Physical Benchmarks: The Lock Sill (-5.5m CD) is the "doorstep" ships clear to enter. The Dock Bottom (-8.8m CD) is the actual basin floor.

Tidal Extremes: The highest tide recorded at Avonmouth was 15.13m CD (+8.63m mAOD) in 2014. The lowest predicted tides approach -0.24m CD.

Lock Operation: The water level inside is held constant near 12.5m CD (+6m mAOD) by pumps.

Portbury dock lock level is typically maintained at approximately +5.8m to +6.2 mAOD (metres Above Ordnance Datum). 0 mAOD at Portbury is assumed to be 6.5 m above CD.

Live River Data:
• mAOD: Environment Agency (Avonmouth Portbury) or Natural Resources Wales
• CD: Port of Bristol Tide Predictions