Lesson video

Hello, my name is Mr. Conway.

I'm very pleased to have this opportunity to guide you through today's geography lesson.

The emphasis is going to be very much on using GIS or Geographical Information Systems. So let's get started.

Our particular focus in this lesson is using GIS to visualise the impact of physical and human processes on coasts within the unit coastal landscapes.

It's possible that the learning we do today in GIS maybe new, but I'm here to help you along the way.

So by the end of today's lesson, you'll be able to use GIS aerial imagery and web maps to visualise the impact of physical and human processes on coastal landscapes.

To help us achieve the outcome we're gonna need to learn or remind ourselves about certain keywords.

These are the keywords for today's lesson, historical imagery, temporal data, historical map, and geo-referenced.

Let's look at the definitions for these words in some more detail.

Historical imagery includes photographs from any time in the past, which can be compared with more recent photographs.

This includes aerial, satellite and conventional images.

Temporal data is any information which is linked to a particular point in time so that the data can be what's called time enabled.

And this is also known as spatial temporal data.

Combining the idea of spatial data with time so that we can visualise changes in places.

Historical maps are maps from any time in the past, which can be compared with any more recent maps.

And the final key word geo-referenced, is really important in GIS.

It means information which has been tied or linked to a particular location.

Sometimes we say it's been geo-located using an agreed system, typically latitude and longitude.

Today's lesson is about how to use GIS to visualise the impact of physical and human processes on coasts.

And the first learning cycle is going to consider how GIS can help us to visualise physical coastal processes.

The second learning cycle is going to address how GIS can help us visualise human coastal processes.

So we're going to look at the first of these learning cycles now.

And we're gonna start by looking at a case study from Malta.

And Malta is a small archipelago nation in the Mediterranean Sea, south of Italy and north of Libya.

Archipelago is a word we use to describe a group of islands, and the two largest islands of the Maltese Archipelago are Malta and Gozo.

The island of Malta and Gozo have some interesting and sometimes spectacular land forms. So we're going to see how we can visualise the action of coastal processes in Gozo.

One very famous coastal land form in Gozo, was an arch called the Azure Window.

But notice I'm using the past tense to talk about it.

Perhaps there's a reason for that.

It was truly spectacular.

It was at 28 metres tall or 92 feet.

It was made from limestone rock and it had long been a must see for visitors over many, many years.

And it became especially well known when it was used in a major TV series and achieved worldwide coverage.

So it really was a very major tourist attraction until it disappeared on the 8th of March, 2017.

Overnight it was gone.

One day it was there, the next day it was gone.

How can GIS help us to find out what happened? GIS can help us to visualise and analyse how the coastline can be changed by erosion caused by both physical and human processes.

GIS includes geospatial data such as digital maps, aerial and satellite imagery.

We can also use images from the past such as this 1912 photographic plate from the Geographical Association archive showing the famous old Harry Rocks in Dorset.

We can compare that with more recent data.

Such images are called historical imagery.

If we're using geospatial data, which visualises changes in geographical space over time, we call it temporal data or spatial temporal data.

We can also make very good use of maps from the pre-digital era, which were usually printed on paper or other materials such as leather.

And they often used all sorts of different projections or scales.

We call maps from before the digital era, historical maps, they can be quite tricky to compare with modern maps, but such comparisons can be made a lot easier if the historical maps have been geo-referenced, which makes sure that they are tied or aligned to a particular location that means they've been geo-located and we need to use an agreed system of doing that, such as very precise latitude and longitude.

So we're going to see how geo-referenced historical imagery can be used to visualise how coastal landscape has changed over time by erosion.

We're going to use the Esri World Imagery Wayback app, which is a GIS tool, which can be easily accessed online.

So we're going to see how geo-referenced historical imagery can be used to visualise how a coastal landscape is changed over time by erosion, we're going to use the Esri World Imagery Wayback app, which we sometimes just call the Wayback app for short, and it's a GIS tool that can be easily accessed online.

So the following video clip provides a step-by-step guide demonstrating how to use the Wayback app.

We're going to see how GIS can help us to visualise physical coastal processes, and one of those ways is to use historical images or historical imagery.

And a very good way to do that is to use the Esri Wayback app, which is a kind of library of historical satellite and a imagery going back for about 10 years already.

