case study - sand mining Flashcards

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1
Q

where is the area of study?

A

mangawhai-pakiri coastline, 50km north of auckland on the east coast of NZs northland peninsula

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2
Q

why is sand in central mineral resource in a modern economy?

A

used for:
-Construction
-concrete making
-Glass manufacturing
-Beach replenishment

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3
Q

Where is the high-quality sand found?

A

-nearshore zone at mangawhai-pakiri

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4
Q

what is Auckland?

A

New Zealand’s largest and economically most dynamic metropolitan region

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5
Q

What is Auckland’s population?

A

Over 1.5 million

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6
Q

What does Auckland’s regional account for?

A

over one third of New Zealand’s, total population, and 35% of the countries GDP

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7
Q

how is the region rapidly growing?

A

-Finance and high-tech industries are growing
-Tourism is a large part- in 2015, 2.3 million tourist were recorded

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8
Q

where is nearshore sand dredging done?

A

-On the 20 Km coastline between mangawhai and pakiri, which has operated for over 70 years

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9
Q

how much material was extracted between 1994 and 2004

A

165000 m³ per year

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10
Q

when did mining end and where?

A

It ended in mangawhai in 2005, but continued at pakiri beach

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11
Q

what are current rates of extraction?

A

75,000 m queued per year until 2020

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12
Q

What is a large proportion of sand used for?

A

replenishing Aucklands tourist beaches and in construction industry with many holiday homes and hotels being built

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13
Q

what is sand and When was it deposited onto the beach?

A

sand is a non renewable resource and is deposited during the Holocene (past 9000)

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14
Q

What are the inputs of sediment?

A

-Few rivers in the area, but most sand comes from offshore

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15
Q

what is the area viewed as?

A

a closed system

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16
Q

how does the sediment budget in the area work?

A

outputs of sand through nearshore mining may not replaced by inputs from rivers and offshore waves

17
Q

what are extraction rates at pakiri beach

A

they Exceeded inputs by 5X

18
Q

What is the effect of mining on the sediment budget?

A

it depletes the total sand supply, stored in dunes, beaches and the seabed(up to 2km offshore)

19
Q

what happens to the beaches as they starved of sediment

A

-become wider and flatter and less effective at absorbing waves, so higher energy waves erode beaches and landforms such as dunes, and spits become vulnerable

20
Q

what do fordune ridges develop?

A

they are undercut by wave action, and develop a steep seaward facing scarp

21
Q

what does loss of vegetation cover mean?

A

It makes him susceptible to wind erosion

22
Q

when was the storm and what happened?

A

1978 storms caused a 28 meter breach at the base of mangawhai spit
-this altered title currents and led to sedimentation of mangawhais harbour this shallow water made waterfront susceptible to flooding .

23
Q

what helps restore equilibrium?

A

dredging of harbour and groynes

24
Q

What did studies by Auckland regional Council suggest?

A

increased amounts of erosion are likely in the future with declining natural protection from increased storm events

25
Q

What is the long-term retreat estimated at?

A

36 m and width of coastal zone susceptible to erosion varies from 48 to 111 m
-higher than any of aucklands 123 beaches