Memoranda

East Anglia and Elevated Flooding

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Sea Wall at Horsey

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Sea Wall near Eccles-on-Sea

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Sea Palling in 1953 Flood

As long forecast, increasing Global Warming produced an elevated all time record rainfall this past week, but, exactly as expected, it was peculiar to the UK's North West. There is far less fear of such in East Anglia, which area on the whole will suffer a reduction of rainfall, indeed more droughts in the Summer months of the year. Our main threat is that posed by the sea, as another major surge greater than that of 1953 becomes more likely as each year passes.

The major 1953 flood did not come on the highest tide, yet due to surge conditions (see 'North Sea Surges' at http://www.marinet.org.uk/mad/nseasurges.html ) reached a peak of 2.1 metres above nominal. The Great Yarmouth area wall was built one foot (30 cm) above that 1953 peak level. But at that time our sea levels were far lower, our defensive dunes higher and our beaches far deeper and more extensive. Climatic conditions were not then so severe. Furthermore, few houses were then built in known flood plains.

Since then thermally induced sea expansion, glacial and polar icecap melt and East Anglian sinkage has been giving an equivalent additional sea level increase of up to six millimetres per annum. This too is increasing. Thus even nominal sea level now approaches over one third of a metre more than was the case 56 years ago, and a future major surge could produce sea levels of over three metres above that experienced in 1953. So East Anglia could be hit far more severely in the next major surge, three weeks either side of mid-February being the most dangerous time.

Yet another factor due to man-made Global Warming is the increasing frequency and the severity and duration of winter gales, these producing higher tides, larger and more frequent surges and bigger waves. The eroding power of a wave is proportional to the height of the wave crest, so now the more frequent and severe northerly winter gales strip more sand and gravel from the shoreline out to sea, where it then naturally replaces that sea bed area removed by dredging instead of returning to the shoreline with the undertow accompanying the offshore winds of the summer.

Yet a further factor in the equation is that the increasing and deepening barometric lows that accompany Global Warming produce far higher sea levels over the beaches and so bring the sea up to the dunes and sea defences to threaten further underminement. Thus these surges additionally serve to escalate erosion and the rise and inland progression of the North Sea, so to increase the threat of marine flooding.

Despite all this the main threat is not overtopping of the existing sea defences, but underminement of the protective sea walls and dunes that are threatened with collapse when the sand is stripped from under and around them. If they go, or are allowed to go along our east to north coast, all low laying areas with existing or newly created marine access could be inundated.

As for determining the areas of inundation, you don't have to rely upon EA mapped areas. You can 'do it yourself' by using the excellently defined and detailed Google Earth maps. As you run your mouse pointer over the map, the Latitude, Longitude and a.s.l. will appear at the bottom of your screen. According to the sea level experienced, you can soon spot the vulnerable areas as any being below that.

Pat Gowen