Under combined heave and roll motions the keel of ULCSs can hit the seabed
3. In the very shallow water above the Wadden Islands, breaking waves can hit the side of the ship, resulting in a large upward jet of water reaching the containers, which are 20 to 40 m above the surface of the sea. These enormous volumes of water, also called ‘green water’, hit the bottom and the side of the containers at high velocity, which can lead to substantial damage. Complete stacks of containers can also be pushed over like dominoes. A comparison of the locations on the ship model where green water impacts were observed with those of the damaged bays of containers on the MSC Zoe found that green water impacts may have played a role in the loss of the containers.
4. Finally: the hull of the ship was also hit by breaking waves. This can result in vibrations throughout the ship, damaging containers and lashings.
Further investigations necessary To prevent this type of disaster from occurring in the future, it is important to look more closely into the matter and consider other ship types and sizes that sail in this busy area. The same four phenomena will occur for smaller ships, but
16 report
their sensitivity and the limiting weather conditions for safe operations will be different.
Following extensive research and taking into account the annual traffic levels above the Wadden Islands, MARIN advised the Ministry of Infrastructure and Water Management to conduct further investigations into three ship types: ULCSs with lengths of up to 400 m, a shorter and narrower Panamax, nearly 300 m long, and a smaller container feeder with a length of 160 m. The importance of extending the study to the feeder class was confirmed on February 11th 2020, when the 170 m OOCL Rauma lost seven containers while sailing in the same area. “Due to the large array of ship sizes it is essential to take the human factor into consideration. The captain of a feeder shall obviously behave differently than the captain of a ULCS when he gets caught in bad weather,” Bastien emphasises.
MARIN is currently performing studies for both the shallow southerly route directly above the Wadden Islands, as well as the slightly deeper, more northerly route. Based on these results the government can
determine what policy is required. For example, this could range from the Coastguard offering advice to ships in the area to the closure of an entire route under certain conditions.
The report of the Dutch Safety Board, the international report and MARIN’s technical report can be found at www.
onderzoeksraad.nl/en/page/13223/ safe-container-transport-north-of-the- wadden-islands.-lessons-learned.
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