The 2023 Baltic Sea storm surge: The night the Baltic Sea ravaged the harbours

Three years ago, sailors along the German Baltic coast experienced a night that many of them have not forgotten to this day. On 20 October 2023, an exceptionally violent easterly storm caused water levels to rise to historic heights. Waves crashed over harbour jetties, jetties snapped, and yachts broke free and sank. When the water receded the following morning, numerous harbours were left with scenes of unprecedented destruction. According to estimates at the time, more than 150 yachts had sunk, hundreds were damaged and many were beyond saving. Regionally, it was the worst Baltic Sea storm surge since the disaster of 1872.

The warnings ahead of 20 October

It came as no surprise. Days before 20 October, weather models had already indicated a dangerous development over the Baltic Sea. On Monday, 16 October, initial forecasts from the Federal Maritime and Hydrographic Agency (BSH) suggested unusually high water levels in the western Baltic Sea. The following Tuesday, the BSH issued its first storm surge warning. In the days that followed, the forecasts were repeatedly revised upwards. Meteorologists warned of an exceptional combination of strong easterly winds, high water levels and heavy seas.

The cause lay in a particular large-scale weather pattern. Storm ‘Wolfgang’ – also known internationally in connection with Storm ‘Babet’ – moved from the Atlantic across the Bay of Biscay towards Great Britain. At the same time, a strong, virtually stationary high-pressure system called ‘Wiebke’ had built up over Scandinavia. A marked difference in air pressure developed between the two pressure systems. A persistent easterly flow took hold over the Baltic Sea, which lasted for several days and strengthened considerably.

Why the water built up in the western Baltic Sea

This wind direction was particularly dangerous for the western Baltic Sea. Unlike in the North Sea, the astronomical tidal range plays only a minor role here. Water levels are largely determined by wind, air pressure and large-scale movements of water masses. The easterly wind, which persisted for days, drove water into the western Baltic Sea bays. The particular geometry of the shallow western Baltic Sea and its fjords exacerbated the build-up of water. In addition, already elevated initial water levels and natural oscillations of the Baltic Sea water – known as seiches – influenced the situation. The water continued to build up further and further in the bays and fjords.

Another crucial factor was the duration of the event. What was unfolding was not merely a brief storm surge with a temporary rise in water levels. Water levels on the Schleswig-Holstein Baltic Sea coast had been rising since 18 October, and on 19 October the storm surge threshold of one metre above mean sea level was exceeded in many places. On Friday, 20 October, the wind and water finally reached a critical combination. Waves struck sections of the coast that had already been under the influence of unusually high water levels for many hours.

According to official measurements, wind speeds of around 20 metres per second and gusts of approximately 26 metres per second were recorded at the Kiel lighthouse, equivalent to around 94 kilometres per hour. Even stronger gusts were reported in some areas. The impact of these figures on the harbours was particularly evident where the easterly wind was able to build up unhindered across a large expanse of open water. The high water level reduced the protective effect of the existing breakwaters, whilst the heavy seas surged into the harbour basins with great force.

Additional mooring lines and vulnerable mooring berths

By Friday morning, the situation was already tense. Many boat owners had laid out extra lines, reinforced their fenders, secured their furling sails particularly well, or tried to move their yachts to more sheltered moorings. Others had managed to have their boats hauled out of the water just in time. However, crane slots were in short supply, and harbours in many places were still unusually full. September had been warm, and many owners had extended the season. As the storm surge drew nearer, there were therefore still many yachts in the water that might otherwise have already been in winter storage at this time of year.

The danger was underestimated by some. Boats in the harbours were still secured with simple mooring lines, roller-furling sails were hoisted, and yachts were moored in berths that presented a large surface area to the expected wind direction. The stern lines attached to the dolens were particularly critical. During extreme high tides, conventional rope loops could slip over the tops of the piles. The vessels would then lose their hold, even though the mooring lines themselves had not snapped. The length of the lines also became a problem: when the water level rose by more than two metres, the usual reserve length of the mooring lines was in some cases insufficient.

Webinar tip: You can find further practical information on lead handling, shock absorbers and abrasion protection in the Webinar on safe mooring. The third part of the series looks in more detail at securing the mooring.

Eyewitnesses recount the hours leading up to the disaster

The well-known sailor, author and DIY boatbuilder Jan von der Bank later described just how dramatic the events had been in a detailed account of his experiences for YACHT described. His self-built BM 31 ‘Rémy’ was moored in the Olympic Harbour at Kiel-Schilksee. As early as the night before Friday, he had driven once more from his home to the harbour, some 50 kilometres away, to secure the boat further. He reinforced the stern lines, checked the securing of the laid-down mast and also attended to several neighbouring boats that had not been adequately secured. When he returned to Schilksee on Friday, parts of the jetties were already too unsafe to walk on.

