Expert explains why Norwich has problems with sinkholes

Rock boffin Matt Williams explained that by building Norwich on notoriously unsteady material - sand - modern-day city folk are paying the price.

Mr Williams said that you'll often see the start of a sinkhole as just a dip in the tarmac (Image: Newsquest)

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The 65-year-old said: "Norwich is largely built on just sand overlaying chalk.

"Neither are very strong and there are concentrated pockets of water running in and between those layers.

"But once Norwich started being known as the sinkhole capital it opened up all sorts of mythology with people thinking it was to do with the mines.

Retired geologist, Matt Williams, says that sand and chalk are to blame for the sinkholes appearing around the city (Image: Matt Williams)

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"It's not collapsing into mines - the sand is just being washed away."

And Mr Williams warned the city's current preoccupation with roadworks could cause even more issues: "When roads are dug up for any reason the trench it creates must be backfilled.

Mr Williams said that the continued roadworks could cause more sinkhole issues around the city (Image: Newsquest)

"You'll often see the start of a sinkhole as just a dip in the tarmac - particularly close to drains or sewers.

"If it's not, it will create pockets of empty space which sand then washes into and creates more issues later."

A sinkhole which appeared near a number of houses in a city suburb (Image: Christopher Yallop)