Flood Risk to the Strategic Road Network in England

Abstract

It is vital that flood risks from multiple sources to the national Strategic Road Network are well understood, to help minimise disruption, reduce risk to people and to help prioritise maintenance programmes. Highways England have undertaken research to update their current understanding of risk based on improved flood mapping, plus data collected on flooding ‘hot spots’ through a concerted programme to record flooding events, severity and causes over the last 5 years. Building on the previous risk assessment, the roads layer was interrogated against new flood hazard data for multiple sources of flooding. The road network was divided into 100m segments in order to capture a strong spatial understanding of predicted flood risk from each source, but also summarised on a 1km scale and a management area level to aid prioritisation at varying scales. The 1 km grids were then ranked across England according to each source of flooding, and also an overall rank was derived through summing these ranks together. This was validated against detailed spatial ‘hot spot’ database recorded by Highways England, based on over 12,300 records, collected over 5 years.