Coastal Landscapes and Change, Continued Flashcards
Sea level Change in General
long term sea level changes occur over thousand of years
long term sea level change is due to eustatic, isostatic factors and tectonics
tides, variations in air pressure and wind can create bulges in sea level
Eustatic Change
change in global sea level, due to a change of high volumes of water in oceans
how is water transferred (eustatic)
from land store back to oceans, increasing there volume of water in the oceans and raising global sea levels
how is a global fall in sea level achieved>
a decrease in the volume of water in the oceans
how much did sea level rise from 1870-2010
21cm - Humans are thought to be accelerating interglacial warming
Eustatic Rise in Sea Level
end of glacial period, melting ice sheets return water and sea level rise globally = global temperature rise = thermal expansion more water in ocean.
Eustatic Fall in Sea Level
ice sheets form on land, water evaporated from the sea is locked up on land as ice = sea level falls
What is isostatic change
change in local land level
local land level rise = sea level falls
post glacial adjustment
accretion - sink regions in sediment cell experiencing no deposition = land built up
tectonics
local land level falls = rise in sea level
subsidence
tectonics
post glacial adjustment
post glacial adjustment
weight of ice depresses the crust in areas below ice sheets = solid lithosphere forced down into asthenosphere
rigid nature of crust = sections of crust are depressed by ice adjacent areas are uplifted in seesaw affect
melting of ice effects - Post glacial adjustment
ice covered crust slowly rebound upwards whilst adjacent areas subside
UK - Ice Age
last ice age 12000
Uk covered with ice down to Birmingham
North Britain = isostatic fall in sea level, land lifted 1.5mm per annum
South Britain = isostatic rise in sea level, land lowered by 1mm
Tectonics and Eustatic Change
rising magma at constructive plates = reduce capacity of the ocean and produce eustatic sea level rise
uplift of crustal plate reduced Indian Ocean capacity - 0.1mm eustatic rise
Tectonics and Isostatic Change
Lava, Ash from volcanic activity produces isostatic fall, Hawaiian hot spot island chain
Sea floor spreading - carries volcanic island away from uplifted crust at mid ocean ridge, more dense crust subsides and sea rises, fIJI, Kiribati
Sedimentary rock folding at destructive plate produces an isostatic fall in sea level
Devonian Glacial Eustatic Change
sea levels lowered by 120mm
how are emergent coastlines produced
post glacial adjustment, parts of littoral zone where fall in sea level exposed land once part of sea bed
what is a raised beach
relict beach above high tide
flat surface covered by sand
usually vegetated by plant succession
what is a Fossil Cliff
steep slope found at back of raised beach exhibiting evidence of formation through marine erosion, now above sea level
may contain wave cut notches, caves, arches
Isle of Arran
raised beach 5m above sea level
Three levels of raised beach produced at different stages of post glacial adjustment
what is a submerging coastline
sections of littoral zone where sea level rise inundated areas that were previously part of terrestrial land
where are submergent coastlines found
southern England and east coast of America
what is a ria
drowned river valley - section of the river valley flooded by the ocean making it wider
where are rias common
periglacial areas that were adjacent to land covered ice during the devansian
what type of coastline is ria
estuarine coastline
Example of a Ria
Kingsbury Estuary - South Devon
6M Long
2 large drowned tributaries extend from east side of the ria with frog more creek 2 km long and 500m wide
why does a ria have a cross section and v
rivers eroded steep sided v shaped valley into frozen landscapes = v shaped cross section when valley flooded
what are fjords
drowned glacial valleys - section of glacially eroded valley flooded by the sea
where are fjords common
glaciated areas, covered during devensian eg western norway
why are fjords deep
glacier erosion if often cut deep into the landscapes often thens of metres lower than the adjacent land
what is a Dalmatian coast
long narrow island running parallel to the coastline and separated from the coast by narrow sea channels call sound
how are Dalmatian coast produced
sea level rise flooding the coastline
how are sounds formed
sea level rise at the end of the devensian glacial floods synclines to form sounds
Dalmatian region example
Croatia - limestone coastline stretching 520KM NW-SE with 1240 island parallel to the coast
how does climatic warming lead to eustatic sea level rise
melting of mountain glaciers (ALPS, Himalaya), polar ice sheets increasing the amount of water in ocean store
melting of sea ice
has no effect on sea level as the ice was already displacing the equivalent water that has now been melted
thermal expansaion and sea level change
94% increased heat energy in climate system is transferred to oceans
tectonic activity and sea level change
emission of geothermal heat into oceans by underwater volcanic activity can cause thermal expansion of ocean water
