Tag Archive for: Clark County

Giving Thanks to the Women and Men of Harris County Flood Control

A reader who visited a trade show recently in Las Vegas sent me several links to news stories about flash flooding there. 1.24 inches of rain caused widespread flooding, killed at least two people, and resulted in dozens of high water rescues!

CBS Video posted on YouTube of Las Vegas Flooding

See also:

His comment: “Imagine if those types of videos were in Houston – for less than two inches of rainfall. You can’t, because it doesn’t happen.”

Why Houston Doesn’t Flood On Two Inches

While HCFCD employees take a lot of heat every time someone floods, we should remember that it takes far more rain for people to flood here. There are several reasons for that.

First, Harris County formed a flood control district in 1937. Clark County, Nevada (Las Vegas) didn’t start its until 1985. So, we had an almost 50-year head start on them.

But sadly, some fast-growing counties around Harris County STILL don’t have flood control districts! (We’ll save that discussion for the next legislative session.)

Second, our topography is different. Because Harris County is so flat, rainfall spreads out and starts soaking into the ground before flooding starts. Rainfall in Las Vegas is funneled by the rugged landscape. It picks up velocity, so it doesn’t have time to soak in. Concentrated rainfall turns into flash flooding. The Las Vegas Wash funnels a 1,879 square mile watershed toward a metro area of 2.29 million people.

From Flood Hazards and Flood Risk in Nevada’s Watersheds

I was almost killed by a flash flood in Tucson once. While hiking along a stream bed with friends in the desert, we saw rain in the distant mountains. They immediately suggested moving to higher ground. Minutes later, a wall of water 6-8 feet high came boiling down that stream bed!

Third, we build to different rainfall standards. Las Vegas averages 4.18 inches of rain each year. Harris County averages 51.84 inches.

In Harris County, new building codes and flood-mitigation standards currently use the 24-hour, 100-year amount shown in the Atlas-14 table below – 17.3 inches.

atlas 14 rainfall probabilities
Atlas-14 rainfall probabilities for northern Harris County now form the basis for building codes and flood-mitigation projects.

In other words, we build things to withstand more rain in a day than Las Vegas receives in FOUR YEARS.

That takes some talent. Especially when surrounding areas send ever-increasing amounts of floodwater downstream because of lack of comparable controls upstream. And that could be why flood control districts around the country try to recruit talented HCFCD employees.

Despite our occasional frustrations, we should never forget: They stand between us and disaster.

Posted by Bob Rehak on 8/13/2022

1810 Days since Hurricane Harvey

VR Video Shows What It’s Like From Driver’s Point of View to Get Swept Away in Flash Flood

Most people who die in floods die in their cars … after they drive into water. But how do you communicate the danger to people? It’s one thing to say, “Turn around; don’t drown.” It’s another altogether to get them to feel the risk and act on it. But this VR video (virtual reality) does an excellent job. The Clark County (Las Vegas, NV) Regional Flood Control District produced it. And it won first place in last year’s National Association of Flood and Stormwater Management Agencies (NAFSMA) Communication Awards.

Still frame from award-winning video. To see video, click here or on image.

Water Always Wins

They named their campaign “Water Always Wins” and produced a scary, virtual-reality video showing a car of teenagers returning from a day trip in the desert. As they get off the freeway near home, they approach a flooded intersection and decide to try to make it across. Their car becomes buoyant and loses traction. It floats down the road into deeper water. The floodwater starts to fill the interior of the vehicle. It loses power. The teens can’t get the windows down. Water pressure on the doors keeps them locked in the rising water. And pretty soon, the occupants run out of breathing space. (Spoiler alert: There is a rescue at the end.)

Made for the Desert, but Applies to Houston

The video realistically illustrates a worst case scenario (minus the rescue, of course). If you have a teenager learning to drive, this is highly recommended viewing. The video was produced for a desert audience, but the location could easily be Houston. I had a similar near-death experience on Little York when a bayou rose up over the road. I narrowly escaped. I must say that what I experienced bears a striking resemblance to what you will see in this video. And the water wasn’t even moving as fast as the water in this video.

Confronts Mortality Head On

Such videos have one problem though. They sometimes become so hard to watch, the audience rebels. Teenagers, especially, may try to make fun of it, because it confronts them with their own mortality. And most teenagers have an unshakeable belief in their own immortality. This video has received more than 5 million views. It also received thousands of snarky comments from teens.

Still, if I had teenagers in the house, I would make them watch it. Next time they come up to a flooded intersection, they may remember the video and forget their snarky comments.

To view the video, follow this link. The VR experience starts after a brief animated intro.

Posted by Bob Rehak on 2/22/2021

1273 Days since Hurricane Harvey