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River levels

Request for information – FOI14552


Thank you for your email of 23 May 2015, requesting the following information in accordance with the Freedom of Information Act (FOIA) 2000:

What the river level is it that you use to define the limits of the river.

Likely answers are:

1. No particular level

2. We avoid floods/droughts

3. We aim to use the average river flood 4. We aim to Q50% flow level (flow exceeded 50% of the time)


Under our duty to provide advice and assistance as stipulated in Section 16 of the FOIA, we can provide the following explanation which may assist you in this matter.

The OS MasterMap real-world object catalogue (page 409) PDF states that for non-tidal rivers “The width to be shown is that at normal winter level.” Expanding on this our current large scale capture specification states, "For features represented by Topographic Area features the limits of the water are captured in the location that represents their normal winter level, which can normally be determined as the point where vegetation ceases to grow."

Please be aware that our current capture specification also includes minimum survey distance rules for some types of features: The OS MasterMap Topography Layer user guide (page 36) PDF states that “Rivers, streams and drains are shown at their true scale width. A single line is normally used where their width is less than 1.0 m in urban areas and 2.0 m in rural, mountain and moorland areas.”

I hope the above is of use to you.

Internal review

Your enquiry has been processed according to the Freedom of Information Act (FOIA) 2000. If you are unhappy with our response, you may request an internal review with our FOI Internal Review Officer, by contacting them as follows:

FOI Internal Review Officer
Customer Service Centre
Ordnance Survey
Adanac Drive
SO16 0AS

Email: foi@os.uk

Please include the reference number above. You may request an internal review where you believe Ordnance Survey has:

  • Failed to respond to your request within the time limits (normally 20 working days)
  • Failed to tell you whether or not we hold the information
  • Failed to provide the information you have requested
  • Failed to explain the reasons for refusing a request
  • Failed to correctly apply an exemption or exception

The FOI Internal Review Officer will not have been involved in the original decision. They will conduct an independent internal review and will inform you of the outcome of the review normally within 20 working days, but exceptionally within 40 working days, in line with the Information Commissioner’s guidance.

The FOI Internal Review Officer will either: uphold the original decision, provide an additional explanation of the exemption/s applied or release further information, if it is considered appropriate to do so.

Appeal to Information Commissioner's Office (ICO)
If, following the outcome of the internal review you remain unhappy with our response, you may raise an appeal with the Information Commissioner’s Office at:

The Case Reception Unit
Customer Service Team
The Information Commissioner’s Office
Wycliffe House
Water Lane

Email: mail@ico.gsi.gov.uk

Telephone helpline: 0303 123 1113 or 01625 545745 for advice, Monday to Friday.

In the meantime, should you need to contact Ordnance Survey regarding your request at any time, please quote the allocated reference number FOI14540 in any correspondence.

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