Lesson video

Hello, my name's Ms. Gilyeat and I'm going to be your geography teacher for today.

In today's lesson, we are going to be looking at river management.

Let's get started.

So our lesson outcome for today is that you can describe different types of river management and explain the advantages and disadvantages of different approaches.

We have got five key words for today's lesson.

The first one is hard engineering, which is the building of fixed structures to help prevent river flooding.

Soft engineering is working with nature to reduce the risk of river flooding.

Costs and benefits are the negative aspects of doing something and the good reasons for doing it.

Mitigate is take action to make the effects of something less severe.

And flood risk is the probability of a flood event occurring and its potential impact.

We've got two learning cycles, so we're gonna think about some of the hard engineering river management strategies and then we're gonna move on to soft engineering.

So let's get going with learning cycle one.

Now, flooding can cause short and long-term social, environmental, and economic effects.

Looking at that photograph, what effects of flooding can you see? Might be worth just having a quick chat with your partner.

Okay, we can see there that there's a man walking in the flood water.

Well, first of all, that might actually not be that safe.

We can also see there are a couple of shops there that have become underwater, okay, or flooded.

That's gonna have a really bad impact on the businesses that own them.

Now, flood management aims to prevent rivers from flooding and mitigate the effects.

There are two main approaches to river flood management, hard engineering and soft engineering, okay? So when we're thinking about flood management and river management, it's not just about stopping the floods, because, well, sometimes you do try to do that, you put strategies in place which stops the river from bursting its banks, however, it is also mitigating the effects.

So thinking, well, if the river does flood, how can we make the effects of that flood less severe? Now, hard engineering involves building artificial structures to control rivers and reduce the risk of flooding.

They tend to be expensive, but they can be very effective.

Now, some of the hard engineering strategies include dams and reservoirs, river straightening, channel dredging, embankments, and flood relief channels.

Now, all of these different strategies have costs, so not so good things about them, but they also have benefits as well.

So what we're gonna do is we're gonna look at some of these strategies in a bit more detail, look at how they work, and some of their individual costs and benefits.

Let's check our understanding.

Hard engineering is fairly cheap.

That is false.

And can you tell me why? Hard engineering tends to be expensive, but it can be very effective.

Okay, so the first one we're gonna look at is dams and reservoirs.

So we've got a picture there of a very large dam, and that's not being taken in the UK, actually that's a picture in Europe.

So how it works.

Now, a dam is built across a river channel, okay, and in doing that, it stops the flow of water downstream.

Okay? So behind the dam, a reservoir starts to form.

Now, this helps with flood management because the dam, you can actually control the flow of water, okay? So it's storing water behind it, so downstream you can control how much water flows downstream.

They've also got quite a few other uses as well, so we're gonna look at this.

So they can provide a water supply, okay? So you can use the water from the reservoir, yep, for local communities and populations.

They can also be used to generate hydroelectric power.

Because you can control the amount of water that is going through the dam, within those dams you can put turbines, which as the water flows through, it will generate electricity, okay? So they can be a form of hydroelectric power, which is a renewable energy source, which is good for the environment.

Costs of them, they are very, very expensive.

They can displace communities, so when you flood the area upstream of the dam, that means that if there were any people that were living in that area or people had farmland, that area is now flooded.

So they might have to leave the area, or if it's used for farmland, they might have to move their crops, their livestock elsewhere.

It also can have a big effect on ecosystems as well because you are flooding an area.

So for example, woodland might be destroyed in that process and therefore it's destroying local habitats.

Okay, the next one is river straightening.

Okay, so this is basically what it says on the tin, it's when you straighten out a river.

So if you remember the name for a bending river is a meander.

So you cut through those meanders to create a straighter river channel.

The idea of this is if there's no or if there's less bends in the river, that means that the water leaves the area much quicker, okay? Yep, so moves water away from an area quickly, reducing the risk of flooding.

However, that can mean because that water is moving through an area quickly, it can mean that flooding is actually worse downstream, okay? As well, if you are chopping parts of the river out, you are going to be disrupting the local habitats of that area as well.

The next one is channel dredging.

So this is when there is a river channel is made deeper by removing material from the bed of the river, okay? So big diggers, et cetera, will come and dig out material from the base of the river, okay? In doing so, it should mean that the river channel can hold more water, okay? A benefit of this strategy is that it can be done fairly quickly.

It's not as expensive as some other hard engineering strategies.

It needs to be done frequently.

That's a cost of this strategy because, yeah, it requires a lot of maintenance because due to transportation, deposition, eventually the river channel will refill with sediment, debris, et cetera.

Again, it can affect habitats.

Embankments.

Now, embankments are raised banks on the side of the river, okay? Now, so the idea is if you raise the banks of the river, it means that the river will be able to hold more water and therefore increase the channel's capacity.

