Local Scale Coastal Management

Antonia Blankenberg
Note by Antonia Blankenberg, updated more than 1 year ago
Antonia Blankenberg
Created by Antonia Blankenberg almost 4 years ago
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Description

Learn about techniques of hard and soft engineering with regards to search for a solution to the problems of erosion and removal of sediment at the coastline.

Resource summary

Page 1

Hard Engineering and Soft Engineering

Techniques of hard and soft engineering search for a solution to the problems of erosion and removal of sediment at the coastline.   Hard engineering is when large artificial structures are built to combat coastal issues. These structures are usually expensive and do not blend with the landscape. Hard engineering methods include; sea walls, groynes, gabions, and rock armour.     Soft engineering attempts to use 'natural' methods of solving coastal issues. These methods are usually cheaper, but also less effective than hard engineering solutions. Soft engineering methods include; beach nourishment, beach reprofiling, and dune regeneration.  

Page 2

Sea Walls

Sea walls provide barriers between waves and the land. They are placed at the back of the beach. They are usually flat but curved walls tend to be more effective in refracting waves, albeit more expensive to implement. Curved walls turn waves back on themselves so that the next wave loses its energy to erode the coast. Benefits: A sea wall gives a social sense of security to the local population. Sea walls are very effective in wave refraction and can last many years. Sea walls do not impede the movement of sediment to/from beaches.   Costs: Sea walls can restrict local residents' access to the beach. If waves break over the sea wall in storm conditions, it can lead to coastal flooding. Sea walls can be an eyesore, driving away tourists. Can cause wave scouring if not positioned correctly. Sea walls are very expensive to build, costing about £5000-6000 per linear meter. Repairs and maintenance are also expensive.  

Page 3

Groynes

Groynes are wooden or stone structures built in the foreshore. Groynes are built perpendicular to the coastline and are spaced at regular intervals. Groynes are traditionally built from wood, but modern groynes are mostly made from stone. These structures are built to trap sediment being transported by longshore drift, building up sediment on one side of the structure. Benefits: Groynes can act as viewpoints or walkways for fishing. Groynes are relatively cheap to build and can last up to 40 years if maintained. This method promotes larger beaches, which draws in more tourists. Costs: Groynes can impede local habitats. They can act as hazards as they have shallow water on one side and deep water on the other. They can also be a danger to windsurfers who may collide with them. Groynes make it difficult to walk along a beach. Sediment supply down-drift can be restricted. Ineffective in stormy conditions. Can be considered unattractive.

Page 4

Gabions

Gabions are large wire-mesh cages filled with various sized rocks which are placed at the back of beaches to diffuse a wave's energy. May also be placed in front of cliffs to give stability and prevent landslides. Benefits:   Are relatively cheap and easy to construct; only £110 per meter. Can last 20-25 years. Blend better with the environment than other hard engineering methods. Can be covered by vegetation. Costs: The use of gabions is restricted to sandy beaches as larger sediment would cause damage. Regular maintenance is needed as they damage easily. Gabions can be very dangerous when damaged. Very unattractive. Bird's feet can get damaged in them.   

Page 5

Rock armour

Rock armour (rip rap) is made up of thousands of durable rocks, such as granite, compiled together to act as a barrier between waves and the land. It is important that the rocks are large enough so that they are not moved by storm waves. Their downward slope arrangement to the sea deflects wave energy as water can enter the gaps between the rocks. Benefits: Relatively cheap; rock armour is much cheaper to implement than sea walls and aims for the same effect. The structure can be built quickly and requires little maintenance. This method is versatile, rock armour can be placed in front of a sea wall to increase its lifespan. Costs: Rock armour makes access to the beach difficult, even dangerous in wet conditions or if the rocks are unstable. Rocks are generally taken from Norway or Sweden rather than local quarries, which makes them prone to inflation and can worsen the effects of climate change. Visually intrusive on beaches. Can be damaged in particularly heavy storms.

Page 6

Beach Nourishment

Beach nourishment is a broad term for the replacement of lost sediment at beaches. Beach nourishment comprises of beach recharge and beach recycling. Beach recharge occurs when sand is taken from a nearby bay and placed on the beach. Bulldozers are often used to distribute sand. Beach recycling moves sand from a down-drift area and places it in an up-drift area. This can take place multiple times a year. Benefits: Creates a wider beach which attracts more people. People living at the coast are more protected from coastal flooding. Reduces sea wall maintenance costs. Natural and blends with the environment. Costs: Beaches can be restricted for long periods of time during re-nourishment. Though cheaper than hard engineering methods, beach nourishment is still a relatively expensive method.

Page 7

Beach Reprofiling

Beach reprofiling is the artificial reshaping of the beach. After winter storms, sediment is moved back up the beach, Benefits: Can act as a buffer between land and sea. Is natural and blends with the environment. Costs: Restriction to the beach area. Major reprofiling can be expensive. Can sometimes look unattractive.

Page 8

Sand Dune Regeneration

Dune regeneration involves the creation of artificial sand dunes and the restoration of existing dunes. Sand dunes act as a barrier between land and sea, absorbing wave energy. This is done through the planting of marram grass, building of fencing and the addition of extra sand. Benefits: Can be popular as picnic and walking areas. Local grass is often planted so costs are minimal. Can be used as habitats for rare animals and insects. Costs: Areas of regeneration are often blocked off during establishment, warding off tourists. Dunes are dynamic and are not always stable. They are easily damaged and can cause damage to nearby houses. Additional hard engineering methods are often needed.

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