Let's find out what it can show us about the Azure Bridge in Gozo.

So we're gonna search for Gozo just here.

So I'm gonna type Gozo in Malta.

And it appears there is Gozo with its country code MLT.

So I'm gonna select that and it zooms straight to it, Now it goes there quite quickly.

So let's have a little look and see exactly where that is in the world.

We just zoom out for a moment.

We can see that Malta is an island in the Mediterranean Sea.

It's just south of Italy, and we can see exactly where it is, if we just move in a little bit more slowly.

There's the coast of Tunisia in Africa and there's the coast of Sicily at the centre of Italy.

So we have Malta, including Gozo just to the south of Sicily.

And the Azure Bridge was located on the western side of Gozo.

So we'll have a look at that in a little bit more detail now.

The location of the Azure Window can be a bit tricky to find.

So a quick way is to look for a nearby bay, which we're gonna type in here now, it's called Dwerja Bay, Malta.

So if we zoom into that, we'll probably find it quite easily.

Well, we can see Dwerja inland C, so it's near there.

However, what you'll notice is the imagery is showing different years.

What we actually need to do is go back before the Azure Window disappeared, which was in 2017.

So we go back to 201414 and click that.

We can hopefully see it and if we zoom into the coastline, indeed we can, it's right there.

Then we need something called swipe mode, and you can see an icon on the left and it says toggle swipe mode.

So if you click that, it then splits the screen so that you've got photos from potentially from two different times and two different sets of spatiotemporal data.

So we're going to leave the 2014 image, but on the other side, we're going to change to some time after we know that the window collapsed.

So to be on the safe side, I'm gonna on 2019.

The reason is that 2018 is quite close to that time, and sometimes these dates aren't entirely accurate.

So I'm gonna click 2019 and see what happens.

So hopefully you can see that we've got a different image on the right hand side, so we're going to use the swipe tool to see what that reveals.

So we're looking at 2014, and then we're going forward to after 2014, around 2019.

And sure enough, we can see that the Azure Bridge was no more, it had been destroyed by coastal erosion, by physical processes.

Now, it'd be nice to be able to share this swipe with other people and for future reference, and there are three ways you could do that.

One is to copy a link to the clipboard from this page, and if you share that, it'll take you to exactly this spot with the years concerned.

Another way is to record the swipe from the screen using software that's appropriate for that and edit it later.

And the third way within the Esri Wayback app itself, is to create an animation.

So we go to toggle animate mode, and what you're presented with is the possibility of all the years that we have, and you can see it scanning through those at the moment, that can be quite useful, but in our case, we're gonna keep it simple and just select the two years we were looking at.

So we untick the years that we don't want.

2018 and then all years after 2019.

So we literally have two years.

And the animation speed, as you can see is very quick, probably too quick.

So we're just gonna slow that right down so it's a little bit easier on the eye.

Then we can download the animation by clicking this button here.

And we're offered lots of choices, perhaps too many.

The horizontal ones are probably gonna be the most useful, and we do that, click one of those and it'll create the MP4.

And once downloaded, we can see it's ready there.

We can convert that if we need to or want to, to an animated GIF.

Soon you'll have a chance to create maps in the same way as you saw in the demonstration.

But before we do that, let's just check to see if you've picked up a few key points from the presentation.

So the first question is, in Esri Wayback, which button is used to show historical imagery from two dates? You may wish to pause the video here and restart it when you've selected your two answers.

Well done.

If you selected C, toggle swipe mode.

It's important to remember the word swipe is often used in GIS to compare layers with each other.

Let's move on to our second check.

In Esri Wayback, which button is used to show historical imagery from more than one date.

Pause the video here and restart it once you've selected your answer.

Well done if you selected B, toggle animate mode.

This is useful to remember if you are using temporal data.

Now for the tasks which will help you to use historical imagery with the Esri Wayback app to visualise coastal landscape processes as demonstrated in the video clip.

In order to do these tasks, you'll need to open the link you can see in front of you there, which will actually take you straight to the Azure Window area.

But the guidelines show you how to find it from scratch, as it were, in case you open the Esri Wayback app from its default location, which generally defaults to show somewhere in the USA.

