Mangawhai-Pakiri - New Zealand

• Sand taken from sand dunes and shallow water near Te Arai Point
• Storm in 1978 caused breach of 28m spit - shift in tidal current deposits sediment at harbour entrance
• plan to mine continental shelf near Auckland - Effects beaches as sand isn't replaced by other inputs
• Needed for filling roads, reclamations, building sites and renourishing beaches - makes concrete
• Sand for glass - Window glazing, containers, optics
• Foundations beneath parking drains groundwater freely, sand doesnt change with moisture content like soil
• Mixed with cement to make concrete
• Beach nourishment - Tourism - Course sand lasts longer
• 2.3 million foreign tourists to Auckland's coastline
• Dredging for 70 years
• 165,000 m3/year - 1994-2004

  Currently 75,000
• Closed as few rivers contribute sediment - mostly offshore
• Mining causes less absorption of waves and erosion of landforms such as spit and dunes, less vegetation
• Why is there a need for sand mining in New Zealand?


  1. making glass

  2. making concrete

  3. use in filling

  4. beach re-nourishment
• How is Auckland significant to this coastline?


  1. it is located 50km away and generates 35% of New Zealand's GDP- high demand for resources such as glass and concrete

  2. there were 2.3 million foreign visitors in 2015
• How is sand used in making glass?

  glass requires high quality, clean sand which this coastline has
• How is sand used in making concrete?

  sand is needed to make cement, used in construction- lots of development and construction in Auckland, so in high demand
• How is sand used in filling?


  sand used as a foundation beneath parking spaces, buildings and roads as it drains groundwater and doesn't move
• How is sand used in beach renourishment?


  Auckland is popular for its beaches- there were 2.3 million foreign visitors in 2015, so the cost of this method can be justified by tourism income
• Where in New Zealand does the sand mining occur?


  the nearshore area of Managwhai-Pakiri on the East coast of the Northland peninsula
• Origin of the sand...
• How is sand formed?


  from rock that has been weathered under a layer of soil and vegetation
• What is the main component of the sand?

  silica- may have come from volcanic eruptions
• What happened to sand after the last ice age?


  sea levels rose 120m and moved sand from beaches and dunes with it
• What has added sand to the beaches?

  rivers- soils with sand erode into rivers, but this is limited
• What type of system is this coastline? Why?

  closed system- sand stays on the coastline to form beaches and dunes after being transported by wind and waves
• Offshore mining...
• How long is the coastline?

  20km
• How long has nearshore sand dredging operated along the coastline?

  70 years
• Where has sand been mined from? Since when?

  since 1966

  1. Pakiri beach dunes

  2. shallow sea near Te Arai point

  3. shallowed entrance to Managwhai Harbour
• What permit was enforced?


  a permit by the Auckland Region Council allowed 65,000m3 to be taken per year between 1994 and 2004
• What happened in 2005?


  mining at Mangawhai ended, but continued at Pakiri beach
• What is evidence to suggest that the sand mining here is unsustainable?


  extraction rates at Pakiri now exceed natural inputs from rivers and offshore by 5x
• Impacts on coastal processes and landforms...
• wave energy...


  1. beaches with less sediment become flatter and narrower

  2. less effective at absorbing wave energy and percolation after swash

  3. higher wave energy eroded beaches and cliffs even more- positive feedback

  4. also making Managwhai spit more vulnerable
• What happened in 1978?


  1. storms caused a 28m breach of Mangawhai spit

  2. this altered the tidal currents causing sedimentation of the Mangawhai Harbour

  3. affected the waterfront community
• erosion...


  1. will be increased erosion rates in the future

  2. storm events erode sand

  3. further decline in natural protection
• long-term retreat...


  long-term retreat is estimated at 35m by 2100, higher than any other of Auckland region's 123 beaches- shows impact
• entire coastal system...


  1. when sand is removed, new balance of physical factors is found leading to new beach profile

  2. this alters the shapes of beaches, dunes and sea bottom as these are maintained by physical factors eg. tides, wind, waves
• disturbance to marine organisms...


  a mining company proposes to skin the sea floor over a large nearshore area- disturbing habitats and marine fauna