The Risk of Surge-Tide Flooding Remains
Between 1974 and 1980, it was calculated that one million people living in 350,000 dwellings in an area of 75 square miles and the one-and-a-half million working population in this stricken area were at risk. Flooding to a considerable depth would take place in a period of less than an hour. All basements within the danger area would be flooded, with widespread cessation of electricity supply and contamination from released sewage. The water-level would be ten feet (more than three metres) above ground-level in the worst affected areas. There would be massive damage to property, infrastructure, power stations and industry and the entire central sector of the underground between Hammersmith, Stratford, King’s Cross and Clapham would be flooded and out of action for up to a year. In the 1953 flood there were 307 deaths in the UK, with a heavy toll on Canvey Island on the North Bank. Given the high level of development on both sides over the last 30 years, it would be prudent to think of material damage in real terms at a high multiple of the earlier estimates and a much higher number of fatalities, if, for some reason, the Barrier failed to close and the freak tidal surge was much above previous levels.
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A Delicate Matter
Since 1980, the first new high-rise buildings such as at Canary Wharf have settled more into the London clay than was planned, while high springtide levels are well above and are much more frequent than what had been expected in 1972-84. The complex machinery of the Thames Barrier will not last for another forty years without significant and costly upgrading and very careful maintenance while the terrorist risk can only be met by diligent and prompt security, and rigorous police and military contingency arrangements. Understandably, the authorities are reluctant to alarm the public unduly, and rightly continue to regard their emergency response procedures as highly confidential.
Accidents can also happen. One vessel approaching the Barrier on a strong ebb tide and in thick fog crashed into one of the gates and remained firmly stuck, demonstrating that navigational error or engine failure is still a risk and a hazard in providing adequate protection for London. The solution must almost certainly, sooner or later, rest with a new and higher permanent barrage incorporating a new well-tried lock system. There has been much talk about this but very little action. Meanwhile the authorities became increasingly interested in another ingenious interim solution.
The Flood Essex Policy’
This new, but in fact 3000-year-old, answer to the tidal flooding problem is not (so far as I know) on the official public agenda, but is known by every Thames Waterman I have spoken to as the Flood Essex Policy’. Instead of closing all the sluices downriver in the event of a rogue surge-tide, all or some of them would be opened to divert the flood water over huge areas of low-lying land and abandoned industrial sites. If any residents and animals needed to be moved temporarily, they would have at least 6-12 hours notice thanks to the excellent warning system of tidal measuring stations now operating from the extreme North of Scotland down the East Coast and up the Thames Estuary. Coach and truck contractors on retainer contracts would be ready to provide ample emergency transport to designated temporary accommodation.
Up the East Coast it is possible to see how effective these measures can be. Between Burnham and Fambridge on the River Crouch, for example, the high sea-wall raised and strengthened after the 1953 flood was dynamited at intervals leaving large gaps through which the incoming tide can pour in and out harmlessly twice a day and now also provides adequate additional capacity to absorb freak surge-tides. Such a solution will help protect the town of Burnham on Crouch from the six-foot flooding it experienced in the High Street in 1953. The Flood Essex Policy’ does, however, require investment within the flood zone in adequately walling round all installations, facilities and buildings requiring protection (see figure 1 overleaf) but it is a very cheap and simple interim alternative to the massive engineering and dredging projects previously on the drawing-board.