The damage and destruction caused by Hurricane Matthew this month has got flooding on my
mind.
Water is one our most basic needs, but it also can be our worst enemy.
You may know that managing water is one of the most important aspects of civil engineering,
so today we’re talking about hydraulic structures.
I’m Grady and this is "What’s that Infrastructure?", where we divulge and discover the manmade
world around us.
Vincent sent me this awesome photo from his exchange term in Korea.
Those blocks you see in the foreground are called tetrapods.
They are specially engineered to interlock with each other to armor shorelines against
waves.
They dissipate the wave energy easily without becoming dislodged.
And speaking of breakwaters, I was in Port Aransas, Texas in September and took a walk
out on the jetty which forms the south side of Aransas Pass.
This is a popular channel used by cargo ships entering and exiting the intracoastal waterway,
which is a nearly 5,000 kilometer-long shipping channel that runs along the southern and eastern
United States.
These jetties were built by the U.S. Army Corps of Engineers using massive blocks of
granite quarried from the Texas Hill Country.
They are a popular fishing spot, but they also serve a more important purpose: to break
the waves and slow down the erosion of the barrier islands so the channel stays open
for shipping traffic.
Here’s another canal: Joachim took these photos on a ferry to Norderney, Germany.
He said the tides get so low that they had to dredge a channel almost all the way to
the island.
And while we’re talking about ships, Johannes sent in these photos of a cantilevered pole
hanging off a bridge in Belgium.
At the end is a funny shaped object.
This is a radar reflector designed to warn ships of an upcoming hazard.
The unique design is called a corner reflector, a type of retroreflector, which returns radar
waves back toward the source no matter which direction they came from.
Lydia sent in these photos from Elm Grove, Wisconsin where crews are reconstructing a
drainage culvert under a street.
Lydia said that the city center in Elm Grove is built on top of an actively flowing stream.
This is actually an extremely common practice in urbanized areas.
Small streams get buried in tunnels and culverts to make room for the rest of the manmade environment.
I don’t know the details of this project, but it looks like it might be part of the
growing movement in Urban Design to bring streams and rivers back aboveground, also
known as daylighting or deculverting.
Obviously, this isn’t feasible everywhere, but it’s good that we’re starting to recognize
the fact that streams serve a more important purpose in our communities than just to carry
rainwater away.
And speaking of urban drainage, David sent in this photo of a storm drain manhole.
Notice the round sticker.
If a storm drain goes straight into a waterway rather than to a treatment plant, they’ll
often have a marker as a reminder.
If you dump something into a drain like this, you might as well have dumped it straight
into a stream, so please always dispose of your waste correctly.
Peter sent me these photos of a river in Munich.
There’s a dam or spillway here that creates a hydraulic jump, and people use the standing
wave to surf on.
A hydraulic jump is a specific phenomenon that happens when fast moving water transitions
into a slower moving flow.
Someday I’d like to build a demonstration and do a video all about hydraulic jumps.
Here’s a few more photos from Karl Jansen’s blog both in Ann Arbor, Michigan: a small
weir with a bridge, and a spillway making releases through a radial lift gate, also
known as a tainter gate.
Richard sent me this awesome photo of a weir on the River Avon in Bath, England.
This structure is probably designed to hold the river to a constant level, since it is
an amenity in town.
But when flows increase, we’d prefer if the river didn’t rise too much accordingly.
Flow over a weir is a function of the weir length and the height of the water over the
crest.
So if you want to let more flow through without increasing the depth of water, you have to
increase the length.
Instead of widening the channel, engineers sometimes just bend the weir to get more length
into the same area.
In fact, engineers have found some very creative ways of cramming more and more weir length
into a small area, including the piano key weir and the labyrinth weir.
Thanks again to everyone who sent in photos.
I never expected that so many people would be so interested in videos about infrastructure,
and it is really encouraging to receive so many enthusiastic emails.
If you’ve got a picture you’d like to share, send it in to Whats.That.Infrastructure@gmail.com.
Make sure you mention that it’s okay for me to use in a video, and include your mailing
address.
Because if I use your photo in a video, I’ll send you a Practical Engineering sticker.
And by the way, I now have T-Shirts available on my website, and I’m really happy with
how they came out.
I think they look great.
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As always, thank you for watching, and let me know what you think.