4.1(Spec2) - Portballintrae + Lyme Regis

Question 1

What are the types of hard engineering?

Answer 1

• Groynes
• Sea walls
• Rip Rap
• Revetements
• offshore breakwaters/reefs
• Gabions

Question 2

What are offshore breakwaters?

Answer 2

• rock boulders aligned in short lengths in shallow water parallel to shore
• absorb/dissipate wave energy before back shore and foreshore are damaged
• allows LSD to occur behind them as breakwater is offshore

Question 3

Advantages of offshore breakwaters?

Answer 3

• can create sheltered water areas for recreational use (beach + windsurfing)
• effective at protecting vulnerable sections of coast
• can create calm water conditions, ideal for harbour entrances

Question 4

Disadvantages of offshore breakwaters?

Answer 4

• can be unsightly as they do not match geology of area they are placed in usually
• cost £1-2 million
• needs other coastal engineering to complement eg. Sea walls to fill gaps between breakwaters
• creates increased deposition on landward side, reducing effect of LSD

Question 5

What is Rip Rap?

Answer 5

• tetrahedron boulders made of erosion resistant materials
• dissipate wave energy
  Can hold back mass movement on unstable cliffs

Question 6

Advantages of rip rap?

Answer 6

• are long lasting and flexible in use
• can be placed at susceptible points on back shore, to protect sea wall, or as a breakwater, or as groynes

Question 7

Disadvantage of rip rap?

Answer 7

• cost £50 per cubic metre
• can create accessibility issues, can’t be easily climbed over
• water still passes through, so erosion still occurs on back shore

Question 8

What are revetements?

Answer 8

• sloped wooden walls, parallel to backshore, placed slightly ahead of backshore
• take force of breaking waves, reducing erosive strength of waves, protecting backshore

Question 9

Advantages of revetements?

Answer 9

• absorb wave energy
• traps beach sediment, reduces removal by backwash or LSD
• allows movement along beach
• cheaper than sea walls
• -

Question 10

Disadvantages of revetements?

Answer 10

• costs about £1500 per metre
• reduces access down width of beach
• may need constant maintenance as waves can damage wood

Question 11

What hard engineering was done in Lyme Regis?

Answer 11

• Granite breakwaters/rock armour brought in from Norway
• 1,000 deep bored pins in cliffs to prevent instability
• bore holes in cliffs
• sea walls
• groynes

Question 12

What soft engineering was done in Lyme Regis?

Answer 12

• beach nourishment with material from France

Question 13

What is the hazard at Lyme Regis?

Answer 13

• coast is subject to large landslips
  
  • 400m section collapsed in 2008
• increased urbanisation and tourism has increased stress on coastline
• sea level rise and increased storm frequency has resulted in increased marine erosion

Question 14

What coastal management option is in practice at Lyme Regis?

Answer 14

• Hold the line
  
  • aim is to protect cliff from further mass movement as well as protecting beach from erosion by sea

Question 15

How many people live in Lyme Regis?

Answer 15

• 5000
  
  • majority live within 1km of coastline

Question 16

How many tourists visit Lyme Regis every year?

Answer 16

• 15000

Question 17

How much did the coastal management cost in Lyme Regis?

Answer 17

• Preliminary investigation: £1.5 million
• Proposed cost of entire project: £30 million
• beachfront closed for 2 years
• car park access restricted temporarily
• beach huts temporarily closed

Question 18

What did the coastal management at Lyme Regis achieve?

Answer 18

• 2000 more visitors in year after coastal management was implemented
• ramp access improved
• beach kept in place

Question 19

What is the geology at Portballintrae?

Answer 19

• rocky headlands
• reworked glacial sands

Question 20

How much sediment has been lost from Portballintrae since the 1800s?

Answer 20

• 1000m²/yr
• beach is now dominated by large sediment (eg. Boulders)

Question 21

How much has been spent on hard engineering over the past century at Portballintrae?

Answer 21

• > £1.5 million

Question 22

What role has Leslie’s Pier played in Portballintrae?

Answer 22

• causes wave refraction
• waves focus on centre of bay
• LSD moves sediment to east of bay, away from centre
• combined rip currents move sediment offshore to deeper water
• beach is deprived of sand

Question 23

What hard engineering has been done in Portballintrae?

Answer 23

• Groynes (1904, 1970s, 1997)
• Sand Nourishment, failed as sediment is carried away by LSD and rip currents
• Sea walls (1997, 2003 with groynes)

Question 24

What is the scientific advice on Portballintrae?

Answer 24

• removal of Leslie’s Pier
  
  • done 2022
• remove hard engineering
  
  • sea walls are placed incorrectly
  • resulting in scouring of beach sediment against wall

Question 25

What is the average price of houses in Portballintrae?

Answer 25

• £350k-£400k