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University of Nottingham
Department Civil Engineering
H23A13
Are Rising Sea Levels a Cause for
Concern for the UK?
By
Simon Crowther
4188377
May 2015
A report submitted in part consideration of
module H23A13 for the degree of BEng (Hons) in
Civil Engineering
2. 1
Contents
Abstract 2
Section 1: Background Information into Sea-Levels 3
1.1 Brief History of Sea Level Change due to Ice Age 3
1.2 Why does Sea Level Change? 3
1.3 Types of Sea Level Change 4
1.4 Human Causes of Sea-Level Change 4
1.5 Coastal Landforms 5
Section 2: What has happened/is happening in the UK? 7
2.1 Sea Level Change 7
2.2 Land Movement 12
2.3 Looking to the Future 14
2.4 Storm Frequency 18
Section 3: The Impact 19
3.1 Predicted Level Rise Map 19
3.2 Financial Impact 20
3.3 Social Impacts 22
3.4 Environmental Impacts 23
Section 4: What Options Are There? 25
4.1 Retreat 25
4.2 Defend 25
4.3 Attack 26
4.4 Shoreline Management Plan 26
4.5 Thames Estuary 2100. TE2100 26
4.6 Start Bay, Devon Case Study 27
Section 5:
5.1 Conclusion 31
References 32
Appendix 35
3. 2
Are Rising Sea Levels a Cause for Concern for the UK?
Abstract
Global warming and the subsequent sea level rise is a phenomenon which most people
will be aware of. Flooding appears to be happening more frequently and with an
increased sea level the problem can only be exacerbated.
The aim of the report is to provide an insight and investigation into sea level rise and the
effect on the UK. It helps quantify the issue and establish whether rising sea levels are
really of concern to the UK and what should be done about the issue. Most people know
the sea level is rising, but many do not know by how much, or what the impact could be,
especially so close to home.
The report investigates pre-existing reports, and compares this with data analysis of tide
data. The impact is also investigated, and highlights that it is likely to be more of an
issue, than expected. The project includes reports on management strategies, and
focuses on London, along with Start Bay in Devon; which was visited to allow a primary
investigation of the choices available for Britain’s coastlines. The impact is going to need
careful analysis to allow informed decisions to protect the coastline. Over the next few
years it is expected that further investigation with modelling techniques will improve the
reliability of estimates.
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Section 1: Background Information into Sea Levels
Throughout the history of the Earth, the sea level has constantly changed, and is still
changing. There have been rises and falls. Sea level is the average height of the surface
of the ocean, between high and low tide. It is often referred to as the equipotential
surface, which means the level is affected by the force of gravity. Changes in tides and
waves are averaged to allow calculation of a ‘still water level’ that can be used to identify
if the sea level has changed. Records show sea level is currently on the rise. As the
planet warms, the sea rises.
1.1 Brief History of Sea Level Change due to Ice Age
For the past 2 million years, during the Quaternary period, the Earth’s atmosphere has
fluctuated between cooler periods when ice sheets and glaciers have expanded, and
warmer periods when ice sheets have melted and retreated. Eighteen thousand years
ago the British Isles from the Midlands northwards was covered in an ice sheet, and the
rest of the UK resembled Arctic Tundra. At this time Sea level was more than 130m
lower than present. A vast quantity of water was locked up in ice sheets. (British
Geological Survey, 2014)
1.2 Why Does Sea Level Change?
Sea level changes for many different reasons and over varying time scales. Today sea
levels are rising for two reasons: land-based ice is melting, and ocean waters are
warming and therefore expanding.
There is not a direct effect on sea level when sea-based ice melts (British Geological
Survey, 2014). In the same way that a glass does not overflow when ice melts - the ice
floats because it is less dense than water and it displaces an equal mass of water and is
already part of the ocean system. There is the indirect effect that the albedo (reflecting
power) is reduced. A reduced albedo means that as Arctic ice melts, polar regions will
absorb more energy and therefore warming leads to further warming. A positive
feedback cycle is set up. There is also concern about the Arctic melt releasing ancient
methane, which is the second most prevalent greenhouse gas. This ancient gas could
impact climate change, and feed further warming, but how threatening and serious this
is, is controversial. (Black, 2012)
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1.3 Types of Sea Level Change
The types of sea level change: isostatic and eustatic, are well documented in a variety of
sources. The British Geological Survey explains that an isostatic change is on a local
scale as land levels change after a load is applied or removed. A eustatic change is due
to a change in the volume of the water in the oceans due to ice sheets either forming or
melting. (British Geological Survey, 2014)
Examples of large changes in sea level due to the last Ice Age are widely reported in
textbooks and examples can be seen across the UK to prove this (Milliman and Haq,
1996). If the two main ice caps melted; Greenland and Antarctica, then it is calculated
that the oceans would rise by sixty-six metres above the current level (British Geological
Survey, 2014). Clearly these are extreme values and in the foreseeable future a sixty-six
metre rise is likely to be unrealistic. It is therefore important to study the topic in more
detail to provide information for future Emergency Planners and Councils. The eustatic
change in sea level is not a true reflection of sea level rise unless it is known how much
the land is moving to provide a relative rise. Melting of sea ice in the Arctic Ocean and
the ice shelves bordering Antarctica is not expected to increase the volume of water in
the oceans, because the floating ice is already displacing a weight of water equal to its
own.