rising magma at constructive plate boundaries produces a doming upwards of curst along mid ocean ridges reducing the ocean basin volume
tectonics destructive plate margins and sea level change
folding of plates increases ocean basin volume lowering sea levels
earthquake along boundary can allow rebound of non subjecting margin uplift of sea floor reduces ocean volume raising sea levels
how do destructive plate margins cause isostatic change
faulting uplift sections of crust lowering sea levels
sea floor spreading transports volcanic islands away from uplifted crustal zone along constructive boundaries or hotspots to the ocean is colder, denser
PAST CHANGE OF SEA LEVEL
level risen 125m since devensian glacial
IPCC suggest sea level rise was 0.5mm pa from 6000BP to 1860
Future SEA LEVEL RISE
IPCC - sea level rise 18-59cm by 2100
why wide range of prediction for sea level change
science of relationship between climate warming and rate of ice melting
uncertainties about rate of population growth and economic growth
why are coastlines at risk
low lying ones - coastal flooding through marine transgression
low lying volcanic island. Maldives in the Indian. ocean, Kiribati islands in the pacific ocean
volcanic islands at risks from tectonic activity and global warming
how does sea level ise affect numbers of people
estuaries and deltas are ideal for trade, navigable access inland up rivers
low lying deltas ideal for agriculture due to fertile
many low lying coastlines are densely populated as beaches and ocean attract tourist
river deltas that support megacities
Shanghai, Yangtze Delta China
Dhaka, Bangladesh,Ganges - Brahmaputra
Karachi, Pakistan
what does the IPCC predict for coastal regions
2060 12% world population in coastal regions - 10m above sea level
how does height increase flood risk
temporary flood risk from storm surges, permanent flooding from global sea
rise
low lying coastlines 1-2m high above sea level so at risk from flooding
Kiribati and Height that increases flood risk
group is islands 33 coral atolls
most population lives on Tarawa where height is 3m above
Maldives and height that increase flood risk
highest point is only 2.3m
main island and capital is protected by 3m sea wall
how does human activity cause local subsidence
weight of cities and built environment = sediment compressed, leading to subsidence (Venice)
Drainage of saturated sediment for ground water abstraction to supply cities Venice - reduces sediment volume causing subsidence
non human factors flood risk
low lying coastlines in estuaries, deltas are subject to natural subsidence through settling and compunction of deposited sediment
Isostatic readjustment after ice sheet retreat Southern England
Vegetation removal flood risk
salt marshes, mangrove forest reduce flood risk
vegetation absorbs wave energy - reducing the impact and erosion
50% worlds mangrove forest removed since 1950, lost removed for tourists beaches
global sea level rise, flood risk
increase risk of flooding in low lying coastlines
Maldives - Flood risk
50cm sea level rise would flood 77% islands
what is storm surge
temporary rise in local sea level produced when a depression, storm, or tropical cyclones reaches coast
rise in sea level during storm surge is accentuated
high tide, during spring tide
shape of coastlines funnels increasingly narrow space
sea bed shallows towards coast
storm surges on low lying coastlines
severe coastal flooding
storm surges coasts
force of onshore current can cause rapid coastal erosion
storm surges, destructive waves
impact is increased by destructive waves whipped up by strong storm winds on top of high sea level = coastal erosion rapid
short term impacts on storm surges
homes destroyed
deaths, injuries
diseases from sewer systems and freshwater pies destroyed
business destroyed
Bangladesh CASE STUDY
Cat 4 cyclone. 6M Storm surge 240MPH 15000 people killed 55000 injured 1.6 million homes destroyed 1.7 Billion in damage 8000KM infrastructure 900 fresh water tube wells
how did the bangladsh cyclone worsen
coastline from unconsolidated delta sediment easily eroded
deforestation of mangrove swamps
2007 cyclone in Bangladesh compared to 1970 Bhola Cyclone
impacts in the 2007 were much lower due to improved warnings, embankments and cyclone shelter network saves many lives
Storm Xavier, December 2013 UK CASE STUDY
80MPH Wind Storm coincided with spring tide 2 killed 18000 evacuated Coastal defences breached, 1400 homes flooded £100Million lost
why was the impacts of storm Xavier less than 1953 storm surge UK
improved flood defences - thames barrier raised during storm, 800000 homes protected
improved forecasting, efficient evacuation,
mitigated in areas where flooding or erosion still occured `
What did IPCC predict in 2014
climate change warming of atmospheric and oceans would increase intensity of atmospheric circulation
why is the pace and extent of sea level uncertain
population growth, economic development, natural positive and negative feedback, political commitment to restrict GHC emissions
adaptations affecting predictions of sea level
