And, so I guess that kind of got ingrained in your DNA then helping you figure out what needed to be done and to get things to an operational level.
[00:44:56] David Maidment: Yeah, what happened was, the first couple of days, we hardly knew anything. It was, we were almost completely in the dark, and so all these resources started pouring in from around the country to try to help Texas. And people would come and say, what do I do? I deploy? Do I deploy from what city? Do I deploy from Conroe?
Do I deploy in San Antonio and fly in? Where do I deploy from? I, didn't know what to say. I didn't, couldn't really help them.
People outside started creating flood maps of the Brazos River today, or the Trinity River tomorrow and all that. And, start things started to come in. And then after a, week or so, we were just absolutely overwhelmed. There was just so much information just pouring in fragments of this and that and so on.
It was just like a river, and we couldn't absorb it all. It just was impossible. So the intentions were good, but what it showed was that we needed one water map. In other words, we needed to be able to see across the whole landscape what is going on, more or less, as the people who are there can see it.
And we need that map like at seven o'clock at night, what's going to be the condition? Seven o'clock in the morning now seven o'clock in the morning. What will we see? Seven o'clock tonight? That's it. Those centers run on a 12 hours rhythm. It's a 12 hours on 12 hours old system. And and it was, that's what we need.
That's what we now have, but it was, didn't exist then in 2017. So, things really have improved significantly. But that experience during Harvey was certainly a– it was a transformative experience for me. And the irony of it was I was teaching class as well at the same time, right?
This is the beginning of the fall semester, right? August 25th, right, we're just starting the fall semester. So I'm down here in the bunker helping out with the flood information, and I climb up to the ground level and go down and teach my class. Then back down into the bunker again.
And at night I was checking the flow in the 10 largest rivers in Texas, starting with like the Nueces River out to the Sabine River. And I was comparing the flow that was being forecast with the historic high-level floods that had been observed in the past. I was making a report of that, just for my own purposes, for research purposes really.
And I was sitting there in the state operations center and next to me there was somebody from the Justice Department and he said, oh, what's that? And I said, I just showed him this report. And he said, oh, can I have that? And I said, oh, yeah, sure. So I just gave it to him and a couple of days later I met some police guy from Southeast Texas and he said, oh, you are the guy that produces these reports that are being used for deploying police in Southeast Texas.
What? But it shows that. Even fragmentary information prepared for purely academic purposes at the time, when there was no other information that served as a basis for action, decisions that were being made. And, that showed me that we really needed to be in a better shape than we were. I mean, for sure.
[00:47:56] Bridget Scanlon: Right, yeah, and since Kerrville last year, you have been engaging with the local communities there and with Shreiner University and their Center for Texas Institute for Hazard Risk and Readiness. And I really think that is so important and really admire you for making those connections and helping them connect with UT Austin and, various groups to help them.
And I think now they're talking about tabletop exercises and all sorts of things, so I think that would be extremely valuable.
[00:48:26] David Maidment: Yeah. I thought, we can't expect everyone to say, well, okay, UT Austin's got all the answers or something, right? I mean, it's better to say, here is a university, it's called Schreiner University. It's located in Kerrville. Kerrville is the center for the Texas Hill Country. People go there for medical treatment and other things.
It's a large community, has about 50,000 people in the county, other counties, for example, Real County, which is next to Kerr County, has 2,600 people. Yeah, so Kerrville's a leader in the Hill country and the university is there. And it has about 1400 students, and it's a teaching institution, but the students are drawn from this flood impacted area.
I mean, that's where the catchment area is for the university. So I thought if we can help them and they can then interact with their community, then that's a good way of being able to be supportive without trying to say, UT Austin has the answers and things like that. So I contacted the president of the university and said, if you wanted to respond or do something, then UT Austin will support you.
We'll help to make what you're doing technically credible. And, at first, he wasn't sure, well, really, and should we be doing this? Or, who are you really? And, but after a considerable period of time, eventually they created this institute that you mentioned the director of, which is coming shortly to visit Bureau of Economic Geology.
So, yeah, so I, I feel like there's situations like that, for example, where the Bureau and the Jackson School of Geosciences has a much stronger bench than we do in civil engineering and our little center here at Center for Water and the Environment. And so I hope that they can develop through time and that we can build a better science.