Okay? Now, the main benefit is that they can protect an area of flooding, but also if you look on the picture here, the embankments, they can also create nice pathways for people to walk along the river as well, so they can be used for leisure purposes.

Costs, they can lead to worse flooding downstream, and sometimes they can look quite unnatural as well.

A flood relief channel, like we have got on the slide here, is a separate artificial channel which is opened to take overflow during high rainfall.

So let's say there was a storm, a heavy flooding event, and it looked like the river was going to burst its banks.

If you have already built a channel, which can take some of this excess water, they can open that up so it diverts some of the water from the mainstream.

In doing so, it's less likely that the main channel will burst its banks, okay? So it diverts excess water, reducing air pressure on the main channel.

A negative, this can be very expensive, it requires space and they also require maintenance.

Okay, so which of the following is not a hard engineering strategy? That is planting trees, that's soft engineering.

Now, when decisions are made about how to manage a river, all of the costs and the benefits of the different strategies have to be considered, okay? So they need to think about, what is the best strategy for this area along the river, okay? Now, all different rivers and catchments will be unique, they'll have their own characteristics with different management strategies which will be most suited to that area.

Now, it's important to be aware that channel straightening, dredging, and embankments can speed up the flow of river water and increase the capacity of water the river channel can hold, okay? So that's great, that they can hold more water, okay? So therefore protecting some areas flooding, however, they can shift the flood risk.

Now, that might mean if you are making that area more protected from flooding, you're getting rid of the water quickly from that high risk area, it then means that further downstream the water will be going to that place quicker, so it's just shifting the flood risk.

So it needs to be really considered whether using those strategies will just move the risk rather than reducing it.

Okay, let's check our understanding.

True or false? Some hard engineering can make flooding worse downstream.

That is true.

Okay, and can you tell me why? Channel straightening, dredging, and embankments can all make flooding worse downstream as the channel can hold more water and speed up the flow.

So well done if you got that right.

Okay, so we're on to our first task for the lesson.

What I would like you to do is complete the table of costs and benefits of river flood management, okay? So you're gonna write down in the first column how that strategy works.

Then you're gonna write the benefits and then you are going to write the costs down.

Some of them have been completed for you to speed you along a little bit.

Okay, let's check our answers.

So it might be worth pausing the video here and just double-checking that you have written something similar to what I have put for dams and reservoirs and river straightening.

Okay, and we're on to the next one, so channel dredging and embankments.

Pause the video and check your answers.

And finally, flood relief channels.

Okay, so we're on to our second learning cycle now, which is looking at soft engineering river management.

Soft engineering, river management refers to more sustainable methods of managing rivers and reducing flood risk.

These strategies tend to be cheaper, but are more focused on managing flood risk rather than stopping it.

They include flood warnings and preparations, flood plain zoning, and planting trees, okay? So as I said earlier, it's not just about stopping the floods, it's about thinking how we can reduce the effects of the flooding.

All of these strategies have costs and benefits which we're going to look at.

Okay, let's check our understanding.

True or false? Soft engineering is less sustainable than hard engineering.

That is false, and the reason for.

Soft engineering river management refers to more sustainable methods of managing rivers and reducing flood risk.

Well done if you got that right.

Okay, let's have a look at these in a little bit more detail.

So flood warnings and preparations.

So what this is basically is telling people that a flood is coming or that they need to prepare for one.

So informing communities about flood risk and how to prepare and respond.

Now, this reduces the damage and improves the safety.

So again, this isn't about stopping flooding, it's about letting people know that a flood is going to happen, what they need to do, and how they can prepare for the flood.

So for example, moving their furniture from the bottom floor upstairs so it's less likely to become flooded.

If the flood risk is really, really high, you might be making sure that they are getting to somewhere of safety during the flood so they are not going to become injured or even worse.

Benefits of this, it's low cost and it's very easy to implement.

You could use TV, you could use radio, social media, signs like we've got on the slide here, making sure that people are aware.

However, it does rely on people taking action and warning systems being placed.

So there's no guarantee that people will listen and follow the instructions of what to do during that flooding event.

Okay, so an example of how people, a lot of people get their information about flood warnings in the UK is on the Met Office website, okay? So on the Met Office website there is a page which provides weather warnings for the UK.

Now, here is one that I got for the day that I created this lesson.

So in Northern Ireland that day, there was a yellow warning of rain for the area that's been shaded in the map there.

Now, on the website, it tells people what they should expect during the flood.

So for example it says, a flooding of a few homes and businesses possible, perhaps some interruption to power supplies, stuff like that so people know what is going to happen, okay? Also it says underneath what they should do in that flooding event, okay? So it's a very easy way for people to find out information if they're at risk and what they should do in the event of the flood.

