Liz Lewis, Newcastle University
To avoid catastrophic flooding, planners also need to know where it is likely to occur. To get this glimpse into the future, researchers like New Castle University hydrologist Liz Lewis use physical and computer model simulations. Sam Mahaffey went to see their newest piece of kit, an augmented reality sandpit, but first took a look around the facility.
Sam - Iím meeting Liz in the Novak Hydraulics Lab at Newcastle University. Itís a long, high-ceilinged room full of pipes, pumps, and huge tanks of water running from one end to the other. The noise you can hear is the sound of water gushing into a big open top channel right in the middle of the room. I asked Liz why itís so difficult to predict where floods are going to hit?
Liz - In some ways itís very easy because we know how water flows Ė water flows downhill and it pools when it canít get out, but there are lots of other compounding factors such as, the drains might be blocked and the ground's already wet. Somewhere might have flood defences in place already but they might not have been opened or shut at the right time and thereís a big human element of it. So it might happen in the night when roads getting flooded isnít so bad, but it might happen at rush hour which means you get lots of traffic jams so knowing where the waterís going to go is one thing, but its knowing how thatís going to affect our transport networks and our distribution networks.
Sam - How do scientists and engineers do this?
Liz - There are lots of things to think about and we do it with models. We have physical models like you can hear in the background, and we also have computer models which lets us run thousands of simulations of something happening and have a look at a whole range of outputs.
Sam - When I think of a model, I think of what Iím looking at right now. Which is this sort of scaled down river with water flowing through it; there is sand and gravel thatís like the river bed. How useful are these kinds of physical models?
Liz - These models are very useful, but we probably donít use them like you would think, so we donít build a physical model city. Instead what weíve got here is kind of a segment of a river bed and we use it for understanding how water flows. We look at how the water will move the sand and the gravel around, so looking at sediment transport. So we use it more to understand the processes which we can then build into our computational models.
Sam - These computational models sound really complicated but Liz promised to show me something that would explain it all and it gave us chance to get away from the noisy labÖ Iím in a dimly lit room but in front of me is a big box of sand and projected onto the sand is a map with contours and some little Lego pieces in the corner Ė donít know what weíre going to do with those. Liz, what am I looking at here?
Liz - So this is the departmentís augmented reality sandbox. What weíve got set up here is a kind of a metre square sandbox, full of sand and above it weíve got a projector and we also have an X-Box Connect, which is a 3D camera, so that can sense the surface of the sand. And so what that does is the camera senses the surface of the sand, that feeds down into the computer thatís at the bottom and that projects back on to it these contours, which is the topography, which the model uses to figure where to route the water.
Sam - What does this sand correspond to?
Liz - So, what weíre doing with the sand is basically building hills and a valley, so we can make a nice flat catchment like youíd find in Cambridge on the Fens, or we can build a really steep sided catchment like youíd find in Scotland and we can use that to demonstrate how waterís going to flow in these different environments. Shall we have a go?
Sam - Yes, lets.
Liz - What weíre going to do now is build some mountains.
Sam - Okay. So Liz is gouging out a big valley into the sand.
Liz - The map thatís projected onto the surface of the sand has changed completely now the contours are in a completely different place.
Sam - You can kind of see that itís looking like some hills now.
Liz - At the bottom of this valley and where the river widens out, weíve got this kind of flood plain now Ė so a of flat bit, and this is historically where towns and villages were built along next to a river. So what we are going to do is put our lego houses and build a mini city at the bottom of this valley to see what happens when different amounts of rain occur and to see where itís going to get flooded.
Sam - So this is what the lego's for. Weíre going to build a model village. Okay, so now weíve got our topography and weíve got a little village at the bottom. Please can we make it rain..
Liz - Yes, so we make it rain by holding our hands above the surface and, again, the 3D camera is sensing that my handís there and so what it does is it simulates water directly underneath where my hand is. So Iíve put it over the top of the catchment - so this is kind of at the very top of the valley where itís steepest, and we can see that this digital simulated water is flowing really quickly down the sides, and really quickly down the river, and the waterís swooshing up the sides and completely devastating the little lego town that we built.
Sam - It looks like an aerial view of what you might see during a flood. As you hover your hand over, rainfall is collecting on the ground, just flowing downhill straight towards our lego houses. Behind this sandbox presumably thereís lots of computery things going on thatís working out whatís downhill and what will affect where the water goes?
Liz - Thatís right. So, there is a computational model behind this which is using proper hydraulic equations to route the water. So that basically means it knows the shape and size of the channel and it knows how much water has been simulated.
Sam - What kind of uses do you have for these computer models?
Liz - There are lots of reasons that we build models. Firstly to understand where might flood; to understand how big the flood is going to be; to understand what itís likely to impact. So is it going to flood near our hospital or is it going to flood near our supermarket. And then lastly, the really important thing is what can we do to prevent flooding. So what we can do now in this sample box; we can put a little lego wall in here, and we can empty all the water out and then we can create another storm and this time, when the water flows down the sides and it gets towards the city, it doesnít enter the city because weíve built this big flood defence.