Coasts (Mock 1) Flashcards
What is dip?
- Tectonic feature
- Angle of inclination of rock strata
- Sedimentary rocks are deposited
- Tilted by tectonic forces
What is the case study for horizontal dip?
Glamorgan Heritage Coastline - Carboniferous Limestone
What angle is the strata on high angle seaward dips?
45°
What angle is the cliff face on a low angle seaward dip?
Over 90°
Where has experienced mass movement via rotational slumping
Christchurch Bay - Barton on Sea
Where has experienced mass movement due to rockfall?
The Jurassic Coastline - South Dorset in April 2020
Where has a discordant coastline
Bantry Bay, SW Ireland
What is the strata at Bantry Bay
RS: Devonian Old Red Sandstone
WS: Carboniferous Limestone
Where has a concordant coastline?
Lulworth Cove, South Dorset Coastline
What is the strata at Lulworth Cove?
RS: Portland Limestone
WS: Wealden Clay
What is the sediment cell in?
Dynamic equilibrium
Example of negative feedback loops
Wave cut notch -> blockfall -> natural rock armour -> blockfall less likely as cliff protected
Example of positive feedback loops
High winds remove plants from sand dunes -> no roots -> soil less stable and leaves don’t reduce wind -> Increased recession rates -> more sediment in the cell
Name a plant that grows in sand dunes?
Marram Grass
Name three policy options for coastal management
- Do nothing
- Managed realignment
- Hold the line
What is hard engineering?
Man made invasive structures that reduce flood risk
What is soft engineering?
Works with nature to protect the coastline
How long is the sea wall at Hornsea & Bridlington?
4.7 km
Where has a sea wall?
Hornsea & Bridlington
Where has groynes?
Holderness coastline -> Hornsea
How much do groynes cost?
£150 for every 2.5 km
How much does beach nourishment cost?
£2 million for every km
Where has experienced mangrove replanting?
Bangladesh - Sundarban
How much of Bangladesh has experienced mangrove replanting?
450 hectares
Where is at risk of sea level rise?
Maldives
If the sea rises by 50cm, what % of the Maldives will be lost?
77% - most resorts are only 100m from coastline
How many homes will be at risk of flooding in 2050?
32,000 UK homes
Where experienced economic losses at coastlines?
2014 South Devon Mainline
How much did the South Devon Mainline cost to repair?
£35m to repair -> cost SW £60m in losses
What causes eustatic sea level change?
Volume of water in ocean
What causes isostatic sea level change?
Uplift of coast
In the Devensian period, how much lower were sea levels?
120m lower
What % of sea level rise does the IPCC predict to be due to thermal expansion?
40%
How much has the Ganges Brahmaputra delta sunk by?
1.5m since 1960
What are four physical & human factors that impact coastal recession?
- Removal of mangroves in Bangladesh
- Seasons
- Dredging - Hallsands
- Wind direction & fetch
How much sediment was removed from Hallsands?
1500 tonnes of offshore sediment removed
How long is the fetch up to North Norfolk - and what are the recession rates?
1600km
8m / year
Stats about removal of mangroves
100m belt of mangroves reduces wave height by 40%
-Over 70% of Sundarban’s area has mangrove removal
How much of the Jurassic coastline fell and how much did it weigh?
300m of cliff fell away - weighed over 4000 tonnes
