2.3 Coastal management Flashcards
What are the conflicts between different users and their views on how certain coasts should be managed?
Conservation v Development
What are storm surges and how do they cause coastal flooding?
Storm surge
Description
- A significant rise in localised sea level which leads to large scale coastal flooding. This also creates much more dangerous waves It is fast acting and powerful.
- When combined with high tide the impact of a storm surge are even more significant.
Explanation of cause:
Hurricanes as well as major storms. It is the water brought up from the ocean by a storm due to the low pressure in the centre which brings up water.
Example
Hurricane Milton with storm surges of up to 15ft which
What are tsunamis and how do they cause coastal flooding?
Tsunami
Description
- These are large and wide waves that come in to the coastline as a result of underwater land displacement normally caused by earthquakes or volcanic eruptions/landslides.
- As the waves race towards the shoreline, the reducing depth of the sea bed causes greater friction, causing the waves to increase in height, often to heights of 5-10m. The volume of water displaced means that it is not just one wave but multiple coming in meaning flooding can be very significant.
Explanation of cause:
Sudden movement of tectonic plates as well as a volcanic eruptions and landslides can cause a large wave to be created which builds in size until it makes landfall.
Example
2011 Japan Tsunami - A 9.0 magnitude earthquake caused a tsunami that killed more than 18,000 people and caused a nuclear emergency at the Fukushima Daiichi nuclear power plant.
What is global warming and how do they cause coastal flooding?
Climate change
Description
- Climate change can lead to rising sea levels which causes flooding. It can also cause increasingly unpredictable and extreme weather.
- High tides are much higher than they used to be with higher sea levels so areas previously above sea level will now be repeatedly inundated, plus during storm conditions the waves will be able to reach further inland as sea level is higher.
- More extreme weather due to climate change may also increase the likelihood of flooding from storm surges from TRS.
Explanation of cause:
Rising temperatures lead to ice melting at the poles. Therefore lots of water goes into the oceans causing the average levels to rise. This may be slower acting but can be detrimental to coastal based civilisations. Rising ocean temperatures also leads to more powerful tropical storms containing more water and higher wind speeds.
Example
The Maldives is vulnerable to rising sea levels because 80% of its islands are just a metre above sea level. The Maldives is projected to see up to 0.9 metres of sea level rise by 2100
How is coastal flooding predicted?
Forecasting hurricanes
Observations from ships can give information on storms out at see. Additionally, reinforced aircraft, fitted with instruments, fly through and over tropical cyclones, and weather radar can locate storms within 200 miles of the radar station. In addition, tropical cyclones are tracked by satellites, which provide very useful information both to forecasters and numerical forecast models.
Hurricane education
The website is called: What to Do Before the Tropical Storm or Hurricane. It tells the potential risks a hurricane brings such as high winds and storm surges. It also educates people on how to prepare for a hurricane such as having an emergency kit and plan in the event of a hurricane as well as boarding up houses. It also tells people how they should respond in the aftermath of the a hurricane such as being careful of gas leaks and continue listening to NOAA weather radio.
Hurricane evacuation
During Hurricane Milton Florida has issued different evacuation zones for different states depending on their vulnerability. For example, Charlotte County Emergency Management has issued mandatory evacuation orders for residents in Red Zone-A and Orange Zone-B. The evacuation also includes residents in any zone living in mobile and manufactured homes.
How is coastal flooding planned for?
Moving communities on Fiji
In fiji they are relocating homes and villages due to the increasing threat of climate change from sea levels rising to powerful cyclones. At present, 42 Fijian villages have been earmarked for potential relocation in the next five to 10 years, owing to the impacts of climate crisis. Six have already been moved. Every new cyclone or disaster brings with it the risk of yet more villages being added to the list.This means that homes are less vulnerable to rising sea levels.
How is coastal flooding prevented?
Floating homes in Holland
Floating homes have been introduced in Holland. When a heavy storm hit in October, residents of the floating community of Schoonschip in Amsterdam were confident they would be safe. During the storm their neighbourhood slid up and down its steel foundational pillars, rising along with the water and descending to its original position after the rain subsided.
Artificial islands in the Maldives
They have created artificial islands in the Maldives.The new island, built by pumping sand from the seafloor onto a submerged coral platform, rises about 2 metres above sea level. The extra height could make the island a refuge for Maldivians who are eventually driven off lower-lying islands due to rising seas. It could also prove to be an option for evacuations during future typhoons and storm surges.
What are groynes?
Groynes
Description
- Stone or wood structures built out to sea, used to trap sediment transported by longshore drift, and build the beach up.
Advantage
- Able to trap sediment which can help to develop beaches. This is useful because it prevents longshore drift.
- Bigger beach can enhance tourist attraction
Disadvantage
- Unsightly - who doesn’t like a beautiful beach with lots of wooden or metal barriers all over it?
- About 5,000 per metre.
- Takes away sediment from other beaches which can increase erosion in other areas. Further up the coast
What are sea walls?
Sea walls
Description
Concrete barrier with a usually concave shape, at the top of the beach, used to deflect wave energy back seawards and protect cliffs and or coastal developments.
Advantage
- Particularly useful at protecting the foot of cliffs from being further eroded. This is important because it stops the coastline from retreating backwards.
- It can provide a walkway/promenade for people to use.
- Depending on maintenance it can be 30-50 years
Disadvantage
- Expensive at 5-10,000 pounds per metre. May take away from money available to protect other areas.
- Not aesthetically pleasing
- Concrete has a high carbon footprint.
What is rip rap/ rock armour?
Rip rap/rock armour
Description
Piles of boulders dumped at the foot of the cliff to absorb wave energy and reduce ability of waves to erode the cliff.
Advantage
- Relatively cheap (£1000-4000) and easy to maintain and effective at reducing wave energy
- Can add interest to a coast
- Has a more natural look however it still doesn’t look that nice.
Disadvantage
- Can be obtrusive
- Reduces the size of the beach
- Rocks are imported from other areas can contribute to climate change.
What is cliff drainage?
Cliff drainage
Description
Gravel drains reduce saturation of cliffs by allowing water to funnel out of rock and therefore reduce the risk of slumping
Advantage
- Where cliffs are made of clay and easily saturated materials and permeable features like red crag. Also where there is high rainfall
- Relatively cheap
Disadvantage
- Not very aesthetically pleasing
- It does not help with cliff foot erosion through wave action.
