Mangawhai-Pakiri

Question 1

Located

Answer 1

50km North of Auckland (major city), 20km long coastline

Auckland is 1/3 of population of NZ + accounts for 35% of GDP
Auckland is growing economy (BUSINESS, HIGH-TECH, TOURISM)
2015 - 2.3 million foreign visitors

So high demand for high quality sand

Question 2

Sand at MP

Answer 2

Offshore sand mining has operated for 70 years (ended at Mangawhai in 2005)

High-quality + suitable for construction industry + used for replenishing Auckland’s tourist beaches

Question 3

Nearshore extraction current rates in Pakiri

Answer 3

75,000m3 until 2020

Question 4

Problems with sediment budget

Answer 4

Sand deposited during Holocene (9000 years ago) so is non-renewable
- not many sizeable rivers in area + most sand would have been derived from offshore
So coastal sediment budget is closed system (outputs of sand not replaced by inputs from rivers)
- extraction rates exceed inputs by 5x at Pakiri

Question 5

Impacts on landforms

Answer 5

1978 - storms caused 28m breach -> altered tidal currents -> increased sedimentation in harbour + Mangawhai community more at risk of flooding

• beaches flatter + less effective at absorbing high energy waves
• foredune ridges undercut by high energy waves leads to mass movement which causes steep seaward facing scarps
• loss of vegetation cover = more prone to wind erosion

Question 6

Future change

Answer 6

Rising sea levels + effects of sand mining will cause long term retreat estimated at 35m