Storm surges in themselves are rare and, on their own, pose little threat to the city of London. However, if global warming continues to affect sea levels, this threat will be increased. Additionally, supposing sea levels have significantly risen, if a storm surge hits at high tide, and only at high tide, it could prove to be disastrous to the capital. But if only one of these three variables is missing, flooding is very unlikely. This page explains how these factors work together.
Global warming refers to the increasing temperature of the Earth’s atmosphere. Scientists have calculated that in the past century the average temperature of the Earth’s surface has increased by 0.8ºC (1.4ºF), the majority of which has occurred in the last thirty years. The predicted affect of an increase in atmosphere temperature is the melting of ice at both of the Earth’s poles, which will naturally result in higher sea levels. Higher sea levels imply reflected high water levels in the world’s rivers including the River Thames. Though some of the Water Voles who have the entrances to their homes on the bank of the River Thames may experience minor water damage, elevated water levels alone are highly unlikely to cause severe floods to the city. But they do increase the effect that a storm surge would have on the city.
Storm surges are swells of water that occur at sea. They are caused by strong winds pressing on the surface of the water in areas with low atmospheric pressure (known as depressions). A depression causes the water to be sucked upwards into a hump and happens when two winds collide. Imagine holding a sheet of paper to your lips and breathing in through your mouth. The paper will be sucked inwards with the decrease of pressure. Breathe out and the paper will billow outwards as the pressure put
upon it increases. This follows the same principle as depressions. When a hump occurs under a depression and strong winds are acting against this hump, it creates a tidal movement known as a storm surge or tidal surge.
Most storm surges experienced by the UK originate around the east coast of Canada and travel across across the Atlantic Ocean unnoticed. But occasionally a northerly wind will blow the hump into the North Sea. As it is forced into the narrow space the hump will grow, putting pressure on the east coast of England and the coast of mainland Europe. Surges that make it as far south as London can be funnelled into the estuary of the River Thames by the momentum of the Earth’s revolution, causing a flood threat to London as they make their way inland along the river.
Storm surges alone can cause the city damage. The storm surge of 1953, known as the North Sea Flood, occurred before the Thames Barrier was erected and was the primary cause for its construction. On the night of the 31st of January a tidal surge measuring 5.60 metres swept down the coast of England. By the time it reached the Thames it had fallen to 2.59 metres, though the funnel shape of the river is likely to have caused the height to increase as the surge travelled inland. The docklands were flooded but, luckily, the rest of the city remained dry. 307 people were killed on land in the UK, 30,000 were evacuated, and 24,000 lost their homes. The total death toll across Europe is estimated at 2,551.
10 years earlier a tidal surge of 3.66 metres was recorded in the Thames, but luckily it hit at low tide, leaving the city unscathed. However, if it had hit at the highest possible tide of the year (known as spring tide, just before the advent of a full or new moon), the height of the surge would have been increased by 3.20 metres, giving a potential tidal surge of 6.86 metres. The height of the Thames Barrier is 6.90 metres. Given the effects of global warming since then, it’s not hard to imagine the barriers being overwhelmed in a worst case scenario. To find out what would happen in such an event clik on East London, Central London and West London.