4.b. Economic development unintentionally causes change within coastal landscape systems.

Question 1

Why is sand important to New Zealand (and the world)?

Answer 1

Very important for resources such as concrete, glass, construction and beach recharge.

Question 2

What can be found in the East Coast of New Zealand’s North Island?

Answer 2

Very high quality sand found on the nearshore.

Question 3

How long is the Mangawhai to Pakiri coastline?

Answer 3

20km.

Question 4

How much sand has been mined on the Mangawhai to Pakiri coastline from 1994 to 2004?

Answer 4

165,000m³/ year.

Question 5

How long has sand been mined for on the Mangawhai to Pakiri coastline?

Answer 5

Sand has been being mined for more than 70 years.

Question 6

Where is the Mangawhai to Pakiri coastline located?

Answer 6

50km North of Auckland (capital city).

Question 7

What is Auckland? What is the population?

Answer 7

New Zealand’s capital city and economic hub.

There are over 1.5 million people there.

Question 8

What percentage does Auckland contribute to New Zealand’s GDP?

Answer 8

Auckland contributes to 35% of New Zealand’s GDP.

Question 9

What sectors are growing quickest in Auckland?

Answer 9

It is rapidly growing in tourism, finance and technology.

Question 10

How many people visit Auckland in 2015?

Answer 10

2.3 million.

Question 11

What does Auckland have?

Answer 11

Auckland has many quality coastal amenities.

Question 12

What did Mangawhai do in 2005?

Answer 12

In 2005, mining stopped at Mangawhai - but continued at Pakiri.

Question 13

Is sand still mined to Pakiri? How much? What is it used in?

Answer 13

From 2005 to present day.

75,000m³ of sand is mined from Pakiri.

This is used in construction and beach recharge in Auckland.

Question 14

What is the Holocene?

Answer 14

The past 11,700 years of the Earth.

Question 15

Is sand renewable?

Answer 15

No, sand is not a renewable source on the Mangawhai to Pakiri coastline.

Question 16

Why is sand dredged offshore at the Mangawhai to Pakiri coastline?

Answer 16

Few large rivers, so sand is dredged offshore.

Question 17

As the coastal sediment budgets is a closed systems, why is nearshore sand not replaced after mining?

Answer 17

There are no inputs of rivers and waves offshore.

Question 18

By what factor do extraction rates at Pakiri beach exceed inputs?

Answer 18

Extraction rates at Pakiri Beach exceeded inputs by a factor of 5.

Question 19

What effects have there been on sand mining on the Mangawhai to Pakiri coastline?

Answer 19

Depleted the total sand supply in the beaches, dunes and on the sea bed.

Question 20

What are the current rates of sand extraction like on the Mangawhai to Pakiri coastline?

Answer 20

Current rates of sand extraction are unsustainable.

Question 21

State 3 impacts of sand depletion on the Mangawhai to Pakiri coastline?

Answer 21

Sand depletion is having an impact on landforms and landscapes.

Beaches starved of sediment have become wider, flatter and are less effective in absorbing waves.

Higher energy waves erode the beach and landforms such as dunes and spits become vulnerable.

Foredune ridges are undercut by wave action, developing steep, seaward facing scarps.

Loss of vegetation cover makes the beach susceptible to wind erosion.

Question 22

What happened on the Mangawhai to Pakiri coastline in 1978?

Answer 22

Storms caused a 28 m breach at the base of the Mangawhai spit.

This and a second breach altered tidal currents, which led to the sedimentation of Mangawhai’s harbour.

Shallower water in the harbour also threatened Mangawhai’s waterfront community with flooding.

Question 23

What actions helped to restore equilibrium after the 1978 Mangawhai spit breach?

Answer 23

Dredging of the harbour and groyne construction on the spit.

Question 24

What did studies of the Mangawhai-Pakiri coastline by the Auckland Regional Council suggest?

Answer 24

Increased rates of erosion are likely in the future with a declining natural protection from storm events.

Coastal retreat is already evident; this is attributed partly to sand extraction. It has been complicated by rising sea levels and climate change.

Question 25

On the Mangawhai to Pakiri coastline, what is the coastal retreat meant to be at by the end of the century? What width of coastal zone is said to be susceptible to erosion?

Answer 25

Long-term retreat by the end of the century is at ~35 metres.

The width of the coastal zone that is susceptible to erosion varies from 48 metres to 111 metres.

(This estimate is significantly higher than any of the Auckland region’s other 123 beaches).