Fluctuations in the volume of water held in the ocean can also be caused by changes in
sea temperatures. Seawater expands thermally and for every 1 degree Celsius the
temperature rises, the sea expansion raises the water a further 0.8m. Changes in the
salinity of sea water can also alter the sea level. If more fresh water was to flow into the
ocean and lower the salinity, the sea level would also rise. (Dove, 2009).
Plate movements and tectonic activity can also increase or decrease the ocean basin
capacity and therefore a decrease in capacity could increase the sea level. This could
occur if the sea floor was pushed up across a plate boundary. Over a very long period of
time the deposition of sediment in the ocean from weathering and erosion of the land
will lead to an increase in world sea levels. (Dove, 2009)
1.4 Human Causes of Sea Level Change
Human actions can also cause sea level change on a global and local scale. Locally the
abstraction of groundwater from coastal aquifers can cause the land to subside and
therefore, there is a relative rise in sea level. A similar phenomenon has occurred in Los
Angeles where oil has been extracted and the overlying sediments have subsided
allowing marine transgression to occur.
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Alongside this there is the overarching impact of global warming, and whether or not
human activities are playing a part in this. A recent study published in Geophysical
Research Letters, studied climate models to see if human activities such as burning fossil
fuels were responsible for sea level rise. The results found that human activities are
responsible for 87% of the sea level rise which has occurred since 1970. This rise is
known as a thermosteric rise. It is due to the ocean swelling in volume, and the increase
in ocean height is caused by the increasing volume of the ocean that occurs when
seawater warms up and expands. (Marcos and Amores, 2014)
The new study, showing that the warming of the top layer is mainly due to human
activity, means that all the consequences – sea level rise, higher storm surges, flooding
are because of human activity. This study is very new, but in the future years, it will be
seen if it is valid and reliable. If it is correct, the consequences of human actions will
need to be taken very seriously.
1.5 Coastal Landforms
Changes in sea level have produced a variety of different landforms across the UK, and
can be broadly categorised into submerged and emerged coastlines, although in reality
many coastal areas have experienced both rises and falls in relative sea level at different
points in history.
An example of a submerged coastline, which is common in Britain, is a ria. A ria is an
inlet of rugged relief where the lower reaches of a river valley have been drowned by a
rise in sea level. The shape is controlled by the form of its pre-existing river valley. Rias
are common in Devon and Cornwall and a good example is Kingsbridge Ria. Other
submerged landforms include: drowned estuaries, dalmation coastlines, submerged
forests, buried river channels and offshore notches.
Emerged coastline examples can be seen around the UK. To investigate, a visit to
Langerstone Point in Devon was organised. Langerstone point is an example of an
emerged or raised beach. There are beaches which stand well above the present sea
level. These are shown in figure 1.5.1 below. Raised beaches are created by an uplift of
the land, or a fall in sea level. The raised beaches are about 5-8m above the current sea
level. They were cut by high sea levels during interglacial periods in the Pleistocene.
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Figure 1.5.1 Langerstone Point (Personally Taken Photograph, 2015)
Other examples of emerged coastlines include widening areas of salt marshes and
mangroves.
These features help to highlight the fact that sea levels have changed dramatically in the
past, and without mankind causing global warming. It therefore makes Marcos and
Amores’ study more fascinating, because it states 87% of sea level rise is due to
humans, and it is open to question from sceptics.
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Section 2: What has happened/is happening in the UK?
2.1 Sea level Change
To determine how sea level has fluctuated previously, the five longest sea level records
in the UK were analysed; namely those are in Aberdeen, North Shields, Liverpool,
Sheerness and Newlyn. The data used was the annual mean sea levels at each location.
These five stations are spread across the UK and as such give a good coverage of what
has happened in the past, allowing future predictions. The map below shows the five
locations of the tide data stations:
Figure 2.1.1 Tide Station Map
Data sources
The UK sea level data is collected and supplied the by Permanent Service for Mean Sea
Level (PSMSL) dataset. (Permanent Service for Mean Sea Level, 2014)
The Permanent Service for Mean Sea Level has been responsible for sea level data,
recorded from the global network of tide gauges since 1933. The database of the
Aberdeen
North Shields
Liverpool
Sheerness
Newlyn
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contains monthly and annual mean values of sea level from nearly 2,000 tide gauge
stations around the world.
