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Coastal Processes - StormsStorms have a major influence on the coast especially on the soft defences such as the beach, dunes and salt marsh. They are defined on the Beaufort Wind Scale as having a wind speed between 48-55 knots and violent storms between 56 - 63 knots.Storms occur due to dramatic localised changes in atmospheric pressures producing strong, often damaging winds and copious precipitation. The strong winds result in high waves that contain a lot of energy. It is these waves that have the highest impacts on the soft coast. The effects of the storm are further exaggerated due to the low pressure raising sea level known as a storm surge. Storm surges can move quickly and flood areas in a short space of time. In some instances storm surges of 3m have been recorded. If the storm coincides with a high tide then the effects can be even worse. Both the high tide and storm surge allow the waves to travel further up the shore before their energy is dissapated. Often the waves reach the top of the beach and it is these waves that are the most damaging. The impact from the storms can severely damage salt marsh and dune systems causing large initial erosion as sediment is redistributed across the shore. This can often result in cliffing of the frontal dunes. Major storm events have caused 10/20m of erosion of the frontal dunes. There is often a rapid accumulation of the sand or silt at the top of the beach in the days/weeks after the storm. Assuming there are no other serious storms then the dunes or salt marsh should recover. The frequency of storm events is a major factor in the damage the coast receives. One scenario of climate change is the increased frequency of storm events. This could lead towards increased erosion of the frontal dunes in certain areas. For example there is a possibility that a storm of an intensity such that in 2004 we would expect it to occur every 50 years might by 2080 occur every 3 years. Storms can also have dramatic impacts on hard defences such as sea wall and rock armour as well. Often after a severe storm there are some local damage to these hard defences but the last major incident occurred in 1977 when a storm surge overtopped older defences in Crossens. The 1st February 2002 storm event was the second highest recorded water level during the period 1991-2003 and the highest since the February 1990 event. A level of 10.686m chart datum was recorded.
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