Lesson video

Hello geographers.

My name's Mrs. Hormigo and I'm looking forward to teaching you today.

I hope you're going to enjoy the lesson and learn lots.

Let's get started.

Today's lesson looks at the costs and benefits of river management strategies.

And by the end of the lesson, you're going to be able to assess the costs and benefits associated with hard and soft engineering strategies that are used to manage river flooding.

There are three key words for today's lesson: Sustainable, hard engineering, and soft engineering.

"Sustainable" is the meeting the needs of the present without compromising the ability of future generations to meet their own needs.

"Hard engineering" is the use of artificial structures and technologies to control natural processes such as flooding or river erosion.

And "soft engineering" uses natural processes and landscape features to reduce the risk of flooding and erosion.

There are two parts to today's lesson: "The costs and benefits of hard engineering" and "The costs and benefits of soft engineering." So let's get started by looking at hard engineering strategies.

Before we do that, let's think, why is it that we manage rivers? It's to reduce the risk of flooding, to reduce erosion, to protect property and infrastructure, to support sustainable development, to allow safe land use, and to improve water quality and wildlife habitats.

And river management reduces the risks and it increases the benefits that rivers bring to people, the economy, and the environment.

Hard engineering is the use of human-made artificial structures to control natural river processes such as flooding and erosion.

The methods are often expensive, very effective in the short term, but they will have an impact on the environment.

So here are some examples.

We've got dams and reservoirs, embankments, flood relief channels, and river straightening.

We're going to look at these in a little bit more detail now.

As we look at these, we need to make sure we remember each of these strategies has costs and benefits.

Costs are the negative impacts or expenses associated with planning or building and maintaining a scheme.

The benefits are the positive outcomes, especially in relation to flood control, erosion prevention, or land use.

Let's start with dams and reservoirs.

We've got here an image of a dam with a reservoir behind it.

There are large barriers that store water and they can regulate river flow and store water for dry periods.

However, they have benefits and costs.

The benefits are that it's storing water and it can control the flow of water through the river channel.

They can also be used to generate HEP, hydroelectric power, a renewable source of energy.

However, they are very, very expensive, millions of pounds.

And in order to build them, we may well lose land upstream as it's flooded to create the reservoir.

This may displace people or farmland may be lost, and this can have an impact on people and the environment.

Here we have an image of an embankment or a levy, and you can see the arrow is pointing to a raised area of land next to the river channel.

Now these can be made out of natural materials, earth that is often dredged from the river, or concrete.

And the idea is that they contain the river, so they create a higher bank to the river so that during flooding, less water is likely to spill out.

The benefits to it are that it's increasing the channel capacity and it can be relatively cheap, especially if it's used made using earth, which is dredged from the river.

However, it needs regular maintenance.

It can be eroded or weakened itself over time, and so become ineffective.

And the flood water can sometimes break through or go over the top of the embankments.

Now, if this happens, it becomes very difficult for the water to flow back into the river, and this can have consequences.

Check for you now.

Can you identify this example of hard engineering? And secondly, can you then identify two correct benefits of this strategy by looking at the table below? Pause the video and come back when you're ready.

Hopefully, you recognised it was an embankment or a levy, and you could pick out that it increases the channel capacity by raising the river banks.

And it's relatively cheap to instal, as they can use material dredged from the river.

Well done.

Let's have a look now at river straightening.

This is where the river channel is artificially straightened.

So it's try.

It removes the natural meanders that the river has created and it allows water to move more quickly through the area.

This map shows the Mississippi River in the USA, and you can see there it's got areas where it's had the large meander loops cut out and then creating a much straighter channel that links the river up.

And this helps to control the flow by moving water through more quickly and reduce the risk of flooding.

I see there that the arrow is pointing.

The dotted white line is the old river course and the straightened section is that new river course.

So joining up the river much more quickly than going around the meander bends.

Let's have a look now at the benefits and costs then.

So the benefits are that the water is moving quickly through high risk areas, so potentially areas that have high economic value, and that reduces the flood risk there.

It also reduces river erosion on the meander bends, so you're going to be protecting the valuable land.

However, it's expensive to instal and it's very disruptive to the ecosystem.

And by increasing the flow of water downstream, it may increase that risk of flooding further downstream.

Look now at flood relief channels.

So these are artificial channels that are built near to the main channel, but can be used to divert excess water away from that main river channel.

It may be that they stand empty or that they have some water in it all the time, and can receive excess water during floods.

The benefits being is that it protects urban areas by taking water out of the main river, so reducing the flood risk in the main river.

And if they have water in all of the time, they can be used for recreation or provide a habitat for wildlife.

However, it can be expensive and disruptive to build them and to find the land to do that.

And in doing so, it can damage habitats and ecosystems as you're potentially changing the land use quite considerably by creating them.

If we look now at flood barriers, these are movable barriers that can be raised during storm surges or high tides in order to block flood water from reaching the vulnerable areas.