I'm dismayed by the fact that. The work that's going on now for building local flood warning systems is using hydrology models with hydrology that's been blessed by the engineering community, but is not modern in any sense of the word. And I would like to think that the knowledge that you and your colleagues at the bureau bring to, just what is the geology and the soil conditions and Geomorphology and all that in the Texas Hill country, and how does that impact what is really happening there and how can we use all this new measurement that's going to be made there to develop better scientific solutions that we can have a greater degree of confidence in?
For example, we are trying to do real time data assimilation on flows. We're trying to do real time data assimilation on soil moisture. Okay. Those are two different things. And you've got two knobs there. Maybe they are not even consistent with one another. And so I think there's a substantial contribution that we at UT and other academic institutions can make. Another thing that I have done is to contact the Texas Division of Emergency Management their training program and say, how do we get improved flood training for first responders in, make that an actively pursued subject.
And that is a collaborative effort with UT Arlington and UT San Antonio because the Texas Division of Emergency Management has academies for first responders in those in Fort Worth and in San Antonio. So it's not just, how do we do better science, but it's how do we do better science in a way that can be translated to the people who have to rescue people during floods?
[00:52:02] Bridget Scanlon: Right, yeah. And I know you officially retired from the university many years ago, but it seemed like you're going gangbusters and busier than ever. And think you mentioned that the last 10 years you've been more productive than your entire career. So, kudos to you for all of this effort and, one of your latest efforts is this book called Geowater.
[00:52:22] David Maidment: Oh yeah. Yeah, So we just finished it actually. Geowater, a Geographic Approach to Water Data and Forecasting.
[00:52:31] Bridget Scanlon: Congratulations. That's fantastic. I, don't think I have the energy to write a tweet, not to mind a book.
[00:52:39] David Maidment: Right, it was a lift. It was a lift. Bridget. But anyway, we got it done. So that's the main point.
[00:52:46] Bridget Scanlon: Right, right. And lastly, David I know you're originally from New Zealand and you're helping those folks with their flooding issues. And. I was talking to them recently about drought issues and they said it's very difficult to work in drought when you're subjected to floods at the moment.
[00:53:01] David Maidment: Yes, well, it's– flooding has become an issue in New Zealand to a greater degree than they, they had experienced it before, especially in urban areas. So 80% of New Zealanders live in urban areas now, and one third of the population of New Zealand lives in Auckland in one city. So that's a higher concentration in one place than any, New York or London is, for example, the new Auckland is a higher proportion of the population of New Zealand in one place. And they had a bad flood or two floods actually in 2023. And a lot of houses were washed away. And they had to spend nearly a billion dollars on New Zealand dollars and buying people out. That's a huge cost for a small country. And other places were hurt even worse, although they were in rural areas was the impact wasn't as great as in Auckland.
So now that's set off a whole national effort for flood mapping and flood modeling and all that type of thing. And yeah, it's become a real issue. And as you said, there was another heavy rain and flooding just last week in Wellington, actually the capital of New Zealand. So, no but, it's, you start to see that, climate change is starting to have some impacts there. they become, they're starting to talk about tropical cyclones now impact in New Zealand, and I remember that when I was young. That in other words, that the atmospheric activities strengthened enough that these circular motions that are coming out of the tropics get down as far as New Zealand now.
Okay, that's an important piece of information. And yeah, they become much more conscious of it. And I'm trying to help them a bit.
[00:54:45] Bridget Scanlon: Right. Well, that's great when you can help your home country and thank you so much David. People often say, oh, I thought David Maidment was retired, and I say, what?
[00:54:55] David Maidment: My wife says I've failed retirement.
[00:54:57] Bridget Scanlon: Yes, I think you definitely have. So our guest today is David Maidment. He's professor emeritus at the Cocker School of Engineering at Duty Austin.
And, I really appreciate all you are doing for flooding and communicating flooding and all of that and improving flood or risk management in Texas. So keep it up David, and I hope you'll be doing it for the next 20 or 30 years.
[00:55:20] David Maidment: Well thank you, Bridget, I appreciate the opportunity to chat.