Note that there are three suggested ways to save the imagery should you want to keep a copy.

So pause the video now to take some time to do the tasks, and when you are ready, press play again to obtain some feedback on the tasks.

So see you on the other side of the tasks.

Hopefully that task went well for you.

So hopefully your visualisation looks something like this.

So that you can move the central bar to swipe between the historical imagery for 2014 and 2019, shown quite clearly the disappearance of the Azure Bridge.

Let's look at our second learning cycle, which addresses the question, how can GIS visualise human coastal processes? This time we're going to use a different online app, which is National Library of Scotland Maps.

Sometimes it's called NLS Maps for short.

On their website, they provide access to millions of historical maps, and many of these have been painstakingly geo-referenced, to enable them to be very much more easily compared with other historical maps or present day maps.

And we're gonna use that to look at one particular area of the country to do with coastal processes.

And the area we're gonna study is the East Riding of Yorkshire, and a particular part of that called Holderness.

Now Holderness holds a dubious honour of being the fastest eroding coastline in Europe.

We're going to see how GIS can help us to find out how fast is that coastline eroding and how can human processes change the erosion rate along the Holderness coastline.

Before we do that, here are some important things to know about the part of the Holderness coastline we're going to study, which is around Mappleton, and that's a small settlement on the coast, which is under extreme threat from coastal erosion processes.

In an effort to protect Mappleton, in 1991, a 2 million pound coastal management project was completed.

It involved the installation of three very large rock groynes.

They were made from granite boulders dropped into place, and that's a type of hard engineering.

So how do these rock groynes actually work? Well, rock groynes like the ones at Mappleton, are designed to trap sediment from longshore drift in order to slow down the rate of erosion.

So what happens is that the rock groynes block the movement of sediment from longshore drift, trapping it mainly on the up drift side.

That's where the long longshore drift is coming from, and the trapped sediment absorbs the wave energy, which reduces erosion along the coastline.

However, on the downdrift side, you may notice in the photograph that the sediment is very much reduced, so that much less energy is absorbed on that side.

And that's because of the sediment tract on the updrift side.

So there are consequences of coastal management.

How can GIS help us to find out about the impact on the rate of coastal erosion? The following video clip provides a step-by-step guide demonstrating how we can use historical maps, geo-referenced by the National Library of Scotland to visualise human coastal processes at Holderness.

How can GIS and specifically NLS Maps help us to visualise human coastal processes at Mappleton? Well, what the National Library of Scotland or NLS Maps collection provides us with is literally thousands of historical maps.

So we can go back in time to see what the landscape looked like when the surveying was actually quite accurate, and compare that with what conditions are like on later dates, right up to the present day.

So we're going to look at that using the National Library of Scotland Geo-reference Maps, which means they're located very accurately and we can use the side by side with swipe on, which means we can move the central panel to look between maps of different times.

So the first thing we're going to do is search for Mappleton.

If we go to the search box here and we type Mappleton, we're gonna use the modern spelling of it.

If you spell it with one P, it won't find it in the search, even though in the past it used to be spelt with one letter P, so that's potentially confusing, but that goes with the territory of looking for old maps sometimes.

So we click Mappleton, East Riding of Yorkshire, which is the modern spelling, and it'll take us straight there.

Then minimise both choose a layer panels by clicking X and then we can use the swipe control to look between the historical map and the recent imagery, which at this scale is mainly aerial imagery.

And what you might notice is there's a bit of a contrast in the coastline at these two points in time.

So the temporal data is suggesting to us there's been a big change.

If we zoom in just a little bit, we can see some detail.

So if we swipe to and fro, we can see that there's certainly been the loss of some coastline over the years in spite of the fact that the land here, you can see from the spot heights is nearly all over 50 feet above sea level.

So it would've been on the top of these cliffs and the cliffs have been receding.

There's also been some loss of a little bit of infrastructure.

You can see Cliff Lane there has pretty much gone and there was another lane possibly down there.

And the other thing is you can see a slight change in the buildings in Mappleton, which to all intents and purposes is intact.

You see some new builds around here and possibly some new builds around here.

So that we can spot these changes over time.

We can go a step further because these historical maps, this temporal data has been geo-referenced very precisely.