And we can see here, this is a photo of the Thames barrier in London, and this shows you some of the 10 steel gates.

And these gates are raised during flood threats, which prevents a storm surge from flowing upstream.

So you've got the tidal movement of water and you've got the river flow of water, and it's trying to prevent there being a surge of water upstream.

This has proved very successful in London.

It was finished in 1982 and it's been used over 200 times, which will have protected millions of people and billions of pounds worth of property during that time.

So the benefits to it is that they can be very effective in protecting very large urban areas, and they're reliable.

However, they are very expensive to build initially, and they can take a long time to build, and in order to maintain and make sure that they're working.

And if they're not closed in time, it takes time for them to close, then there may be a flood risk associated.

So check for you, now.

Which of these are costs? So general costs, things that appear on lots of the examples, of hard engineering strategies.

A, very expensive to construct and maintain; Strong physical protection for infrastructure; Damages ecosystem; And increases the risk of flooding elsewhere.

Pause the video and come back when you've made your decision.

Hopefully, you identified it was three of the four.

They do tend to be very expensive to construct and to maintain.

They can damage ecosystems and they can increase the risk of flooding elsewhere.

So for example, if you think of this river straightening, by increasing the speed at which water moves through the upper section, it may cause an overwhelm in the lower, or downstream, which may cause flooding down there.

A positive thing that we've got there is that they are strong physical protection, and that's why we often see them in large urban areas.

Your task now: Complete the costs and benefits of these hard engineering strategies.

So we've got three strategies: Dams and reservoirs, river straightening, and flood relief channels.

The purpose has been completed for you, but can you identify the costs and benefits of each of them? Pause the video and come back when you've had a go.

So your table may have looked something like this.

For the first one, dams and reservoirs which store water to control the flow and prevent flooding, you might have said the costs were it displaces communities, when the reservoirs are made it can cause flooding upstream, and it can destroy habitats, and they are very expensive.

The benefits, however, is it's very effective flood control, you can store water for water supply or irrigation, and they can provide hydroelectric power.

The second, river straightening: Speeding up the river flow to reduce a local flood risk by removing the meanders.

The cost of that is it can increase the risk of flooding elsewhere, and it can be expensive to instal and maintain.

The benefits, however, though, the water flows through the area of high risk more quickly and so the risk of flooding lowers.

And finally, your flood relief channel, which is an artificial channel that diverts excess water away from the main river channel.

The costs to it is that construction can cause damage to ecosystems and it changes the land use, which can have impacts to people and the environment.

The benefits are that it lowers the water levels in the main river during high flow, so it reduces the flood risk of the main river, and it can create areas for wildlife and recreation.

Well done if you managed to complete your table in a similar way.

Let's move now to the costs and benefits of soft engineering.

So soft engineering is a river management approach that uses natural processes and landscape features to reduce the risk of flooding and erosion.

It's usually less expensive, more environmentally friendly, and more sustainable than hard engineering.

And these are some examples: Afforestation, floodplain zoning, flood warning system, and river restoration.

We'll have a little look at these in a bit more detail.

But Jacob says, "So soft engineering must be "a better option than hard engineering.

"Less expensive, more environmentally friendly, "and more sustainable." But Alex is thinking about things a little bit more carefully, and he says, "I think it will have some costs too, "otherwise it would be used everywhere.

"Its benefits might vary," and that's a clever point he's realised.

It depends on the location and the scale of the flood risk as to what type of strategy is the most effective.

Well done, Alex.

Let's look at the first then.

So floodplain zoning.

We can see here that we've got a map of Shrewsbury, showing areas that have a high risk, and medium risk, and a low risk of flooding.

And this is created by the environment agency.

It collects data to produce these maps.

By identifying these high risk, medium, and low risk areas, we can control the development.

By controlling this development and restricting development in high risk areas, we are reducing damage and ensuring a natural flood absorption by creating a natural floodplain.

This is good because it keeps people and buildings away from flood prone areas, and it's of low cost.

However, by doing this, we are limiting the land for development and it can be hard to enforce in built-up areas where land is under pressure and we need to use it.

Afforestation.

So the planting of trees increases the interception of rainfall and slows surface runoff.

This reduces the speed at which water reaches the river channel, reducing the flood risk.

This may happen in some urban areas, in parkland or open areas, but it's more likely to happen in the more natural environments, in the valley further upstream.

The benefits to this are that it's relatively cheap to plant trees.

And when doing so, we are creating new habitats and we're increasing the biodiversity.

So it has huge environmental benefits.

However, trees take a long time to grow.

And as I've mentioned, it's not suitable in all areas.

So it's not necessarily suitable in urban areas.

And in some areas, planting trees will reduce the space for farming, so it does have impacts.

The next one is flood warning systems. So by monitoring river levels, combined with satellite data on the potential rainfall, we can create accurate predictions of the flood risks.

