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coasts as a landscape (Salt marshes HALOSERE (Low energy zone that forms a…
coasts as a landscape
Salt marshes HALOSERE
Low energy zone that forms a transitional area between land and brackish salty water
saline area
salt marshes develop on depositional coasts, bay, estuaries as they are low energy
sediment deposits, and coagulates
coagulation makes the sediment heavier and fall out of suspension, causing it to accrete in sedimentation
continually happens and mud builds up and is therefore out of water for longer
increased sedimentation means the sediment goes above high tide
seeds can germinate and grow roots
small halophytic pioneer plants such as seablite start to colonise
these plants start to consolidate the mud, oxygen gets into the mud and aerates it
decomposition adds organic matter into the soil adding bioconstruction and soil fertility
can now harbour less halophytic plants such as sea lavender
climax species such as reeds and rushes
Coastal dunes PSAMMOSERE
Starts beyond backshore
sand has to be high up enough to be out of high tide for long enough
on shore winds blow seeds and sediment up the beach
other sediment is moved by saltation up the beach
sand becomes trapped and accumulates behind driftwood and berms
pioneer plants grow (halophytic and xerophytic)
marram grass is embryo dunes plant
die and decompose releasing nutrients
less tolerant plants grow in foredunes an these are flowering plants
shrubs and small trees grow in the grey dunes - climax species
sea level change
scientists believe sea level was 120 times lower 20,000 years ago
eustatic
sea level rise and fall
temps increase globally, increased river discharge as stored ice water melts, increased by 1.8mm per year in 60's, 3mm per year in 90's, predictions of 8mm per year
isostatic ride in Scotland causes a sea level fall
submergent coastlines
drowned by eustatic sea level rise
rias and fjords
ria - drowned river valley
fjord - drowned glacial valley eg Norway
isostatic fall in sea level - bounceback
Dalmatian coasts eg Croatia - where several valleys have flooded/drowned
emergent coastlines
relic caves
abandoned WCP
how can we manage the coast
hard and soft engineering
cost benefit analysis -compare costs and benefits, tangible and intangible, if costs outweigh benefits - unlikely to go ahead
shoreline management plans - document about coastline as a whole, work on basis that sediment cell is contained and their work will have no effect elsewhere, holistic view
integrated coastal zone management - sustainable levels of activity
the coastline as a whole
made up from landforms
concordant - rock strata is parallel
discordant - rock strata is perpendicular
Depositional landforms
Spits - thin, linear, coastal extension, curved/hooked, made from sediment, sheltered low energy marshland behind the spit, can have small scale human development, eg
Spurn Head, Yorkshire
Bars - spit across a bay, lagoon, low enrgy eg
Loe Bar, Cornwall
Tombolos - spit joins to an offshore island
Erosional landforms
Wave cut platform - erosional landform, flat area of coast at base of a cliff, abraded rough and rough, number of surface depressions, visible at low tide, successive coastal retreats, zone of attack is between high and low tide
Headlands and bays - protrudes out into sea, irregular shape, more resistant, semi circular inlet, caused by discordant coastlines.