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The 695th Lord Mayor’s Lectures: The Thames Barrier – Immediate Future or Long Past?

This was a super presentation by the Water Conservators’ Thames Warden, Professor Carolyn Roberts.  She pointed out that many people in London are living in a floodplain and flooding is a matter of probability: it does and will happen.

Issues include the length of warning time, and time of day for evacuation.  Much depends on the type of event – snowmelt and heavy rain and high tide (1928), tidal surge (1953) – and everybody’s level of preparedness.  There are major challenges – persuading politicians and the public that this is an issue, against a backdrop of not trusting experts and general disbelief that it will happen.  What is urgently needed is a prioritisation of the risks and challenges, of what can be saved or protected.  There is an urgent need for better cooperation amongst organisations, and an understanding of the indirect implications of emergency planning decisions (such as those which emerged during the flooding in Gloucestershire in 2007).

Carolyn pointed out that the Thames Barrier is part of a greater provision against flooding of the Thames: there are eight other barriers on tributaries, 200 miles of walls and embankments, many in private ownership (of which 2.5% were below par in 2021), and 400 other structures such as floodgates, outfalls and pumps.  There are also some ‘buffer’ areas of important ecological interest such as saltmarsh, generally not considered in 1970s but which have increased a little in area.

The sea level rise with ice melting and thermal expansion is accelerating.

  • 4mm/yr rise 1911-2018
  • 6mm/yr1990-2018
  • EA predict cumulative rise 2000 to 2125 1.6m (without ice sheet collapse)


Thames Estuary 2100 Plan and Ten-Year Review:

The original Plan was intended to raise defences downstream in 2040, upstream in 2065 and replace the Barrier by 2070. Now the prediction is for 2050 for upstream defences, no change downstream.  The proposal is to reassess options by 2030, and decide on a replacement strategy for the Barrier by 2040, rather than 2050. Provided it is not too late!

This lecture is well worth watching again!

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