Coasts KQ 4 Flashcards
What does hold the line mean ?
Anita in , sustain or improve existing defences
What is managed realignment ?
Existing defences moved to more sustainable positions , usually further inland
What is NAI ?
No active intervention
When the land is of low economic value or enviornonmental value
What is the coastal landscape management case study?
Sandbanks , Dorset
Where is sandbanks located ?
South coast of England
North of Swanage
Dorset
North entrance of Poole harbour
What are the 6 needs for coastal management at sandbanks ?
Tourism
Commercial property
Residential property
Protection of Poole harbour
Water sports
Climate change
Why is there a need for management bcos of tourism - sandbanks ?
Beaches
Blue flag award for water quality
Gently sloping so safe for family swimming
Why is there a need for management bcos of commercial property - sandbanks ?
High value commercial properties
Sandbanks hotel and the haven hotel
Significant employee opportunities
Generate spending in local economy
Why is there a need for management bcos of residential property ?
High demand and command premium prices
4th most expensive in world per square metre currently
Large , detached
>£10 million properties
Luxury apartments over 2 million
Why is there a need for management bcos of the protection of Poole harbour ?
Popular and safe place for water sports
No good for ships and ferries
Home to yacht clubs and marinas
Why is there a need for management bcos of water sports ?
Wind surfing
Sailing
Water skiing
Attract more people
Local economy
Why is there a need for management bcos of climat change - sandbanks ?
Sea levels predicted to rise by about 0.6m in the next 1000 years
Flooding many properties
Cut off from the mainland
£18 million worth of damage to residential properties will occur in next 20 years
Who is responsible for the management strategies at sandbanks ?
Poole harbour commissioners
Poole borough council
Environment agency
Strategies employed for part of the Two Bays Shoreine management plan
What is the two bays shoreline management plan ?
Based on the sediment cell covering Poole bay and Christ church bay
What management stratergies are being used at sandbanks ?
Rock groynes
Dune planting
Beach recharge (rainbowing)
Dredging and sediment dumping
Why are rock groynes used at sandbanks ?
Minimise the movement of sediment along the beach
Why is dune planting used as a management strategy in sandbanks ?
Planting of marram and protection of developing dunes from trampling by fencing
Why is marram used in dune planting ?
Spreads rapidly and grows up through accumulating sand
What is beach recharge (rainbowing) and why was it used in sandbanks ?
Used to conserve beaches
Sand dredged from offshore is sprayed onto beach
Costs £20 per meter cubed
What happened in the 2015 trial of sediment dumping ?
Sediment dredge from the harbour just offshore is much cheaper , costing only £3 per meter cubed
What is dredging and sediment dumbing on sandbanks ?
Poole harbour commisioners (phc)
125,909 m^3 of suitable sand or this 83.9% , 88,031 was placed on the beach
How has longshore drift been changed at sandbanks ?
Groynes have Reduced amount of sediment being moved by lsd
LSD has been interrupted and no sediment is carried past the end of the penninsular into the harbour
How has erosion been changed in sandbanks ?
Erosion rates have been reduced
Less sediment is now removed from the beach because of the groynes and sea wall
Rock groynes reduce wave energy
What has happened to the profile of the beach ?
The beach is now wider and has been built up so that it is higher
What evidence is there that the management of sandbanks has been successful ?
Without coastal management erosion rates would be 1.6 m per year
The width of the each is increasing and the coastline is actually advancing
What is the case study about human activity unintentionally causing change ?
Sand mining along the Mangawhai-Pakiri coastline , New Zealand
Describe the location of the manga what - pakora coatsijne ?
North of the north island
North of Auckland
To the west is the Tasman sea
Why is sand mined along the M-P coast ?
Glass anufacturing
Concrete manufacturing
Beach nourishment
What is the main reason sand is mined along the m-p coastline ?
Used for replenishing Auckland’s tourist beaches as the sand is of good quality
Why is demand for sand increasing in the Auckland area ?
