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

Question 1

background of Mangawaii-Pakiri

Answer 1

50km North of Auckland

Auckland accounts for:
1/3 of NZs population
35% of NZs GDP

Tourism centred at their beaches -> 2.3 million visitors in 2015

Question 2

economic uses

Answer 2

Wide ranges of uses essential in modern economy:
- glass manufacture
- construction
- concrete making
- beach replenishment

high quality holocene sand occurs in nearshore zone -> essential mineral resource

Question 3

unintentional impacts

Answer 3

Beaches starved of sediment -> making them wider + flatter -> less effective at absorbing waves

Higher energy waves -> as waves are carrying less sediment -> therefore not wasting as much energy
-> meaning higher rates of erosion + flooding
-> erodes landforms -> dunes + spits become vulnerable

Extraction rates 5x more than inputs -> outputs not being replaced by inputs -> disrupting equilibrium

Question 4

effects of impacts

Answer 4

Sediment cell = is a closed system

Extraction rates 5x more than inputs -> outputs not being replaced by inputs -> disrupting equilibrium

as a result ->

• movements of sand between the major stores have been diminished e.g. beaches, dunes, sea bed (up to 2km offshore)
• depleting the total sand supply

Nearshore sand dredging on the 20km coastline between Mangawhai + Pakiri operated for over 70 years

Between 1994-2004 -> 150k m3/ year was extracted

In 2005 -> mining stopped in Mangawhai but it still continued in Pakiri

Current rate of extraction -> 75k m3/ year

Question 5

consequences

Answer 5

Climate change -> increased risks of storms + coastline has little natural defence -> higher energy waves -> coastal retreat is already evident

High energy waves with little sediment -> threatens beaches + impacts tourism

Erosion of spits has lead to loss of vegetation
-> more susceptible to wind + wave erosion

A breach at the Mangawhai spit has led to sedimentation of Mangawhai harbour -> the shallow area has made it harder for ships to travel across

Coastal management has been put in place to mitigate the impacts
Groynes constructed -> to absorb wave energy (only on the spit)