Tom Evans
CORF204 Duncan Jones talk on over the graph results
The storm Brigid in 2014 from January 30th to the 4th of February generated a period of
relatively very high waves that hit the coastline of Cornwall, England. They had a range of
wave speeds shown in table 1, ranging from 27.63 miles per hour to 38.38 miles per hour.
The storm started due to a series of depressions and swells along with very high tides
(Cornwall council, 2015). The storm travelled across the Atlantic effecting a number of
countries throughout its duration, England was provided with some natural shelter from the
storm due to the positioning of Ireland, France and Spain (Shown in the weather maps).
Each line in the table represents a 12 hour period except for maps 6 - 7 and 7 - 8 what show
a 24 hour period due to the lack of data for the 2nd of February 2014 at 12.00.
Table 1 (Evans. 2015)
The significant wave heights through storm Brigid ranged from 10 to 15 meters in height, this
is significantly larger than waves Cornwall normally gets. Graph 1 shows the comparison in
the significant wave height at every 12 hour period during the storm in blue (numbers 1- 9)
while the Orange bar (number 10) is the average wave height in 2005 for Cornwall and the
yellow bar (number 11) is the highest recorded wave for Cornwall in 2005 (BBC. 2005).
Graph 1 (Evans. 2015) showing wave heights in Cornwall
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
Storm Brigid resulted in some very high wave lengths, up to 624.84 as shown in Table 1, as
a result of these factors it caused there to be high levels of wave energy and group wave
energy. The storm starts of at a higher level than is normal, on top of this it increases in
energy, wavelength, period and wave height quickly. This sharp increase is short lived
however as the storm seams to weaken slightly and enter a small yoyo stage where it drops
then jumps till the 4th of February represented in graph 2, what shows the spikes in wave
energy throughout storm Brigid. As the weather maps show there is a general movement of
the wind generating area from west to east. The fetch is high for most of the charts with only
two < 1000. A fetch of over 1000 will be a key contributing factor in to the storms power, a
fetch under 1000 could be a restrictive factor. Another restrictive factor for some of the
weather charts was time, the period being 12 hours for most charts led to a slight limitation
for some results.
Graph 2 shows the wave energy levels of storm Brigid (3 – 11) and the wave energy levels
for the data of average waves in 2005 (1) and highest recorded wave in 2005 (2), the
average wave in 2005 had an energy of 5.03 Kpa while the highest wave in 2005 had an
energy of 101.81 Kpa. The lowest wave energy during storm Brigid was 125.69 Kpa, this
was also the most common wave energy level during the storm and is 61.91 x the amount of
energy the average wave in 2005 caused. The highest however was 282.81 Kpa, this is 2.7
x the amount of energy produced by the highest wave recorded in 2005. When compared to
graph 3 the wave energy that UK Sea defences have been based on, is to deal with wave
energy at a max of 180.99 Kpa, there is only 2 recordings during Brigid that are over this
level of wave energy, however most sea defences in Cornwall are not built to deal with the
maximum amount.
Graph 2 (Evans. 2015)
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
Storm Brigid had some strong implications for the Cornish coastline, the UK based their
coastal defences on Graph 3 what shows that the max wave period and height (12m and
16s) the UK thought these would be the maximum period and height of waves that the nation
would be exposed to. It has now been recorded that these are not the maximum height and
periods of waves the UK can be exposed to. Seeing as storm Brigid resulted in waves equal
to and higher than 12 m and wave periods higher than 16 s. This means that many of
Cornwall’s sea defences would be unable to prevent flooding and damage from the storm.
Due to my results of wave height and period being obtained through use of this graph I had
to use an educated guess as to what results would be for wind speeds over 35 m/s.
Graph 3 (Jones. 2015)
Cornwallguide (2015) state that wave speed around Cornwall is about 20 m/s, the mean of
the wind speed during Brigid is 31.55, this is 11.55 m/s faster than the average wind speed
in Cornwall. Graph 4 shows the wind speeds recorded during Brigid (2 – 10) and the
average of these wind speeds (11) when compared to the average for Cornwall (1).
