l2 risk of flooding
TRANSCRIPT
Increasing risk of coastal flooding
Coastal flooding is the second physical processes (after erosion) that you need to learn about.There are 2 types of causes of long term sea level change, Eustatic and Isostatic changes.
A. long term causes of sea level change 1.Isostatic change
• Localised upward and downward movements of the land relative to the sea. These movements are caused by tectonic uplift or subsidence.
• Another cause is the upward movement of a continental mass when released from the pressure of an ice sheet.
• Currently the south of UK is sinking whilst the north is rising due to the lifting of the ice sheet 10,000 yrs ago. The ice was thinker in the north.
Where was the beach once? What has happened to the land?
A. long term causes of sea level change 2. Eustatic change
• Global changes in the volume of the oceans is caused by melting of ice sheets at the end of a glacial period or
• Over the past 18,000 years the rising global volume of ocean water as this ice melted, together with complex, localised Isostatic changes, has generally produced an increasing mean sea level of about 0.1-0.2mm per year in the past 100 years.
• Video of the UK’s eustatic sea level rise
B. Short Term (recent) Causes of Sea level rise
Global warming has led to rising sea levels for several reasons.
1. Rising atmospheric temperatures have caused increased melting of ice caps and glaciers resulting in an increase in water in the oceans and seas.
2. As the atmosphere warms, so too does the sea with the result that it increases in volume due to thermal expansion. (remember your science GCSE, what happens when you heat water?)
Storm Surges
• Surges are caused mainly by the action of wind on the surface of the sea.
• They are examples of short term sea level rise. • When pressure decreases by one millibar, sea level
rises by one centimetre. • When air pressure is high, sea level falls
correspondingly. • Around the UK, the effect of a strong wind coupled
with very low pressure can be to raise sea level in eastern England more than two metres.
Your turn!
In groups you need to research into an event below and prepare a PowerPoint OR handout for the rest of the class to be delivered next lesson; 1. Storm Surge.
Case study: North Sea storm surge 1953
2. Tsunami. Case study: Japan 2011
3. Sea level rise in low lying areas. Case Study: Thames Estuary
Your turn!
• For each presentation you need to include specifics as well as focusing on;– What happened / is happening? (one slide /
paragraph)– What was the impact / would the impact be on
people (social, economic, environmental)? (three slides / paragraph)
– How much are people at threat who live on the coast in these areas? (one slide / paragraph)