Lesson video

Hello, my name is Chloe and I'm a geography field studies tutor.

This lesson is called Fieldwork: Analysing, Concluding and Evaluating River Data.

It forms part of a unit of work called Rivers: How do rivers shape the land? In this lesson, we're going to be looking at what we can do with our river data in order to better understand how river processes work and the different characteristics that we have.

We'll be taking our data that we collected in the field and actually looking at it in more depth and also thinking about how we might change our investigation if we were to do it again.

Let's get started.

By the end of this lesson, you will be able to analyse and reflect on your river data to create meaningful conclusions and an evaluation.

There's some keywords for us to review first of all.

There's interpolation, this is finding the value of data in a set by examining the data that falls either side of it in sequence.

Extrapolation is similar, but it's about finding the value of data in a set by extending the correlation beyond the known data.

Ethical considerations are areas of the fieldwork investigation where geographers consider the impact their study may have on people and the environment.

There are three parts to our lesson today.

We're going to be analysing our river data, drawing conclusions from it, and then finally we're going to be evaluating our entire geographical enquiry.

But let's start with that stage of analysis.

So here we are in the fourth stage of our enquiry cycle, the data analysis stage.

Geographers often start their analysis by making some simple descriptions, such as commenting on the most or the least of something.

Here, Laura says, "The line of best fit shows that as the depth of the channel increases, so too does the flow velocity." That's a great start.

It's a simple way of describing the correlation.

She then goes into more detail by saying, "The velocity values have a range of 0.

22 metres per second from 0.

48 to 0.

7 0 metres per second." So she's actually picked out some aspect of the data to comment on further.

The direction of the line of best fit tells us about the nature of the correlation.

If as one variable increases, so do too, does another, it is known as a positive correlation.

The line will look like this, extending from the bottom left to the top right.

If as one variable increases, the other decreases, it's known as a negative correlation.

You can see here the line is moving in the opposite direction.

Jacob says here, "The correlation between channel depth and bedload size is negative.

As the channel depth increases, the bedload size decreases." You can see there the line is angled from the top left down to the bottom right.

Once geographers have described their data, they then try to explain it.

Aisha here is trying to look at why it is that as channel depth increases, the channel velocity increases as well.

She says, "The shallower the channel, the larger the proportion of water in the channel that is influenced by friction.

Therefore, the deeper the channel, the faster the flow is likely to be." You can see that here in the two diagrams, the deeper channel has more water that is not in contact with the beds or the banks.

Therefore there's less friction acting on that water and that means that, in general, it's going to be flowing far faster.

Let's check our understanding around describing our data.

What is the value range for bedload size? Take a look at the graph that we've got here.

Look at it very closely and see if you can work out what the range of data is.

Pause the video and then come back to me.

Obviously you are going to be reading this off the screen, so you might have a slight difference to me, but it's going to be round 14 millimetres.

So our lowest value is 18 millimetres and our highest is 32.

Geographers use the trendline in a scatter graph to predict unmeasured values.

Andeep wants to know the likely flow velocity of the river when the channel is at 0.

5 metres deep.

Now, 0.

5 is not one of the measures that he actually took in the field.

So how is he gonna work out what the flow velocity was at that point? The line of best fit is used as a guide.

Andeep can plot the 0.

5 metre depth on the line of best fit and then read off the velocity at that point.

You can see now that the velocity is 0.

58 metres per second at the 0.

5 metre depth, even though Andeep did not actually measure a river that was 0.

5 metres in depth.

This strategy is known as interpolation.

If geographers want to predict a value beyond the current range of the dataset, they use a technique called extrapolation.

The trendline is extended using a dotted line.

Additional values can then be read off using that extended line.

So here Izzy would like to know the likely velocity of the river when the channel is 0.

25 metres deep.

What is her predicted value? You can see here we have added in those helping guidelines.

So from 0.

25 metres depths, we've gone up to our extrapolated line of best fit and then we can read off the velocity at that point.

0.

35 metres per second.

