Coasts - KQ2 (protecting coastlines) Flashcards
1
Q
Why is Norfolk vulnerable?
A
- Continued eustatic sea level rise/isostatic sinking in the south east
- Global warming on a lowland coast
- Cliffs made from low-resistant boulder clay and outwash sands = very susceptible to marine erosion
- Local taxes cannot fund £100M+ needed for coastal defences for next 10 years (67km of man made defence)
2
Q
What are the names and locations of the case studies?
A
Sea Palling
- East Norfolk
- 19.6 miles north-east of Norwich and 140 miles north-east of London
Overstrand
- North coast of Norfolk
- Two miles east of Cromer
Abbotts Hall Farm
- Essex
- Great Wigborough in the Blackwater estuary
3
Q
Why does Sea Palling need protection?
A
- 1953 storm surge in North Sea led to extreme flooding and water broke through dunes
- Cliffs made from weak clays and sands which will absorb rainwater which percolates the cliff
- Fens inland of Sea Palling is home of significant human activity
- Previous flooding means protection is needed
4
Q
Why does Overstrand need protection?
A
- Village of 1100 people on a 35 metre high cliff (with a history of collapse)
- 1994 and 1995 20m lost each of the cliff (only 5m away from the road)
- Cliffs underlain by Upper Chalk which is easily eroded
- Landslide in 1994 means people cannot sell homes easily/have insurance
5
Q
Why does Abbotts Hall Farm need protection?
A
- Large areas of salt marsh and mudflats lost to coastal erosion and development = significant impact on flora and fauna
- Heavy engineering could damage environmental and economic opportunities
- Many fish spawning and vegetation habitats in the salt marshes which needed protection
6
Q
What are the main coastal defence strategies in Sea Palling?
A
- 100,000 tonnes of boulders in front of the sea wall to prevent it collapsing
- Beach replenished with 1 million cubic metres of sand
- New set of offshore bars to break the waves before they reach the beach and absorb wave energy during storm events
SMP
- Maintain existing sea walls and reef structures
- Replace groynes and replenish beaches
7
Q
What are the main coastal defence strategies in Overstrand?
A
- Concrete sea wall built which protects majority of area
- Revetments and groynes
- Recurved sea wall with drainage holes
8
Q
What are the main coastal defence strategies in Abbotts Hall Farm?
A
Realignment of the coast = managed retreat
- Construction of counter walls at both ends of the existing sea wall (protect neighbouring farms)
- Construction of earth bunds to protect freshwater areas from saltwater intrusion
- An Environmental Impact Assessment was carried and area was monitored for 3 years prior to realignment
9
Q
What are the two types of coastal defence methods?
A
Hard engineering = controlled disruption of natural processes by using man-made structures
Soft engineering = more long-term and sustainable, with less impact on the environment
- Less expensive than hard engineering
10
Q
Sea wall
A
HARD
- Expensive (£5000 a metre to build)
- Can slowly erode (hydraulic action in the gaps between concrete sections)
- Curved wall to reflect wave energy
- Vertical to protect base of slop from marine erosion
11
Q
Wooden revetments
A
HARD
- 45* angle = large surface area for wave to break on so energy is dispersed and power reduced
12
Q
Gabions
A
HARD
- bundles of rocks in a metal mesh
- Placed at the base of a cliff in an attempt to reduce the impact of waves on the cliff and prevent the cliff from being undercut
- Not particularly effective and they’re quite unsightly but very cheap
13
Q
Groynes
A
HARD
- Low lying wooden walls that extend out to sea
- Capture sand that moves down the beach via longshore drift and helps build up a larger section of beach in front of an area that’s experiencing coastal erosion
- New beach will increase the distance that waves have to travel to reach the coast and, in the process, they’ll lose most of their energy, reducing their impact
- Effective but will remove a lot of the sand that’s present down-drift of the beach which will result in a thinner beach at this area = sections of the coast will be more exposed to erosion down drift of the groynes which can create new problems
14
Q
Rip Rap
A
HARD
- Rocks and stones that have been put against the base of a cliff
- Similar to gabions in their purpose but they aren’t bound together in a mesh = look slightly more appealing as they blend into the environment better however the rocks are susceptible to being moved by the sea
15
Q
Beach nourishment
A
SOFT
- Sand and shingle are added to a beach in order to make it wider
- Increases the distance a wave has to travel to reach the cliffs and so the wave will lose more energy and have less erosive power when it reaches the cliffs
- Sand and shingle has to be obtained from elsewhere and is normally obtained from dredging