To give an insight into sea level change, the tide data was analysed by plotting values of
average mean sea level per year, against the year. By using a linear regression line an
average rise per year was calculated for each site.
Data Attached in Appendix
Aberdeen:
Figure 2.1.2 Aberdeen Sea Level Graph
The linear regression line has a gradient of 0.9593. We can therefore conclude that there
is a mean rise of approximately 0.9593mm/yr between 1932 and 2013.
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North Shields:
Figure 2.1.3 North Shields Sea Level Graph
North Shields appears to have had a mean sea level rise of 1.902mm/yr between 1833
and 2006.
Liverpool:
Figure 2.1.4 Liverpool Sea Level Graph
Liverpool has had a mean sea level rise of 1.498mm/yr between 1858 and 2011. In the
last decade the level appears to have risen faster. This could be due to local land
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movements, or error in the data, as half the years between 2000-2010 did not have any
data available.
Sheerness:
Figure 2.1.5 Sheerness Sea Level Graph
Sheerness has large gaps in the data, but despite this there still appears to be strong
correlation and the linear regression line shows a mean rise of 1.658mm/yr between
1833 and 2006.
Newlyn:
Figure 2.1.6 Newlyn Sea Level Graph
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Newlyn shows an average mean rise of 1.7789mm/yr.
The Tidal Observatory was established in Newlyn to determine the mean sea level that is
the starting point for levelling in the UK. It Is located on the tip of the Cornish Peninsula.
Newlyn has two separate data sets, which used different measurement techniques. For
data continuity, only the more recent data set was used.
Compiled Results:
Location Annual mean sea level rise/mm
Aberdeen 0.9593
North Shields 1.902
Liverpool 1.498
Sheerness 1.658
Newlyn 1.7789
Table 2.1.1 Compiled Results
The results give an average rise of 1.56mm/year for the UK, however the results are
from varying lengths of time for each data set, and therefore they could be interpreted
differently for a set period of time for all stations.
The UK Environmental Change Network has used tide-data to estimate global mean sea
level change over the past century, and calculated it is between 1-2mm per year, but
the results vary, depending on which combination of gauges are used (Sparks and
Cannell, 2014). Past efforts to determine the rise, concluded that sea levels rose by
around 1.6-1.9mm per year. These figures were included in the most recent
Intergovernmental Panel on Climate Change (IPCC) report. The data appears to be
reliable and accurate when compared with existing literature. The obtained results could
have been different if other stations were used, and as such there is variability in
existing reports.
The tide data graphs show that there is some variation in the levels per decade. A
particularly good example of this in Liverpool, where the level has risen dramatically in
the last decade. With just a decade’s worth of information it is hard to predict if this will
continue to be the trend or just a variability of sea level on decadal timescales. A lack of
ability to account for decadal variability results in more uncertainty in the calculation of
long-term sea level trends. Mean annual sea level even fluctuates from year to year and
much of this variation is related to the position of the Gulf Stream. Studies have shown
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that high sea levels occur when the Gulf Stream follows a northerly path. (Sparks and
Cannell, 2014)
2.2 Land Movement
Dr Richard Bingley, from the Institute of Engineering Surveying and Space Geodesy
IESSG, explains: "The measurements from tide gauges are not a true reflection of
changes in sea levels unless you know how much the land is moving." (Haran, 2003)
Studies have therefore been conducted into the changing land-level in the UK, as without
this the relative sea level change cannot be calculated, and the impact not known.
Scotland has already rebounded by 100m since the ice sheets retreated, and is still
moving (Dove, 2009). Without measurement to a more precise scale this does not
provide insightful information into what is currently happening and what is expected.
GPS (Global Positioning System) was once just used by the military, but more recently it
has been used by scientists and engineers to track the millimetre movements of the
Earth. It has been used in the UK to accurately and precisely track the land movements
of the UK to help provide a sea level change relative to the land. Defra have been
funding research using GPS into the scale and impact of rising sea levels on the UK since
1997 in the hope of understanding long term changes, future sea level rise and to
improve estimates of climate change on sea level. The results were published in a
technical report in 2007. The technical report quantifies the proven trend of sea level
rise, and the South of England sinking as Scotland rises up. The report estimates that
the South of England is subsiding by up to 1.2mm/yr and Scotland rising up by 1-
2mm/yr due to Great-Britain’s tilt. When decoupled from the land movement it predicts
sea level had risen by 0.9-1.2mm/yr over the last century (Department for Environment,
Food and Rural Affairs, 2007). Despite this report being based on ten years of research,
it still has uncertainties in the results with potential bias, and includes recommendations
for improvement. The Defra study shows how effective GPS can be for surveying.