Let's check our understanding around interpolation and extrapolation.

What is the likely flow velocity of this river if the channel is 0.

2 metres deep? Is it A: 0.

4 metres per second? Is it B: 0.

05 metres per second? Or is it C: 0.

3 metres per second? Pause the video and see if you can work out what the flow velocity is likely to be at 0.

2 metres deep.

Well done if you got that the answer is 0.

3 metres per second.

You can see we've added in the lines here to help us work it out.

We've gone up from 0.

2 metres, the channel depth, we've met the line of best fit and then we've gone across to our flow velocity and you can see that is where we are reading off the velocity there.

0.

3 metres per second.

Our first practise task of this lesson.

Look at the two scatter graphs that you created of the data from your local river.

Describe and explain the correlation you see in each of your graphs.

Carry out an interpolation on one of your graphs and extrapolation on the other.

Record the unknown values that you have managed to calculate.

So there's a little bit of work involved here.

Do pause the video so that you can have a go at each of those tasks.

Then come back to me and I'll show you some of the ideas that I had.

So first of all, you were asked to describe and explain the correlation that you saw in each of your graphs.

So your answer might include something like this.

The line of best fit shows that as the depth of the channel increases, so too does the flow of velocity.

That's my description.

I then move on to my explanation.

This is because the shallower the channel, the larger the proportion of water in the channel that is influenced by friction.

Therefore, the deeper the channel, the faster the flow is likely to be.

Your other graph might look something a little like this.

The correlation between channel depth and bedload size is negative.

As the channel depth increases, the bedload size decreases.

So there's my description again.

Now I move on to the explanation.

In shallow channels, the flow is slower and the river has less energy, leading to deposition of the larger bedload.

Therefore, in deeper channels, the bedload is likely to be much smaller.

So you then had to carry out an interpolation and extrapolation.

Let's start with the interpolation.

So really of course it depends on what your data in your graph shows, but you must make sure that your interpolation occurs somewhere within the existing line of best fit.

So you've got a new value that you can predict based on that line.

Here I've predicted that if the channel depth is 0.

5 metres, the flow velocity is likely to be 0.

58 metres per second.

We then move on to the extrapolation, and this is where you extend your line of best fit either above or below its current range.

Here you can see that, in my case, the channel depth is 0.

25 metres.

I've predicted that the flow velocity is likely to be 0.

35 metres per second.

We now move on to the second part of our lesson.

We're gonna be looking at a conclusion to all of this river data that we collected.

Here we are on the conclusion part of the enquiry cycle.

Geographers begin their conclusion by reviewing the main points of their analysis.

They need to decide which of their observations are most important and have the strongest evidence to support them.

The strength of a correlation has nothing to do with the angle of the line of best fit.

Both of these graphs show a strong negative correlation, even though the angle is quite different.

The strength of a correlation instead is decided by how close the plots lie to the line of best fit.

So in our first diagram there, you can see that that is a weak positive correlation because lots of the points are lying quite some distance from our line of best fit.

When we look at our second graph though, we can see there's a strong negative correlation.

The lines is pretty much touching each of the points.

Maybe only a couple are sitting just outside it, so it's a much stronger correlation.

Geographers can then answer their enquiry question.

Let's just remind ourselves of ours.

It's "Does our local river behave like a theoretical river?" Jun is reviewing his analysis and the strength of his evidence, and he makes some notes on this.

He notes that channel depth appears to be relatively strongly positively correlated to flow velocity, so the points are pretty close to that line.

So he's saying that that is a good strong evidence.

However, when he looks at the weaker evidence, he notices that the points for his bedload size against channel depth, those are plotted a little further from his line of best fit.

So it's relatively weakly negatively correlated.

By drawing on the data that produces the strongest evidence, Jun is now ready to write his conclusion and answer his enquiry question.

Let's check our understanding around correlations.

The angle of the line of best fit tells geographers how strong the correlation is between the variables.

Is that true or false? Have a think about what you've just learned.