As the afternoon wore on, it became increasingly clear that a disaster was looming. Whilst the water level continued to rise, the waves were already breaking over the harbour piers. Work on the jetties had become life-threatening. Anyone still trying to secure mooring lines or catch a yacht that had broken free had to expect to be swept into the water themselves. From the quay, it was reported how the harbour masters finally warned people not to enter the mooring areas alone. Later, the term ‘danger to life’ was explicitly used.

YACHT editors, too witnessed the development first-hand on board their own boats. In Strande, Lasse Johannsen had, as a precaution, moved his Vindö 40 to a more sheltered mooring. He laid out additional mooring lines and secured the boat to the posts to prevent it from sliding up. On Friday evening, he decided to leave the boat. The jetties were already well submerged, and the breakwaters were being washed over. In his judgement, staying on board any longer would have been too dangerous.

Other sailors spent the night on their boats. In Sønderborg, Fridtjof Gunkel was beset by a constant stream of problems. Mooring lines slipped, parts of the jetties broke, and flotsam was being pushed against the boat. At times, a motorboat that had broken free from the windward side threatened to drift into his yacht. Gunkel secured his dinghy to the stern for extra protection and checked the remaining lines. In the end, all he could do was trust that the remaining connections would withstand the strain.

Between 6 pm and 10 pm, the situation escalates

The critical hours came on Friday evening. Between around 6 pm and 10 pm, the situation escalated in several harbours. The water reached its highest levels, whilst the storm continued to blow with great force from the east. In Schilksee, yachts began to break free from their moorings. Some drifted into neighbouring vessels, whilst others crashed against jetties and dolphins. Wherever a boat lost its mooring, the neighbouring yachts were suddenly at risk too. The first collisions led to further mooring lines being torn loose and damage to the jetty facilities. A chain reaction set in.

Jan von der Bank later described the hours between 6 pm and 10 pm as “an apocalypse and one of the worst things I’ve ever experienced in connection with sailing”. His “Rémy” came through the night with relatively little damage. Many other boats were less fortunate.

Schilksee: 48 sunken ships

The situation at the Olympic Harbour in Kiel-Schilksee proved particularly devastating. The harbour, known worldwide as the venue for the 1972 Olympic sailing competitions and as the centre of Kiel Week, became one of the main theatres of the disaster. The stone breakwaters, which normally protect the boats from the swell, were washed over by the waves. The harbour basins behind them were at times left virtually unprotected against the heavy seas. Mooring lines snapped or came loose, jetties were damaged and yachts were pressed against the stone quays. In some cases, boats were hurled out of the water onto the harbour grounds.

According to Sporthafen Kiel GmbH, 48 boats sank in Schilksee alone. Others were left severely damaged, stranded on broken jetties or had been thrown against the shore defences. The waves had eroded the breakwater, and parts of the harbour infrastructure were destroyed. When the full extent of the damage became apparent on Saturday morning, the scene was one that many observers could scarcely believe: sunken boats, toppled masts, broken jetties and debris everywhere. One eyewitness described the situation in these words: “Schilksee looks like a battlefield.”

Damaged jetties in Damp, Maasholm and Schleswig

The situation at Damp Marina on Eckernförde Bay was no less dramatic. The marina, which faces east, was hit particularly hard by the floodwaters and the heavy swell. The waves surged over the protective defences, destroying jetties and damaging numerous vessels. Of the 100 or so yachts which, according to reports at the time, were still in the harbour, around 35 were severely damaged, sank or were washed ashore. The mooring facility itself was subsequently only usable in small sections. Where there had previously been 365 berths, initially only around 110 remained available for limited emergency operations.

Maasholm, at the mouth of the Schlei, was also severely devastated. The headland and the jetty were no longer able to withstand the force of the water. Parts of the jetty head were washed away, trees were uprooted and jetties were damaged. Around 20 boats sank. At the Wiking Marina in Schleswig, situated well inland from the Schlei and, at first glance, better protected, almost all of the 150 or so boats moored there were affected. According to the harbour’s assessment at the time, only around ten are said to have remained undamaged. The breakwater was washed over, and the marina was severely damaged.

The damage extended far beyond these three ports, which were particularly hard hit. At Wassersleben Marina on the Flensburg Fjord, a good dozen boats sank. In Heiligenhafen, up to 15 sunken vessels were reported; jetties collapsed, and the coastguard had to rescue sailors after a jetty connection to the mainland was severed. In Großenbrode, boats sank or were washed onto jetties. On Rügen, too, in Lauterbach and Stahlbrode, the storm damaged harbour facilities and watercraft. It became apparent that, how differently the event itself affected different parts of a district. Some ports suffered enormous damage, whilst facilities just a few nautical miles away, in a more favourable location, got off relatively lightly.

