3.10 Managing coastal erosion and flooding

Question 1

What is hard engineering?

Answer 1

This involves building structures along the coast e.g. sea walls, groynes and revetments. It aims to stop physical processes all together or alter them to protect the coast

Question 2

What is soft engineering?

Answer 2

An approach designed to work with natural processes in the coastal system in order to manage it (but not necessarily to prevent erosion)

Question 3

What are groynes?

Answer 3

Timber fences built at 90 degrees to the coast

Question 4

What is the purpose of groynes?

Answer 4

To prevent longshore drift of sediment and encourage deposition, building a wider, higher beach

Question 5

What are the advantages of groynes?

Answer 5

-The built up beach increases tourist potential and protects the land behind it
-groynes work with the natural processes to build up the beach
-not too expensive

Question 6

What are the disadvantages of groynes

Answer 6

-groynes starve beaches further along the coast of fresh sediment , because they interrupt longshore drift- terminal groyne syndrome. This often leads to increased erosion elsewhere
-groynes are unnatural and rock groynes can be very unattractive

Question 7

What are the costs of groynes?

Answer 7

£5000 to £10,000 each (at 200m intervals)

Question 8

What is the purpose of a sea wall?

Answer 8

a physical barrier against erosion
they often also act as flood barriers
designed to dissipate rather than reflect energy

Question 9

What are the advantages of a sea wall?

Answer 9

-effective prevention of erosion
-often have a promenade for people to walk along

Question 10

What are the disadvantages of a sea wall?

Answer 10

-Older ones reflect wave energy rather than absorb it
-can look intrusive and unnatural
-expensive to build and maintain

Question 11

What is the cost of a sea wall?

Answer 11

£6,000 a metre

Question 12

What is the purpose of a rip rap (rock amour)

Answer 12

They break up and dissipate wave energy
they are often used at the base of sea walls to prevent them from undercutting and scour

Question 13

What are the advantages of a rip rap?

Answer 13

-relatively cheap and easy to construct and maintain
-often used for fishing or sun bathing

Question 14

What are the disadvantages of a rip rap?

Answer 14

-rocks are usually from somewhere else, so they don’t fit in with the local geology and look out of place
-can be very intrusive
-rocks can be dangerous for people climbing over them

Question 15

What is the cost of a rip rap?

Answer 15

£100,000 to £300,000 for 100m

Question 16

What are revetments?

Answer 16

Sloping wooden, concrete or rock structures- placed at the foot of a cliff or the top of a beach. They break up the wave’s energy

Question 17

What is the purpose of revetments?

Answer 17

to absorb wave energy and reduce swash distance by encouraging infiltration
-reduce erosion on dune faces and mud banks

Question 18

Advantages of revetments

Answer 18

Relatively inexpensive

Question 19

Disadvantages of revetments

Answer 19

intrusive and unnatural looking
need for high level of maintenance

Question 20

What is the cost of revetments?

Answer 20

Up to £4500 a metre

Question 21

What is an offshore breakwater?

Answer 21

a partly submerged rock barrier designed to break up the waves before they reach the coast

Question 22

What’s the purpose of an offshore breakwater

Answer 22

they force waves to break offshore rather than at the coast , reducing wave energy and erosive force

Question 23

What’s the advantage of an offshore breakwater?

Answer 23

an effective permeable barrier

Question 24

What’s the disadvantages of an offshore breakwater?

Answer 24

-visually unappealing
-potential navigation hazard

Question 25

What is beach nourishment?

Answer 25

its artificially replacing sediment on the beach

Question 26

What’s the purpose of beach nourishment?

Answer 26

-replaces sediment lost by erosion
-enlarges the beach, so it dissipates wave energy and reduces wave erosion
-increase the amenity value of beaches by adding fresh sand

Question 27

What are the advantages of beach nourishment

Answer 27

-relatively cheap
-looks natural
-increases tourist potential by making the beach bigger

Question 28

What are the disadvantages of beach nourishment?

Answer 28

Needs constant maintenance because of erosion and longshore drift

Question 29

What’s the cost of beach nourishment?

Answer 29

£300,000 for 100m

Question 30

What is cliff regrading and drainage?

Answer 30

Cliff regrading reduces the the angle of the cliff to help stabilise it
Drainage removes water to prevent landslides and slumping

Question 31

How does cliff regrading and drainage work?

Answer 31

1. slope stabilization by planting vegetation through a tough, flexible geo-textile membrane to keep the soil in place. Regrading cuts the cliff slope back to a more stable angle
2. In cliff drainage pipes channel groundwater out of the cliff, reducing pore water pressure
3. rock armor or revetment at the toe of the cliff- rock bolts anchor the armor and the rock within the cliff

Question 32

What are the advantages of cliff regrading and drainage?

Answer 32

-can work on clay or loose rock
-cost effective

Question 33

What are the disadvantages of cliff regrading and drainage?

Answer 33

effectively causes the cliff to retreat
drained cliffs can dry out and lead to collapse

Question 34

What is dune stabilization and what’s its purpose?

Answer 34

Marram grass can be planted to stabilise dunes
Areas can be fenced off to keep people out of the newly planted dunes
Absorbs wave energy to protect low lying coastal areas

Question 35

What’s the advantage of dune stabilisation?

Answer 35

-Maintains a natural coastal environment
-provides wildlife habitats
-cheap and sustainable

Question 36

What are the disadvantages of dune stabilisation?

Answer 36

-time consuming to plant marram grass
-overgrazing
-people may respond negatively to being kept off of certain areas
-storm surges breach dune systems

Question 37

What is the cost of dune stabilisation?

Answer 37

£200-£2000 for 100m

Question 38

What’s the purpose of marsh creation?

Answer 38

Allows low lying areas to be flooded by the sea
-The land becomes a salt marsh

Question 39

What are the benefits of a salt marsh?

Answer 39

-Creates an important habitat
-relatively cheap as it often involves reverting land to its original state