Pause the video and then come back to me.

Well done if you recognised it's false.

Now try and explain why that statement is false.

Yes, it's because the strength of the correlation is decided by how close the plots lie to the line of best fit, not the angle of that line.

Well done.

The conclusion then addresses any hypotheses made at the start of the enquiry.

Let's review Alex's hypothesis.

He said that as the depth of the river channel increases, the flow velocity of the river will also increase.

You can see from our scatter graph that Alex's hypothesis can be accepted.

Though there is a correlation between the two variables though, this does not mean that one automatically causes the other.

All we have done is recognised that there is an increase in one at the same time as an increase in the other.

It doesn't necessarily mean that one is causing the other.

Let's look at Sam's hypothesis now.

She said that as the depth of the river channel increases, the size of the bedload will decrease.

Sam's hypothesis can be partially accepted.

Though there is a correlation, it's a relatively weak correlation, so we have to be a little bit cautious in accepting it fully.

Where the correlation is weaker than expected, geographers try to explain this weakness.

Lucas says, "The Bradshaw model is designed to be understood along a whole river, from source to mouth.

As Sofia points out, "We only sampled one part of our river, so maybe that's why our correlation is relatively weak.

So he's suggesting that possibly if they had measured from source to mouth and done a lot more sites, actually it would've been a clearer and stronger correlation.

Lucas and Sofia raise a really important point.

If geographers are comparing their fieldwork data with a theoretical model like the Bradshaw model, they should have a sample of data that compares directly with the sample size or the area that the model is based on.

The Bradshaw model is based on an entire river, so really they should have measured an entire river when they were collecting all of their data and instead they only had a small sample of it.

So maybe it's not surprising that their correlation was relatively weak in this case.

Let's check our understanding now.

Why should a geographer be cautious of saying that increased depth in the channel leads to increased flow velocity? Why would they be cautious about saying something like that? Is it because the graph may only show a correlation which does not necessarily indicate a cause? Is it that the graph may show a weak correlation between channel depth and flow velocity? Or is it that the line of best fit on the graph may be showing a negative correlation? Think really carefully about each of those statements.

Why would a geographer be cautious about saying that one thing in a graph automatically leads to another? Pause the video and then come back to me.

Yes, it's a little bit tricky, this one, isn't it? It is answer A.

Yes, it's about the idea, the difference between a correlation and causation.

There may be a correlation between two bits of data, but it doesn't necessarily mean that one thing is causing another.

Now we move on to our second practise task.

I'd like you to write a conclusion in relation to your own data analysis.

State whether any hypotheses you made are accepted, partially accepted, or indeed completely rejected.

Pause the video here so that you can have a go at that task.

Let's take a look now at your answer.

Now, it depends on, of course, on what your data actually showed, but you should make sure that your conclusion has a statement that answers your enquiry question directly.

There should be a summary of the strongest evidence and you should have a statement that says whether your hypotheses are accepted, partially accepted or rejected, and indeed why you are accepting or rejecting your hypothesis.

Have a look through your answer and check that you've got those points.

Now we move on to the final part of this lesson where we are evaluating a geographical enquiry.

Here we are in the final stage of our enquiry cycle.

In every fieldwork enquiry, there are things that could go well and as expected, and there's other things that do not always go to plan.

Aisha and Izzy are reflecting on their fieldwork enquiry.

Aisha says, "I felt the depth measurements were really accurate.

We took our time and we made sure the metre sticks were straight before we read off and recorded the data." Sounds great.

Let's see what Izzy says.

"One of our scatter graphs showed that there was a weak correlation between depth and bedload size, so maybe we needed more samples from more sites to come to a clearer conclusion." It's a sensible idea that yes, the more data you have, the better your conclusions will be.

As well as evaluating the enquiry they carried out, geographers also reflect on how they might extend their investigation, such as by investigating other and related variables.

Aisha says, "We only looked at channel depth, bedload size and flow velocity.

I would like to look at other variables too, such as gradient or the wetted perimeter.

