This was the lowest bridging point on the Severn for centuries, until the 19th century rail bridge and then the 1966 supension bridge were built. The bridge shown in the main picture was designed by Telford. In turn it was replaced by modern road bridges, it still carries a footpath. Here the river is still tidal, the bore passes under these bridges, but there are no intertidal areas. So this is the lower reaches of the river more that the upper reaches of the estuary really.
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Jump to the place marker on the SES map here
The Severn Estuary Survey (SES) 