case study - sand mining Flashcards
where is the area of study?
mangawhai-pakiri coastline, 50km north of auckland on the east coast of NZs northland peninsula
why is sand in central mineral resource in a modern economy?
used for:
-Construction
-concrete making
-Glass manufacturing
-Beach replenishment
Where is the high-quality sand found?
-nearshore zone at mangawhai-pakiri
what is Auckland?
New Zealand’s largest and economically most dynamic metropolitan region
What is Auckland’s population?
Over 1.5 million
What does Auckland’s regional account for?
over one third of New Zealand’s, total population, and 35% of the countries GDP
how is the region rapidly growing?
-Finance and high-tech industries are growing
-Tourism is a large part- in 2015, 2.3 million tourist were recorded
where is nearshore sand dredging done?
-On the 20 Km coastline between mangawhai and pakiri, which has operated for over 70 years
how much material was extracted between 1994 and 2004
165000 m³ per year
when did mining end and where?
It ended in mangawhai in 2005, but continued at pakiri beach
what are current rates of extraction?
75,000 m queued per year until 2020
What is a large proportion of sand used for?
replenishing Aucklands tourist beaches and in construction industry with many holiday homes and hotels being built
what is sand and When was it deposited onto the beach?
sand is a non renewable resource and is deposited during the Holocene (past 9000)
What are the inputs of sediment?
-Few rivers in the area, but most sand comes from offshore
what is the area viewed as?
a closed system
how does the sediment budget in the area work?
outputs of sand through nearshore mining may not replaced by inputs from rivers and offshore waves
what are extraction rates at pakiri beach
they Exceeded inputs by 5X
What is the effect of mining on the sediment budget?
it depletes the total sand supply, stored in dunes, beaches and the seabed(up to 2km offshore)
what happens to the beaches as they starved of sediment
-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
what do fordune ridges develop?
they are undercut by wave action, and develop a steep seaward facing scarp
what does loss of vegetation cover mean?
It makes him susceptible to wind erosion
when was the storm and what happened?
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 .
what helps restore equilibrium?
dredging of harbour and groynes
What did studies by Auckland regional Council suggest?
increased amounts of erosion are likely in the future with declining natural protection from increased storm events
What is the long-term retreat estimated at?
36 m and width of coastal zone susceptible to erosion varies from 48 to 111 m
-higher than any of aucklands 123 beaches
