Coasts and Rivers case studies

Question 1

Where is Christchurch Bay?

Answer 1

• Located on England’s South coast near Bournemouth
• There are lots of residential areas and developments, such as in Highcliffe, Barton-on-Sea and Christchurch

Question 2

Why does Christchurch’s coastal location affect it’s landscape?

Answer 2

• The Coastline of Christchurch Bay experiences the full force of waves brought from the Atlantic, that have a long fetch, so they’re very powerful
• Powerful waves quickly erode the cliff bases through hydraulic action and abrasion which makes them unstable and vulnerable to collapse

Question 3

Why does Christchurch Bay’s geology affect its landscape?

Answer 3

• The cliffs on the coastline are made of sandstones and clays, which are easily eroded, and they’re also very permeable
• High permeability means water can easily infiltrate and saturate the cliffs during wet periods, which adds weight, increases instability and encourages mass movement and collapse

Question 4

Why does Christchurch Bay’s physical features affect its landscape?

Answer 4

• Several rivers in the area flow to the coast through steep sided coastal gorges called Chines
• The rivers usually infiltrate and flow through the permeable rock by the time they reach the coast which causes instability and erosion

Question 5

How have settlements affected Christchurch Bay’s landscape?

Answer 5

• Decades of erosion have caused the cliffs to retreat by tens of metres, and now many buildings are very close to cliffs
• Extra weight on the cliff tops from buildings combined with existing instability can cause cliffs to collapse

Question 6

How have planning and managing affected Christchurch Bay’s landscape?

Answer 6

• Coastal defences in some areas have failed to work and actually led to increased erosion
• Poor planning resulted in ‘terminal groyne syndrome’
• This is where groynes cause sediment buildup on one side of the groyne but starve an area of sediment on the other side
• Groynes were built on Christchurch bay to protect cliffs on the West but it starved the beach of sediment further East and caused very rapid erosion

Question 7

How have developments affected Christchurch Bay’s landscape?

Answer 7

• Residential and industrial developments have created impermeable surfaces further inland and altered the natural drainage system of the coastal area.
• More water is drained directly into the coastal cliffs rather than into soil and groundwater stores inland

Question 8

Where is Boscastle and when did it flood?

Answer 8

• A small coastal settlement in the south-west of England
• It flooded in August 2004

Question 9

What were the causes of flooding in Boscastle?

Answer 9

• Heavy localised rainfall (89mm in one hour)
• Saturated ground from previous rainfall
• Topography of the land (Upstream is a steep-sided valley)
• Narrow river channels

Question 10

What has Boscastle done to prevent future flooding?

Answer 10

• £4.5 million spent on a flood defence scheme
• The scheme stretches along the valley, incorporating drainage, sewerage systems and land re-grading
• Boscastle car park has been raised in height
• New drains allow water to run into the lower section of the river quicker
• The river channel has been made deeper and wider

Question 11

Which rivers flooded in Boscastle?

Answer 11

• Valency
• Jordan

Question 12

What were the social impacts of the Boscastle flood?

Answer 12

• Costly rescue operation involving helicopters, lifeboats, and the fire service
• Loss of 50 cars
• Damage to homes and businesses
• A loss of tourism

Question 13

What were other impacts of the Boscastle flood?

Answer 13

• Environmental damage to local wildlife habitats
• Coastal pollution as debris and fuel from cars flowed out to sea
• Long term disruption to the village