Case Studies Coasts

Question 1

Mangawhai pakiri - economic development

Answer 1

Sand can be used for construction, glass manufacturing and beach replenishment - mangawhai pakiri particularly effective for construction
Located 50km from Auckland - largest and economically most developed region

Question 2

Mangawhai pakiri- offshore sand mining and the sediment budget

Answer 2

Between 1994 and 2004 - 165000m cubed per year extracted
Current rates are 75,000 per year

Large proportion of sand is used to replenish Auckland’s tourist beaches

Closed system - outputs of sand through nearshore mining are not replaced by inputs from rivers and waves offshore

Question 3

Mangawhai pakiri- impact on coastal landforms

Answer 3

Beaches starved of sediment have become wider and flatter - less effective at absorbing waves - erosion of dunes and spit

Foredune ridges undercut by wave action developing steep seaward facing scarps. Loss of vegetation cover makes them susceptible to wind erosion

1978 - storms caused a 28m breach at base of mangawhai spit. This and a second breach altered tidal currents leading to sedimentation of mangawhai harbour

Shallow water at harbour led to flooding

Question 4

Need for coastal management at sandbanks

Answer 4

High value commercial properties - sandbanks hotel - employment opportunities, generate spending in local community

Residential properties command premium prices
Major tourist attraction - blue flag award for water quality

Poole harbour - cross channel ferries and catamarans as well as commercial shops carrying goods such as timber.

Climate change - sea level rise cause floods, could breach peninsula at lowest point causing the end to be cut off

Question 5

Management strategies at sandbanks

Answer 5

Rock groynes

Beach recharge

Question 6

Rock groynes impact in sandbanks

Answer 6

Minimise movement of sediment along the beach by long shore drift
Restricts sediment from entering harbour entrance
Absorbs energy and reduces rates of erosion- without this erosion rates would be 1.6m per year

Question 7

Beach recharge impacts at sandbanks

Answer 7

Sediment dumped is dredged
From the harbour just offshore - cheap - £3/m cubed

Natural currents will eventually transport sand onshore building up beaches

Question 8

Low energy coastal environment - the river Nile

Answer 8

Mean annual rainfall-600m

Average discharge is less than 300 cubed

Carries huge sediment load - 30% clay, 40% silt and 30% sand - 91.3 billion tonnes for whole blue nile basin in Ethiopia

Question 9

Three subunits of the Nike delta

Answer 9

Foreshore plain - elongated rideges running almost parallel to present shoreline, salt marshes and alluvial deposits in depressions between them

Frontal plain - south of foreshore plain - scattered eroded limestone outcrops, clay deposits

Sandy zone - sheets, dunes and hummocks

Question 10

Construction of the Aswan dam - Nike delta

Answer 10

Before the construction in 1964, the niles annual flood briefly covered much of the delta each year and deposited a think layer of silty mud

Question 11

Geology - salt burn - flamborough head

Answer 11

Fh- chalk headland
North York moors - sandstone, limestones, Carboniferous rocks
Cliffs topped with till - glacial deposit

Question 12

Energy - s fh

Answer 12

Waves from north and northwest
Most exposed - north facing cliffs (salt burn)

Areas of relatively weak shale and clay experience erosion rates of 0.8m per year whereas more resistant sandstone andlimestone only erode less than 0.1m per year

Wave heigh often exceeds 4m

Long shore drift from north to south - sediment movement sometimes interrupted by headlands and then sand and shingle accumulate to form beaches in bays - Filey bay

Question 13

Sediment store - s fh

Answer 13

Sediment supplies by cliff erosion - sandstone, chalk, boulder clay

River - the esk enters the North Sea at Whitby - limited amounts of sediment due to construction of weirs and reinforced banks

Question 14

Cliffs - s fh

Answer 14

Sedimentary rocks are horizontally bedded
Layer of fill
Flamborough-chalk-tightly bonded
Saltburn- stepped - higher levels (sandstones and limestones) Lower levels (clay)

Question 15

Shore platforms - s fh

Answer 15

High energy waves and erosion means that cliffs are retreating along the coastline leaving behind rocky shore platforms - robin hoods bay - eroded into lower lias shakes

Question 16

Headlands and bays - s fh

Answer 16

Robin hoods bay - has been eroded into relatively weak shakes with more resistant bands of sandstone either side forming headlands

Headland of flamborigh - formed of chalk, bays either side formed from clay

Question 17

Landforms on headlands - s fh

Answer 17

As a result of wave refraction, wave energy is concentrated on resistance headlands

Weaknesses such as large joints or faults are then explored by the erosive actions of the waves enlarging them to form caves and arches - selwicks bay - master joint in the chalk has been enlarged

Stack - green stacks pinnacle - isolated at the end of the headland following the collapse of arch roof

Over 50 geos - facing ne

Blowholes - where joints inchalk have been enlarged

Question 18

Beaches - s fh

Answer 18

Very few well developed beaches - Scarborough and Filey bay

Elsewhere deposits of sand and shingle accumulate slowly due to slow rates of erosion and low input from rivers

High energy waves also remove sediment before it can accumulate