Inland waterways: categorisation of waters
Guidance for owners, operators and masters of vessels on inland waters, explaining the classifications and how to apply for categorisation.
Inland water categorisation policy and processes are dealt with by the Navigation Safety Branch (NSB) of Maritime and Coastguard Agency (MCA).
This guide is for commercial vessel operators, and anyone else who needs to know the correct categories of waters. Knowing the categories will affect:
- the type of vessel you can operate
- the safety equipment and crew qualifications you’ll need onboard
What inland waters are
Inland waters are any area of water, such as canals, tidal and non-tidal rivers, lakes, and some estuarial waters, not categorised as ‘sea’.
The UK has over 4,000 miles of inland waterways. They’re not regarded as ‘sea’ for the purposes of most merchant shipping legislation.
How inland waters are classified
Inland waters are classified as one of four categories:
- Category A: narrow rivers and canals where the water is generally less than 1.5 metres deep
- Category B: wider rivers and canals where the water is generally 1.5 metres or more deep, and where the significant wave height couldn’t be expected to be more than 0.6 metres at any time
- Category C: tidal rivers, estuaries and large, deep lakes and lochs where the significant wave height couldn’t be expected to be more than 1.2 metres at any time
- Category D: tidal rivers and estuaries where the significant wave height couldn’t be expected to be more than 2 metres at any time
Water categorisation matters are co-ordinated by the Navigation Safety Branch of MCA.
These categories are defined and listed in MSN 1837.
How to apply for categorisation or re-categorisation of waters
You (as an individual or organisation) can apply for categorisation, or to change an existing categorisation,of a defined area of inland water. You must have an interest in the area requested.
MCA will consider any request for the categorisation of new or for changes in the existing categorisation of areas. The NSB co-ordinates the categorisation of a defined area of water.
Contact your local marine office to get advice about categorisation of a particular stretch of water and making an application.
Your application to your local Marine Office needs to be fully supported with:
- chart of location
- recent sounding charts
- levels of vessel movement
- types of vessel using the area
- physical description of the area
- predominant wind chart for the area
- general rationale to support the application
- supporting letter from the local harbour or navigation authority
- details of significant wave heights (see ‘more about significant wave heights’)
More about significant wave heights
For your application, you must also give evidence showing how the significant wave height has been established.
In each category, a maximum significant wave height has been given. Your evidence needs to show that the wave height does not go above this limit at a representative point (or points) in the area you wish to have categorised or re-categorised.
This evidence could, for example, be based on information taken from a mathematical model of the geographic area. This should be validated by wave height observations from a wave rider buoy, or a seabed pressure sensor.
Maximum significant wave height limits:
- Category B: up to 0.6 metres
- Category C: up to 1.2 metres
- Category D: up to 2.0 metres
MCA will not normally ask for wave data evidence for Category B limits, as long as it’s satisfied that the waves are unlikely to go above 0.6 metres.
The time of year your application covers will also be a factor. For an application for a winter or summer seasonal area, measurements should represent the period of worst weather. For all-year-round applications, measurements should represent the worst winter conditions.
In addition to wave height data you should also consider other factors such as the:
- strength of any tidal stream
- effect of the prevailing wind against the tidal stream which can shorten the sea - giving rise to steeper waves which are more liable to break
- height of banks at the water’s edge and the degree of shelter that may be found in bad weather
- effect of any surrounding high land which may give rise to sudden and unpredictable wind shifts and strengths
- fetch of the wind - especially in long, straight estuaries with a low lying hinterland
- effect of underwater banks on the tidal streams
- effect of shifting underwater sand banks which result in changing navigational channels
- relevant local phenomena, such as a tidal bore
How your application is processed
Send your application and supporting documents to the local Marine Office for the attention of the Surveyor-in-Charge (SIC) or Area Operations Manager (AOM).
The SIC or AOM will consult the District Safety Committee or Small Passenger Ship Steering Group as appropriate.
If they’re content with the application they’ll send their comments or recommendations to the NSB. If not, they’ll ask you for further or clearer information.
The NSB will review the application and submit it to the next bi-annual meeting of the Limits Committee of Focal Point Group 2 (FP2).
FP2 will make recommendations to MCA’s Technical Advisory Group for review, and whether or not to grant approval.
The NSB will send the TAG’s decision to the local marine office. The marine office will then tell you the decision.
See the map and full list of UK navigation authorities on the Association of Inland Navigation Authorities (AINA). It represents the organisations which operate and manage navigable inland waterways in the UK.