Coastal Flooding Flashcards
How does the height of a coast increase flood risk (local factor)?
Flood risk increases for low-lying coastal areas, like coastal plains, estuaries and river deltas. Low-lying land = water can seep onto land easier.
How does the degree of subsidence increase flood risk (local factor)?
Areas that are experiencing isostatic shrinking are more vulnerable to coastal flooding, as are areas where drainage causes land shrinking.
How does the removal of vegetation increase flood risk (local factor)?
Ecosystems such as salt marshes and mangrove forests are important in reducing flood risk. They provide protection and shelter against storm winds, floods and tsunami by absorbing and dispersing tidal surges.
1/2 of mangrove forest globally lost.
How do mangroves reduce coastal flooding?
-They reduce the height of the waves, reducing wave erosion of the coast.
-Their roots trap sediments, raising the height of the coast.
-They reduce storm surge levels - by 0.5m for every 1km of forest that seawater has to pass through.
Why do humans live on the coast?
Sea and river trade.
Farming/fishing.
How do storm surges form?
Low pressure over the sea allows the water to bulge upwards in a dome. The lower the pressure, the higher the dome. Storm surges are made worse by storm winds on top of the dome, which increases the height of the water at the coast, increasing the risk of flooding.
When the low pressure system moves towards a coast, the dome of seawater surges ashore. The shape of the coastline can also increase storm surges if it acts to funnel the storm surge towards an area of shallow offshore water.
How does climate change increase the risk of flooding?
Sea level rise would increase the risk of flooding for low-lying coastal areas. It is not clear how far/fast sea levels will rise, but increasing rates of melting of Antarctica ice sheets has led experts to believe it will be 2m by 2100.
Global warming will mean that depressions and tropical cyclones have more energy and are stronger/more frequent. This could increase the risk of flooding/storm surges.
