Yr12 Coasts: Coastal flooding – Physical & Human Causes & Physical, Socio-Economic Consequences
(Case Study)
Definition: Coastal flooding, which is confined to coastal plains (low-lying areas), deltas and river estuaries, results from
water levels increased substantially above normal high-tide levels. This can be caused by:
Waves and surges generated by the passage of a tropical cyclone (hurricane); such as hurricane Katrina in 2005
Tsunamis – the secondary effect of earthquakes caused by movement at plate boundaries at sea; such as the Tohoku
earthquake off the east coast of Japan on 11th March 2011.
A combination of low pressure, high tide levels and high river discharge; such as the North Sea Storm Surge of 1953.
Globally, the consequences of coastal flooding maybe potentially catastrophic; with 14 out of 17 of the world’s largest cities
located along coasts with between 1 to 10 million people per city. In the UK, 20% of the population live by the coast, with
the most vulnerable areas including some of the most densely populated along the south-east coast and around major
estuaries such as the Thames – compounded by isostatic tilting downwards into rising sea levels.
Case study: Towyn floods, Wales
Where: Towyn is located on the north-west coast of Wales between Colwyn Bay
and Rhyl
When: 26th February 1990
Why:
Specific Physical Causes:
Weather: deep low-pressure system of 951mb created gale force dominant northwesterly winds in the Irish Sea with gusts in excess of 70mph and a storm surge
of up to 10 metre high waves. Combined with high ‘spring’ tides between the 26th
and 27th February made this a 1/500 year event.
Topography: Low-lying; particularly at Morfa Rhuddlan meant that land elevation
was at or only slightly above sea level.
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Yr12 Coasts: Coastal flooding – Physical & Human Causes & Physical, Socio-Economic Consequences
(Case Study)
Specific Human Causes:
Inadequate maintenance of ‘hold the line’ hard management techniques: 140 year old sea wall protecting the Towyn
section of the railway embankment had been eroded and breached in a storm 14 days earlier on 12th February; which
weakened and made it more vulnerable to storm damage.
Failure of 3km embankment protecting Morfa Rhuddlan and the Chester to Holyhead railway line from inundation, which
included an armoured slate revetment on the seaward side and a number of sea walls.
Development: the building of retirement bungalows along the sea front, requiring culverts to drain surface run-off
underground and into the Irish sea.
What were the consequences of coastal flooding in Towyn?
Specific Physical Consequences:
The consequence of the broken embankment meant flooding of 10km2 of land between Towyn and Kimnel Bay, with the
worst affected areas submerged by up to 2 metres.
Impact on farmland with the salt water contamination of the soil
Specific Socio-Economic Consequences:
 Over 5000 people were affected in Towyn; with the cost of restoring flooded homes and businesses at £30 million.
 2800 properties were evacuated, 1880 in Towyn. In Kimnel and pensam 4512 people were affected by flood damage.
 6000 caravans were damaged
 40% of households had no contents insurance and 15% had no buildings insurance – probably affecting the poorest
members of the community disproportionately.
 Clywd County Council estimated £1.4 million spent on immediate work on property and a further £3 million on
structural damage of roads and other infrastructure such as the railway line to make the area fit to live in again.
 Insurance claims were expected to cost over £20 million, with an estimated £10.5 million needed to build new coastal
defences.
 In the first 2 weeks, 3000 people were in temporary accommodation; with still 1000 not able to return home after 3
months.
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Yr12 Coasts: Coastal flooding – Physical & Human Causes & Physical, Socio-Economic Consequences
(Case Study)
Assessment:
The physical causes of coastal flooding at Towyn suggest that these were the most important. Significantly, the deep lowpressure system of 951mb providing the atmospheric conditions for destructive waves with considerable energy, combined
with high spring tides and a storm surge of 10 metre high waves meant that even the most heavily managed coastlines would
find it difficult to protect against inundation; particularly where there is low-lying land such as at Morfa Rhuddlan.
Therefore, the human causes serve mainly to increase the scale of flooding; in this instance to 10km2 of land due partly to
the poorly maintained 140 year old sea wall at Towyn.
It could also be argued, however, that the socio-economic consequences of coastal flooding are more significant compared
to the physical impacts, given the displacement of 5000 people with the cost of restoring the area at £30 million. This was
exacerbated given the fact that this town has a high retirement population with a significant number of bungalows located
towards the sea front. This meant that all the rooms in the house would have been affected by flood damage, resulting in
1000 people still waiting to return to their homes after three months. Likewise, tourism as an economic activity in the town
suffered as 6000 caravans were damaged and needed replacement; as well as £3 million in structural repairs to make the
area accessible and fit to stay in again.
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