Denmark’s ports are also being hit hard

The storm surge also hit the Danish coast. The southern islands and the harbours on the east coast were particularly hard hit. In Mommark on Als, the outer jetty, jetties and parts of the harbour infrastructure were destroyed; the harbour restaurant was severely damaged and sections of the adjacent campsite were washed away. In Sønderborg, according to initial reports, several yachts sank, whilst others were pushed onto damaged jetties or drifted away. In Hesnæs on Falster, the waves caused such extensive damage that the harbour was initially virtually destroyed. Aabenraa also reported exceptionally high water levels. The Danish Meteorological Institute classified the event as the most severe storm surge in 119 years.

It wasn’t just the marinas that were affected. In Flensburg, large parts of the harbour areas were under water. In Eckernförde, roads, buildings and waterfront facilities were flooded. Along the Schleswig-Holstein Baltic Sea coast, regional dykes burst, including in the Schlei area near Arnis. Beaches were washed away, cliffs eroded, and campsites and promenades were damaged. The pier in Dahme and the Kiel lighthouse also sustained considerable damage. The storm also claimed one life: on Fehmarn, a 33-year-old woman died on Friday afternoon when a falling tree struck her car.

Water levels during the 2023 Baltic Sea storm surge

The official water level measurements highlight the extraordinary scale of the event. The Schleswig-Holstein Coastal Protection Report states that the water level at the Schleswig gauge reached a peak of 2.29 metres above mean sea level. This corresponds to 2.23 metres above the long-term average water level used for the analysis. In Flensburg, the water level reached 2.22 metres above this average, and in Eckernförde 2.10 metres. For large parts of the northern Schleswig-Holstein Baltic Sea coast, this was the highest storm surge since 1872. At that time, a far more devastating Baltic Sea storm surge had claimed the lives of numerous people.

What was exceptional about 2023 was not only the height of the water, but also its duration. According to subsequent analyses by the BSH, water levels of at least one metre above the usual level were recorded in Flensburg for more than 50 hours throughout the event. Particularly high water levels also persisted for many hours. Coastal defences, harbour jetties and jetties were consequently subjected to prolonged strain. Where breaking waves struck the structures unimpeded, the damage was exacerbated.

It was not until the night leading into Saturday that the storm abated significantly. Water levels began to fall again; in many places, it took until mid-morning or midday before they had dropped below the storm surge level. For many boat owners, this marked the start of the second phase of the disaster. It was now clear which vessels were still afloat, which had run aground and which had been washed ashore by the waves.

The initial assessment of the damage and the consequences for owners

As early as the morning of 21 October, they met the first reports of damage with yacht insurers. The Hamburg-based insurance broker Pantaenius initially reported 50 total losses, but soon anticipated more than 200 economic or actual total losses. The scale of the damage was almost impossible to gauge in the first few days. Later estimates from the industry suggested that around 400 vessels had been severely affected, including around 150 that had sunk.

For many owners, the loss was particularly bitter. Some had maintained and restored their boats over decades, whilst others had only recently invested substantial sums in repairs and equipment. Even yachts with comparatively minor external damage could harbour serious hidden damage. Where hulls had struck dolens or stone edges, leaks developed. Cleats were torn from decks, windows were smashed in and parts of the rigging were destroyed. Flooded vessels lost their electrical systems, engines, upholstery, interior fittings and personal equipment.

The rescue operation is turning into a major logistical operation

The salvage of the sunken and stranded yachts turned into a major logistical operation. Salvage companies, divers, boat builders, insurers and port operators had to coordinate their efforts. In the destroyed harbour facilities, regular crane sites were often inaccessible, some jetties were no longer passable, and sunken boats were wedged beneath the rubble. Salvage vessels equipped with floating cranes had to be deployed. Before a boat could be lifted, underwater surveys were often required to assess the condition of the hull and identify any potential obstacles.

In Kiel-Schilksee The YACHT accompanied the crew of the salvage vessel ‘Noorcat’ at work. One of the most impressive salvage operations involved the Farr 40 ‘Farr-Laessig’.

Support also came from divers from the German Navy. Using sonar and by diving, they surveyed the underwater areas, searched for obstacles and marked hazardous spots. At the same time, pumps, buoys, tugs and mobile cranes were deployed all along the coast. Not every vessel could be salvaged immediately. In some cases, access routes first had to be cleared or other vessels secured to make salvage operations possible at all.

