Rivers: For bridges on rivers, the vertical clearance is usually given in relation to the ‘Mean High Water’ (MHW). This means there is usually more room at high water, as MHW rarely occurs.
Canals: As the water on canals is less subject to water level differences, the clearance heights on canals are often more accurate than on rivers. However, besides bridges on canals we often also look at the maximum permitted dimensions for that particular waterway and what the Department of Public Works and our users tell us.
Depths:
Rivers: Depths are usually given relative to the ‘Mean Low Water’ (MLW). For the Wadden, coastline and Scheldt, we use a different reference, namely LAT.
Channels: As with clearance heights, depths are often determined by the maximum permitted dimensions.
Current water levels:
Green icons: The green icons for water levels are up-to-date, with a margin of about 50 minutes.
Sailing at low water:
Least sounded depths: At low water on major rivers, it is important to take the MGD into account. You can find it here (in Dutch).
Commercial shipping: Commercial vessels often sail in the middle of the channel at low water and adjust their draught accordingly.
Classifications:
BRTN and CEMT: Almost all waterways in the Netherlands have a classification (BRTN for pleasure craft, CEMT for commercial shipping). These classifications determine the maximum dimensions allowed.
Guaranteed dimensions: Although there is sometimes more space, these classifications guarantee that you can sail safely with a particular vessel.
Learn more
Calculations: We are working to display Rijkswaterstaat’s calculations for clearance heights more clearly. in the app. For examples of how Rijkswaterstaat does this, see:
