- If you look at this map of deadly flash flooding reports, there's a clear bullseye in Texas, and in fact, it focuses on just one river basin.

We wanted to know what's so different about this river, because this river is the deadliest river in the US.

You already know the Guadalupe River because on July 4th in 2025, it catastrophically flooded, killing at least 135 people, including 27 at a girl's summer camp.

And what makes this tragedy so haunting is how preventable it feels.

But it isn't just this flood.

For as long as we've kept records, this river has been uniquely dangerous.

But why?

Well, we went to Texas Hill country to find out, and honestly, we started to get uneasy before we even got there.

But when we finally reached the river, it didn't look dangerous at all.

So I wanted to know, how can a place this calm be so deadly?

Especially when safety was often just a few hundred feet away.

- She was like, I can't get out.

It's already in the house.

Water had never been in the house.

When she told me that, I'm like, holy crap, this one's a little different.

I'm like, get out.

- And most importantly, can we stop this from happening again?

- 4, 3, 2, 1.

There are preventable tragedies that are happening.

We're gonna stop flood deaths in Texas.

That is our goal.

- On our way to the headwaters, we passed HTR RV Park where dozens of people were washed away.

Then Camp Mystic, where 27 girls and counselors died.

We were driving along this gentle winding river, a place where people come to relax, swim, camp, and escape the nearby cities for the cooler, quieter Texas Hill country.

Every local we talked to knew the river was dangerous, but most didn't think it was more dangerous than any other rivers in the region.

We met one camp owner who spent decades on the Guadalupe, and we asked whether he saw this river as especially hazardous.

- I don't think so.

I can't imagine how it, I mean, we, there's, you have to be aware of your own surroundings and where you are and stuff.

And if you're next to a river in the big hills, you better pay attention.

- But storms often hit at night dumping up to 18 inches within hours like the 2025 flood.

And when the water rises that fast while you're asleep, there's almost no time to react.

- The wind like you couldn't see.

The intensity, the darkness of the night, you know, the lightning storm, the rain's coming sideways.

My decision was that if I go out there right now, is gonna be dangerous.

- The Guadalupe River is in a part of Texas, known as flash flood alley stretching from Dallas to the US Mexico border.

Flash floods are the most dangerous type of inland flood event, and they're common on all of the rivers in this corridor.

Water can rise extremely fast here.

And on the morning of July 4th, there were reports of the Guadalupe rising 30 feet.

The reason so much flooding happens at night here is a strange combination of flash, flood alley's meteorology and topography.

- This just happens to be the region where all of these things converge and they all synergize, and then they start creating this weather event.

- The Gulf of Mexico is exceptionally warm compared to the open ocean at the same latitude, which speeds up evaporation, loading the air with moisture.

But air over the great plains gets even warmer as it's heated by the sun.

So it rises up towards the Rocky Mountains creating a low pressure area that pulls Gulf Air inland.

This south to north air flow is like a jet and often strengthens overnight.

So storms building during the day can get a fresh surge of warm, moist air while people are asleep.

And that shows up in the record of deadly flooding.

But it takes more than just a surge of moisture to create flash flood alley.

As the air moves over Texas, it runs into two more key ingredients.

First, it hits a band of hills called the Balcones Escarpment, which helps force air upward.

It also encounters pollution in nearby cities like Austin and San Antonio.

Those extra aerosol particles give water vapor more surfaces to condense onto.

So as the air rises and cools, that moisture begins to condense around the tiny particles in the atmosphere, helping storms form.

- And so you create this zone of convergence where the winds and the moisture can start coming together.

And think about it like you have this big sponge which is starting to get squeezed as you come towards Texas and you start getting this rain out.

- And what makes this setup particularly dangerous is that weather fronts tend to stall right over flash flood alley and fed by a steady stream of moisture from the Gulf.

They just keep dumping rain in the same place.

And in the Guadalupe, that rain lands on shallow soil, which absorbs very little of the runoff - Combination of these essentially impermeable canyon rivers that can accumulate water, the landscape that can shed the water really, really quickly.

And can't absorb water at the rate that rain is arriving.

- This region is full of steep valleys and limestone, leaving it vulnerable when rain inevitably falls because the water has no place to go.

But this is true along all the rivers in flash flood alleys.

So why is the Guadalupe so much more dangerous than its neighbors?

The nearby Colorado, not to be confused with THE Colorado is bigger and wider than the Guadalupe.

Plus, that river has more flood controls, more monitoring and warning systems, making it safer for residents and visitors.