Recovery time limits and insurance matters

The time pressure was also considerable. The Kiel Port Authority ordered a few days after the storm…that damaged and sunken vessels, including their parts, should be salvaged by specialist firms by 31 October 2023 at the latest. The main reasons for this were, in particular, the risks to the environment and to shipping. Given the extent of the damage, the deadline proved almost impossible to meet and was subsequently extended. Salvage teams were still working in Schilksee as late as early November, whilst work in Maasholm and Damp was already at a more advanced stage.

At the same time, the insurers began assessing the damage. Experts had to decide which yachts could be repaired and which should be classified as a total economic loss. Both the salvage costs and the repairs could run to considerable sums. For owners with suitable comprehensive insurance, Storm damage and recovery were generally covered by the agreed terms and conditions. Those who, on the other hand, only had third-party liability insurance might, under certain circumstances, have had to expect to bear substantial costs themselves. Recovery operations ordered by the authorities also raised complex issues under insurance law.

Between residual value, disposal and reconstruction

Dealing with the total losses led to further developments. Yachts that had sustained severe damage in storm surges were increasingly appearing on second-hand boat websites. Some owners hoped to at least recoup some of the residual value. Other boats went to specialist buyers or shipyards that intended to restore them at considerable expense. However, for many wrecks, the only option was to scrap them. Even this proved to be a complex and costly process, as the boats had to be transported, dismantled and the various materials disposed of in accordance with regulations.

However, not every owner was willing to part with their damaged vessel. The story of the Bothmer family was a remarkable one from Kiel. Their Hanseat 68 ‘Persante’ had sunk in Schilksee and had been submerged for seven days. Four generations of the family had learnt to sail on this boat. With an insured value of 30,000 euros, the yacht was classified as an economic total loss. Nevertheless, the family decided to save it. The boat was salvaged, cleaned, dried out and repaired at a shipyard. For the family, the “Persante” was more than just a damaged piece of equipment.

Ports need to modernise their infrastructure

For the port operators, too, a huge task lay ahead following the salvage operation. Entire jetty systems had to be replaced, new groynes driven into the seabed, jetties repaired, electricity and water pipes replaced, and the harbour basin cleared of sunken debris. As many hydraulic engineering firms were already working at full capacity and sourcing materials took time, the reconstruction became a race against the 2024 sailing season.

In Kiel-Schilksee, key parts of the facility were restored relatively quickly. As early as the winter, tradespeople were already working on new jetties and substructures. The damaged breakwater was restored to its former height. Nevertheless, the question remained as to whether the existing protective structures would be sufficient to withstand comparable extreme events. A significantly higher pier could not simply have been achieved by adding another storey; according to the port operator’s assessment, it would have required a complex new construction costing millions.

Elsewhere, the restoration proved considerably more difficult. The Damp marina, in particular, turned out to be a long-term restoration project. Even years after the storm surge, only part of the original mooring capacity is available there. Disputes over funding, responsibilities and the necessary construction work delayed the restoration. In the spring of 2026 YACHT reported on extensive dredging and backfilling work, whilst the marina, with around 110 berths, remained open only on a limited basis. This shows just how far the economic and infrastructural consequences of that stormy night extend beyond October 2023 itself.

Lessons for sailors and harbour operators

For the sailors themselves, the storm surge was also a harrowing experience. Many had previously found it hard to believe that a yacht moored in the harbour could be completely destroyed in the forecast weather conditions. The events showed that Common mooring techniques in extreme water levels can reach their limits, and that a supposedly sheltered mooring does not offer absolute safety. At the same time, it became clear just how dangerous it can be when owners try to save their boat right up to the last moment. The decision to leave the boat and the jetties in good time may be more important than saving one’s property.

Three years after the flood of the century, the images are still striking. The yachts piled on top of one another in Schilksee, the destroyed harbour jetties in Damp and Maasholm, the damaged sailing boats on the Flensburg Fjord and the immense efforts of the salvage teams bear witness to a natural disaster the likes of which many water sports enthusiasts on the Baltic Sea had never experienced before. Anyone who looks back at the reports and images from that time can see how a forecast weather system turned into a disaster with far-reaching consequences within the space of a few days.

Book recommendation

Weather at sea explains how different weather patterns develop and shows where sailors can obtain reliable weather information. The book covers low- and high-pressure systems, local and regional weather events, as well as sea states and ocean currents. Clear diagrams and explanations on meteorological trip planning help readers to better understand weather developments and their significance for sailing.

What was your experience during the 2023 Baltic Sea storm surge, and what has changed at your mooring since then? Please share your thoughts in the comments.