Liz Bonnin introduces a clip which examines the coastal features of a spit, backwash and longshore drift.
LIZ BONNIN: Hi, I鈥檓 Liz Bonnin. Now if I say the word 鈥榮pit鈥 and 鈥榖ackwash鈥 to you, you might think I鈥檓 about to start talking about a trip to the dentist. Don鈥檛 worry, I鈥檓 not.
This is physical geography, where a spit is a stretch of beach that juts out into the sea, and backwash is the force with which the waves return to the sea causing it to move and change.
To demonstrate this, let鈥檚 check out a clip featuring Katie Knapman from the Countryfile team, who鈥檚 in Spurn Head, off the coast of Yorkshire. A place where shifting sands are a serious business.
KATIE KNAPMAN: Although this spit has been here for hundreds of years, it鈥檚 a very dynamic piece of land. It鈥檚 always on the move. The sea may have shaped it and built it, but it also has the power to move it.
Despite this constant shift, people still live and work here. There鈥檚 a permanently manned RNLI Lifeboat station at the point, and piloted boats are on hand to guide vessels through one of our busiest shipping channels.
Out there on the horizon, just over two miles away, you can just about make out a met mast, which is a piece of equipment used to measure weather conditions. It also marks the point where the coast line was in Roman times, and that shows you just how much this landscape has changed over time.
On average, the spurn moves west up to two metres, or nearly 7 feet, a year. It鈥檚 all down to longshore drift, a natural process that never rests. I鈥檓 meeting geologist, Dr Yan Zalasiewicz, from Leicester University, to find out more.
Longshore drift, classic geography term.
DR ZALASIEWICZ: It is, yes.
KATIE KNAPMAN: Can you explain that?
DR ZALASIEWICZ: Well, I suppose it鈥檚 a classic spit, which is formed by material being washed by the sea out of these cliffs of boulder clay. The waves attack them. They break them down actually at the rate of one or two metres a year. The mud and the sand and the pebbles are washed out. The waves will carry the pebbles up the beach like this. Normally coming at an angle. And then the backwash comes, so it will simply drop back down the beach here. The next wave will come, pick it up, take it diagonally again and down it goes again. So it will go on travelling, it will do a zig-zag along the beach, and simply, will carry on.
KATIE KNAPMAN: So more and more material will be taken from one side of the beach, right along, and that is how the spit will form.
DR ZALASIEWICZ: It is how the spit forms. It鈥檚 an ongoing conveyer belt. Material is always coming out of the cliffs, that鈥檚 the supply, and it鈥檚 carrying on down, and it鈥檚 just travelling. You know, it鈥檒l travel miles and miles.
KATIE KNAPMAN: In the past, man has tried to check this movement and prevent erosion by protecting the land from the sea鈥檚 natural passage. The Victorians set up a series of sea defences to hold back the waves. They were maintained by the MOD until the late 1950s.
Since then, the Yorkshire Wildlife Trust has been responsible for the management of the spurn. Now a designated National Nature Reserve.
Andrew Gibson is the full time warden in charge and he鈥檚 going to show me around the reserve.
Now the sea is just over this bank here.
ANDREW GIBSON: It is, it鈥檚 just over on our left.
KATIE KNAPMAN: When you鈥檝e got your spring tides, is the sea actually washing over this bit of land?
ANDREW GIBSON: It will come over. Believe it or not, that鈥檚 what we want. We want it to wash over and move westwards which is what it would do naturally.
KATIE KNAPMAN: You want nature to shape this land?
ANDREW GIBSON: We do but we need to manage it for our own benefit as well, and it鈥檚 striking that compromise between the two things.
KATIE KNAPMAN: There we go. Oh my goodness, it鈥檚 blowing a gale! So what鈥檚 the important thing about this bit of road and that bit of road?
ANDREW GIBSON: Well, that鈥檚 your traditional tarmac road which would say bad road. This is good road. This is a removable interlocking concrete block. But it allows us to do is you can see the sand migrate over this very easily, and if the dynamic coastline, as it moves, washes it away, we can pick this material up, put it back in the recycler and bring it back out. Whereas the tarmac road is fixed, it鈥檚 hard, it needs a sub-base. It鈥檚 a hard scar on the landscape should we say. Whereas what we need is dynamism.
LIZ BONNIN: I love that. The ground beneath you keeps moving, so of course, you need a road that you can recycle. Fantastic.
Katie Knapman defines the coastal feature of a 'spit' before visiting Spurn Head to examine the impact of shifting sands.
The clip shows a spit as a dynamic landscape that is constantly changing due to longshore drift and the effect of backwash. It explains that the area used to be managed with coastal defences, before a decision to designate the area as a nature reserve without coastal management techniques.
The team visit a new road surface that is recyclable - meaning that if the coastline changes and the road needs to be moved, it can simply be picked up and relocated elsewhere.
Teacher Notes
Key Stage 3
Students could watch this short film before or after learning about the formation of a spit and use it as a basis to consider why a spit is not in a set position on the landscape.
Students could use the clip to consider whether coastal areas should always be protected or whether it is right to let the sea claim some land.
Key Stage 4
This short film could be used to reinforce the idea of coastal landscapes as dynamic and ever-changing.
Students could draw a series of diagrams showing what might happen to the spit in the future under a range of different scenarios.
The idea of the recyclable road can be linked to sustainable coastal management and the idea of ensuring that infrastructure is sustainable in the long-term.
Curriculum Notes
This topic appears in Geography at KS3 (Hydrology) and KS4 / GCSE (Rivers and water) in England, Wales and Northern Ireland and National 4/5 in Scotland.
More geography clips with Liz Bonnin:
What is the water cycle? video
Iain Stewart describes the water cycle including evaporation, condensation and precipitation.
How does a river change as it travels downstream? video
An archive clip of Sir David Attenborough as he follows the course of the Amazon River as it travels downstream.
The erosion of the Grand Canyon. video
Liz Bonnin introduces the Grand Canyon - its ancient geology and what can be learned from the erosion of the rocks.
What coastal management techniques are being used on Hayling Island? video
Introduces the coastal management techniques used on Hayling Island in Hampshire to control drift and flooding.
The geology of the Jurassic Coast. video
Exploring the Jurassic coastline and its geological significance with rocks spanning the Cretaceous, Jurassic and Triassic periods.
How have physical processes impacted the landscape of Yorkshire? video
Julia Bradbury explains the formation of Malham Cove including limestone pavement, highlighting the impact of glaciers on the landscape.
Glaciation and the UK coastline. video
Alice Roberts explains how Britain was once connected to Europe, but changed due to rising sea-levels following the Ice Age.
How has glaciation shaped the landforms of the Northern Hemisphere? video
Iain Stewart explains the glaciation of the Northern Hemisphere, focusing on the Yosemite Valley in California.
What evidence is there for climate change in the UK? video
Tom Heap considers the evidence that the UK climate might be changing - with more droughts, higher summer temperatures, but wetter winters.
How can plate tectonics impact oceans? video
Exploring how the plate tectonics impacts the coastline, focusing on California through study of the San Andreas fault.
Plate tectonics in the UK - Anglesey. video
Nick Crane explores the geology and seismology of Anglesey - earthquake hot spot of the UK.
Deforestation and the growth of soya in Paraguay. video
Simon Reeves visits Paraguay to consider the deforestation that has occurred there to grow soy and the challenge of conservation vs development.
