Why Is The Risk Of Coastal Flooding Increasing?

The report for the Welsh Government report gives a number of reasons why the risk of coastal flooding is increasing. We are going to look at what it says and then work out what it means.

Quote 1

“Projections for the future of our coastal areas are of increasing risk, as a consequence of climate change and in particular sea level rise.” 

• This is what might happen in the future. This is based on large computer models a bit like a game.

• The future of our coastal areas are of increasing risk is much easier to understand that there is more of a chance (in this case of flooding) to our coastal areas.

• As a consequence of climate change and in particular sea level rise means that this is due to changes to our global climate (which is getting warmer). The most important part of this is the sea level going up.

Quote 2

“Global temperatures have risen 0.85°C from 1880-2012. There has been an associated rise in global sea level which is now increasing at approximately 3.2 mm per year. The IPCC state that it is very likely that the 21^st Century sea level rise rate will exceed the 1971-2000 rate, for all modelled emissions scenarios.“

• The IPCC is a research group set up by the United Nations to look at climate change.

• The IPPC writes regular reports the information comes from the report written in 2014.

• The IPPC say that between 1880 and 2012 temperatures have increased by 0.85°C. 

• This causes sea levels to increase by 3.2mm each year.

• All of the models say that in the future it will be more than 3.2mm each year.

Quote 3

“A central estimate of 0.47m increase is projected by 2081-2100, relative to the 1986-2005 baseline. An increase of 0.5m is estimated to result in 10-fold to 100-fold increase in the frequency of sea level extremes (relative to present day) in northern Europe by the end of the century. This would mean a coastal flooding event that has a return period of 100 years at present will potentially occur on average between every year and every ten years by 2100.”

• The central estimate is what is most likely to occur.

• By the end of this century this estimate is that sea levels will have gone up by 0.47 (nearly half) a metre.

• This means that extreme sea level events that at the moment happen on average only once every 100 years will happen on average once every 1 – 10 years.

Photo by Oosoom used under CC BY

This photo shows the railway at Llanaber near Barmouth which was damaged and nearly washed away in the 2014 storm event, could this happen every year?

Quote 4

“Storminess and precipitation extremes are also important factors that will be exacerbated by climate change and contribute to the increased flood and erosion risk. Already, the Met Office have recorded an increase in days of heavy rain in the UK, such that a rain event with an average return period of 125 days in the 1970's now has a return period of 85 days.”

© NASA

• Storms and precipitation (all water coming from the air to the surface surface) will be made worse by climate change.

• This will make chances of flooding or coastal erosion happening higher.

• The Met Office is the government agency that studies weather and climate and also produces forecasts.

• There have been more days with heavy rain each year.

• Big events that used to happen on average every 125 days in the 1970’s now happen every 85 days.

Quote 5

“In terms of storminess the Met Office suggests that while there have been no significant changes in storm frequency in mid latitudes in the north Atlantic, the intensity of individual storms has increased.”

Photo from Geograph Project by Noel Jenkins used under CC BY

• The Met Office has not found proof that there are more storms each year.

• However it has found that the storms are stronger.

Quote 6

“It is important to recognise that the fundamental physics of global warming provides certainty that continuing (and historical) emissions will lead to further warming of both the atmosphere and consequently the oceans, making further significant sea level rise due to thermal expansion inevitable. Moreover in south and mid-Wales isostatic land subsidence will inevitably exacerbate sea level rise too.”

Photo from NOAA published data by Robert A. Rohde used under CC-NC-SA

• The world is controlled by physics.

• Physics tells us that releasing gas such as CO₂ in the past and now will lead to more warming of the air and oceans.

• Thermal expansion is what happens when things get warmer – they get bigger. As the sea gets warmer it will increase in volume and sea level will rise.

• In South Wales and even Mid-Wales the coast is actually sinking slightly which will make rising sea waters even worse.

We had bad storms in 2013 and 2014 but we did not have a big storm, hit with a big storm surge exactly on a very high tide such as the supertides of spring 2015. If this were to happen we would be in a lot of trouble. The problem is this is getting more likely every year.