Sylt - Geography

Geography

With 99.14 km², Sylt is the fourth-largest German island and the largest German North Sea island. Sylt is situated at 9 to 16 km off the mainland, being connected there by the Hindenburgdamm. Southeast of Sylt the islands Föhr and Amrum are located, to the north lies the Danish island Rømø. The island of Sylt extends for 38 km in a north-south direction and on its northern peak at Königshafen is only 320 m wide. Its widest distance, from the town of Westerland in the west to the eastern Nössespitze near Morsum, measures 12.6 km. On the western and northwestern shore a 40 km sand beach is located, east of Sylt the Wadden Sea is situated, which belongs to the Schleswig-Holstein Wadden Sea National Park and mostly falls dry during low tide.

The island's shape has constantly shifted over time, a process which is still ongoing today. The northern and southern spits of Sylt are exclusively made up of unfertile sand deposits, while the central part with the municipalities of Westerland, Wenningstedt-Braderup and Sylt-Ost consists of a geestland core, which becomes apparent in the form of the Red Cliff of Wenningstedt. The geestland facing the Wadden Sea gradually turns into fertile marshland around Sylt-Ost. Today sources show that Sylt has only been an island since the Grote Mandrenke flood of 1362. The so called Uwe-Düne (Uwe Dune) is the island's highest elevation with 52.5 m above sea level.

On Sylt a marine climate influenced by the Gulf stream is predominant. With an average of 2 °C, winter months are slightly milder than on the mainland, summer months though with a median of 17 °C are somewhat cooler, despite a longer sunshine period on Sylt. The annual average sunshine period of Sylt is 4.4 hours per day. It is due to the low relief of the shoreline that Sylt had a total of 1899 hours of sunshine in 2005, 180 hours above the German average. Clouds cannot accumulate as quickly and are generally scattered by the constant westerly or northwesterly winds.

The annual mean temperature is 8.5 °C. The annually averaged wind speed measures 6.7 m/s, predominantly from western directions. The annual rainfall amounts to about 650 millimetres. Since 1937 weather data are collected at Deutscher Wetterdienst's northernmost station on a dune near List, which has meanwhile become automated. A number of commercial meteorological services like Meteomedia AG operate stations in List too.

The island in its current form has only existed for about 400 years. Like the mainland geestland, it was formed of moraines from the older ice ages, thus being made up of a till core, which is now apparent in the island's west and centre by the cliff, dunes and beach. This sandy core began to erode as it was exposed to a strong current along the island's steep basement when the sea level rose 8000 years ago. During the process, sediments were accumulated north and south of the island. The west coast, which was originally situated 10 km off today's shore, was thus gradually moved eastward, while at the same time the isle began to extend to the north and south. After the ice ages, marshland began to form around this geestland core.

In 1141, Sylt is recorded as an island, yet before the Grote Mandrenke flood it belonged to a landscape cut by tidal creeks and at least during low tide it could be reached by foot. Only after this flood, the creation of a spit from sediments began to form the current characteristical shape of Sylt. Thereby mainly the northern and southern edges of Sylt were and still are the subject of great change. E.g. Listland was separated from the rest of the island in the 14th century and from the later 17th century on, the Königshafen (King's Harbour) began to silt up as the "elbow" spit began to form.

In addition to the constant loss of land, the inhabitants during the Little Ice Age were strained by sand drift. Dunes shifting to the east threatened settlements and arable land and had to be stopped by the planting of marram grass in the 18th century. Consequently though, material breaking off the island was increasingly washed away and the island's substance continued to decrease.

Record of the annual land loss exist since 1870. According to them, Sylt lost an annual 0.4 m of land in the north and 0.7 m in the south from 1870 to 1951. From 1951 to 1984, the ratio increased while to 0.9 and 1.4 m respectively, while shorelines at the island's very edges at Hörnum and List are even more affected.

Severe storm surges of the last decades have repeatedly endagered Sylt to the edge of breaking in two, e.g. Hörnum was temporarily cut off the island in 1962. Part of the island near Rantum which is only 500m wide is especially threatened.

Measures of protection against the continuous erosion date back to the early 19th century when groynes of wooden poles were constructed. Those were built rectangular into the sea from the coast line. Later they were replaced by metal and eventually by armoured concrete groynes. The constructions did not have the desired effect though to stop the erosion caused by crossways currents. "Leeward erosion", i.e. erosion on the downwind side of the groynes prevented sustainable accumulation of sand.

In the 1960s it was tried to break the power of the sea by installing tetrapods along the groyne bases or by putting them into the sea like groynes. The four-fingered structures, built in France, were too heavy for Sylt's beaches with tons of weight and were equally unable to prevent erosion. Therefore they were removed from the Hörnum west beach in 2005.

Since the early 1970s the only effective means so far has been flushing sand onto the shore. Dredging vessels are used to pump a mixture of sand and water to a beach where it is spread by bulldozers. Thus storm floods will only erase the artificial storage of sand, while the shoreline proper remains intact and erosion is slowed down. This procedure causes considerable costs. The required budget of an annual €10 million is currently provided by federal German, Schleswig-Holstein state and EU funds. Since 1972 an estimated 35.5 million cubic metres of sand have been flushed ashore and dumped on Sylt. The measures have so far cost more than €134 million in total, but according to scientific calculations they are sufficient to prevent greater loss of land for at least three decades, so the benefits for the island's economic power and for the economically underdeveloped region in general would outweigh the costs. In the 1995 study Klimafolgen für Mensch und Küste am Beispiel der Nordseeinsel Sylt (Climate impact for Man and Shores as seen on the North Sea island Sylt) it reads: "Hätte Sylt nicht das Image einer attraktiven Ferieninsel, gäbe es den Küstenschutz in der bestehenden Form gewiss nicht" (If Sylt did not have the image of an attractive holiday island, coastal management in its current form would certainly not exist).

The enforcement of a natural reef off Sylt is being discussed as an alternative solution. A first experiment was conducted from 1996 to 2003. A sand drainage as being successfully used on Danish islands is not likely to work on Sylt owing to the underwater slope here.

Parallelly to the ongoing sand flushing, the deliberate demolition of groynes has begun amid great effort at certain beach sections where they were proven largely ineffective. This measure also terminated the presumably most famous groyne of Sylt, Buhne 16 — the namesake of the local nude beach.

A number of experts, however, fears that Sylt will still have to face considerable losses of land until the mid 21st century. The continuous global warming is thought to result in increasing storm activity, which would result in increased land loss and, as a first impact, might mean the end for property insurances. Measurements showed that, unlike in former times, the wave energy of the sea is not any more consumed off the beach, today it carries its destructive effects on to the beaches proper. This will result in an annual loss of sand of 1.1 million m³. The dunes of the island constitute nature reserves and may only be entered on marked tracks. So called "wild paths" promote erosion and are not to be followed. Where vegetation is tread upon and no roots are left to hold the sand, it will be removed by wind and water.

The Wadden Sea on the east side between Sylt and the mainland is nature reserve and bird sanctuary since 1935 and is part of the Schleswig-Holstein Wadden Sea National Park. The construction of breakwaters in this area shall abate sedimentation and is used for land reclamation.

Also the grazing of sheep on the sea dikes and heaths of Sylt eventually serves coastal management, since the animals keep the vegetation short and compress the soil with their hooves. Thus they help create a denser dike surface, which in case of storm surges provides less area for the waves to impact.