Variations can occur due to localised processes such as sediment compaction and
tectonics and past/present variations in land ice. The research done for Defra in 2007,
using GPS to study the UK’s land movement, is therefore of paramount importance, as
without this information there isn’t a true reflection of the scale, situation or impact
Global positioning systems are evolving as we improve the accuracy of them, and it is
likely it will be used to greater extents to measure wider global issues, including aiding
weather forecasts and storm predictions. This would no doubt also help councils,
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residents, and agencies prepare for extreme weather and storm surges. GPS could help
lessen the impact by providing a warning.
The reason for the variability in the results for different areas can depend on local land
movement, caused by things such as groundwater extraction. It could also be due to
variability in air pressure and geodetic movement.
Defra funded a study (UKCPO9) which features very comprehensive climate projections.
The study investigated land movement and the results are shown below in figure 2.2.1:
Figure 2.2.1 Land Movement (Jenkins et al., 2009)
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2.3 Looking to the Future
There are numerous investigations into sea level predictions, and much of the
information is compiled in the IPCC reports by the United Nations, and the UKCP09 by
the Met Office and Defra for the UK.
The tide data used previously in this report was analysed with a linear regression line, to
give an annual average mean rise, but it can be seen in some circumstances that the
level is rising more rapidly more recently, and the linear line may not be suitable in later
years such as at Liverpool.
Using more recent tide data, (1950-2010) it was possible to average the data for the five
respective sites, and then plot the data on a graph, and use a quadratic regression line,
to allow for the expected acceleration in rise in the future.
Figure 2.3.1 Averaged Sea Levels (1950-2010)
Using the trend line, the year 2000 UK average sea level is 7069mm, and by 2100 it
would become 7390.3mm. This would be a rise of 32.13cm. It is obviously a very crude
prediction, which does not take account for emissions or the rate of global warming and
has a relatively small sample set, but it compares favourably with the UKCP09.
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UK Climate Projections 2009 (UKCP09) is a climate analysis tool, funded by Defra, which
features very comprehensive predictions. It gives a detailed guide on how the UK’s
climate could change in the 21st century, as it responds to rising levels of greenhouse
gases in the atmosphere. It is designed to allow informed risk based decisions on how to
avoid the dangers of what is to come.
Chapter 3 of the UKCP09 report looks at projections for sea level rise, both absolute and
relative. The absolute sea level rise is averaged around the British Isles, and comes from
projections made by international climate models. The land movement is also derived
from constrained land models, allowing the calculation of relative sea level change
around the UK. (Jenkins et al., 2009)
The following table shows the UKCP09 estimates for rise over a 100 year period,
dependent on emissions:
Figure 2.3.1 UKCPO9 Global mean sea level rise estimates (Jenkins et al., 2009)
The tide data extrapolation is therefore within the ranges the UKCP09 predict. The
UKCP09 analysis gives projections of UK coastal absolute sea level rise for 2095, ranging
from 12–76 cm. When coupled with the land movement the relative rise is higher than
the absolute in Southern Parts of the UK. Where the land is subsiding, the report
estimates for a medium emissions 5th
-95th
percentile there would be a rise between 21-
68cm for London, between 1990–2095. In Edinburgh the report predicts that there is an
expected 7–54 cm relative rise for Edinburgh (5th to 95th percentile for the medium
emissions scenario). It is therefore very important to know how much the land is
moving, for emergency planning.
Absolute sea level may also not rise uniformly. Climate models and satellite data show
that in some regions the rate can be several times the global mean rise, which can be
due to non-uniform changes in temperature and salinity and related to changes in the
ocean circulation. (Alexander and Allan, 2013)
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Whilst the UKCP09 report was very rudimentary and based on considerable research, it
used predictions from the Intergovernmental Panel on Climate Change (IPCC) 4th
report
which has now been superseded by the 5th
report. Since the 4th
report was released, new
satellite data has found that the rise in sea levels is already accelerating beyond
predictions, and that sea levels rose globally by 3.2mm/yr for the past 30 years, and not
2mm/yr as previously predicted. If this trend was to continue it is estimated the rise by
2100 could be 120cm. In 2012, Stefan Rahmsdorf, of the Potsdam Institute for Climate
Impact Research stated ‘the IPCC is far from alarmist, but in fact has under-estimated
the problem of climate change and ambitious targets to cut carbon are needed.’ The
topic is therefore in hot discussion as small islands could be wiped out. (Gray, 2012)
The Fifth Assessment Report from IPCC is currently the most up-to-date, comprehensive
and relevant investigation and report on the changing climate. The IPCC 5th
report‘s
predictions are far higher than the 4th, both at the low and the high end. A direct
comparison is made possible by table 13.6 of the report, which allows a comparison of
old and new projections for the same emissions scenario over the time interval 1990-
2100:
IPCC 4th
Report average predicted rise: 37 cm
IPCC 5th
Report average predicted rise: 60 cm.
