Section 4.5 - Challenges for the Coastline Flashcards
Why is the sea level rising? Give two factors
1) The greenhouse effect (where greenhouse gases trap heat rays in to the earths atmosphere) means that polar ice is melting into the sea causing the sea levels to rise
2) Thermal expansion, as water is heated up, it takes up more space. If the temperature of the sea were to increase, the volume of water would also increase causing sea level rise.
How bad will sea level get? How will it affect different places around the world?
- If all of the Antarctic ice sheet melted, the sea level would rise by about 61.1 metres.
- By 2100 there could be increases (on the English Channel) by around 30cm to 1m
- Low lying areas such as the Maldives are under real threat from sea level rise (they are only 1.2 metres above the sea level)
- Bangladesh has a population of 112 million. It is also very low lying and could be under threat from sea level rise
How will climate change effect erosion/deposition?
Climate change will mean that cliffs being undercut and collapsed will retreat at a faster rate. Higher sea levels could also cause : damage to roads, railways and homes ; salinate farmland rendering it useless. Beaches could also be submerged.
How will climate change affect storm frequency, intensity and storm surges?
A warmer atmosphere has more energy and has the potential to create more storms, and make these storms more powerful. If there is a period of low pressure, a storm surge could have a more significant impact.
How will storms and storm surges affect people and the environment?
Sudden storms can cause large amounts of erosion, destroying homes because of retreating cliffs
Explain how groynes and sea walls work?
Groynes are used to trap material into a certain area this interrupts the process of LSD. They would typically be used to stop erosion of popular tourist beaches.
Sea walls are curved so that they deflect the energy from the waves back out to sea. They are used to stop undercutting on a cliff.
Explain how beach replenishment and slope stabilisation work?
Beach replenishment involves moving sediment from one area to another beach that has suffered erosion.
Slope stabilisation is where plants are grown on the slope, and drainage
pipes are constructed below the slope. This reduces the risk of saturation and the plant roots help bind the sand together
Give one advantage and one disadvantage of slope stabilisation
- It is a very natural method to keep the cliff in place and safe for beach users
- It is very difficult to actually construct, and the beach may be closed for quite a while
Give one advantage and one disadvantage of a sea wall
- It gives very good protection against undercutting of the cliff
- It is not considered very attractive and could make the beach difficult to access. They are also very expensive
Give one advantage and one disadvantage of using groynes
- They are very good for preserving a popular tourist beach
- Traps sediment into one area so down the beach can be starved of material
Give one advantage and one disadvantage of using beach nourishment
- The beach looks natural and attractive for tourists
- Often, the sediment needs to be replaced often as it can easily be washed away
What is the difference between hard and soft coastal engineering?
Hard engineering is when very industrial building is used to stop erosion (i.e using steel, concrete defences), they are typically short term solutions. Soft engineering uses more natural engineering methods for long term protection against erosion.
What engineering technique works best?
Hard engineering works best as a “hold the line” technique, as it uses the industrial methods to stop erosion at all costs. However, long term, soft engineering works best as it is often cheaper and much better in the long term.
What is strategic realignment? What areas might be left to erode?
Strategic realignment is where lower value areas are left to be eroded by the sea in order to protect the higher value areas. Farmland and unused land would be put on the line to protect roads or villages.
