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

Question 1

what economic activity is happening in Pikiri and why?

Answer 1

• sand mining at Pikiri to make concrete and glass for buildings. its cheap and high quality
• Its close Auckland 50km - cheaper to transport and reduces carbon. Auckland has 1/3 of NZ population and 35% of GDP.
• 1:5 inputs:outputs

Question 2

unintentional impacts on the Mangawhai spit/harbours?

Answer 2

• sand mining until 2004 and dredging of harbour due to accumulation of material.
• Less sediment is moved to the spit by LSD due to there being less sediment available down the coast
• dues and spit vulnerable to wave erosion
• loss of veg = foredune ridges susceptible to wind erosion
• sediment is relict = human impacts are not sustainable

Question 3

unintentional impacts on Te Arai point

Answer 3

• this is the main sand mining area, the reduced sediment has lead to increasing wave energy as it doesn’t slow the waves down
• dunes eroding

Question 4

unintentional impacts on Pakiri

Answer 4

• sand is still extracted from here, the loss of sediment makes it less effective at absorbing waves therefore there is more erosion
• beaches are wider, flatter, starved of sed and less absorbent of waves

Question 5

consequences on Mangawhai spit landscape

Answer 5

• 28m eroded from the spit, 30 years ago the spit breached which led to flooding and the beach being eroded further
• breach altered tidal currents - sedimentation shallower water threatened waterfront from flooding - dredging of harbour and groyne on spit to try restore equilibrium

Question 6

consequences on Pakiri landscape

Answer 6

beach profile flattened

Question 7

future consequences?

Answer 7

• LT retreat by end of century = 35m
• width of zone risk to erosion = 48-111m