BOS and BES closure strategy
As soon as the water level at Rotterdam, Dordrecht or Spijkenisse exceeds the "closure mark", the BOS initiates action. If the level is too high at Spijkenisse only, it will be sufficient to close the Hartel Barrier. If dangerous water levels are also noted at Rotterdam or Dordrecht, however, the BOS examines whether the closure of just the Hartel Barrier will be sufficient to reduce the water level. If not, it will then also close the New Waterway Storm Surge Barrier.A trial closure takes place once a year, in consultation needless to say with the Rotterdam Municipal Port Authority. The meteorological conditions need to be such that a closure does not have any adverse effects on the barrier itself.