Highways·California Department of Transportation (Caltrans)·—·California Department of Transportation (Caltrans)

Caltrans Gleason Beach Roadway Realignment

Highway 1 relocated 150m inland · 476m bridge over coastal gully · habitat restoration

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Key insight

Sometimes the most cost-effective adaptation is strategic retreat — permanently moving infrastructure inland is a one-time capital cost versus indefinite maintenance and emergency repair costs as a coastal road erodes.

Transferability to UK: MediumRoad realignment away from eroding coastlines is applicable to UK coastal highway routes (A-roads and B-roads) where continued maintenance of existing alignment

A 1.5km section of California's iconic Highway 1 was permanently realigned 150m inland at Gleason Beach in Sonoma County, where continuing coastal erosion had left the road at imminent risk of collapse into the Pacific Ocean. A new 476m bridge spans the coastal gully. The project included habitat restoration of the vacated highway alignment, converting former pavement to coastal habitat.

Climate drivers

Coastal floodingStorms and high winds

Impacts

→Coastal erosion→Road damage→Highway closure

Adaptation measures

  • Highway realignment (150m inland)
  • New bridge construction (476m)
  • Habitat restoration
  • Nature-based coastal management

Assets affected

Road pavementBridgesCoastal highway

Investment

Not reported in data available

Band: £10m–£100m (estimated)

Delivery period

—

  • Studies indicate that the historical erosion rate in the Gleason Beach area is approximately one foot per year, a rate that could increase to 1.5 feet (0.5 metres) per year by 2050 and 4.6 feet (1.4 metres) per year by 2100 due to rising sea levels .
  • The impact of this climate hazard is substantial. Coastal erosion has already led to the collapse of several homes along the cliffs and continues to threaten existing structures. The erosion also poses a significant risk to SR 1, a vital transportation route for residents, tourists, and commerce .

Ref: ID_34 · California Department of Transportation (Caltrans) · Curated & verified by HIVE

Transferability to UK: Medium

Road realignment away from eroding coastlines is applicable to UK coastal highway routes (A-roads and B-roads) where continued maintenance of existing alignments becomes uneconomic due to accelerating coastal erosion. The bridge-over-gully approach is transferable to coastal landslide zones.

UK contexts

UK coastal A-roads threatened by erosionSW England coastal road corridorsYorkshire and Scottish coastal transport routes

Applicable to UK coastal

Transfer to other sectors (AI)