So we can do some calculations using the measure tools in the top right hand corner.

The measure tool we want is measured distance, and as soon as we click it, an orange dot appears.

So I'm gonna place the dot roughly where the coastline was back in the day about 120 years ago.

I'm gonna click the dot once to start the measurement process, swipe the map back so I can see what the coastline is like nowadays.

Then I'm gonna try to find a point where the coastline is nowadays with the orange dot.

And ideally that should be perpendicular at right angles to the coast.

It isn't at the moment, so I'm gonna adjust the line until it's closer to being perpendicular.

It's not perfect, this will give a fairer judgement of how much the coast has receded.

Then I double click to get the answer, which is 132.

82 metres.

That's very useful information to us.

If we divide that number by 120 years, we can find out the rate of erosion.

And doing the calculation it works out to be about 1.

12 metres or about 112 centimetres per year over the last 120 years on average.

So there's no question that the coastal erosion here is pretty rapid and Mappleton is under threat.

We can see how close it is to the coastline compared to where it was 120 years ago.

But what's happened in its favour is that it has quite substantial coastal defences.

If we look and see what's happened now, we can see three rock groynes that were installed in 1991 to protect Mappleton and the way they work is that they tried to collect sediment from longshore drift so that the beach material builds up in sufficient quantities in front of the cliffs by Mappleton.

Absorbing the wave energy and thereby reducing the rate of erosion in front of Mappleton to offer it some protection from coastal erosion.

The groynes have obviously bought some time for Mappleton, but have they had any other impacts? Let's have a look bit further down the coast.

We're going to drag the map back so that we can look and see the place names.

And move the map slightly further south to a place called Great Cowden, which is a slightly smaller settlement right on the coast.

There are quite a few buildings, most likely houses, together with a Methodist chapel, a pub, a historical feature remote, and a certain amount of infrastructure.

You've got footpaths and roads and so forth.

And the spot heights on the map indicate that Great Cowden is much the same height above sea level as Mappleton.

That is well over 50 feet.

We can measure the amount of coast lost here in a moment, but we can also use the swipe to give us some impression of how Great Cowden is getting on.

Oh dear, we see that the whole settlement has completely disappeared.

This coastline has been eroding so fast, the Great Cowden community no longer exists.

The loss of Great Cowden is one of many sad stories along this coastline where we think about 30 settlements have been washed into the sea over the last few hundred years.

There are clearly natural physical processes at work on the coastline, but have human processes had a role to play? Let's use the measure tools to see if we can compare the rates of erosion at Great Cowden with that at Mappleton.

So we go to measure distance, we see the orange dot appearing, and we're gonna find a spot just in front of the pub, it was called the Cross Keys Pub, and see how much of the coastline is eroded there.

So we click once, then we draw back the map to show the imagery now.

Now we try to find a perpendicular line back to the coast and just about there we double click and we find that distance is 241.

73 metres of coastal erosion in their last 120 years.

So if we divide that by 120, we find that the rate of erosion is over two metres per year.

To be precise, it's 2.

01 metres or 201 centimetres per year, which represents a significant difference between Great Cowden and Mappleton of about 0.

89 metres per year over the last 120 years on average.

So our investigation has shown that the coastal defences at Mappleton have made a significant difference.

You can actually see quite a significant difference in the rate of erosion between the area which has the groynes and therefore more sediment protecting the coastline and the area further to the south or down drift, which is being eroded significantly more quickly than the area to the north.

Soon you'll have a chance to use NLS maps just as you saw in the video demonstration.

But before we do that, let's just check and see if you picked up a few key points from that.

Your first check is to select the key word referring to maps from the past, which can be compared with more recent maps.

You may wish to pause the video here and restart it when you've selected your answer.

Hopefully you chose historical map and well done if you did.

Now for the second check.

In NLS Maps, which GIS tool helps us to find the average rate of coastal erosion in metres per year, which we've abbreviated.

Pause the video here if you wish, and restart it when you've selected your answer.

Well done if you chose Measure distance, which is not to be confused with Measure Bearing, Asmuth or area, which are other options available in the measure tools part of NLS maps.

Now for the tasks which will help you to use historical maps which have been geo-referenced to visualise human coastal processes as demonstrated in the video clips, in order to do these tasks, you'll need to open the Oak link shown for NLS maps and complete these tasks, including some calculations.