This would give us a better idea whether our river behaves like a theoretical river or not." She's raised a really good point.

Only some of the characteristics of the river were measured.

She could actually extend her study by looking at some others too.

Let's check our understanding there.

Complete the sentences with the missing words.

Pause the video so you can have a scan through the paragraph and then see if you can come up with those missing words.

Right, let's see what you got.

In an evaluation, geographers say what went well in their fieldwork enquiry as well as what they would improve.

They also looked at how they might extend their investigation, such as by also collecting data on other related variables.

Well done if you got those two points.

Geographers also evaluate how they treat other people and the environment when they do their fieldwork.

These are known as ethical considerations.

Let's listen in on this conversation between Andeep and Laura.

Andeep says, "At one site, the river was close to some houses, so we made sure we were not too loud and creating a disturbance." That's really respectful and that's exactly what we would hope geographers to be like in the field.

Laura says, "Being too loud would also disturb bird life in the area, especially during nesting season." So Laura is also thinking about the environmental side of how they conducted themselves in the field.

How else might Andeep and Laura have negatively affected the river field sites? Have a think about that.

What other impacts could they potentially have had while they were doing their fieldwork? Andeep and Laura made sure that they didn't: drop any litter or leave food waste, such as apple cores lying around.

They didn't pick flowers, they didn't pick up stones and throw them around the river.

They also kept their walking routes to footpaths, so it meant they weren't creating additional erosion on the landscape, and they stored equipment carefully so that it not cause an obstruction to members of the public.

They also had permission from the landowners to actually be at the river site, and that's a really, really important point.

Let's check our understanding of those points.

Which of the following should be considered ethically before conducting a river fieldwork enquiry? Should you be wearing the right type of footwear? Should you think about how polluted the river might be? Might you look at how steep the river banks might be? Or might you think about where equipment might be stored when it's not in use? Pause the video and have a think about the ethical side of fieldwork and then come back to me with a good answer.

Well, the interesting thing about these answers is that you should be doing all of these things, but not all of them are to do with the ethics of your research.

Wearing the right type of footwear and thinking about how polluted the river is and how steep the banks are.

Those are all things you should look at, but from a health and safety point of view, to check that you're not putting yourself into any kind of adverse risk.

Where the equipment might be stored, though, that then comes into looking after members of the public, so that would be an ethical consideration.

So well done if you got that point.

Let's move on now to the final practise task of this lesson.

Write an evaluation based on your river fieldwork enquiry.

Include the following points: I'd like to see a discussion about something that went well, a discussion about a way that you might extend your study, a discussion about any ethical considerations that you took while you were carrying out your enquiry Pause the video here, and maybe have a discussion with others that you collected the data with and see what their thoughts are on each of those points.

Then come back to me and I'll tell you some of my ideas.

So let's have a look at your evaluations now.

Your answer might include things like this: The depth measurements were really accurate.

We took our time and made sure the metre sticks were straight before we read off and recorded the data.

So here we've got a statement around something that went really well in the fieldwork.

Then we move on to thinking about the extension of the study.

To extend the study, I would look at other variables too, such as gradient or wetted perimeter.

This would give me a better idea about whether our river behaves like a theoretical river or not.

We then think about the ethical considerations.

We made sure that we were respectful of the natural surroundings by keeping our voices at a low volume.

We also made sure that we took all our litter home with us.

Let's now summarise our learning from today.

Geographers analyse their data by describing and explaining it.

They look for correlations between variables and reflect on how strong those correlations are in order to write their conclusions.

As part of an evaluation, geographers will consider their potential for causing harm to people and the environment and discuss how they managed to minimise such harm.

Well done, there were a lot of new elements there with regards to the analysis, the conclusion, and the evaluation of fieldwork.

You did really well at giving it a good go.

It might feel like there's a lot to be thinking about when you do fieldwork, but the more you do it, the more confident you'll become in those different elements and the more natural fieldwork will feel as part of your geography studies.