The new estimate is almost 60% higher than the old 4th
report’s standard estimate. It is
reported that the estimates of the 4th report were already known to be too low at the
time the report was published.
For high emissions the IPCC 5th
report now predicts a global rise of 52-98cm by the year
2100, but even with aggressive reductions in emissions there is still a predicted rise of
28-61cm. This is a highly optimistic scenario where there are drastic reductions in
emissions starting a few years from now and reaching zero emissions by 2070 and then
carbon dioxide being actively removed from the atmosphere. Even with this a rise of
over half a metre may still be seen which could seriously impact many coastal areas with
coastal erosion and flooding. There is a large inertia in the sea level response, and it is
very hard to make it stop once it has started again, and there could be a larger
difference seen in the 22nd
century. (Rahmstorf, 2013)
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The IPCC 5th
report’s 4 scenarios:
Scenario Sea level Rise/cm Range
RCP2.6 44 28-61
RCP4.5 53 36-71
RCP6.0 55 38-73
RCP8.5 74 52-98
Table 2.3.1 Aberdeen Sea Level Graoh
Representative concentration pathways (RCPs) are different greenhouse gas
concentration scenarios. The pathways are used for climate modelling and research.
There are four possible situations all of which are considered conceivable depending on
how many greenhouse gases are emitted in the years to come.
The following figure shows the different scenarios:
Figure 2.3.2 RCP emissions scenarios (Symon,2015)
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High emissions could give a mean rise of seventy four centimetres which is far higher
than the rise in the twentieth century, and therefore it is paramount to know what can
be done to protect the coastlines and the cities at risk.
Using the most recent data, even with stringent carbon dioxide emission reductions, sea
level could still exceed 60cm by the end of the century and it seems too late to
implement measures that could stop a half metre rise in sea level by 2100. The
opportunity for early mitigation to stop this has passed, but it is key to avoiding higher
sea level rise in the future, given the slow response of sea level. (Schaffer et al., 2012)
Emergency planners require an upper limit for planning purposes, as coastal defences
need to be able to defend against the worst scenarios. Engineers would like to be sure
that their defences will not be breached. The range up to 98 cm is the IPCC’s likely
range, i.e. the risk of exceeding 98 cm is considered to be 17%. It is thus clear that a
metre is not actually the upper limit, and the IPCC does not give an upper limit. In
contrast, the UKCP09 does give a scenario which looks at the highest levels actually
plausible. As this does not rely on the data from IPCC 4th
report, it is still likely to be
reasonably reliable. This scenario is called High-plus-plus (H++) and represents a wider
range of relative mean sea level rise and storm surge changes. The top of the H++
scenario range is derived from indirect observations of sea level rise in the last
interglacial period. The upper part of the range of sea level increase is thought to be
unlikely, but is provided for contingency planning. This estimate gives a sea level rise of
93-1.9cm by 2100. The low probability high scenario was developed in partnership
between the Met Office and the Environment Agency. This range is beyond the Met
Office projections, and is unlikely to occur by 2100, but it cannot be completely ruled
out.
2.4 Storm Frequency:
According to the IPCC, rainfall intensity has increased, and higher temperatures are
responsible for this. The heat intensifies and and accelerates the hydrological cycle.
Models suggest the precipitation will occur less often, but there will be an increase in the
number of extreme events. This combined with rising sea levels will inevitably increase
coastal flooding. With sea levels already being higher, a storm surge could be much
worse and have catastrophic effects.
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Section 3: The Impact
The area most under threat in the UK is the South and East of the country, where the
land is flat and at very low altitudes. Unfortunately these areas are densely populated.
Parts of the East Coast are also made up of boulder clay, which is very vulnerable
because it is easily eroded. The most exposed locations, including low lying areas, and
estuaries will be susceptible. The Norfolk Broads are a low lying area, and are also a
large tourist destination and farming area, where sea level rise would destroy the area
and habitats. Valuable agricultural land will be lost through flooding and the
contamination of ground-water with salt.
Sea level rise will be felt along the whole of the UK coast. There will be different types of
impacts ranging from erosion to flooding. The rise will have different levels of impact in
different areas, from estuaries to ports, and rural and urban areas. The impacts will be
felt most by communities that rely on the immediate coastal area for their residence,
communications and economic and social activity. Hallsands in Devon is a prime example
of a village affected by coastal erosion, and therefore a site visit was conducted, which is
discussed later in this report.