Okay, the next one is flood plain zoning.

So this is controlling what types of land use are allowed near rivers, which reduces damage when floods do happen.

So it's thinking about, so if we know this area is going to be a high risk of flooding, we're going to make sure that we are not going to put things there which are of high value.

So businesses, for example, we wouldn't build a new shop there or people's houses.

So it's thinking about where's at risk and how can we manage that land so it's a less of a problem if it does flood, okay? So benefits to this is low cost if the area of land hasn't been built on, but we're gonna talk about that in a second, what you do if the area has already been built on, and it's more sustainable in the long term.

So it says for a cost limits development and may not be possible in already developed areas.

So if we have a look at this map of Shrewsbury, for example, the areas which have been shaded in the darker blue colour are areas at high risk.

The areas in the lighter blue are at lower risk and the area that hasn't been shaded in at all, okay, is not at risk of flooding.

But we can see from that image that there's already buildings that are in that high-risk area.

So if that is the case, it is still useful to have these maps, but it's unlikely that those buildings will be knocked down and just left, okay? People have to manage the flooding there if they already live there or have a business there.

Okay, so looking, we can see the flood zone map and a little bit more clearly there, and the key on the right which shows the different colours of the different flood risk.

Okay, so it might be worth you just pausing the video there and looking at what areas are at high risk and which areas are at lower risk of flooding.

Okay, let's check our understanding.

Is the train station at high risk of flooding? Have a quick chat with your partner.

Got an answer from Lucas here.

No, the train station is not at risk of flooding as it is not in a shaded area.

Well done, Lucas, you got that right.

Okay, so the next one is planting trees.

Okay? So this is another example of a soft engineering strategy.

How it works.

Planting trees in the river catchment area, the trees intercept rainfall, reducing surface runoff and lowering the flood risk, okay? So if you remember from the previous lessons, leaves and vegetation can collect rainwater and therefore less rainwater gets to the surface of the earth and therefore less gets to rivers, okay? Now, we already know that deforestation can increase flood risk.

So the opposite to that is to plant trees as a strategy to reduce flood risk.

A benefit is that it improves biodiversity, so it's not only just good for flooding, but it's good for the local area, and it can reduce soil erosion.

A cost, it can take time to be effective because you have to wait for the trees to grow and it might not be suitable for all areas.

So for example, in an urban area, there might not be the space to plant a lot of trees.

Okay, so let's just have a look about what I said earlier.

So there's the tree there which collects rainwater and can store it, and from that tree, a small amount of water will actually just evaporate.

Therefore, there's less water getting to the surface of the earth and therefore less into the river.

Okay, let's check our understanding.

Which of the following is not soft engineering river management? The answer is dredging, that's hard engineering.

Okay then.

So our task for this lesson is, what I'd like you to do is look at the flood zone map of Shrewsbury and just the general map of Shrewsbury where you can see the different buildings.

Now, on the map of Shrewsbury, I would like you to label two places at high risk and two places at low risk of flooding.

Now I'd like you to answer these questions.

So the first one, why might some councils prefer soft engineering strategies over hard engineering? Why might some residents that live in an area prone to flood risk prefer hard engineering? And what would an environmentalist's preference on river management be and why? Okay, so pause the video and have a go at those three questions.

Okay, let's go through our answers.

So I've labelled on here some of the areas that are at high and low risk, but you might have found other ones as well, and that is absolutely fine.

So the County Recreation ground is at high risk of flooding.

Shrewsbury High School is at high risk.

Abbey Foregate Yard is at low risk and the car park is also at low risk.

So if you've got those ones, fantastic, if you've got other ones, also brilliant.

Okay, let's have a look at the answers to this.

So for the first question, why councils might prefer soft engineering, I have put soft engineering tends to be cheaper, therefore councils may prefer this as it doesn't cost as much.

Now, councils are tight on budgets, they've got lots of different things to spend on.

Flooding is one of the things that they have to spend money on.

However, if they've not got loads of money, they might prefer a soft engineering approach 'cause it costs less.

Why might a resident prefer hard engineering? So some residents may prefer hard engineering to be implemented as they may see it as a safer option for protecting their home.

And for the final question, an environmental conservationist would prefer planting trees to be used, as this method improves biodiversity.

Also, some hard engineering strategies can damage habitats.

Okay, we've got a summary for today's lesson here.

Hard engineering is the building of structures to help prevent river flooding.

Soft engineering is working with nature to reduce the risk of river flooding.

There are economical and environmental costs and benefits to different types of flood management.

And flood management in one part of the river will have an effect on other parts of the river downstream.

Now, that's it for today's lesson.

You've done a fantastic job, and I'll see you next time.

Bye.