Lesson video

Hello, my name's Ms. Giliet and I'm your geography teacher for today.

In today's lesson, we are learning about the upper course of a river, which is lesson four of the river's topic.

Let's get going.

So our lesson outcome for today is that you can describe the characteristics and bland forms associated with the upper course of a river.

We've got five keywords for today's lesson.

So the upper course is the part of a river's course closest to its source.

A V-shaped valley is a narrow, steep sided valley with a river at the bottom.

Interlocking spur is ridge like features found along the sides of river valleys.

A waterfall is a point in the river where there is a vertical drop in the water, and a gorge is a very narrow valley with steep sided rocky walls.

Now all of these keywords are highlighted in bold throughout the lesson if you need to refer back to them.

Okay, we've got three learning cycles.

So first of all, we're gonna look at what it is like in the upper course of river.

Then we're gonna learn about how V-shaped valleys form and then we're gonna look at how waterfalls form.

So let's start off with what is it like in the upper course of a river? Now, geographers use specific terminology for talking about rivers.

Okay, now, you might remember this from the drainage basin lesson.

So the diagram here shows the drainage basin of a river system.

Okay, so a drainage basin is the area of land that a river and its tributaries drain.

Okay, now, a river can be divided into the upper, the middle, and the lower course.

Right, now, there's the upper part.

Now the upper part is where the sources of the river are, if you like.

There's the middle section and there's the lower course.

So today we are going to be focusing on the upper course of the river.

Now, this is where the river begins and often starts in a mountainous or hilly environment.

Okay, so let's check our understanding.

Can you name the different sections of a river? Okay, so this isn't about specific landforms. This is about the part of the river's journey.

So A is the upper course, which is what we're focusing on today.

We've got the middle and the lower course down here.

Now this video shows the upper course of a river.

What do you notice about what the river looks like? So look at how wide it is.

Look at the types of rocks there are.

Look at how fast it's playing, what do you notice about it? Have a quick chat with the person that you are sat next to.

Now, let's go through some key features of what the river and the area around is like in the upper course.

Okay, so the river channel tends to be very, very narrow in the upper course, especially near the source where the river and the tributaries start.

The banks and the rocks in the river are often steep and can be quite jagged.

So that means quite sharp.

The river channel is shallow, the river is flowing slowly as it has to move around rocks.

So you can see there in the image it's winding around a little bit.

And because the water is having to flow between big pieces of rocks, it is meaning it is not actually going that fast, and there's actually quite a lot of friction.

And we are in a mountainous or hilly environment here.

Okay, so this is what it's like in the upper course of a river.

Now, in the upper course of a river, vertical erosion dominates.

This means the river is eroding in a downwards direction.

Okay, so the river is eroding down into the ground below.

So if we have a look, we've got the cross section of a river channel there.

Vertical erosion means that the water due to hydraulic action, attrition, abrasion, solution, the river is eroding downwards.

Okay, so it's going steeper and steeper down.

Okay, so we've got an OS map here.

So the OS map shows the upper course of a river.

Now looking at that section of an ordinance survey map, how can you tell that is in the upper course? Okay, have a quick chat with the person that you are sat next to.

So there's a few pieces of evidence that we can see from here that were in the upper course.

So first of all, there's very steep land.

So the contour lines are very close together, which indicates we're in a mountainous environment, okay? We can see sources of the river there, okay? And there's lots of little tributaries, again, indicating that we are in the upper course of a river.

And also, there's a spot height here of 1,344 metres at the top of Ben Nevis, okay? The highest point in the UK.

Now, this shows again that we're in the upper course of a river because we're in a mountainous environment.

So well done if you spotted those.

Let's check our understanding.

So the river in the upper course has, and tick all that apply.

Okay, so it should have a narrow channel, a steep gradient, and a shallow channel.

Okay, so well done if you got that right.

Okay, so our first task for this lesson is I'd like you to look at the OS map and label three pieces of evidence from the map, which suggest it's in the upper course of a river.

