Coasts Flashcards

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1
Q

When was the Aswan dam built?

A

the 1960s

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2
Q

How much did river discharge fall after the Aswan dam was built?

A

35 billion cubic m/year to 10 billion cubic m/year

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3
Q

What happened to the sediment output when the Aswan dam was built?

A

Went from 130 million tonnes to 15 million tonnes

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4
Q

what happened to the erosion rate when the Aswan dam was built?

A

went from 20-25 m/year to 200 m/year

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5
Q

Give an example of a place where dredging took place

A

Hallsands in the 1890s

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6
Q

How much sediment was removed a day from Hallsands?

A

1500 tonnes

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7
Q

What happened to the beach level at Hallsands?

A

Began to fall due to the dredging

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8
Q

What effect did dredging have on the Hallsands by 1900?

A

The village was under serious threat from coastal erosion because there was no longer a beach to protect it.

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9
Q

What happened in 1917 at Hallsands?

A

A storm breached the coastal defences causing massive damage.

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10
Q

What is Hallsands like now?

A

It has been completely abandoned

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11
Q

Give an example of somewhere at risk of sea level rise

A

The Maldives

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12
Q

What is the population of the Maldives?

A

400,000

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13
Q

What is the highest elevation in the Maldives?

A

2.3 m

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14
Q

How much of the Maldives will be lost if sea levels rise by 0.5m?

A

77% of the land area

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15
Q

What is the average annual erosion rate at Holderness?

A

2 m/year

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16
Q

What is Holderness geology made up of?

A

Boulder clay left behind after a glacial retreat

17
Q

How long is the fetch along Holderness?

A

500-800 km to the north sea

18
Q

Why is erosion such a problem for Holderness? (waves)

A

Ocean currents move north around the UK from the atlantic to the north sea, depression weather systems cause frequent storms, and sea floor is deep in the north sea reducing energy lost by waves

19
Q

why is erosion such a problem for holderness? (geology)

A

boulder clay erodes easily and produces fine sediment which get lost out to sea

20
Q

where have sea defences been built at holderness?

A

At Withernsea, Bridlington, Mappleton and Hornsea. This is because cost benefit analysis showed that these areas had assets worth defending.

21
Q

where have defences not been built at holderness?

A

At Kilnsea the council did not fund sea defences due to a lack of assets worth protecting.

22
Q

What sea defences were built at Mappleton?

A

6000 tonnes of granite rock armour and 2 large groynes.

23
Q

What was the name of the tropical cyclone that hit Bangladesh in 2007?

A

Storm sidr

24
Q

What were the characteristics of storm sidr?

A

Storm surges 6m high and gales reaching 200 kph

25
Q

impacts of storm sidr?

A

3500 deaths due to drowning, sea water intrusion, and destruction of homes and infastructure

26
Q

What % of Bangladesh is currently protected by embankements?

A

60%

27
Q

Why is Bangladesh’s coastal management approach shifting from hard to soft engineering?

A

Hard engineering is expensive and may not be as effective in the long term.

28
Q

What are two ways Bangladesh is using soft engineering to reduce coastal recession?

A

Growing of artificial oyster reefs and mangrove planting.

29
Q

How do oyster reefs mitigate coastal recession?

A

once established they can grow to hundreds of metres, they promote sedimentation. This stabilises the land and allows vegetation to flourish.

30
Q

How much do mangroves reduce wave velocity?

A

29-92%

31
Q

According to the world bank if mangroves were lost how many more people would be affected by flooding a year?

A

18 million

32
Q

Why are mangrove planting and oyster reefs beneficial?

A

they offer ecosystem services such as providing food sources, marine habitats, and improving water quality.

33
Q

how do Bangladesh’s soft engineering schemes help locals? (economically)

A

There is a higher abundance of fish, shrimp, and crabs near the oyster reefs.

34
Q

How do mangrove forests play a role in climate mitigation?

A

They store significantly more carbon than terrestrial forrests.

35
Q

Why are eco-engineering strategies sustainable and cost-effective?

A

They don’t require costly repairs, they’re self-maintaining, and they can trap sediment to keep up with sea level rise.