Flooding 3 – Case study UK

Key idea

Lesson objectives:

By the end of the lesson you should be able to

•Name an area in the UK that has experienced devastating flooding.

•Be able to state some of the physical reasons behind the flooding.

•Be able to state what impacts the flood had on the area and local people. (Some of you may be able to classify these impacts into those that were social, economic and environmental, and whether they are long or short term impacts.)

•Be able to state how people responded to the floods. (You may consider how effective the response was)

•Explain the measures taken to try to prevent future flooding events in this area.

Poem

What happened?

• http://news.bbc.co.uk/player/nol/newsid_4150000/newsid_4155600/4155688.stm?bw=bb&mp=wm&news=1&bbcws=1#

http://www.metoffice.gov.uk/education/teens/popup/popup_wboardap_sat_image_boscastle.html

RainfallThe rainfall rate key shows how the colours in the image relate to the rate the rainfall is falling. For example, the red areas indicate that rain is falling at between eight and 16 mm per hour.

• A line of very heavy rain starts at about 1 p.m. on the moors close to Boscastle. It remains over the area for about six hours. Rainfall rates of at least 32 mm per hour are being measured.

Weather chart• The wind is blowing

anticlockwise about the low pressure area, so the air is arriving into Boscastle from a south-westerly direction. It is a warm and moist tropical maritime air mass.

• The line labelled (known as a trough line) caused very heavy rain and thunderstorms. A trough is an area of localised rain and thunderstorms. A line of convergence formed near the coast line, where air moving in almost opposite directions collides, this helped to increase the rate of ascent and produced very heavy rain.

Causes of the flood:

1. Heavy localised rainfall. 89mm of rain fell in an hour.2. Saturated ground from previous rainfall.3. Topography of the land – the landscape upstream of

Boscastle acts as a funnel, directing vast volumes of water into the village. The valley sides are steep sided.

4. Narrow river channels in the village itself.

Boscastle Harbour

Saturated ground.

16 August 2004, Boscastle, CornwallA summer storm dropped 200 millimtetres of

rain in four hours90 millimetres of rain fell in one hour The water ran down steel hillsides in to the River Valency and River Jordan causing two rivers to burst their banks. The confluence of the two rivers lies just above BoscastleA 3 metre high wall of water swept through the village. Residents had little time to react. Cars were swept out to seaBuildings were badly damaged.Fortunately, nobody died - thanks largely to a huge rescue operation involving helicopters.

Effects …• Destruction of houses, businesses and

gardensFloodwater gushed into houses, shops and pubs.

• Cars, walls and even bridges were washed away.

• The church was filled with six feet of mud and water.

• Trees were uprooted and swept into peoples' gardens.

• The weight of water eroded river banks, damaged gardens and pavements.

Short Term effects● Roads were blocked off by the floodwater, making

emergency access difficult except from the air. Even when rescue helicopters arrived, the valley was only big enough for two to operate at any one time, prolonging the operation & putting lives at risk from the still rising flood waters.

● Property was destroyed by debris such as entire trees & vehicles speeding down the valley at high speed, pulled out towards the sea by the raging torrent. Buildings were smashed, especially in the main street where the river channel flows.

● People were trapped in buildings by the floodwater & forced to seek refuge on the roofs of the buildings & await rescue.

● People were left homeless for the night, so emergency accommodation had to be set up. Nearby hotels & guest houses were packed with tourists who had arrived in Boscastle in the morning & had lost their cars.

● A burst sewage main & damaged buildings made much of Boscastle inaccessible for health & safety reasons for at least a few days.

Long Term Effects● Floodwater damaged a great deal of properties.

Possessions were lost, river water & a burst sewage main spoiled the ground floor of many houses & thousands of pounds worth of damage was done.

● Repairs had to be made after the damage. This was very time consuming & costly. Some buildings were beyond repair & their owners have had to consider rebuilding from scratch.

● The damage not only affected the residents, but also insurance companies.

● Boscastle's main industry is tourism. The town was effectively closed to tourists after the flood, causing a massive loss of revenue.

Human Impacts

There was a huge financial cost to the floods. This included:

• the rescue operation - involving helicopters, lifeboats, and the fire service.

• the loss of 50 cars • damage to homes, businesses and

land • a loss of tourism, a major source of

income for the area

Other key impacts on Boscastle and its inhabitants

• environmental damage to local wildlife habitats

• coastal pollution caused as debris and fuel from cars flowed out to sea.

• long-term disruption to the village, as a major rebuild project had to be carried out.

• long-term stress and anxiety to people traumatised by the incident.

Responses

Immediate

• Emergency services responded speedily and efficiently

• Helicopters airlifted 80 people to safety from roof tops

Medium and long term responses

• £800,000 flood defence scheme completed in Boscastle by April 2005

• Engineers investigating future flood control works on River Valency

A £4.5m scheme to improve flood defences.

Boscastle main car park.

The scheme stretches along the valley, incorporating drainage, sewerage systems and land re-grading.

Boscastle main car park.

The river bed is being deepened by six feet to accommodate more water volume in times of flood.

Boscastle car park is being raised in height. This will stop the river from bursting it’s banks so easily.

This drain allows water to run into the lower section of the river quickly.

• A concrete culvert running behind a row of eight cottages. This converts to a concrete pipe running down a road to an outfall into the river Valency, downstream of the main bridge through the village

The river channel is being made deeper and wider so that it can accommodate more water.

The lower section of the village.

New sewerage systems are being put in place.

The lower section of the village.

Bridges that hindered the drainage of the floodwater are being replaced by stronger bridges that are less likely to get blocked.

The lower section of the village.

Notice attempts to draw in much needed custom.

The new lower bridge is an important part of the £4.6 million flood defence scheme, as it spans a channel specially widened to help reduce flood risk to local residents, homes and businesses near the harbour.  It will carry traffic as well as pedestrians and will replace the existing bridge

source

Many buildings have indicators to show the

height of the flood water.

The core of the village.

Plenary

• What is the significance of these numbers?

• 16

• 90

• 3

• 4.5 million

• 0