Once you've done that, I'd like you to write a short paragraph using your evidence describing what the upper course of a river is like.

Okay, so pause the video and have a go at those two questions.

Okay, let's check what our answers.

So here we've got labelled the source of river, steep land by tightly space contours, and we've got a spot height there of 807 metres, which shows we are in the mountains.

Okay, so well done if you've got those right.

Okay, so here's my paragraph.

Now, the upper course is in a mountainous environment, as we can see, due to the contours being close together and the high spot height, many sources of the river can be found.

This is where the river begins.

The river usually has narrow and shallow channels, okay? So it might be worth you just pausing the video there and just comparing your answer to mine, double checking that you've got the right amount of detail.

Okay, let's get going with our second learning cycle.

Looking at how V-shaped valleys form.

Now, river erosion, which is the wearing away of the land creates different land forms, okay? So river erosion can create these ones, waterfalls, V-shaped valleys, interlocking spurs and gorges.

Okay? So we're gonna learn first of all how V-shaped valleys form.

Okay, before we do that, let's check our understanding, which of these are examples of land forms created by erosion.

Okay, so the answers are V-shaped valleys and waterfalls.

Now, hydraulic action and abrasion are types of erosion.

They are not landform created by erosion.

Okay, so V-shaped valleys are narrow, steep sided valleys, and their cross-section is a V-shaped.

So we've got a nice picture of a V-shaped valley on the slide here, okay? So the river channel is shallow and narrow, and the water flows fairly slowly due to friction.

So if we look here, it's the shape of a V.

So steep sides, a river at the bottom, and often the river channel is quite shallow and quite narrow.

Okay, so let's go through how one of these forms. First of all, the river erodes vertically, which deepens the channel and steepens the valley sides.

Okay, so if you remember from what I said in the first learning cycle, in the upper course, vertical erosion dominates.

Okay, so this is what happens.

Next, the steep side of valley sides are weakened by weathering processes.

So biological weathering might be happening, chemical weathering, physical weathering, meaning that those sides to the river become unstable.

Now, if we look at the pitch on the diagram here, we can see that the river channel is very, very steep.

So it's weakened by weathering processes, and eventually it won't be able to stay as upright as that because it is so steep.

Then the valley sides collapse in on themselves creating a V shape, okay? So eventually the material that was on the sides of the river will collapse in on itself, and it will mean that that material goes into the river channel and eventually will be transported downstream through the river.

Okay? So now we can see that we've got, this V shape has been formed as the channel sides have fallen in on themselves.

Over time, this vertical erosion continues and the process repeats itself.

So this V-shaped valley over time will get deeper and deeper and the the V will form larger basically due to this repetition in the process.

Interlocking spurs are ridges extending into the river's course, which the river winds between, in the upper course the river lacks the power to erode through them.

So if we have a look at the picture that I've got here, those kind of ridge lines that come down are interlocking spurs and they're called interlocking spurs because they, they kind of interlock.

Now what has happened here, because the river doesn't have much energy, because it doesn't have that much water in it, the river can't erode straight through, and instead it winds in between these spurs.

Okay, so that's why it's called an interlocking spur.

Okay, right, let's check our understanding.

Can you name the land form of erosion for A, B, and C? Okay, so for A, we've got a V-shaped valley, B a waterfall and C, an interlocking spur.

Or spurs, well done if you got that right.

Okay, we're onto our next task for the lesson.

So I'd like you to put the statements in the correct order around the diagram.

Okay, so the statements on the right are muddled up, they're not in the right order.

Can you put them in the correct one? Okay, let's go through the answers.

So number one, the river erodes vertically, which deepens the channel and steepens the valley sides.

Number two, the valley sides collapse in on themselves creating a V-shape.

Number three, the steep valley sides are weakened by the process of weathering.

And number four, vertical erosion continues and the process repeats itself.

So well done if you got that right.

Okay, we're onto our final learning cycle which is looking about how waterfalls form.