So when a storm hits, it often rises slower with more warning.

The San Antonio River can still flood fast, but it doesn't get as large as the Guadalupe until it's outside the steepest parts of Hill country.

So it typically takes a larger rain event to create the same kind of sudden, catastrophic surge.

The Nueces River flows over an aquifer, which allows water to drain into porous rock, reducing the risk of flooding.

Flooding can happen on any of these rivers, but the Guadalupe is especially dangerous because it combines several worst case features at once.

Fast runoff, limited absorption, and a channel narrow enough to concentrate that water quickly, all causing the Guadalupe to rise with extraordinary speed.

But these same characteristics can also be found in places like the slot canyons of Utah, which are even steeper and more concentrated.

So while the meteorology and geology help explain the Guadalupe's extreme tendency to flash flood, they still don't fully explain why it's been so deadly.

The Guadalupe is situated between Austin and San Antonio, two major Texan cities, and it attracts urban residents because it is cooler than the cities and has access to nature.

So there are a lot of out- of-towners in a remote, unfamiliar area.

- There are areas that you can be in, and I personally have been out in those areas of the hill country where you can have zero cell phone service.

- So that means sometimes getting a text is difficult, especially when one isn't sent.

In the United States, emergency warning texts are most commonly sent out by the emergency management coordinator.

- In the bulk of our counties, it is a full-time person, but in a rural county, it might be someone who's doing that part-time, or it might be a couple of people who share that job and responsibility.

- And on July 3rd, that person in Kerr County was sick, so he missed the emergency management briefings and unfortunately didn't wake up until the next morning.

And that was after a summer camp and RV park were washed away.

The National Weather Service did send out an alert, but locally nothing went out.

Along the Guadalupe, there are two neighboring RV parks, Blue Oaks, and HTR Texas Hill Country.

HTR is owned by a Boston based company, and Blue Oaks is local.

The host at Blue Oaks were from the area while the HTR hosts were from out of town.

On July 4th at 4:45 AM the fire department called the hosts of HTR to tell them to evacuate.

A minute later, they text the guests and residents of the RV park, got in their car and honked an SOS signal to alert them.

Just two minutes later, emergency responders watched an RV swept away by powerful flood water, hit a tree and split in half.

Right next door at Blue Oaks, local hosts didn't receive a text, but they did wake up when the flashing lights of the first responder vehicles came through their window.

They sprang out of bed and went door to door alerting residents, which is the most effective kind of emergency warning possible.

37 people died at HTR and four people died at Blue Oaks.

During a flood, timing is critical, and receiving a timely warning could mean the difference between life and death.

But the challenge isn't just getting out a warning.

It's making sure that that warning is clear, trusted, and impossible to ignore.

The hosts at HTR tried to warn the residents, but the warning wasn't clear and it was issued far too late for people to evacuate.

So how do we create a warning system that does work?

- People vary.

People are different.

They have different technologies.

They use their technologies in different ways.

Some people don't use technologies.

So the key to devising warning systems is to have it be multi-layered.

- Research shows the most effective warnings share three characteristics.

First, they're timely, reaching people quickly, giving them enough time to act.

Second, they're accurate, coming from trusted channels with information people know they can rely on.

And third, they're specific telling people exactly what the danger is, what to do, and where to go.

And then, like Keri said, they need to be layered.

This is because no single alert system is enough.

Experts say the key is to create a tree of overlapping communication channels like sirens, texts, and local neighborhood networks to increase awareness as a result of the 2025 tragedy along the Guadalupe that's already happening here in Kerr County.

This is River Sentry, a group of parents whose kids go to summer camps along the river, they're out placing towers along critical points of the Guadalupe River to detect rising water levels.

- The idea is that we place this tower in such a point that if water gets to this area, that it's too dangerous for people to be sleeping in that building anymore.

So we set off an alarm that will wake up everybody in that building and shine lights and shine up the hill to their evacuation point.

Two switches, two speakers, two lights, two ways of actually setting the whole thing off because we believe in redundancy.

- But learning that you need to evacuate just minutes before water might reach you is an absolute last resort.

And currently most warning systems come with no time to spare.

But what if they didn't have to?

During the recent LA Fires, which was the costliest disaster in the world in 2025, many civilians began downloading Watch Duty, which is an app that helps track fire conditions and evacuation zones in real time.

- It's manned by 300 something volunteers now.

About 50 or so paid staff who are disseminating that information through our app.

And so push notifications are sent to you on your phone.

- So with creative layered warning systems dramatically reducing flood deaths feels like a real possibility.