TIDELIGHT
More info
Bristol is a city built on the rise and fall of the tides. Historically, the tides would make their presence felt, right in the heart of the city, lifting boats up to the quaysides at high water and stranding them in the mud below at low tide.
From the beginning of the 19th century, however, with the creation of the Floating Harbour, the water level was kept constant and that connection was lost.
‘Tidelight’ will symbolically re-establish that dynamic connection between the city and the sea.
The interior of Bristol’s glass-fronted M Shed museum will be filled with light that changes colour in direct response to the rise and fall of the tides. At night the whole building will become a giant ‘lantern’ on the waterfront, responding to the sea beyond.
Prior to the construction of the Floating Harbour (completed in 1809), the river Avon was completely tidal with water rushing up and down the river channel creating huge variations in water level right in the heart of the city. With the construction of the floating Harbour, the water level was kept constant in the commercial centre of the city. The river was diverted to the south in to the New Cut. The rise and fall of the tides can still be seen in this channel just south of M Shed. This map excerpt is from Rocque’s survey of the City of Bristol of 1750 held at Bristol Museum & Art Gallery.
The history of Bristol’s waterfront environment can be traced through maps using the interactive tool, Know Your Place
To make Tidelight happen, continuous, real-time water level data from tide gauges out in the Bristol Channel is sent back to a computer inside the building.
A piece of software converts this data, on-the-fly, in to a form that directly controls the colour value of RGB lighting, already installed throughout the building as well as additional temporary lighting in the glass fronted foyer.
Very low water will be translated in to red light. As the water rises on the turn of the tide, the sensor data will gradually cause the hue to transition through shades of orange, yellow, green and blue, all the way to violet at very high tide.
The full tidal range out in the Bristol Channel will correspond to the full colour spectrum.
And as the tidal ranges vary over time, so more or less of the spectrum will be reproduced accordingly. During a neap tide, the tidal range is low. The high tides are less high and the lows less low.
On these occasions the coloured lights in M Shed may only range between orange and green. On a very high spring tide, though, the building will be lit in a particularly intense violet, and during particularly low spring tides, the ‘lantern’ will glow a deep, blood red.
Rising sea levels
Occasionally, on extremely high tides parts of the Floating Harbour are overtopped and areas of the city become flooded. If this were to occur during Tidelight’s run, the lights at M Shed would glow a particularly intense violet in response, reflecting the extreme conditions that would be clear to see.
The colour range of the lights will be set so that they can potentially respond to sea levels beyond the highest tides ever recorded at Bristol. This gives Tidelight a latent capacity to translate in to colour, future sea level rise scenarios. Image from Chris Bodle’s Watermarks Project
Bristol’s connection to the sea has always been a big part of its identity. And the coming and going of the tides has been inextricably woven in to its story.
From John Cabot and his crew waiting for the tide to lift the Matthew off the mud to allow passage along the Avon Gorge – and out beyond the Bristol Channel in to the blue toward that infinite horizon.
To the tides that determined the passage of ships in and out of Bristol during the most shameful chapter of its history – the Transatlantic Slave Trade.
To the network of connections, across the globe, of legitimate trade, that brought such a rich diversity of people, objects, ideas and innovations to the city.
All these things, brought in on the rise and fall of the tide are woven in to the fabric of the contemporary city. In the place names, in the buildings, in the quaysides, in the diverse communities, in the music, in the food, in historic works of art and works of contemporary street art.
This project aims to be a small part of this ongoing story of Bristol’s connection to the sea, as an inland maritime city, and prompt conversations about its history, its geography and our vulnerability to rising sea levels in the face of climate change.
During the day and night
For visitors to M Shed the project will also be visible during the day. The colour changing lights already installed throughout the building will be lit up and change colour in response to the tides through the day during the museum’s opening hours.
As night falls the big lights in the foyer will turn on in addition to the existing lights, making the whole building a responsive ‘lantern’ visible from across across a wide area around the Harbourside. (see map).
The colours and the tides
The colour chart shows how the level of the tide translates in to colour; both the colour of the lights at M shed and as the background of the Live Tides page. This chart shows the full tidal range. It actually goes beyond the highest ever recorded tide in the Bristol Channel. The column on the left shows the level as AOD. This shows how high the tide is in relation to the land. Zero AOD is sea level. M shed and much of the quaysides in Bristol is at around 8.5m AOD. Typically the highest tides will reach around (6.5m AOD) but they can go much higher when there is also a storm surge. Sea level rise will only make these highest tides higher.
Over time the rise and fall of the tides varies. At spring tide the the tidal range is wide; the high tides are high and the low tides are low. At neap tides the highs are less high and the lows less low. At these times Tidelight shows a more limited range of colours.
The real time tide data driving Tidelight is available here and a handy, user friendly predicted tide chart is available here which graphically shows how the tidal range varies over time.
