Coast, Water cycle and Insecurity case studies

Case studies coast

 

Rapid coastal recession is caused by physical factors but can be influenced by human actions.

The Nile Delta

·      240km long coast

·      There are holiday beach resorts, coastal defences, general tourism, marine recreation, fisheries, land reclamation, agriculture, settlements, transport and port infrastructure.

·      There is salt intrusion into the delta due to climate change. As sea level rise and protective offshore bars are eroded, 3.3% of the delta land area will be lost.

·      The building of the Aswan Dam in 1964 reduced terrestrial sediment supplies.

·      A 2015 study classified 32.4% of the Nile Delta coast as highly vulnerable with only 26% as low vulnerability.

·      If sea levels rise by 1m by the end of the century and no action is taken, 2 million hectares of fertile land will be lost and at least 6 million people displaced including about 30% of the city of Alexandria.

Bangladesh

·      In the past 50 years Bangladesh has built 4000km of coastal embankment. About 30 million people live on polders (land enclosed by embankments).

·      In 2014 Bangladesh was planning to upgrade 600km of embankments in the Sundarbans delta region (using $400 million from the world bank)

·      However there is an argument that this would do more harm than good and the embankments constrict and funnel tidal flows, pushing water further inland and increasing the tidal range: the polders should be abandoned and the embankments positioned further back from estuaries to reduce this effect.

 

Local factors increase flood risk on some low lying and estuarine coasts; global sea rise further increases risk.

Bangladesh

·      Most densely populated country:169 million in 2015

·      46% of the population lives less than 10m above sea level

·      Lies on the flood plains of 3 rivers, which all converge in Bangladesh.

·      Himalayan snow melt

·      Subsidence

o   Estuarine islands sunk by 1.5m in the last 50 years.

o   Due to clearance and drainage of more than 50 large islands in the Ganges- Brahmaputra river delta

o   These islands used to be forests but have since been cleared for farming of rice to feed

o   Embankments were built for protection, but they stop natural deposition that used to maintain the islands height

·      Removing vegetation

o   71% of Bangladesh’s mangrove forested coastline is retreating by 200m a year.

 

Storm surge events can cause severe coastal flooding with dramatic short-term impacts.

Bangladesh (LEDC)

·      Cyclone Sidr came in from the Bay of Bengal on the 15 November 2007, bringing with it a storm surge that reached up to 6m high in some places.

·      It brought with it very heavy rain and winds of up to 223km/h.

·      A category 4 storm

·      According to Bangladesh Meteorological department, the eye of the storm crossed the coast near Sundarbans mangrove forests around 9.30om.

Impacts:

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