Extra high tides and flooding on the Medway often happen when the Thames Barrier is closed. In view of the flood event on 21 February 2022, Kelly Tolhurst, MP for Rochester and Strood and MSBA Patron, asked the Environment Agency if there is a causal relationship. Here is the EA’s reply with attachments (spoiler alert: No):
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Medway and Swale Boating Association
The voice of boating on the tidal Medway and Swale
I found this very interesting reading. It is something I have written about in the past for the effects of barrier closures do cause localised rises in the area around Leigh-on-Sea up to barrier across Benfleet Creek below the road bridge onto Canvey Island, and into Smallgains Creek.
What the EA say about the affects in the higher tidal reaches of the River Medway are probably correct – one would need measuring instruments and several events to build a picture…
What I will say is that early closure of barriers seems to have an adverse affect downstream. I remember the 2013 event and marked its height on one of my mooring posts at the Island Yacht Club in Smallgains Creek – it was frighteningly high! That height has since been more or less equalled on two occasions that I am aware of since. The last was the February event earlier this year – discussed above in the web piece.
The Thames barrier is often closed early when fluvial flows are high – if the tributaries of the upper Thames (in the west of the country) have an excess of water, then an early closure allows for a ‘basin’ for fluvial flow to rise within whilst holding the tide back outside of the barrier.
When the Thames Barrier at Woolwich is closed, all downstream barriers are closed simultaneously. The consequence of the early closure of the Benfleet and the East Haven Barriers with a virtually empty creek around the north and west of Canvey Island, does, I believe, cause localised lift of the peak tide level at the eastern end of Canvey Island, and a more numerous flood event for the Benfleet YC.
What that rise is, I have no way of measuring, however, I feel it can be around 100 mm to 200 mm (0.1 to 0.2 m), if not more at times..
It is an observation borne of decades of ‘watching’ the water…
Ultimately, in my lifetime, perhaps (I’m now nearly 67), a barrier will be needed spanning the outer end of Sea Reach between the spine of land at Shoeburyness across to N. Kent, probably east of Whitstable.
I’m sure it is in the planners minds!
In the mean time a greater level of reflooding of low land ‘pinched’ from the sea in the past would help alleviate localised problems.