Dynamic Keel Clearance

the key to better accessibility to the Scheldt ports

The current generations of container ships are increasingly larger and run deeper in the water. The Joint Nautical Authority calculates the time windows within which these ships can safely and smoothly reach the River Scheldt ports. Which is why we are developing a new calculation method: dynamic keel clearance. 

Read here:

From a static approach…

The keel clearance is the distance between the bottom of a ship and the bottom of the waterway. The Joint Nautical Authority calculates the tidal windows (also called tidal gates) within which a ship has sufficient keel clearance to sail safely and smoothly. Tidal windows differ from day to day.

Up until now, the calculation was based on three factors:

  • the bottom of the waterway including barriers, such as sandbars 
  • the expected water levels based on the tide and weather
  • fixed keel clearance percentages

The fixed keel clearance percentages are:

  • 15% at sea
  • 12.5% at the river
  • 10% at the ports

… to a dynamic approach

We are currently developing a dynamic calculation for keel clearance. Besides the bottom of the waterway and the expected water level, it also allows for other factors, such as:

  • the expected water level and the actual water level
  • the wind, waves, and swell affecting the ship's movements
  • the ship’s exact route
  • the ship characteristics, stability of the ship, and draft model (the squat)

Thanks to dynamic keel clearance, we can calculate how much keel clearance a specific vessel has at a specific moment at a specific location. This precise calculation allows the necessary safety margin to be determined for each location. 

This allows us to improve safety and increase accessibility to the River Scheldt ports.


What will change for the ships and the ports?

Dynamic keel clearance makes it both safer and smoother for shipping traffic in the area.

Improved accessibility to the ports

Preliminary studies show that the tidal window is widening in 95% of cases. This will improve accessibility to the ports:

  • ships with larger draughts can sail in and out depending on the circumstances
  • more ships can sail in on the same tide
  • chain planning becomes more flexible thanks to longer tidal windows

Safer shipping

The tidal window is shorter for safety reasons in 5% of cases. For example, this is the case in bad weather or when the waves come from a particular direction. 

Ships will only be allowed to pass if the chance of hitting the bottom is less than 1 in 10,000.

Introduction of dynamic keel clearance

Dynamic keel clearance is in the test phase. We fine-tune the method precisely by carrying out different measurements, analyses and tests, and test runs in recent years. The software is currently being validated by the Flanders Hydraulics Research institute in Antwerp.  The results are expected at the end of 2020. 

If everything goes as planned, dynamic keel clearance will be phased in starting at the end of 2020.