I mentioned in a previous post that we'd visited the Thames Barrier, an amazing engineering project across the river that I remember being proposed and then completed in the early 80's as I recall (work actually began in the mid 70's). Well, although it was a rather wet day, I did take a few pictures with my recently acquired iPhone 5S and here are a couple.
The really clever bit is the semi-circular gate between the piers that rotates into position.
Based on the principle of a simple domestic gas valve, the large steel semi-cylinders control the flow of the water. Interestingly they are full of water when submerged, but empty as they rotate into the closed position.
The design was first proposed back in the 1950's apparently. A major flood in 1953 help focus attention on the need for better defences and the move to containerised shipping made a barrier more feasible.
The barrier is expected to be serviceable until around 2070 and there are already other ambitious proposals for a new barrier further east.
You can visit the barrier on either bank, the visitor centre on the south bank and the park and gardens on the north bank. Sadly there's no easy way to go between the two!