Ipswich Icons: Romans sailed up the River Orwell to supply the garrison and villas in the Gipping Valley

Custom House, on Ipswich Waterfront

Custom House, on Ipswich Waterfront - Credit: Archant

Ipswich has been an international port since... well, since forever! writes John Norman, of The Ipswich Society.

Custom House high water stone

Custom House high water stone - Credit: Archant

It is almost certain the Romans sailed up the Orwell to supply the garrison and villas in the Gipping Valley and we know Ipswich was trading manufactured goods with the Low Countries from the early 7th Century.

An international port would have needed a number of facilities, a wharf (a vertical dock wall against which to tie boats), buildings for both storage and administration (registration, port dues, and taxation) and a dock-side crane.

Over-riding this would have been an understanding of the tides and the potential of the river to flood. A flood in Ipswich can be fluvial or tidal, the first an excess of water flowing down the Gipping (rainwater), the second a particularly high tide pushing the Gipping water back upstream.

Tides are caused by the relative position of the Moon and Sun, if they are in alignment (new Moon/full Moon) the gravitational pull of each will combine to produce a high tide. If these heavenly bodies are relatively widely spread in the heavens (first quarter, last quarter Moons) then the gravitational pull of the Sun will oppose the pull of the Moon and the high tide will be much less pronounced.

There are other factors that affect the height of the tide, for example air pressure (low pressure allows the sea level to rise) and air movement, a strong wind will move the water with the tide, or hold the tide back. Most noticeably a northerly air stream in the North Sea will push the water into the funnel (the English Channel) causing water levels to rise immediately before the restriction.

The key to this understanding is the expectation that high water will not ordinarily overspill onto the quayside, boats won’t float on to the quay to be left high and dry when the water recedes and stevedores and wharfingers remain dry-shod.

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The marked line on the side of the Customs House ‘1Ft above High Water’ is a valuable guide to the builders and civil engineers who have constructed dockside structures since 1845. One foot below this line is the typical maximum height of a spring tide, and if you were to build with the ground floor at or above the line you should, ordinarily, stay dry.

On February 1, 1953 a number of things combined to cause the North Sea to flood, firstly the Sun and Moon were in alignment therefore a spring tide was expected (a normal but very high tide). Secondly there was a depression passing east over the North Sea and this lack of air pressure allowed the sea level to rise, and as this area of low pressure crossed the coast of Holland the anti-cyclonic wind became northerly in the North Sea. This pushed the already high water further south until it reached the mouth of the Thames and the restriction caused by Kent. All of the excess water couldn’t squeeze through the channel so it spilt over on both sides, in East Anglia from Yarmouth to Felixstowe and Essex, and into the low lying coastal plain of the Netherlands. The excess of water pushed up the Orwell, overflowed into Felixstowe Port, up the stream of Langer Road and across the caravan parks close to the Beach Station. In Ipswich it overflowed St Peter’s Wharf and into College Street, Key Street and Salthouse Street, flooded the low-lying middle of Fore Street (between the Nelson and the Sorrel Horse) and left standing water in Princes Street and St Peter’s Street.

Deliberations and establishing who was to pay took ten years, but in the mid 1960s a flood defence wall was constructed – the concrete wall clearly visible today between St Peter’s Wharf and the river – the Orwell was canalised from the flood defence barrier at the mouth of the New Cut as far upstream as Handford Lock and fluvial controls were installed at Sproughton and Boss Hall.

Fifty years later the flood risk has increased sufficiently for the whole to be upgraded, a new bund has been constructed from the railway bridge in Wherstead Road to Bath Street, and across the front of the brewery. New lock gates have been installed and a new flood barrier is currently being built in the New Cut.

It is unlikely that the tide will flood up through the Wet Dock and wet the foundations of the Customs House so we’ll now never know (for sure) if the line is indeed ‘1Ft above High Water’.