The trouble with a lot of real world experiments
is that you can't have a control group.
If you're researching, say, how riverbanks are affected by erosion,
then either you have to observe the erosion happening
in the wild, with lots of messy variables like weather and climate and wildlife,
or you have to rely on tiny scale models or computer simulations.
You can't take an actual river, let it erode its banks for a while,
then stop the water,
rebuild everything, and just run it again with one thing changed.
Unless you build your own river, which is exactly what
the University of Sherbrooke in Canada has done.
Will you start the pumps, please!
- So I’ve done a lot of studies in nature, on real rivers.
You do get excellent information,
but you can't pick out specific variables and play with them.
We built this with the idea that we can study sediment transport
on a scale that represents close to a small river or creek.
The water starts in the reservoir.
The pumps pump from the reservoir, and then it discharges into the
approach channel, which is made to be very large,
so that we diminish any turbulence
that might be brought in there by the pumps.
After that, we have a weir, and then it arrives in the river and goes down.
And that's where we do our experiments.
And the river falls over an overflow into a sediment trap.
From the sediment trap, it goes back into the reservoir.
It’s a recirculating system.
Probably takes 2 or 3 minutes for the water to recirculate.
It is all repeatable.
We can adjust the pumps for a certain level,
have that one day, come back a week later
and have the same flow coming through the system.
We have two 70kW pumps.
At the moment, we have 800 liters per second, and we have room for another pump.
- Okay, compared to the Mississippi, this doesn't look that big.
But here's how powerful it is.
We anchored down a GoPro camera to get those shots
near the weir, and the water just blasted it away.
One of the team here had to wade into save it
before it got washed into the basin, never to be recovered.
“Thank you, Basim!”
So it does a very good job of representing small rivers.
And the processes that happen here are much more related to,
say, a river than small laboratories.
Obviously, in larger rivers you have more scales of turbulence.
But those scales, they should be similar in our size.
- I've seen a small scale model years ago, when I visited the Bay Model in California.
It's a 1:1000 scale copy of the San Francisco Bay,
which means it's the size of a football field.
But the 1960s engineers who built it had to stick a load of copper strips
into the base to make the water behave like it would at full scale.
By all accounts, they did really well, particularly for before computers, but
it's no comparison to having a model that is closer to real-world size.
- This summer we were looking at erosion induced by a bank,
an artificial bar we put in.
Throughout the world there's a problem in understanding
how much erosion is going to happen for a given flood.
So as an engineer, you want to be able to run a model
that will tell you how much bank erosion you'll have in the future.
We would also, next year, like to start looking at ice cover
and the effect of ice on things like bank erosion and floods.
Because ice related flooding is a huge problem.
Having a river where you can model ice would be quite unique.
- A lot of this work can be done with computer simulations now,
but the code for those simulations still has to be validated and checked
somewhere like this.
And sometimes the researchers here
are working on things that there is no computer model for, which surprised me.
I assumed that simulating water was pretty much a solved problem, but no.
There are still new technologies that need to be tested,
and one of them is up there getting the aerial shots for this video.
- To model this river with a particle interaction model
would take many days, months, years to run.
We have projects involving large scale particle image velicometry.
This is a new technique with a drone, you'll take the water surface
and then you can have a velocity, which you can then relate to a discharge:
how much water is moving through a section of river per second.
And having a method of measuring discharge without actually going into the river is
very useful, because it's very difficult to go into these rivers at high flows.
It’s very dangerous, in fact.
The water surface can be affected just by the general wind,
but then that can influence or bias the results of the flow
we actually want to measure.
- And sure, by the grand scales of waterparks and white water rafting centres,
this isn't the biggest artificial river in the world,
but it is one that's built for research.
Even if that does mean that the team here wouldn't let me
bring my own inflatable tube to ride down it.
Nobody has ever been down on an inflatable tube.
It's an interesting idea, but I don't think I would advise it.
I don't think I would advise it!