A sinkhole being investigated on private land in Chesham is the third to make the news in Buckinghamshire over the last month. What's behind this phenomenon? 

In the wake of the widely-reported HS2 rail line sinkhole in Amersham last month alongside another spotted in a High Wycombe car park, we decided to investigate a little into why we're seeing so many pop up around the county.

Are sinkholes a new phenomenon in the area? Are they manmade or natural processes?

A spokesperson from the Environment Agency expressed concern about the impact sinkholes might have on the natural world when referencing an investigation into a sinkhole discovered on a private property in Chesham.

"Our specialist officers work closely with HS2 Ltd and contractors to ensure all relevant legislation is followed.

"We also continue to talk to local people, the water industry and local authorities to ensure the environment is protected throughout the HS2 project."

The development of the HS2 rail line through Buckinghamshire has drawn controversy, especially for being constructed on chalkland which is especially susceptible to flooding.

After a large sinkhole appeared above a HS2 tunnel last month, a representative for the rail line attributed it to "pre-existing ground conditions".

Indeed, sinkholes are essentially holes in the ground that are caused by a collapse of earth and rock - natural sinkholes are formed when underlying rock is slowly eroded by water entering cavities below the earth's surface.

Key factors contributing to the creation of sinkholes, as listed by the British Geological Survey, include heavy flooding, leaking drainage pipes, construction, groundwater diversion and mining.

Geologists have singled out south-east England as an area at particular risk of sinkhole openings, and wet weather at the beginning of the year may have worsened already soluble chalkland. 

Geological investigative company GeoInvestigate say the term is used to describe not only natural but also unnatural collapses of the ground, with the latter often linking to the development of manmade features.

Speaking to the Institution of Civil Engineers, geotechnical specialist Dr Clive Edmonds said: "Sinkholes depend on geology, some rocks are more soluble than others.

"Chalk and limestone deposits may take thousands of years to dissolve but when new cavities occur, they can cause spectacular sinkholes."

He added that construction works can also play a part in pressurising already unstable ground.

"Human development can contribute greatly, especially construction work in areas where you may have dense development.

"There are warning signs you can spot. First indicators are dips and depression in the ground surfaces, deepening with tiny cracks in pavements or buildings leading to them showing slight movement." 

The Environment Agency has opened an investigation into a sinkhole reported on private land near Chesham. Anyone with concerns about this incident can call the 24-hour incident hotline on 0800 807060.