Boscastle floods August 16th 2004

LO: 1. Identify the causes of the Boscastle floods.2. Explain the causes of flooding in Boscastle.

NOTE: You will write an essay in class on this, Thursday April 6th

Boscastle is on the north coast of Cornwall (SW England), has a picturesque harbour and a 16th Century quay, cliff top walks, and is a tourist destination.

Before the flood it looked like this…

The rock type might be significant…

Can you picture the contour lines?

Don’t be fooled by the greenness; there’s a lot of farmland in the hills…

TASK1: As they’re unclear on the map, highlight the course of the rivers Jordan, Paradise + Valency AND mark the confluence points (I’ll show you first)1: Paradise feeds Valency 2: Source of Jordan 3: Source of Paradise 4: Jordan feeds Valency 5: Route of River Valency 6: Another tributary

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TASK2: Study the map; identify features/characteristics of the area which could lead to flooding. You have 4:45mins to come up with an initial list of possible flooding factors indicated through this map at each table, then we’ll make a class list.

TASK3: Circle or label each feature + write an annotation to explain its relevance to flooding – we’ll look at an example linked to the contour lines on the next slide…

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1: Main urban area (town)2: Close contour lines; slope from 257m to sea level within just a few 100m! 3: Lack of vegetation on bare hillsides.4: Farm, grazing animals: in winter there will be even less + grazing animals compact land, reducing infiltration. 5: Mostly impermeable rock

6: Wooded area – crucially, small and at the bottom of the slope…

ExampleThe contour lines being close together show the land is steep. This means when it rains there would not be much infiltration but rapid surface run off, leading to flooding.

This is a short explanation of the point (though it does use some terminology), lacking specific evidence – you should aim for clearer, more developed analysis in your essay!Any suggestions on how we could develop this point?

1. Infiltration2. Saturation3. Meander4. Tributary5. Confluence6. Drainage basin7. Abrasion8. Traction 9. Deposition10. Transpiration

A quick spelling test• Write down the following terms, then we will mark

your spelling /10 and check our understanding of these [freeze screen!]

BBC

BBC

1. Infiltration2. Saturation3. Meander4. Tributary5. Confluence6. Drainage basin7. Abrasion8. Traction 9. Deposition10. Transpiration

InfiltrationSaturationMeanderTributaryConfluenceDrainage basinAbrasionTraction DepositionTranspiration

Here’s how the flood advanced15:43 Bank Full

16:06 +23 min

16:13 +30 min

16:44 +1hr 01 min

16:51 +1hr 08 min

16:53 +1hr 10 min

16:58 +1hr 15 min

18:13 +2hr 30 min

AUGUST 17TH 2004When the flood water receded, the

devastation was clear…

We will look at 2 videos; you can re-view these at home through my blog. stgeog.blogspot.lu

These focus on the impact of the flood; your focus must be on the CAUSES of the flood (the essay title!).

You need to keep updating your list of factors, but also need to take clear, specific notes on facts, figures, data which might help you in your essay!

Video (BBC News explains the floods 2:20mins)

Video clip2: slips of the flood from multi cameras (4:29mins)

You will have a copy of this essay planning framework

ROOM CHANGES• On the following days, to be noted in your planners,

we will be in B348, to help you to carry out research + preparation for your Boscastle essay. Please note:

• Bring headphones if you want to view videos• You cannot access my blog in school; save/email links to

yourself if you want to find these resources• You do not have to use PCs in the lesson – feel free to

practice writing the essay!

• 7CW: Thursday 30th P3 + Tuesday 4th P4• 7PAC: Thursday 30th P4 + Wednesday 5th P6

ESSAY TITLE:Explain the causes of the

Boscastle flood.• What physical factors could you use as a focus for a

paragraph? You will need to pick two of these including the basic element…

• What human factors could you use as a focus for a paragraph? You will need to pick at least one of these (total 3 or 4 main points plus introduction + conclusion)

Amount of rainfall (precipitation) Steep slopes (tight contour lines) … impacts SPEED

(think about drainage basin too) 3 rivers meeting (confluence point; tributaries) Rock type (impermeable)

Farming: lack of vegetation, deforestation, grazing compacting land

Urbanisation Concreting, tarmacking, buildings

Essay WAGOLL – main body paragraph

One of the main reasons why Boscastle flooded was due to the high levels of rainfall. On the day of the flood over 130mm of rain fell in 6 hours. This is especially significant when the average monthly rainfall is only 70-90mm. It meant that the drainage basin couldn't cope with so much additional water. The soil and rock rapidly became saturated meaning that no further infiltration could take place. This meant the water could not get into the soil so had no where else to go other than flow rapidly over the land, as surface run-off, into the bottom of the valley where it led to a rapid rise in the river level leading to a flood.

Your task: PEE colour code this paragraph: Point, Evidence, Explanation

Essay WAGOLL – main body paragraph (PEE)

One of the main reasons why Boscastle flooded was due to the high levels of rainfall. On the day of the flood over 130mm of rain fell in 6 hours. This is especially significant when the average monthly rainfall is only 70-90mm. It meant that the drainage basin couldn't cope with so much additional water. The soil and rock rapidly became saturated meaning that no further infiltration could take place. This meant the water could not get into the soil so had no where else to go other than flow rapidly over the land, as surface run-off, into the bottom of the valley where it led to a rapid rise in the river level leading to a flood.