Dorset Council highways service is progressing a scheme to stabilise the slopes of Dinah’s Hollow on the C13 in north Dorset.
A local geotechnical consultant was commissioned to examine the slope stability and in December 2013 published their report
The Stability Report concluded that while the slopes at Dinah's Hollow have existed for many years without evidence of major failure, changes could cause a major collapse, for example:
- prolonged and intense rainfall possibility resulting from climate change
- changes in surface water area run-off
- vegetation condition
- further under-cutting of the road by vehicles
The risk of landslides poses a serious threat to public safety. As the highway authority, we have a legal obligation to maintain the road and ensure its safety for everyone using the route.
Short-term measure
In 2015, concrete barriers were installed along the road edge as an interim measure to reduce the risk of serious injury from land slippage onto the road.
While the barriers have been in place, there have been landslides in the Hollow in 2016 (when 35 tonnes of soil slipped from the east bank) and in 2021 (when 6 to 8 tonnes of material slipped between the barrier and the road).
These ‘failures’ are not surface slippages but have been generated from the back of the Hollow’s slope (slope plane).
Given the ongoing risk of landslips, full slope stabilisation is necessary to safeguard the road and its users.
Proposed works
The approved stabilisation scheme is a long-term solution using soil nail technologies, with appropriate facing and drainage works, to protect the C13 road from future landslides.
As part of the design process, an application to work within a Tree Protection Order area was submitted. This was granted by the Strategic and Technical Planning Committee on Monday 30 September 2024.
At the Dorset Council Cabinet meeting on 9 July 2024, Cabinet authorised the use of the Council’s powers of compulsory acquisition under section 102, 239, 249 and 250 of the Highways Act 1980 and the Acquisition of Land Act 1981 and such other powers as may be appropriate to secure a compulsory purchase order to deliver the stabilisation scheme.
Nevertheless, the council remains committed to continuing discussions with the landowners with a view to seeking to acquire all necessary land and rights by agreement.
In preparation for the work, a full ecological assessment has been carried out.