Increased monitoring and work to direct the flow of rainwater is recommended for old Castle Road in Weymouth, following a specialist geotechnical report.
The report, received by Dorset Council engineers, has identified the contributory factors associated with a landslide near Old Castle Road and has set out recommendations for the monitoring of the area, and possible action.
In March this year, the highways structures team was notified of a landslip on private land coming to within a few metres of Old Castle Road. Inspections of the area found no sign of distress in the carriageway but as a precaution the road was reduced to a single lane to move drivers away from the immediate area of the landslip.
Temporary traffic lights were put in place to facilitate the single lane operation as driver sightlines are not very good with the narrowing of the road.
Dorset Council commissioned Jacobs to undertake a site inspection and cliff assessment of the area to better understand future cliff recession scenarios and the risk of damage to the highway. Alongside this Dorset Council’s highways team looked at the feasibility of establishing an alternative access to properties and businesses beyond the landslide.
Jacobs’ Old Castle Road landslide report has identified a Translational Landslide – a down-slope movement of material – caused by a natural process of rainwater drainage through the land; nearby inland rainfall soaks through more permeable layers of material until it finds clay, it then runs along the surface of this clay layer downhill towards the cliff.
The effects of groundwater drainage can be seen along the Jurassic Coast, where there is a high risk of landslips following substantial rainfall.
A further contributing factor to the slip at Old Castle Road is rainwater from the highway and private driveways entering the top of the slope.
At Old Castle Road, toe erosion – at the base of the cliff – is very small as only spring tides reach the bottom of the slope, and it is greatly protected from stormy seas by the breakwaters in Portland Harbour.
Cllr Ray Bryan, Portfolio Holder for Highways, Travel and Environment, said: “The details in the reports are essential for us to start planning how to ensure continued access to properties and businesses along Old Castle Road.
“Although the current dry weather means there has been little change in the area of slipped land, as seen along other coastal areas in Dorset, this can change quickly with prolonged and heavy rainfall.
“We will be carrying out some minor highway works to prevent the flow of surface water over the slope and we’ll undertake fortnightly monitoring of the area.
“Due to the slip being on private land, which has planning permission, we are currently investigating the legalities of what can be done, and by who, as engineering work on this land could affect any future development.”
This summer, a continuous kerb line of 45m will be built between the garage adjacent to No.27 Old Castle Road and the footpath down to the beach to prevent surface water from entering the landslide system.
Council engineers will carry out regular inspections for signs of cliff retreat, subsidence and tension cracks to identify ongoing movement and risk. This includes monitoring:
- the road
- the ground between the kerbside and cliff edge
- surface water flows
- toe erosion (at the base of the cliff)
- the landslide itself
At this time, a weight restriction will not be put in place on Old Castle Road.
A drone-based topographical survey of the slipped area will be carried out to help monitor ground activity. If there is any sign of collapse observed in the road, it will have to be closed and alternative emergency access arrangements will be provided for residents.
The Jacobs Report made nine short-term recommendations, which should be carried out while a long-term plan is put into place to shore up the road. Otherwise, the risk is that the road would collapse within a year. Dorset has implemented three of the nine recommendations, and has no long-term plan in place. They are sitting on their hands and hoping. This is not good enough. If the road collapses this winter, it will be Dorset’s fault.
Hi Steve, the team is doing as much as they can at present to monitor and protect Old Castle Road.
The situation is made more complicated by the fact that the slip is on private land, that we believe has recently been sold and we’ve yet to identify the new owner. We are investigating the legal aspects of what work can be done and where responsibility lies.
Our structures team has considered all nine recommendations in the Jacobs report, six of which are now in action. We did consider a weight restriction for Old Castle Road but the practical need for delivery vehicles and other heavy vehicles to access properties and businesses on the road has to be balanced against the current risk of landslide.
The final two recommendations listed in the report require access to private land, and permanent installation of equipment on it. However, a drone-based topographical survey of the slipped area will be carried out as a baseline against which any changes can be measured.
If Dorset Highways wishes to identify the owner of the land, they should consult the Land Registry or if the sale has not completed ask the current owner.
Why not close the road temporarily with access only for residents and members of the sailing club. There is still access to the beaches and cafe on foot or bike. No one needs to drive down here to walk their dog. Would this not protect the road until you can enact a longer term solution? You need to act quickly to prevent further damage and it is disappointing that you have done very little so far despite knowing for at least 10 years that this was going to happen eventually, and you did not appear to work with the previous landowners.
Thank you for your reply.
This is appalling, for years it has been obvious that the road could be compromised and nothing was done.
With this plan will measures be put in place to ensure that Old Castle-Hillcrest does not become a rat run as people attempt to dodge the Buxton road traffic? (one way system on hillcrest?/resident only access across the rodwell trail? more severe traffic calming on the Rylands lane end of Hillcrest?….)
There must be a better alternative than compromising rodwell trail.
As a resident who owns her own property in hillcrest road I think the diversion plans you are suggesting are going to cause major problems. What is wrong with using maintains to get about as we still have too many cars speeding down here despite speed bumps. My driveway has been used for a turning point, my car scratched and my wall near my sons bedroom knocked down. stopping people parking outside their council homes will lead to a big issue with parking in hillcrest, at Anne’s st David’s and Martin road. The residents only found out by leaflet today.