3.1 Predicted Level Rise Map
Using the UKCP09 H++ upper bound, for a reasonable upper limit for risk planning, the
areas at risk can be seen.
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Figure 3.1.1 A 2m rise in sea levels (Environment Agency, 2014)
The maps show that low lying areas are flooded as the sea moves inland. This includes
the flooding of areas such as The Wash, and parts of London. This would inevitably have
environmental, social and economic impacts.
3.2 Financial Impact
The Environment Agency map shows the number of properties that are at risk of flooding
from river or sea if the sea level rose by 2m. The total is 484,753.
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According to Chris Smith, the EA Chairman, the average cost of flooding to a property is
between £20,000-£30,000 (Jha, 2010). A quick calculation estimates there is a potential
damage of around £12 billion. This is just in destruction to properties, and does not
account for other affects to the economy.
The cost of damage could also be higher. The value used is for a one off flooding event,
but if the sea level is at a height where the property is consistently under water, or even
lost to sea, the cost would be even greater.
Coastal erosion will be increased, and we will see more properties disappear into the
ocean. The Holderness coast is particularly at risk due to the weak clay, and stormy
nature of the North Sea. The clay is vulnerable to slumping and erosion. The coastline
today is around 4km inland from where it was in Roman times, and there are villages
which have already been lost. This will only increase as sea levels rise further, and as
such the financial costs will be high, as homes and villages have to be relocated. Defra
has dedicated a £6,000 coastal erosion grant for homeowners who are at risk of losing
their property to coastal erosion. The grant is expected to contribute to costs of
demolishing the property and some basic moving costs. As sea levels rise this is likely to
be utilised more heavily.
The map below shows current and lost towns:
Figure 3.2.1 Lost Towns of Humberside (coolgeography.co.uk, 2015)
It can be predicted that the present towns could become lost towns with sea level rise.
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Although many parts of the UK would be affected, London is the largest cluster of
economic activity, and as such the impacts have been investigated most thoroughly, and
are reported in the TE2100 Thames management plan. London contributes £250billion in
goods and services annually, and although currently protected, a rising sea level would
make it vulnerable, and the costs of a major flood would be severe. The Environment
Agency expects that by 2050 the Thames Barrier will have to close on every tide, and be
overtopped by some. When it was constructed in 1984, it was expected to be closed
once every few years. The costs would be substantial and would be particularly
significant to the financial sector. Economic losses would affect the whole nation. TE2100
estimates that if just one working day was lost, it would cost the civil service £10 million
alone in lost staff time. (Environment Agency, 2011)
London has some of Britain’s most visited tourist sites, and a sea level rise could impact
on the tourism industry, which is worth around £15billion per annum. If London was to
flood, the underground could be disabled, which would have significant impacts on the
economy because it is central to London life. On one day (7th
August 2002), flooding
caused costs of £750,000 just in passenger delays and does not include the knock-on
impact. There would be the financial impact caused by the disabling of ports due to
flooding. The Port of London Authority makes a contribution to the UK economy of
£3.4bn each year, and if it was lost to the sea, there would again be a detrimental
financial impact. (Environment Agency, 2011)
A rising sea level would also mean that storm surges could be much worse. The 1953
storm surge killed 307 people in the UK, and with a growing population and increased
sea level, this number is only likely to increase. Although a life is priceless, in insurance
terms a life is often considered to be worth £1million, so again the financial impact would
be high. (Hickey, 2001)
3.3 Social Impacts
The potential impacts of climate change on social aspects of life has been poorly
researched, although assumptions can easily be made for the effect of sea level rise on
the UK coast. Existing literature suggests that global warming will have negative impacts
on people’s health, especially events like flooding. Flooding poses a risk to life and
health, and rising sea levels will only make the scenario worse. Coastal areas often have
a high number of elderly people who have retired by the coast, and are more vulnerable.
The impacts may therefore be more severe. Rising sea level will impact on the
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livelihoods of those who rely on the sea for employment- e.g fishing and tourism. Local
farmers may lose land, and land may become infertile due to salination. Extreme events
are also likely to impact key infrastructure, and this could prove very serious if health or
emergency services were affected.
Around 1.25 million people live in the Thames tidal floodplain. This floodplain will only
become larger, and could be submerged with the sea level rise. These people are
already vulnerable if the current defences failed, and with the expected rise, the TE2100
report even acknowledges that the Thames Barrier will not be able to protect London up
to 2100. It was initially expected to protect London up to 2030, and this clearly
highlights the impact of the rising sea level. Four hundred schools are already at risk, so
with further rises in sea level the basic infrastructure of family life could be seriously
damaged and disrupted.
