SCOTTISH ROAD NETWORK CLIMATE CHANGE STUDY

6.1 INTRODUCTION

The recommendations identified within this study have been classified as either:

Priority Recommendations, or
Other Recommendations, which are further sub-divided into short or long term classifications.

In addition, recommendations have also been categorised by type, namely:

Design Issues, where changes in the design of the road network are proposed
Operational Issues, where changes in the operation of the road network are proposed
Research Issues, where detailed recommendations are not possible at this time and further research is required
Policy Issues, where recommendations would have an impact on current policies

6.2 PRIORITY RECOMMENDATIONS

6.2.1 Design Issues

Revise the parameters for the design storm for surface water drainage performance. This could be achieved by continuing the use of historical information but for an increased return period, or by basing the approach on further research on rainfall changes arising from climate change.
Revise the parameters for the design storm for watercourse structures. This could be achieved by continuing the use of historical information but for an increased return period, or by basing the approach on further research on rainfall changes arising from climate change.

6.2.2 Operational Issues

Identify locations where flooding of the road network has occurred, and develop potential solutions for evaluation on a cost/benefit basis, prioritising those areas where repeated flooding has occurred.
Pre-emptively clear detritus from channels/watercourse structures in known areas of flooding risk in response to predicted heavy rainfall.

6.2.3 Research Issues

Undertake further research in respect of catchment runoff estimation parameters, and provide guidance on possible risk-based design approaches, including evaluation of alternative solutions on a cost/benefit basis.

6.2.4 Policy Issues

Consider using the VMS network to provide a greater level of locally relevant information to road users on predicted severe weather events, expressed in terms of probability of occurrence.

6.3 OTHER RECOMMENDATIONS

6.3.1 Short Term Issues

Design Issues

Review local experience on the durability of surface dressings and consider whether these or another intervention measure is appropriate for the location concerned.
Consider implications of an extended growing season when developing landscape designs, and specify slow-growing species where appropriate.
Design drainage systems with additional storage capacity, taking account of sustainable drainage techniques, where appropriate.
Introduce surface/sub-surface drainage during maintenance works where these do not exist at present, while recognising that this may not always be possible due to land-take constraints.
When developing new designs, consider whether these will be susceptible to full or partial closure in high winds, and prepare a cost/benefit analysis to assess the opportunity for including wind barriers at these locations.
When developing new designs, consider whether these will be susceptible to coastal flooding, taking account of predicted sea-level changes and the possible effects of storm surges, and consider how the design should take account of any such susceptibility.

Operational Issues

Clarify the investigation requirements for watercourse structures potentially susceptible to scour, in terms of periodic and post-event inspection requirements.
Continue the process of developing a High Winds Strategy for the trunk road network and consider the need for a similar approach on exposed sections of the local road network

Research Issues

Undertake further research on likely changes in wind patterns, including seeking to reduce the significant uncertainty that exists in regard to this issue. This would enable further guidance to be given on future consideration of wind in the design and operation of the road network.
Update this report as necessary following publication of the UKCIP06 report

6.3.2 Long Term Issues

Design Issues
Specify materials with appropriate stiffness to provide greater confidence that pavement deformation at high temperatures should not occur.

Operational Issues

Consider periodic reviews of required pavement interventions, to determine whether high temperatures have been identified as a significant contributing factor.
Consider carrying out earthworks inspections under the principles of Technical Memorandum HD 41/03 'Maintenance of Highway Geotechnical Assets' pending further guidance on landslide risk management arising from the 'Landslide Study', prepared as a companion to this report.
Identify areas of the road network that require full or partial closure in high winds and consider the introduction of wind barriers at these locations. This consideration should include a cost/benefit analysis and, if necessary, an environmental assessment.
Consider whether enhanced parking/turning facilities at locations on the road network susceptible to full or partial closure in high winds would provide a cost effective operational benefit.
Identify locations on the road network susceptible to coastal flooding. This should take account of predicted sea-level changes and the possible effects of storm surges, to consider whether measures such as signage, sea-defences or re-routing are appropriate.

Research Issues

Carry out further research on specific aspects of winter conditions where data does not presently exist, to provide a greater understanding of the likely pattern of change in winter conditions that is expected.

Policy Issues

Consider how enhanced communication could be developed with all parties involved in flood management.
Consider how information on areas known to be at risk of flooding may be integrated with flood warning systems to provide early indication of potential hazards.
Consider the predicted changes in winter conditions to determine how winter maintenance of the trunk and local road networks may be carried out on a cost-effective basis.
Consider developing a road user education programme on the appropriate response to different types of severe weather events.
Consider using the VMS network operated by NADICS to support the above road user education programme.

The Scottish Government