#GACONF15 – Impact of 2013-14 Storms on Coastal Geomorphology in SW England

This was the first lecture I went to on the Friday morning and was a useful subject knowledge update.

The lecture was given by Professor Gerd Masselink, Professor of Coastal Geomorphology at Plymouth University.

Gerd began the talk by stating that last witner (2013-14) was fantastic for storms whereas this year, winter (2014-15) was disapointing, though I would imagine property owners and businesses in the south-west would feel differently!

Coastal Risk is caused by Hazard x Exposure, and coastal risk can take the form of erosion, damage to property, flooding and financial loss.

In the storms that cause the most damage large waves are found at the South of hte pressure system.

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Fistral Beach, Newquay (source)

10m waves are 100 times more powerful than 1m waves.
In the four months between December 2013 and April 2014 there were 20 events where a 6m wave height was exceeded. The impact was larger when tide was high. Specific key events were Hercules 6/1/14 and Petra 5/2/14.
The 2013-14 winter was the most energetic period in the last 60 years (far exceeded the 1990 winter which was the previous highest).
The storm impact was not just a regional event; it also impacted Soulac, SW France.

Images of Damage

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The destruction of the SW Railway line at Dawlish cost between £1-20 million per day, the total cost over 60 days has been estimated between £60 million and £1.2 billion.

How can you compare impact of storm event?

  • Beach survey – profile.
  • Real time kinematic GPS
  • Airborne LIDAR survey (from before or after)

These allow the researcher to quantify the sand lost (erosion) or gained (accretion).

In some beaches after the storm event a 1m strip of beach lost 200m of sand.

Where has the sand gone? (and will it come back)

  1. Offshore Accretion – primarily happened in the North Coast. The sand was washed to 3-4m off low tide level. It is not lost and some is making its way back.
  2. Alongshore (around the corner) – primarily happened on the South Coast, for example at Slapton.
  3. Onshore (over the top) – particularly a feature of gravel beaches, where sediment is washed over the top. There is no natural mechanism to recover the sediment can only be returned by humans.

Conclusion

Storm waves are related to the Atlantic pressure system; storm frequency, intensity and path will be effected by climate change (this year two major storms have missed the SW as the centre of the storm was further North).

Storm impacts show a larger geographic variability – the North Coast with offshore sediment transport and beach erosion, has already half way recovered, and it is expected to be fully recovered within two years. The South Coast had longshore sediment transport and beach rotation will not recover unless there are storms of the same magnitude in the opposite direction.

Increase in coastal hazard due to climate change because of sea level rise, increased storminess (more and more energetic).

There can be be a decrease in exposure to coastal hazards due to coastal management this includes, zonation, protection and managed realignment.

Gerd also shared details of the following website: http://www.channelcoast.org/southwest/, the Plymouth coastal observatory which contains beach profile data.

This post was based on my own notes and any errors are my own.

This is a one of a series of posts on the GA Conference 2015; the main post is here.