Concerns over potential flooding on the Norfolk coast means the flood gates at King's Lynn will be closed on Monday (September 30) morning.
South Quay will also be shut, with the Environment Agency predicting high water in the River Ouse will peak at 4.7m at around 8am. Similar levels are expected on Tuesday, when high water is expected at 8.42am.
The spring tides - as they are called despite the time of year being anything but - bring one of the region's great natural phenomena to the Ouse, in the shape of the Wiggenhall Wave.
This is a tidal wave or bore, more than 1m high, which forms where the river narrows upstream of Lynn when the flood tide begins.
It rushes inland at around eight knots, attracting swimmers, surfers and kayakers to ride on it.
Wave watcher Kevin Holland, who runs a green energy business beside the river at Magdalen, said the wave would occur around 7.30pm on Monday.
The Norfolk Resilience Forum - set up to provide information to the public to warn about emergencies - tweeted that people should stay safe near the coast over the next few days.
The Environment Agency has flood alerts in place for the coast from Heacham to north of King's Lynn; the King's Lynn, West Lynn and The Wash frontage; Hunstanton; Old Hunstanton to Cley; from East Cley to Kelling; from Ellingham to Breydon Water and from Thorpe St Andrew to Breydon Water.
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