Climate activist Geoff Beacon*wonders whether the street’s problems lie underground*
“Land subsidence occurs when large amounts of groundwater have been withdrawn from certain types of rocks, such as fine-grained sediments. The rock compacts because the water is partly responsible for holding the ground up.”
A large plane tree can suck up to 70 cubic metres of ground water in a year.
For the 19 trees in Parliament Street that’s about about 1,330 cubic metres. This effect could be reducing the water table by a metre or so in under two years – if the water table is not refreshed by fresh rain.
A fall in the water table may be the cause of the subsidence in Parliament Street.
Yorkshire has just been declared to be in drought because of this year’s lack of rainfall. And what rainfall there is may struggle to percolate through due to the ‘filling in’ around the trees on the street.
Looking through old photographs, the subsidence appears to have happened over the past few decades – the period when the magnificent plane trees that line the street have grown.
On casual inspection, there aren’t many ways that rainfall can reach Parliament Street’s water table.
Recently the small patches of ground surrounding each tree have been given a covering that may further restrict rain penetration to the underlying water table. Does City of York Council know that they may be making the subsidence worse?
Parliament Street’s tall trees are a wonderful asset. They add life, attracting many people to the city centre.
On hot days, the shade and cooling of the trees make the space much nicer. The benches provided create pleasant places to sit and watch the crowds go by, and listen to the rustling leaves.
It would be a shame to see the trees go but will subsidence mean that major earthworks will become necessary to remedy the problem?
At present the undulating surface adds to the charm of Parliament Street but I worry that rigid minds of planners may think otherwise.
York doesn’t need the expense of a chaos like the never-ending works outside York Station.
My stopgap is to use water from the Foss to pump up the water table in Parliament Street that would be much cheaper and pleasanter than the type of Station Front development.
It would be good to know what York council’s plans are.