Sand dunes, mud flats and salt marshes

Question 1

formation of a salt marsh

Answer 1

• accumulation of slit and clay in low energy environments e.g. estuaries (DEPOSITION)
• plants reduce velocity of tide and increase deposition which increase surface height of marsh
• less salt tolerant species can invade the marsh invasion and succession

Question 2

conditions for dunes to form

Answer 2

• low land coast with large backshore for sand to accumulate
• prevailing on shore winds
• abundant supply of sand in intertidal zone

Question 3

importance of mudflats and saltmarshes

Answer 3

• feeding grounds e.g. ducks and geese
• provide refuge at high tide for birds
• important natural defence against coastal erosion

Question 4

threats to salt marshes

Answer 4

• every year around 100 ha of marsh land is lost to coastal erosion e.g. kent and Essex lost 20% of salt marshes (1973-1988)
• erosion control reduces sediment input into coastal system and upsets sediment budget=starts to contract
• cord grass= doesn’t anchor mud=more rapid erosion

Question 5

formation of dunes

Answer 5

• wind transports dry sand by creep and saltation
• when wind speed falls below critical level sand is deposited
• plants provide resistance to wind-lowering velocity increases deposition
• interaction between wind, transported sand and plants allow coastal dunes to reach heights of 25-30m