1/3 of whole pop of New Zealand live in Auckland
Beaches 4 tourism - need high quality sand
How much sand has been mined and when ?
Between 1994-2004 , 165,000m^3 per year
When did mining end in mangawhai beach ?
2005 but it continued at pakora
What are the current rates of extraction at pakiri beach ?
75,000 m^3 per year until 2020
Why is sand a non-renewable resources at the m-p coastline ?
No major rivers to input more
Closed sediemtnsustem
No waves bringing more from offshore
When was sand deposited at the m-p coastline ?
During Holocene (9,000 years ago)
How is the depletion of sand affecting beaches ?
They are starved of sediment
Have become wider and flatter and are less effective at absorbing waves
How si the depletion of sand affecting foredune ridges ?
They are undercut by wave action
Developing steep , seaward facing scarps
How si the depletion of sand affecting the magawhai spit ?
In 1978, storms caused a 28m breach at the base of the mangawhai spit
This altered currents
How si the depletion of sand affecting the mangawhai harbour ?
The breach of the spit led to increased sedimentation in the harbour
Shallower water so threatens the waterfront community with flooding
What are the consequences of these changes to the system to the position of the coast ?
Coastal retreat already evident
Long term retreat by the end of the century is estimated at 35m and the width of the coastal zone si susceptible to erosion varies from 48 to 111 m
Give some features of hard engineering ?
Short term
Physical barriers
Highly visibl
Expensive
Can cause damage elsewhere
Deflect the power of the waves
Reassuring
What are some features of soft engineering ?
Long term
Sustainable
Less expensive
Work with natural processes
Less impact on environment
Little visual distruption
What is beach stabilisation ?
Fences built on shady beaches encourage sand dune formation by reducing the speed of the wind and increasing deposition of sand
What is beach nourishment ?
The process of dumping or pumping and from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach
What is rock armour / rip rap ?
Large boulders are piled up along the beach or along the base of the cliff
What are Gabino boxes ?
Wire cages filled with rocks that can be built to support a cliff or provide a barrier against the sea
What are groynes ?
A wooden barrier built at right angles to h beach
What are sea walls ?
A wall built on the edge of the coastline
What are the disadvantages of beach stabilisation ?
Fences can look ugly especially if damaged
Takes a long time to develop mature dunes
What is the disadvantages of beach nourishment ?
Requires constant maintenance to replace the beach material which is washed away
What are the disadvantages of rock armour / rip rap ?
Expensive to obtain and transport the boulders
Some come from Norway
What are the disadvantages of Gabino boxes?
Unattractive
What are the disadvantages of groynes ?
Unattractive
Need to be regularly repaired and maintained
Reduced longshore drift
So can starch beaches further up the coast
What are the disadvantages of sea walls ?
Expensive
Over time wall may erode
High maintenance cost
What are the advantages of beach stabilisation ?
Very effective
Helps to encourage sand dune ecosystems which are easily damaged
What are the advantages to beach nourishment ?
Beaches are a natural defence to erosion and coastal flooding
They attract tourists
What are the advantages of rock armour / rip rap ?
Protects the base of the cliffs , land and buildings against erosion
Can prevent coastal flooding in some areas
What are the advantages of Gabion boxes ?
Very good at supporting cliffs made of soft material
Allows water to drain through them back to the sea
Flexible in design as more can be added
What are the advantages to groynes ?
Prevents the movement of beach material along the coast by longshore drift
Allows the build up of beaches and beaches are a natural defence against erosion and an attraction to many tourists
What are the advantages of sea walls ?
Absorbs energy of waves
Allows the build up of a beach
What is the price of beach stabilisation ?
£2000 per 100m
What is the prive of beach nourishment ?
£500,000 per 100m
What is the price of rock armour / rip rap ?
£200,00 per 100m
What is the price of gabion boxes ?
£50,000 per 100m
What is the price of groynes ?
£150,000 each
What si the price of se walls ?
£1,000,000 per 100m
