4- Human Activity On Coasts

Question 1

What is intentional + unintentional human activity
Give examples

Answer 1

Intentional = deliberately changing coastal landscape
Eg: groynes, beach nourishment

Unintentional = activity that has other aims but still affects coasts
Eg: Harbour, sand mining

Question 2

Where is sandbanks spit + poole bay

Answer 2

• South UK in Dorset

Question 3

Why does sandbanks need management

Answer 3

• high value residential area
• Beach tourism
• Concerns about erosion = narrow spit is very vulnerable + losing 70,000m3/yr = negative sediment budget

Question 4

2 main management strategies at sandbanks

Answer 4

Rock groynes
Beach nourishment “Rainbowing”

Question 5

Description of rock groynes as a management strategy -SB

Answer 5

• 12 groynes placed along seaward side of spit
• traps sand on beach = reduce movement of LSD = maintains sediment on beach
• sediment on beach acts as natural barrier to wave energy

Question 6

Description of beach nourishment as a management strategy- SB

Answer 6

• boats spray sand onto beach to replace lost sediment
• 3.5million m3 added in total = costing £7.5 million
• increases sediment budget

Question 7

Effect of management on sandbanks

Answer 7

• beach has becomes steeper + wider as groynes trap sediment = unintentionally the supply of sediment is reduced further along coast = beach become starved of sediment (due to no LSD)
• spit is maintained + coastline has advanced slightly

Question 8

Wind at sandbanks- physical factor

Answer 8

• Prevailing wind over Atlantic =should have high energy but orientation of coastline means that sandbanks is partly sheltered by Isle of Perbeck

Question 9

Where is Mangawhai pakiri bay and how long is it

Answer 9

New Zealand , North island
Pakiri bay = 30km long

Question 10

How is human activity affecting pakiri bay

Answer 10

• mining sand from offshore sources = 75,000m3/year to make concrete to restore beaches at Auckland

Question 11

What is sandbanks spit protecting

Answer 11

• The spit protects Poole harbour (behind spit) absorbing wave energy

Question 12

What is the impact of reduced sediment supply in pakiri bay

Answer 12

• without the mining sediment would be in surplus shown by the formation of beaches and Managawhai spit
• with mining sediment in deficit
  = beaches become flatter , dunes become eroded + spit is breached by erosion

Question 13

Overall consequence at pakiri bay

Answer 13

• retreat of coastline + erosion of many depositional landforms such as spit

Question 14

What is the name of the island that protects sandbanks from high energy waves over Atlantic

Answer 14

Isle of Perbeck

Question 15

What are erosion rates estimated to be in Sandbanks if Management hadn’t taken place

Answer 15

1m / yr

Question 16

How large was the breach at the base of Managwhai spit during the storm in 1978

Answer 16

30m
- led to sedimentation of Managwhai Harbour = shallower = risk of flooding

Question 17

What are beaches like at Mangawhai and Pakiri

Answer 17

Starved of sediment = Wider and Flatter + less effective at absorbing waves = leads to erosion of landforms

Question 18

How far is the coastal retreat estimated to be at Managawhai-Pakiri by end of Century

Answer 18

35m