Tauchprospektion an Flensburgs mittelalterlicher Hafensperre
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In late August I participated in an underwater archaeological survey, carried out between 29.08. and 1.09.2011 in Flensburg Fjord. The survey concentrated on the eastern extent of a linear pile structure believed to be a high medieval sea-barrier. It had been discovered during dredging works at the western side of the harbour entrance, of which some samples were C14 wiggle-match dated to around 1150-1160, thus the earliest archaeological remains which can be associated with Flensburg’s port.
Although it was not before the year 1284 that Flensburg received its municipal charter from King Eric V of Denmark, it must have been deemed important enough already in the mid 12th-century to be protected from seaborne attacks. If this dating is substantiated by a set of further samples taken during this campaign, the pile structure will become ever more significant, as it sheds light on the era of the Wendish Crusades. Similar sea-barriers were built throughout the Danish realm in this period, like in the bay of Vordingborg, were King Valdemar I gathered his fleet for his Wendish campaigns. A fleet anchoring in a relatively small bay or fjord would have been an easy target, for enemies could have easily wreaked havoc with fire-ships to the entrapped vessels. A sea-barrier would have added to the protection of an idle fleet at anchor. While Denmark emerged victorius from the Danish-Wendish struggle for maritime supremacy in the western Baltic Sea and conquered the island of Rügen in 1168, the preceding period was marked by frequent seaborne Wendish attacks on Danish coasts. Despite of the leding – a Scandinavian levy for coastal defence – entire coastal regions became untenatable. The Danish chronicler Saxo Grammaticus describes an event in which a pirate – as Wends were generically referred to – was intercepted:
Ubi quum munditiarum gratia balneis uteretur, animaduertit cuiusdam nauis e septentrione uenientis mentionem foris stantium collocutione crebrescere. Quam ut piraticam intellexit, semiloto corpore uestem poposcit nauemque, quam in porto uelatam dimiserat, remigibus lituo contractis conscensam in altum dirigere curauit.(Friis-Jensen & Zeeberg 2005, 428)
Here he had gone to the bath when he noticed that people were talking outside more loudly about an approaching ship from the north. He soon realized that it had to be a pirate ship, and without finishing washing he called for his clothes, jumped on board the ship, which he had left in the harbor under sail, summoned the crew with a horn signal and set sailrougly translated
The finding of this sea-barrier raises the question whether the Flensburg region – despite being located further inland – was also threatened by Wendish seaborne attacks or if it was an important anchorage for a leding fleet?
The survey on the eastern side yielded fewer and more scattered remains than the western side. From the diver’s perspective, at least, no clear pattern was perceivable. This might be owed to the likely circumstance that the structure is buried deeper in the sediments, but may also point to some sort of inlet. The survey was supervised by Erich Halbwidl and Dr. Ruth Blankenfeld and carried out by AMLA-divers under the auspices of Dr. Martin Segschneider of the State Archaeology Department of Schleswig-Holstein.