Waterfalls occur where water in a river flows over a steep drop.

Okay, now this happens because of a change in rock type.

This can be where a layer of harder rock sits above a layer of softer rock, creating a step in the riverbed.

Okay, so you need a harder rock overlaying soft rock.

Now this is how it starts to form.

So the river erodes the soft rock, the softer, less resistant rock, more quickly than the harder rock, which is more resistant, creating a vertical drop in the riverbed.

So if you have a look at the diagram here, we can see hard rock on the top, soft rock below, the river overflows it but it erodes that softer rock quicker, creating a step.

Okay, so here we've got an image of a waterfall, that bit's the harder rock, and that bit is the softer rock.

As the river flows down the drop, hydraulic action and abrasion further erodes the softer rock below, creating a plunge pool.

Okay, so on the diagram here, that bit where the water falls into is known as a plunge pool.

Okay, so a nice picture of one there for you.

Let's just quickly check our understanding of what we've learned so far, so true or false, waterfalls form when hard rock overlays soft rock.

That is true, okay, and why is that? The river erodes the softer, less resistant rock more quickly than the harder, more resistant rock, creating a vertical drop in the riverbed.

So well done if you got that right.

Now, over time, the harder rock is undercut and collapses.

The rock fall contributes to the erosional processes of abrasion.

So if you have a look at the diagram here, you can see where that hard bit of rock was sticking out, over time, that can't support itself, so it's fallen into that plunge pool and all that material that was on that harder rock layer is now involved in more of those erosional processes.

Okay, we've got a lovely picture of a waterfall there with the plunge pool underneath.

As the waterfall retreats, okay, so it goes further upstream, it leaves behind a steep sided gorge with a river still running through it.

Okay, now, as this process continues of the harder rock collapsing in on itself, that waterfall now has moved backwards a little bit.

Now the whole cycle will happen again, and over time the waterfall goes further, further upstream, but in its place it leads a steep, leaves a steep, narrow passageway known as a gorge.

Okay, so a gorge is a narrow, steep sided valley that is typically found downstream of a waterfall.

It's where the waterfall used to be, okay? It is formed over hundreds of years as the waterfall retreats upstream.

Okay, let's check our understanding.

Can you put these diagrams in the correct order to show the formation of a waterfall? Okay, so there's number one, two, three and four.

Well done if you got that right.

Okay, we're onto our final tasks for this lesson.

First of all, I'd like you to label the picture with the following features.

So hard rock, soft rock, plunge pool, undercutting and vertical drop.

Okay, your second task for this is I'd like you to finish the sentences to explain how waterfalls erode a river channel backwards over time.

So pause the video and have a go at completing the sentences.

Okay, let's check our answers.

So here, now you didn't have to put the label exactly to where I've put it 'cause there's multiple places you could have put it really, but hopefully it'll be in this area.

So we've got hard rock where the waterfall is, softer rocks somewhere underneath, there you've got a little bit of undercutting because you can see that the water is flowing away from the rock.

There's the vertical drop and you've also got a plunge pool.

Okay, so here's my answers for this.

So the river flows over a steep cliff.

The softer rock is eroded backwards, undercutting the hard rock above.

The overhanging hard rock collapses.

A plunge pool develops as the force of the water erodes the bed at the bottom of the waterfall and a gorge develops as the waterfall retreats backwards.

So pause the video and just double check that you've got something similar to what I have written.

Okay? Here is a summary for today's lesson.

A river starts in the upper course at the source, and this is usually in an upland area.

Rivers in the upper course are usually small and slow, but with a steep gradient.

Erosion in the upper course of a river is usually vertical.

Land forms in the upper course of a river include V-shaped valleys, interlocking spurs, waterfalls and gorges.

And V-shaped valleys are steep sided valleys caused by vertical erosion.

Okay, right, that's it for today's lesson.

Great work, there was loads of cool stuff that we learned there, wasn't there? Okay then.

Right, that's it for me and I'll see you next time, bye.