Facilities that could be used to help recover from a major flood would also be put at risk
by the 1.9m sea level rise. Fire stations, clinics, shops and refuge centres could all be
susceptible to coastal flooding and hinder a recovery process. There are 16 hopsitals in
London which have all been catergorised as at risk of flooding. This highlights that not
only would people’s homes be affected, but also the resources for response and recovery
would be impacted. (Zsamboky et al., 2011)
3.4 Environmental Impacts
Sea level rise can have devastating effects on coastal habitats. As marine transgression
occurs, and the seawater reaches further inland, there can be destructive erosion or
flooding of wetlands, contamination of aquifers and agricultural soils. This could mean a
lost habitat for fish, birds and plants. If sea levels continue to rise, there could be a
devastating impact on coastal habitats. The further the water migrates inland, the worse
the damage will be. It can flood wetland, contaminate aquifers and soils, and damage
habitats of fish, birds and animals due to the contamination of fresh water supplies and
soils due to salinization. For example, Slapton Sands, Devon, has a freshwater Ley
behind a shingle ridge. This shingle ridge has previously been breached, damaging the
A397 road. Today the ridge and Ley are designated as a Site of Special Scientific Interest
and a National Nature Reserve in recognition of their biological and geological
importance. With sea level rise, it is likely that beach rollover and marine transgression
will occur, and the sea not just damage the road, but also flood the freshwater ley. This
would obviously have detrimental effects on the nature reserve. It is a similar scenario in
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other locations around the country. In London there are many ecological sites at risk of
flooding with sea level rise.
Conversely, there could be some benefits to the environment; increase of highly
productive wetlands such as salt marshes, and fish friendly shallow seas.
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Section 4: What Options Are There?
It is predicted that there will be some locations where government funding is not
available to build or maintain coastal defences due to the cost of maintaining or building
them.
There are numerous ways to manage the impact of sea level rise. It should be possible
to secure a future for the coastal cities. These cities contribute to the economy, and
house millions of residents, and as such the UK needs a proactive approach to managing
sea level rise. If action is not taken, then consequences would be very severe.
There are 3 main choices that can be made, retreat, defend or attack.
4.1 Retreat
Retreating is different from abandonment and doing nothing. It is a long-term planned
process generally called managed retreat. It is a method of allowing the sea to breach
coastal defences and flood areas previously protected. The aim is to move critical
infrastructure and housing to safer ground, allowing the water into the city to alleviate
flood risk. The line of defence is relocated further inland. Managed retreat is supposed to
reduce the cost of defence and increase sustainability. New habitats are also created in
the inter-tidal zone. New investment must be made to relocate houses and
infrastructure, but money is saved by a reduced investment in flood defences. This has
been done at pilot sites around the UK, but all of these were free from human habitation.
With rising sea levels to the extent predicted we have to question whether it would be
possible to relocate populated areas with infrastructure critical to the nation. (Robinson,
2013)
4.2 Defend
Defending the coastline would be to try and ensure that the sea water does not enter the
current built environment. The defences would need to be built high enough and strong
enough to defend against rising sea levels. In the past, defences have been re-active;
each time there has been coastal flooding, the defences have been raised or
strengthened. As it is proven sea levels are rising, the method needs to be more
proactive to defend the coast. It is a very expensive method and would not be
economically or commercially viable everywhere in the UK. Hard engineering can be
27. 26
unsustainable and damage coastal habitats, but they can provide good protection from
coastal erosion and flooding. By defending the coast, the existing built infrastructure is
protected from floods, without the need to be relocated. It would be incredibly expensive
to ‘move’ London and as such there is a plan ‘TE2100’ in place to defend London up to
2100. (Robinson, 2013)
4.3 Attack
To attack is to advance and step seaward of the existing coastline. This would reduce the
need for urban sprawl into the countryside, and the development could help fund further
flood defences. Land reclamation has been practised all around the globe. The
Netherlands are renowned for their land reclamation of the Polders, creating more
developable space. There are several ways of building out into the water, with pontoons,
stilts and piers all available to enable an expansion seawards. It could be a method of
coping with the increasing population. It is questionable how it is possible to develop
infront of the existing defences. (Robinson, 2013).
4.4 Shoreline Management Plan
A Shoreline Management Plan (SMP) is an assessment of coastal processes, and the risks
they induce. The plans are for schemes to reduce the risks to people and the
environment. Each coastline is broken into manageable sections for an SMP and the plan
takes account of existing defences and likely natural forces. The SMP develops policies
outlining how the shoreline should be managed in the future, with rising sea levels and
increased erosion.
4.5 Thames Estuary 2100. TE2100
The Environment Agency has created the Thames Estuary 2100 project (TE2100) in
which a plan was developed for managing and mitigating flood risk on the Thames
estuary over the next 100 years. It uses the H++ scenario previously discussed, to look
at how the Thames estuary can be protected up until 2100. London is the capital and
most populated city of England, therefore management is paramount for its future.