So there's task one with three components, helping you to use GIS to investigate human coastal processes at Mappleton.

Task two, which has four components, helps you to use GIS to investigate human coastal processes at the nearby settlement of Great Cowden.

So pause the video now to take some time to do the tasks, and when you are ready, press play to obtain some feedback, see you on the other side of the tasks.

Hopefully the task went well for you.

For task 1a, how can GIS visualise human coastal processes at Mappleton? The visualisation on your screen should look rather like this, using NLS maps side by side with the swipe on to visualise coastal change at Mappleton.

For task 1b, you needed to identify some changes between the historical map and recent imagery.

Your answers may have included points along these lines.

We certainly could see some loss of coastline, much of which was over 50 feet above sea level.

We could also observe the loss of some farmland and infrastructure such as roads.

Q And there were some newer buildings which seemed to have appeared especially to the north side of the settlement.

Then for 1c, you needed to use the measure distance tool to calculate the average annual rate of coastal erosion or E at Mappleton.

The answer obtained in the video demonstration was that E equals 132.

82 divided by 120.

That's the number of years approximately, which meant that we got an average rate of erosion of 1.

12 metres per year.

Now, your answer may well have been different to that, depending on where you measured, but your value for the distance letter D, should have been somewhere between 120 and 140 metres, which meant that your answer would've been something like one to 1.

17 metres per year.

For task 2a, how can GIS visualise human coastal processes at Great Cowden? The visualisation on your screen should look something like this, remembering of course that you need to have the swipe on in the side by side facility to visualise coastal change at Great Cowden.

Now for task 2b, you were asked to identify changes to the coastline over the years at Great Cowden, your answers may have noticed things like these.

There's been a major loss of the coastline, much of which just as at Mappleton was over 50 feet above sea level.

There was significant loss of farmland and infrastructure such as roads, footpaths, pumps, a letterbox, and something called the old lime kiln.

And of course, there was wholesale destruction of Great Cowden settlement and the community, including the buildings, probably houses chapel, pub, historical feature called a moat, Lots of things disappeared.

In fact, the whole settlement's gone.

Then for 2c, you needed to use the measure distance tool to calculate the average annual rate of erosion or E at Great Cowden.

The answer obtained in the video demonstration was that E is 241.

73.

That's the D value divided by 120.

That's the number of years, giving us 2.

01 metres per year, which is 0.

89 metres getting on for a whole metre per year faster than Mappleton's rate of 1.

12 metres per year.

Your answer is likely to be slightly different to that, but your value for the distance should be somewhere between 230 and 250 metres, which means that the annual rate should be between 1.

91 and 2.

08 metres per year.

Finally, for 2d, you were asked to summarise what impact the groynes at Mappleton have had on Great Cowden.

And the following ideas would be very good to include.

Sediment has been trapped by the groynes at Mappleton.

That's quite clear, that sediment absorbs wave energy and that slows the erosion at Mappleton.

Consequently however, less sediment is being deposited to the south of the groins, at Great Cowden.

So the erosion rate along that coastline is much faster, and we've got the figures to prove it.

This explains why decisions about coastal management can be controversial.

Well done, we've covered a very wide range of GIS knowledge and skills, and it's highly recommended that you return to them and practise so that your GIS capabilities you've learned have become fluent.

Let's just summarise our learning today.

First of all, GIS uses historical imagery to visualise and analyse how coastal changes happen over time.

In this way, historical imagery becomes what we can call temporal data.

GIS uses historical maps to analyse how the coastline changes using older maps, which have been geo-referenced to enable accurate comparisons.

That geo-referencing is absolutely crucial.

There are various GIS apps which enable us to use temporal data, and the ones we use were Esri Wayback, and NLS maps.

Finally, we learned how GIS can use historical imagery and historical maps to measure changes such as the rate of coastal erosion and the way the rate of erosion can change significantly over a short distance due to human processes.

So we've used here some very useful GIS techniques in two different apps in this lesson, excellent work.

Hopefully you've found the learning interesting and useful and you can use this sort of learning to explore other places that you're studying.

I look forward to learning together with you again in another lesson.

So all the best for now.