How does costal erosion and sea level change alter the physical characteristics of the coastline and increase risk Flashcards
What are the 2 types of sea level change called and explain
Eustatic change - When the sea level itself rises or falls (Global change)
Isostatic change- When the land rises or falls relative to the sea (local change)
What is marine regression and transgression
Marine regression - Where the sea level drops and produces and emergent coast
Marine transgression - Where the coastline is flooded and produces a submergent coast
What type of sea level change is Marine regression and explain
Eustatic fall in sea level (global) - During glacial times, when ice sheets formed on land in high altitudes (far north and south) water evaporated is locked up on the and as ice. Resulting in global sea level fall.
Isostatic fall in sea level - During the build up of ice sheets the weight of the ice causes the earths crust to sink (Isostatic subsidence). As it melts it causes the earth to rebound (Called post-glacial adjustment or isostatic recovery) . Land lifts out of the sea
What is an emergent and submergent coastline
Emergent - Land rising (land being exposed out of the sea)
Submergent - Land sinking
What parts of the UK have been effected by sea level changes
Land in the north west (which was covered by ice) is rising as a result of isostatic recovery
Land in the south east (which was not covered by ice) is sinking. Sediment deposition is causing the crust to sink and relative sea levels to rise
What are the landforms on and emergent coastlines by sea level change and how are they formed
Is it isostatic or eustatic changes
Isostatic changes
Raised beaches - As land rose as a result of isostatic recovery former shorelines and beaches were raised above sea levels
Fossil cliffs can occur behind
Fossil cliffs Cliffs are exposed as a result of isostatic recovery. Often have old wave cut notches and causes evidence of past marine erosion
What are the landforms on submergent coastlines caused by sea level change and explain
Is it an isostatic change or a eustatic change
Eustatic changes
Rias - When valleys in dissect upland areas are flooded due to water being forced back up the mouth of the river during sea level rise they drown lower parts of rivers and their tributaries.
Fjords - Deep glacial troughs are flooded by rise in sea level. Long steep sided with a U shaped cross section. Deeper when inland compared to on the coast
Dalmatian coast - Similar to rias. Rivers flow almost parallel to the coast (not a right angle)
Where is Kiritimati and what challenges is it facing
It is located in the Mid pacific and is apart of the Republic of Kiribati which is a group of 33 islands that straddle the equator
- Raised no more than 2 meters above sea level
- Half of households have already been affected by sea level rise
- LIDC country
- People who have become climate refugees
What are the responses to Kiritimati being under threat by sea level rise
- “migration with dignity” scheme where they aim to create a skilled work force so they residents can find good jobs abroad
- New Zealand has created a lottery where 75 Kiribati citizens can resettle in New Zealand
- Plant Mangrow trees to reduce flooding
- They have low carbon admissions (little to none)
- President have stopped countries tuna hunting in Kiribati waters due to admissions
Why is the Netherlands under threat to sea level rise
- Low lying coasts as 1/4 of the total territory lies below sea level
- Without Dykes this parts of the country would be permanently flooded
- Sea levels in the Netherlands rose about 20cm within 100 years
AC example
Why did the Netherlands start managing flooding
What did they do
31st January 1953 as huge storm happened which killed 1,900 people in the Netherlands and 300 on the English east coast
The built a network of Dams, dykes and storm barriers that is unmatched work wide
Number of people killed by flooding since 1953 is zero
Why is China under threat for sea level rise?
- The sea has rose by 3.3 mm per year since 1993 in China
- Sea levels could rise by 2 meters by the end of the century which is enough to flood Chinas megacity Shanghai
- Worlds largest population living at low altitudes as 126,000 are 10 meters above sea level or below
- If global temperatures keep rising 64 million Chinese people will be flooded
- Low-lying shanghai is in population terms the worlds at most risk from rising sea waters
What type of sea level change is marine transgression and explain
Eustatic rise in sea level - At the end of a glacial period melting ice returns water to the sea causing sea levels to rise globally. The thermal expansion of water causes sea level rise
Isostatic rise in sea level - Land can sink at the coast due to the deposition of sediment. This can happen especially in large river deltas where the weight of sediment deposition causes delta subsistence
Where is the Nile Delta and what is the population like
North Eastern Africa in Eastern Egypt. North of the river Nile where the river splits into two rivers
Home to 41% of Egypt’s population (95 million people)
What are the physical causes of erosion on the Nile Delta
- 270 Km of coastline is at a dangerously low elevation (many parts are 0 - 1m above sea level)
- A 1m rise in sea level that is predicted in the next 100 years will cause 20% of the Delta to become flooded
- A 2m rise in sea level would see 8789km^2 flooded (43.9% of the delta)
How has the Aswan high Dan contributed to erosion on the Nile Delta
- Has disrupted the normal flooding of the delta
- Discharge fell from about 35 billion m^3/year to 10 billion
- Sediment volume fell from 130 million tonnes to 15 million
- The sediment is trapped by the dam + reservoir so less reaches the delta
- In 1965-1970 the erosion rates were 225 m/year
What are the human impacts of erosion on the Nile delta
- Water withdrawals from lake Nasser (behind the dam) that supports industries, cities etc significantly reduced water discharge to the delta
- Removal of coastal sand dunes contributing to the submergence across the Delta coast
- Egypt became Africa’s 2nd largest producer of natural gases, most are extracted from thick layers of sand and shale underlying the delta exacerbating subsidence
How was extraction of ground water played a part in the erosion of the delta
- Over the past 30 years ground water pumping for agricultural, urban and industrial use has been at an exceptional rate causing large areas to subside
What does subside mean
subside means to fall/sink
What are the main factors making Bangladesh even more vulnerable to flooding
- Population density
- Land height
- Location
- Himalayas/rivers
- storm surges
- Monsoon climate
How does Population density and Land height make Bangladesh more vulnerable to flooding
. Population density - Have the highest population density in the world.
This could mean many are living in informal sector housing and slums and many more people will be effected
. Land hight - Low lying land especially around costal areas (2-3m above sea level)
46% of the countries population lives 10 meters above sea level
How does location and the Himalayas/rivers make Bangladesh more vulnerable to flooding?
. Location - Bangladesh lies on the flood plains of 3 major rivers (Brahmaputra, Meghana and Ganges). The 3 converge in Bangladesh and flow to the bay of Bengal
. Himalayas/rivers - Bangladesh lies below Nepal. As an increase of snow melting (due to global warming) flows into the rivers, meaning more water is flowing through Bangladesh so more likely to flood the watershed
How do Storm surges and Monsoon climates make Bangladesh more vulnerable to flooding
. Storm surges - Bangladesh is prone to tropical cyclones which bring regular storm surges to the coast
40% of all storm surges recorded have occurred in Bangladesh
. Monsoon climate - The majority of rain fall occurs between June and October which can bring over 50mm of rain per day to some regions
What is watershed
The max water a river can hold
