River level Chertsey Bourne at Free Prae Road

River levels at this location in the last 5 days

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Key information

• Station name: Free Prae Road
• Station ID: 7220
• River name: Chertsey Bourne
• Typical range: 0.72m to 1.60m
• Highest level on record: 2.63m on 02 January 2003
• Site datum: 10.00mAOD (what does this mean?)

How are river levels measured?

The Environment agency uses a network of monitoring stations across the country. Each one has its own datum - a height in metres fixed relative to mean sea level. This height is expressed as metres above ordnance datum (mAOD). The river levels we provide for each monitoring station are all relative to its site datum.

If we didn't do this, we'd show some very high measurements, which could cause confusion. By using a local site datum, the river levels are easier to understand, especially by users familiar with the data from a particular monitoring station.

A river's height above ordnance datum can be seen by adding the site datum to the river level.

How often are river levels measured?

We use measuring stations like this one to collect water level data, usually once or twice a day. We collect data more frequently when there's a greater risk of flooding. That's why the graph might show a short time lag since the last measurement.

How might river levels affect flood risk?

Typical range

This is the usual range of river levels at this station, based on historical data.

Above typical

This means that flooding is possible because river levels at this station are currently higher than usual.
Many factors can influence the possibility of flooding - river levels are only one indicator. Always check if there's a flood warning in place at a particular location.

Below typical

This means that river levels at this station are currently lower than usual.
Drought or water management measures may be in place. Please check for the latest information on water resources and restrictions in your area.

• View nearby measuring stations

• View the flood information service for England
• Check the long term flood risk for an area in England.

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