Erosion and Coastal Flooding during Extreme Weather Events
(26/03/25)
Low pressure in the atmosphere raises sea levels. A deep depression causes sea levels to rise. Strong winds create large wings that are pushes in front of an advancing area of low pressure, creating even higher water levels. This effect is known as a storm surge.
Anything above 1013mb is high pressure, anything below is low pressure.
A depression of 960mb leads to a 50cm rise in sea levels.
Anti-Cyclones: Clockwise // Cyclones: Anti-clockwise
Waves are formed/influenced by wind and fetch (the distance the wind travels).
Low pressure in the atmosphere is caused by air rising, leading to strong winds and rain.
Storm surges are temporary, localised rises in sea levels caused by low atmosphere pressure.
Every 1 milbar (mb) fall in air pressure leads to a 1cm rise of sea level.
December 2013 there was a storm surge in the UK. The storms led to flooding in many areas.
(31/03/25)
The December 2013 UK floood was caused by a masive tidal surge and high tides. It had a high risk to life, killed 2 people and damaged many properties. Residents living in risk were asked to evacuate, and transportation was delayed by the dangerous weather. Electricity was cut off for many. Worst storm surge in 60 years. Low pressure, strong winds, high tides, led to sea water bulging upwards and attacking the coast. 800,000 homes protected by coastal defences and accurate weather forecast that improved since 1953 floods.
impact
The Yorkshire sea wall was damaged, 270 homes were evacuated in Kent, 400 Humber homes were affected by floodwater, 9000 homes in Norfolk were evacuated overnight. A cliff in norfolk collapsed into the sea. In Suffolk, 1000 sandbags were givven to home-owners. The Essex sea wall was breached and 2500 homes wre evacuated by rescue boats and firefighters. Lincolnshire was flooded.
explanation
If a storm approaches the coast at high tide (happens twice a day) the risk of flooding is increased. The UK’s North Sea coatline is particularly vulnerable to storm surges. The southern part of the sea is shallow and funnel-shaped. When low pressure travels southwards across the North Sea, the bulge of the storm sure can increase in height as water is forced through ths shallow funnel.
The actual sea level was around twice as much as expected. The high tide was nearly 3 metres higher than predicted.
a) High tide was expected from 8pm to midnight and at noon.
summary of how climate change could affect london/the thames gateway
The Thames Gateway is a coastline that has been sinking by around 2mm a year for over 10,000 years (postglacial rebound since the ice age). In addition to the rising sea levels from climate change (around 3mm a year), the Thames Gateway is practically being sunk by 5mm yearly. Estauries have water going in as well as out.
England is sinking the quikest (~5cm per century) and Scotland is rising the quickest. (~10cm per century)
thames flood barrier
The most important flood defense system in the world.
Protects over a million people and billions (pounds ig) in real estate.
Stops a river from pulling London underwater.
The gates rise during high tide, and re-open when there is no longer a threat to let river traffic through.
First used to stop the damage of a storm surge.
Massive concrete foundation and 10 gates (hollow and made of steel)
Fill with water when submerged and empty when rising.
Have a system to communicate with shipmen.
Designed to work with the river’s natural flow.
Can act like a damn.
Slow the river before closing (takes 90m).
1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017
(02/04/25)
Holding the Line (Thames Flood Barrier)
Completed in 1982 in London
Protects two million people from tidal floods
May not be large enough to protect London from future floods
By 2100, London needs to be protected from 2.7m higher flood levels.
TE2100 Plan
Rewnew and replace existing embankments, sea walls, and sluices in Thames Gateway
Increase amount of inter-tidal habitat in Thames estuary by 876 hectares.
Salt marshes to help store flood water.
Storage areas created by realignment projects like the one in Essex
Consider building a new, larger barrier to the east of the existing one, would be around 7 billion pounds.
Property at Risk of Tidal Flooding on the Thames flood plain
Over 500k homes
40k commercial/industrial pro
perties
400 schools
16 hospitals
35 tube stations
>300km of roads
(07/04/25)
Some coastal communities, such as Skegness and Great Yarmouth are more vulnerable to coastal flooding because:
There is a high proportion of people claiming benefits (less money)
A large turnover of people through economic migration (less money)
A lot of poor-quality housing
Over-reliance in tourism (seasonal employment, inconsitent money)
The less people make, the less the government makes from taxes.
Skegness has poor road and rail links, and many live in caravans instead of houses.
Great Yarmouth is a seaside resort with many elderly/retired residents (high unemployment rate), so the economy is in decline.
Farm land is less likely to be protected, both areas are farms.