Graph 4 (Evans. 2015)
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
The wind speeds recorded relate directly to wave height and period, the period of the waves
during Brigid range from 14s – 20s, these are high recordings for wave period, as stated
through graph 3 most UK defences were built on the basis that wave periods above 16
would not affect the UK, this has been disproven with evidence of waves like those caused
during Brigid. Based on Cornwallguide (2015) the average period for a wave around
Cornwall is 9s, this is 5s lower than the lowest period recorded during Brigid shown in Graph
5 where the light blue represents the average for Cornwall and the dark blue shows the
recordings for the duration of Brigid.
Graph 5 (Evans. 2015)
When going with Cornwallguide (2015) stating a m/s of 20 and therefore a period of 9 this
means that the wavelength of waves impacting on the Cornish coast are averagely 126.53,
the average of wavelengths effecting Cornwall during Brigid were 384.84 this is 3 x over the
amount of average wavelength Cornwall deals with shown in Graph 6. Wave lengths of this
length if unprepared for can cause create damage to coastal features.
Graph 6 (Evans. 2015) shows the average for Cornwall (1) the recording for storm Brigid (2 – 10) and the average of the storms
results (11).
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
Figure 1 (Environmental agency. 2015; edited by Evans. 2015) shows the location of sea defences around Cornwall.
Bude in North Cornwall has been circled, there is very little sea defence protecting Bude,
Paul Vincent (2015) the Harbour commissioner for Bude stated that most Spring tides with
little swell often go over the break water. He also mentioned that the sea defences are now
less effective due to the break water no longer being hammered pieces of slate put in to a
wall that can take the power out of a wave and disperse it but instead it is concreate. The
concreate lasts longer but is much less effective allowing waves to go straight over. He
recalled that in 2014 the waves were at least 8 meters in height and cleared the defences
with ease passing in to the cannel behind.
Penzance that is outlined by a square has more sea defences for protection as well as this
Land’s end is a natural block for some of the weather. Neil Clark (2015) states that the sea
defences for Penzance can deal with at low water 8 – 10 meter waves, while at high water it
is more like 4 – 5 meter waves, he also credited the sea defences saying that for the
duration of the storm Brigid they protected the harbour, car park and other locations well.
The only damage that occurred was to the wall itself toward the end of the storm what has
since been repaired.
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
Steven Basset (2015) the harbour commissioner for St Ives shown in figure 1 highlighted
with a triangle, stated that there are not a lot of sea defences for St Ives, they will cope but
only dependant on a number of factors. He states that they were lucky that storm Brigid did
not do too much damage, it flooded cottages close to the sea and water did come over the
defences but due to it not being an easterly wind they were relatively ok. He states that a
combination of an easterly wind and a spring tide will result in the sea passing the defences,
this is a similar response to Paul Vincent for Bude.
The cause for such extreme conditions was due to areas of low pressure along with a high
period of fetch creating a high swell traveling along the Atlantic paired with a long duration
and deep waters. Records are showing that these conditions have a chance to be a more
reoccurring problem however.
Graph 7 shows records of wind speeds taken that approach the UK from the Atlantic, they
show and increase in power but in a yoyo effect seeming to drop and rise around every 10
years. It does show how unusual it is to get wind speeds over 150 kts. However it also
highlights that wind speeds over 100 kts are generally becoming a more regular occurrence,
with 4 records over 100 kts after December 1994 compared to one record over 100kts from
1969 - before December 1994. The Metoffice (2014) stated that storms like Brigid could be
“a one in 5 - 10 year event in the southwest of the UK” this would result in heavy financial
issues throughout the UK and especially on Cornish coastline. To combat this problem and
help reduce the damage and cost caused by such storms many sea defences will have to be
renewed and rebuilt.
Graph 7 (Metoffice. 2014)
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Tom Evans
CORF204 Duncan Jones talk on over the graph results
When observing Table 1 compared with figure 2 it seems that storm Brigid had not caused a
fully arisen sea, figure 2 shows that at 90 Km/hr or 25 m/s that the significant wave height is
19.3 meters, it also states the period of waves is 13.9 seconds. Table 1 for example maps 1
-2 shows a m/s of 29.29 the ways at this point have a period of 14 and a height of 10, this on
the chart in graph 3 shows to have the duration of 12 hours as a limiting factor. Due to the
wave height and period being lower than that shown in figure 2 what shows stats for fully
arisen seas I believe that throughout the duration of Brigid the Atlantic was not fully arisen.