building sea walls
building earth embankments
storm surge barriers across river mouth - Thames Barrier/Eastern Scheldt Netherlands
restoration of mangroves forest - protection belts - Sri Lanka replanting after 2004 Indian Ocean
Delta flooding flood risk
area of the world major deltas at risk from coastal flooding likely to increase by 50%
Medium Confidence of flood risk
wind and waves - evidence of increase wind speeds and large waves
Tropical Cyclones - weak evidence
frequency unchanged - could be larger storms
cyclones intensity increase due to warmer ocean surface temperature and warmed atmosphere holding moisture
Tropical cyclones combination of factors - Weak Evidence
North Atlantic - tropical storms becoming hurricane has risen from 6 in the 1990s to 8 per year from 2000-2016
Number and intensity of tropical cyclones is highly variable each year and decade
Storm Surges Low confidence
Linked to depression that are likely to become more common
Storm surges more intense =
exhibit even lower surface air pressure producing larger sea level rise as storms surge and increase risk of coastal flooding
Economic losses from coastal recession
Housing Business Agriculture Land Infrastructure Property values and inability to sell
How many properties will be lost by 2035
800 properties by Environmental
Agency
Social Losses from coastal recession
Relocation
Break of community
loss of livelihoods
financial problems and job searching
why are economic losses small
erosion happens slowly
property risk looses its value to buyers long before erosion
high density such as towns and villages protected with defences
Consequences in Developed Countries Future - Australia
1M Rise =
£87 Billion worth of commercial property threatened
5 Power stations
116,000 homes causing property damage - £72Billlion
44 water and sewage plants
£67 Billion roast and rail infrastructure
Social costs of a future flood in Australia
break up of communities, loss of livelihoods - fishing, tourism and amenity loss
coral reef effect on future flooding in Australia
coral reef in Great Barrier Reef will due due not being able to grow fast to keep up with sea level =
loss in tourism income
North Sea Flood - UK
storm surges 5m
5 December 2013
Low pressure, high wind and high tidal pressure combined
Social impacts of North Sea Flood
2 deaths UK
loss of livelihood - railway station and southern section of town centre flooded, Suffolk
Economic impacts of North Sea Flood
1400 homes flooded in England, Wales
£1 Billion over course of winter
40,000 homes in Scotland and Northern England
2013 Typhoon Haiyan Phillipines
4-5M storm surge
one of the most powerful tropical storm ever
Economic damages of Typhoon Haiyan
£2Billion in city of Tacloban
90% Structures destroyed or damaged in Tacloban
Social impacts of Typhoon Haiyan
1.9 million homeless
30,000 injured 6300 deaths
6 million displaced
USA, 2012, Hurricane Sandy
$70Billion in damage
$6Million people lost people
350,000 homes in New Jersey damaged/destriyed
what is an environmental refugee
forced to leave their homes due to natural processes, landslides, erosion or rising sa levels
how could environmental refuge be created predicted by the IPCC
flooding
salt water encroachment
coral bleaching (acts as a sea defence
Places at risk from sea level rise by 2100
Tuvalu, Maldives, Seychelles, Barbados
Tuvalu, Maldives, Seychelles, Barbados
Reasons for being at risk and others
high population densities and limited space, relocation not available
small and narrow economies, based on fishing and tourism which is easily disrupted
water supply limited and at risk from salt water incursion as sea level rises and groundwater is overused
80% of people in Seychelles live on the coast
Maldives and Environmental Refugee
400,000 too large for them, can be accommodated elsewhere, Government negicitiating with India, Sri Lanka, Australia to buy land
Environmental Refugees, Hurricane Katrina, USA 2O05
1 million environmental refugee - 7m storm surge flooded New Orleans
most were internally displaced within USA, 30% did not return to New Orleans
Typhoon Haiyan 2013, Environmental Refugee
this and climate change driven storm events since 2008, produced 6.8 million internally displaced refugees
Holderness Case Study
Europes fastest eroding coastline
3 miles been lost since roman times
why is the holderness coast eroding fast
strong prevailing winds creating longshore drift that moved material south along coastline
cliffs made of soft boulder clay which erodes rapidly when saturated
what does the exposed chalk of Flambourgh provide
examples of erosion features such as caves, arches, stacks
Hard Engineering examples of Coastal Management
Hornsea and Withernsea solutions to coastal erosion
What happened at Skipsea
illustrates the human impact of erosion in areas where coastline are not being defended
Spurn Point explained
evidence of Longshore drift
example of a spit
3% material eroded from the coast
Mappleton
site of the most intense erosion
small settlements small population
composed oof unconsolidated boulder clay
2 rock groynes allowing for protection