East Lindsey cannot afford to spent resources on coastal defences as their elderly population is high (60-64 is around eighty percent), meaning there are many retirees. Elderly people need money for hospital stays and for general living, which is supplied for by the local authorities, so the money cannot be spent on coast defence mechanisms.
The table displays that in Skegness, the percentage of those claiming benefits and without academic qualifications is higher than in England. For the percentage working in professional jobs, however, Skegness and Lincholnshire are the lowest.
The government would be advised to appeal for outside help as the population is highly reliant on the local authorities for income and hospital fees, greatly diminishing the available funds to be used on flood defenses. Additionally, only around a third of the population has any academic qualifications, which would make them unreliable to advise on how to best construct coastal defenses.
Individuals should try their best to prepare for sea level rises and take necessary precautions, as that will minimise damages, but the central government should be involved in protecting poorer communities and distrubuting resources.
LECZ - Low Elevation Coastal Zone
Any area close to the sea that is less than 10metres above sea level.
Environmental refugees
People who are forced to permanently leave their homes due to a change in environment. (such as coastal flooding or desertificiation.)
SIDS - Small Island Developing States
Currently 58 with a combined population of 65 million.
Very small and some located in remote/isolated parts of the world.
Most are vulnerable to climate change and natural disasters.
Standards differ with GDP per capita ranging from 51,000 usd (Singapore) to 830 usd (Comoros)
It is estimated that 950 million people around the world will live in LECZ by 2030.
There are 136 coastal cities that are at a greater risk from climate change (identified by the world Bank in 2013).
Poorer people live in the land at risk that no one else wants (by the sea), so rising sea levels post a threat to them.
Sea level rise → Increased risk of coastal flooding at high tide.
Heavier rainfal increases the risk of flash floods in poor drainage areas.
Violent storms/hurricanes → Increased risk of coastal erosion and storm surges.
The world’s major river deltas are potentially the worst-affected coastal communities, there there is subsidence of the soft lland as well as sea-level rise, in deltas such as Bangladesh, Egypt, Nigeria, Vietnam, and Cambodia.
1a) The SIDS are distributed in the tropical regions.
(09/04/25)
The housing is poorly constructed without reinforced material. It is on stilts to give it elevation from the coming tide.
The land at risk of flooding is cheap and unwanted because any infrastructure built there can be destroyed by the water, so those in poverty must live there .
Climate change leads to a rise in sea levels, the stilts the houses are on will eventually be unable to compete with the high sea levels and the houses will be destroyed.
The Maldives
350k population
Main income from tourism, otherwise from fishing.
Vulnerable to sea level rise
Made of 1,190 islands (is a part of SIDS) Only 250 are inhabited.
80% of the land is under a metre above sea level. Nowhere is >3m above sea level.
The maldives is the most vulnerable and threatened by sea level rise.
The government is using hard engineering to hold the line against rising sea levels.
The Maldives highest point is 2.4 metres above sea level.
The intergovernmental Panel on Climate Change predicts sa levels could rise by 25-58cm by 2100.
3-4 mm increase in only a year, a decade could lead to the submersion of low-lying islands.
Islands may be washed away.
The Impact of Flooding Across the Maldives
Male
Japan offered $60 million in aid to fund a 3m sea wall.
All other islands remain vulnerable.
Sea wall needs constant repair that’s paid for through local tourist taxes.
Drinking Water in Short Supply
87% of the population can be supplied by collecting rainwater.
Ground water sources have bene contaminated by salt-water intrusion and bringing in supplies from abroad is unsustainable.
Tourist Industry Under Threat
90 percent of the government tax revenue is from tourism.
The damage caused by the 2004 sea surge destroyed many prize beaches and ruined luxury resorts.
The tourist numbers dropped dramatically for a year as the islands recovered.
Hulmumale (man-made island)
The city is build entirely on an artificial island aiming to fight rising sea levels.
It is 4km squared and currently home to approxiamately 100k people.
It was designed with eco-friendly initiatives such as building orientation to reduce heat gain, streets design with wind penetration optimasation to reduce AC reliance.
Planned city to have schools, parks, and close to housing to reduce car use.
Electric buses and bicycle lanes.
Conference of the Parties (COP26)
Lots of countries agreed to fight against climate change to protect places at risk like the Maldives.
Floating Islands
Artificial islands built in India/Middle East and towed to the maldives. Floating islands will be moored to the seabed using cables to minimise environmental impact.
(thought of by a Dutch company.)
Tunnel on the seabed leading to a floating golf island, underwater clubhouse.
Moving to Australia
Australia is a possible new home if the Maldives disappear beneath rising sea levels.
The Australian government may need to prepare for a mass wave of climate refugees.