One in eight miles at risk: Why 13% of England's road network is a flood resilience wake-up call 

England's roads face a growing and measurable flood threat. New data, revealed in Parliament and supported by fresh research from Ordnance Survey, confirms what many in the infrastructure sector have long suspected: a significant and largely unaddressed proportion of the UK's road network sits squarely within high flood risk zones. 

The strategic road network is exposed 

Responding to a written parliamentary question in March 2026, roads minister Simon Lightwood disclosed that National Highways' latest data shows 1,418 out of 10,873 sub-catchments along England's Strategic Road Network (SRN) sit within high flood risk locations. That translates to approximately 965km of motorways and major A roads, roughly 13% of the 7,400km network exposed to serious flood risk. 

The SRN represents the arteries of England's economy: the motorways and major A roads that move people, freight and critical services every day. When these routes flood, the consequences ripple far beyond the immediate closure. 

The most exposed individual routes include the A38, where 12% of its total length is considered vulnerable to river flooding, followed by the M45 and M32 at 9% each, and the A58 at 8%. 

The problem extends well beyond the SRN 

Zoom out to the full UK road network, approximately 303,000km including local roads and B-roads and the scale of exposure becomes still more concerning. Ordnance Survey research estimates that 7,564km of road falls within the highest-risk flood boundary category. 

The most vulnerable local authority is North Yorkshire, where 102km of road is exposed to river flooding and a further 49km faces sea flooding risk, the highest figures of any local authority in England. 

Why are so many roads in flood zones? 

As Jo Bradley, Director of Operations UK at Stormwater Shepherds, explained: roads were typically built along valley floors, following flat, fertile land near rivers - a pattern established by the Romans and repeated through centuries of infrastructure development. The consequence is a network whose alignment was decided long before flood risk mapping existed, let alone climate change projections. 

A significant adaptation gap 

The figures on adaptation are striking. National Highways Head of Carbon and Air Quality Angela Halliwell revealed in February 2026 that only 7% of the SRN has been adapted to the climate standards. In the same period, National Highways recorded around 1,800 flood events on the network in a single year. 

Rail faces the same challenges 

The flood risk picture is not confined to roads. Ordnance Survey's research found that 3,003km of rail - 20% of England's rail network - intersects the highest-risk flood boundary for flooding. Thirty-six local authorities face the risk of complete rail isolation, with key commuter lines in Marlow and Henley-on-Thames among those vulnerable to being cut off through river flooding. 

From occasional event to persistent reality 

Flooding on the UK's transport network is no longer an edge case to be managed reactively. It is a systemic risk requiring systemic responses: accurate, forward-looking data, proactive investment prioritisation, and operational tools capable of anticipating flood events before they cause disruption. 

The parliamentary disclosure and Ordnance Survey research together provide a clearer picture than we have previously had of where that risk is concentrated. The question now is whether the pace of response - in adaptation, investment, and planning - can begin to match the pace at which the risk is growing.