In the autumn of 2012, a unique archaeological discovery was made in the middle of the IJssel river, across from the Nieuwe Buitenhaven marina near Kampen. During the preparatory work to lower the summer bed of the lower IJssel, the builders stumbled across the wreck of a 15th-century cog.
The ship was 20 meters long and 8 meters abeam, and was well preserved at the bottom of the river. It tells us much about Kampen’s rich Hanseatic history. In order to dredge the river to improve water safety and prevent risks to passing shipping, the cog will be carefully excavated and salvaged in 2015.

Common ships

The cog was a ship that was typically used to carry trade between the Low Countries and the northern regions around the Baltic sea during the Middle Ages. It was designed to sail on rivers and the open sea in order to trade with distant cities. The main cargo carried by the cog was grain and salt. The discovery near Kampen is especially unique, because the wreck is complete and two smaller boats were found in the immediate vicinity: a punt boat and an aak. These were the main types of ships that sailed the IJssel during the peak period of the Hanseatic League.

Hanseatic Kampen

The Hanseatic League was an alliance of trading cities in Northern Europe during the Middle Ages. Their goal was to work together to protect and expand their trade routes. For Kampen the IJssel river delta played a crucial role. It was in the city’s interest to keep the river clear as a shipping channel.

Medieval water management

The archaeological research that has been conducted on the three ships so far indicates that they carried no cargo on board. This may be evidence that the cog was sunk intentionally, probably to block or narrow one of the channels in the IJssel delta in order to protect the harbour against the current. It may have been necessary to sink the cog due to the silting up of the IJssel, which obstructed the harbour and limited access to Kampen. In that context, the intentional sinking of the ships in the IJssel is an example of Medieval water management.

Careful salvage operation

After thorough discussions with the Province of Overijssel, the City of Kampen and the Cultural Heritage Agency, Rijkswaterstaat  decided to salvage the 15th-century cog to dredge the summer bed of the IJssel in order to improve water safety and navigation. The salvage operation took several months. First, the exact location of the wrecks had to be identified using sonar. Next, a screen had to be installed upstream to allow the divers to work safely. Then the aak and the punt boat were uncovered using ‘vacuum cleaners’, after which they were lifted above water using a crane. Only then the cog itself could be freed from the bottom, reinforced with a steel construction and then lifted out of the water. Finally, the wrecks were kept wet and transported to the city of Lelystad for further research.

Water safety and navigation

For this project, leaving the ships where they were found was not an option. The extra stone barrier that would have had to be installed to protect the wrecks would pose an obstacle to shipping. From the perspective of water safety and navigation, and to allow everyone to learn about the past, it was therefore decided to remove the cog and other two ships from their original location.

Room for the River IJsseldelta

The wreck of the cog was discovered during a sonar survey of the river bottom between the cities of Zwolle and Kampen conducted by the Room for the River lower IJssel summer bed dredging project. The project was carried out in combination with the realisation of the Reevediep, a branch of the IJssel that empties in the Drontermeer (lake), under the name Room for the River IJsseldelta. The measures protect the area from Zwolle to Kampen from future IJssel river flooding.


The excavation and salvage of the 20-meter long cog from the bottom of the IJssel near Kampen was a unique operation. To archaeologists, the discovery was a world-class find; for shipping and local residents, the excavation of the wreck - and the lowering of the river bed - has helped improve water safety.



  • archaeological research
  • excavation and salvage of the cog, aak and punt boat



  • improving water safety and navigation