Figure 2 (Pinet. 2006) showing waves of a fully arisen sea.
When viewing the maximum potential wave heights that could have been caused by Brigid it
is clear that if these had occurred and a fully arisen sea had occurred then there could have
been even more damage and series harm to life. 1 shows the 2005 average wave height for
Cornwall, 2 shows the 2005 highest wave Cornwall recorded, 3 shows the maximum height
UK sea defences can deal with. The orange line ranging from 1 to 9 is the maximum
potential height at each recording of Brigid, all at least 8 meters over the height of maximum
UK sea defences.
Graph 8 (Evans. 2015)
The weather maps show the areas of low pressure building up and moving toward the UK
across the Atlantic, it shows how at first there is an area of low pressure in the middle of the
Atlantic that move close to island quickly. As this area of low pressure is moving to the north
of Ireland and out of harm’s way of Cornwall another area of low pressure is building up for
south west than the original low pressure zone and is travelling across the Atlantic towards
the location of the initial zone of low pressure, a gap of 12 hours data causes a jump in the
pressure zone, it is now toward Ireland. While this is happening another low pressure zone is
moving in from the south West Atlantic as well this time heading more toward Spain and
France rather than Ireland.
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Tom Evans
Weather maps (Jones, 2015; Edited by Evans. 2015)
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CORF204 Duncan Jones talk on over the graph results
Tom Evans
CORF204 Duncan Jones talk on over the graph results
References
Basset, S. (2015). St Ives Sea defences. Personal communication. 22 04/ 15.
BBC. (2005). Waves of hope in power research. England. (Available online at)
http://news.bbc.co.uk/1/hi/england/cornwall/4167066.stm. Accessed on the 22/ 04/ 15.
Clark, N. (2015). Penzance Sea defences. Personal communication. 22/ 04/ 15.
Cornwall council. (2015). Flood investigation reports 2014. (Available online at)
http://www.cornwall.gov.uk/environment-and-planning/countryside/estuaries-rivers-andwetlands/flood-risk/flood-investigation-reports/flood-investigation-reports-2014/. Accessed on
the 22/ 04/ 15.
Cornwallguide. (2015). Cornwall surf forecast. (Available online at)
http://www.cornwalls.co.uk/surfing/surf-forecast.htm. Accessed on the 23/ 04/15.
Metoffice. (2014). The recent storms and floods in the UK. Pp 8. (Available online at)
http://www.metoffice.gov.uk/media/pdf/n/i/Recent_Storms_Briefing_Final_07023.pdf.
Accessed on the 23/ 04/ 15.
Vincent, P. (2015). Bude Sea defences. Personal communication. 22/ 04/ 15.
Figure 1: Environmental Agency. (2015). Costal erosion. (Available online at)
http://maps.environmentagency.gov.uk/wiyby/wiybyController?value=tr113bq&submit.x=0&submit.y=0&lang=_e&ep=
map&topic=coastal_erosion&layerGroups=default&scale=7&textonly=off#x=206364&y=5840
6&lg=1,&scale=4. Accessed on the 22/ 04/ 15.
Figure 2: Pinet, P, L. (2006). Invitation to Oceanography. Fourth edition. Waves in the
ocean. Pp 239. Jones and Barlett. London, Uk.
Table 1: Evans, T. (2015).
Graph 1: Evans, T. (2015).
Graph 2: Evans, T. (2015).
Graph 3: Jones, D. (2015). CORF 204. Assignment 1. 3rd February 2015.
Graph 4: Evans, T. (2015).
Graph 5: Evans, T. (2015).
Graph 6: Evans, T. (2015).
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CORF204 Duncan Jones talk on over the graph results
Graph 7: Metoffice. (2014). The recent storms and floods in the UK. Record breaking
weather. (Available online at)
http://www.metoffice.gov.uk/media/pdf/n/i/Recent_Storms_Briefing_Final_07023.pdf.
Accessed on the 23/ 04/ 15.
Graph 8: Evans, T. (2015).
Weather maps: Jones, D. (2015). CORF 204. Assignment 1. 3rd February 2015. Edited by
Evans, T. (2015).
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