Significant investment is required to address climate change, development on floodplains
and aging flood defences. TE2100 was formed after much research, modelling, risk-
assessment, appraisals and infrastructure inspections for managing flood risk through
the 21st century.
28. 27
CH2M HILL helped develop TE2100, leading a range of projects including modelling,
engineering, risk management, options development, appraisal and infrastructure
inspections.
4.6 Start Bay Case Study
Start Bay in South Devon already experiences coastal erosion and with the threat of
rising sea levels becoming more prevalent, a management strategy is needed. Start Bay
is ideal for use as a case study because managed retreat, defence and abandonment
have all been practised in one location, so a site visit was undertaken in April 2015.
Figure 4.1.1 Start Bay (Personally Taken Photograph, 2015)
Coastal management is needed to plan and defend for the inevitable continuing erosion
of the coastal area around Devon.
In 1897 Sir John Jackson dredged 650,000 tonnes of gravel from off shore at Hallsands.
This was used for the Plymouth Docks. This removal of sediment caused beach erosion
to occur and the village was destroyed. A sea wall was constructed, but this was soon
29. 28
demolished by the sea, and after weighing up the cost of defence against the number of
houses or roads, it was decided to do nothing. There are now only a few houses left at
Hallsands. (Abandonedcommunities.co.uk, 2015)
Further round the coast, at Beesands, a wave return sea wall and rock revetment has
been installed. This is to defend and ‘hold-the line’. The sea wall cost three million
pounds and does deflect the waves and prevents further erosion. Despite this, the
houses are still at risk from flooding, and the houses also had flood gates fitted to the
doors. It did not score well on a Bipolar Evaluation because of the high levels of
disturbance and poor access to the beach. The cost benefit was only about two pounds
saved for every one pound spent, so was not a very cost effective method of defending
the 30 houses.
Figure 4.1.2 Beesand’s Defences (Personally Taken Photograph, 2015)
Slightly further North, the village Sunnydale has defences in place to defend itself from
the risk posed by erosion. The residents paid £30,000 for gabions to be installed and
these have already lasted 22 years. They have a very high cost benefit ratio of nearly 50
pounds saved to every 1 pound spent. The gabions have a short life span which is the
30. 29
only issue, however they seem to be lasting well, and have prevented the erosion and
marine transgression for a low cost. They seem ideal for the area, and do not currently
need upgrading. As sea levels continue to rise, they may not offer enough defence in the
future.
At Torcross there is a solid wave return sea wall which cost 2 million pounds to install,
which initially appears expensive. The wall does protect 49 houses and a thriving
community so it was decided to defend the houses whatever the cost. Despite this for
every pound spent, 8 pounds were actually saved. Behind Torcross there are relic cliffs
from where the sea level used to be before the ice age. If the sea level was to rise again
to this level, the wall would be over topped and the houses flooded. As the sea level is
expected to rise by up to two metres by 2100, it may have been better to manage the
retreat, or do nothing and compensate the villagers, letting the sea regain its land. The
sea wall also prevents good access onto the beach and the drop could prove dangerous
to children.
The A397 is a major road in Devon, running through Start Bay and along Slapton Sands.
The road was previously washed away in a storm and was moved inland as part of a
managed retreat scheme. The problem with this managed retreat scheme is that,
although the land may not be overly valuable, there is interruption with communications
and it is expensive to keep moving the road inland. It is to be expected that in the near
future the road will be breached by the sea and the Ley will then flood all the lower part
of Torcross.
Figure 4.3.3 A397 Managed Retreat (Slapton FSC, 2015)
31. 30
Defences can be essential for thriving areas such as London, yet we have to question
whether spending millions on a sea wall in rural Devon is economically viable. Spending
more money on defences than the value of the houses at Beesands Village Green is a
prime example. The coast should be defended in some areas, but the strategies have to
be reviewed and reassessed regularly to establish which are necessary. This should all
be outlined by a Shoreline Management plan.
32. 31
Section 5: Conclusion
Sea level rise is likely to be a cause for concern to the UK. The extent of the impact will
depend on which model is correct, but it is likely there will be at least a fifty centimetre
rise, on top of the fact the South of England is sinking. The expected rise by 2100 could
be nearly 2m. This could have devastating effects on the UK. Due to the inertia of sea
level rise, lowering CO2 emissions is unlikely to help much in the 21st
century. The rise
could have detrimental social, environmental and economic impacts, and effective
management is necessary. The management required is different for each location, and
there is not a simple solution for all areas. The coastlines will require careful individual
management to minimise the impact. It is likely that with technological advances in
modelling and GPS that the accuracy of predictions will continue to improve over the
coming years.
WORDS 7396
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