This uses technology and computer modelling, and then warnings can be generated and then communicated to at-risk areas.

The environment agency collects data like this in order to help provide the warnings.

And warnings are then issued on websites, on social media, on the television, telling people what to expect and what they should do.

And as people become more aware and more educated in this, their responses will be quicker and more effective.

And so, it helps people to prepare and protect themselves.

So by giving people advanced warning of potential flooding, they can get themselves to safety either by evacuating or protecting their property.

We can see here a map which shows areas that are likely to be affected by flooding and that can be used by local authorities to help to close roads, create temporary flood barriers, move people to safety and emergency services in order to support with this.

The benefits to this are that it's accurate because of all the computer modelling that we now have.

It's easy to update and share information.

People have access to it very easily.

And it means that people can then protect themselves and their property.

The costs are that it's not doing anything to stop the flooding or reduce the flooding.

And it does rely on people being receptive and receiving the warnings and acting on them.

So check for you now.

Which of these are soft engineering strategies? Is it A, flood warning systems? Is it B, floodplain zoning? Is it C, flood relief channels? Or is it D, Afforestation? Pause the video and decide which is correct.

Which are correct.

Hopefully, you identified that three of the four are correct.

Flood warning systems, which gives people time to evacuate and protect their property.

Floodplain zoning, reducing the building on high risk areas on the floodplain.

And afforestation, building.

Planting trees in order to reduce surface runoff.

Flood relief channels are an example of hard engineering strategies and they divert water away from the main channel, reducing the flood risk.

The last one we'll look at is river restoration.

That means restoring a river to its natural course.

So it might be that you remove straightened sections, you might remove flood walls or embankments.

And we can see here that the River Cole is flowing through a floodplain in a series of newly created bends.

So allowing the river to meander naturally lengthens the river and slows the flow, so it reduces the flood risk.

The benefits to it are that the natural process of the river restored.

The natural balance of transportation, deposition, erosion is balanced again.

And it has huge long-term environmental benefits, restoring and maintaining the natural landscape and increasing biodiversity.

However, it may not be effective in extreme floods.

And as we've seen, a lot of floodplains have urban development on them, so doing this would not be suitable if the area had dense urban population.

It's going back to that idea of the location, and that is really important in deciding the type of flood defences needed.

So true or false for you here.

"Hard engineering is always "a better option for river management." Pause the video and make your decision.

I hope you said false, but can you tell me why? You may have discussed this already, but think what your answer would be.

Hopefully, something similar to this.

So there are many benefits to using soft engineering strategies in river management, including increasing biodiversity and restoring natural landscapes and processes.

However, some of these strategies take a long time to work and may not be effective in extreme floods.

Final task now.

This area around the River Cam is at risk from flooding.

There is a mixed land use; houses, businesses, and parkland.

What two river management strategies would you suggest using to reduce the flood risk? And we can see here, the flood risk is shown.

So we have an area circled on your left hand image, left hand map, and if you look at the area on the right hand map, you can see that it is at risk of.

A high risk of flooding, medium risk of flooding.

So you need to think, what strategies would you use? They can be soft or hard engineering.

Try to give reasons for your choices.

Pause the video and come back when you are ready.

Your answers may have looked something like this.

I chose embankments.

So embankments are raised banks built along the river to prevent it from overflowing during periods of heavy rainfall.

In an area like the River Cam, embankments would be effective in protecting both the residential areas and businesses from flooding, which is particularly important in urban areas, where property damage could be significant.

Embankments are relatively cost effective compared to other hard engineering solutions, like flood walls or dams, and they can be built at varying heights, depending on the flood risk.

And then, in the areas of parkland and other low risk zones, I would recommend floodplain zoning.

This would involve restricting future development in areas that are at risk from flooding, particularly on the floodplain.

By keeping development away from these areas, the risk of damage during flooding events is reduced.

And this retains the floodplain so it can act as a natural storage area for excess water during a flood.

This combination of hard engineering and soft engineering would offer a balanced and sustainable solution to flood management, ensuring both the protection of people and the environment.

Well done if you chose similar ideas or if you chose different options, just make sure that you've given reasons why.

Okay, let's have a look now at a summary of today's lesson.

So hard engineering, for example, dams, and reservoirs, and embankments, provide immediate and usually effective flood protection, but is expensive and it can harm the environment.

Soft engineering, e.

g.

afforestation or floodplain zoning, is sustainable and cheaper, but may not offer quick results or complete protection.

Both have costs and benefits.

Often, a combination of both can provide the most effective protection whilst also being more sustainable.

And the choice of strategy depends on the location and land use.

With urban areas, which is often more expensive property, often selected for hard engineering, and rural areas, which have a lower land value, selected for soft engineering.

Well done.

I hope you can now talk confidently about the different strategies for river management, both hard and soft engineering, and the cost and benefits of each.

I look forward to seeing you all again soon.