Construction, concrete making, glass manufacture and beach replenishment
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Where is Mangawhai-Pakiri located?
On the east coast of New Zealand's northland peninsula - located 50km north of Auckland
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Auckland
Population of other 1.5 million - a third of New Zealand's total population and accounts for 35% of GDP. In 2015, saw 2.3 million tourists
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How long is the coastline?
20km
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How long has sand dredging been operated for?
over 70 years
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How much was extracted between 1994 and 2004
165,000m3/year
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When did mining end in Mangawhai?
2005
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What are the current rates at Pakiri beach?
75,000m3/year
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Where does a large proportion of this go?
Replenishing Auckland's tourist beaches
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When was the sand deposited
During the holocene (past 9000 years)
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Why is the coastal sediment budget a closed system?
Sand is a non-renewable resource as there are few sizeable rivers in the area so most sand is thought to be derived from offshore.
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How much do extraction rates at Pakiri Beach exceed inputs?
By a factor of 5
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What has this caused?
Movements of san between major stores to diminish
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What effect has this had on beaches?
They have become wider and flatter and are less effective in absorbing waves - higher energy waves erode beaches and landforms such as dunes and spits become vulnerable.
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What has the loss of vegetation caused?
Susceptibility to wind erosion
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What happened in a 1978 storm?
A 28m breach at the base of the Mangawhai spit.
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What did this lead to?
the sedimentation of Mangawhai's harbour. Shallower water in the harbour threatened Mangawhai's waterfront community with flooding. Subsequent dredging of the harbour and groyne construction on the spit has restored some equilibrium
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What do Aukland Regional Council suggest?
Increased rates of coastal erosion are likely in future with declining natural protection from extreme storm events.
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What is the estimated long-term retreat by the end of the century?
35 metres
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What is the width of the coastal zone susceptible to erosion?
Varies from 48 to 111 metres
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Other cards in this set
Card 2
Front
What is the sand used for?
Back
Construction, concrete making, glass manufacture and beach replenishment
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