Syltemade Ådal (Syltemade Stream Valley)
Magnificent extramarginal meltwater valley formed in relation to the Hvidkilde-Ollerup tunnel valleys. The area's many habitats offer a rich and varied animal and plant life.
Syltemade (Syltemae) Ådal is a beautiful meltwater valley located 10 km west of Svendborg. The southern half of the valley is protected and accessible on foot from a small parking lot along the road, Langegyde. A 4.5 km long stretch of the marked hiking trail, Øhavsstien, follows the stream valley. It is one of the few places on South Funen where it is possible to walk along a watercourse. Syltemade Ådal is privately owned, and it is therefore only allowed to walk on the marked path.
The northern part of the trail passes through small woodlands, pastures and meadows with grazing animals, while the southern part, via low wooden bridges, passes through swampy areas with reed beds. The many habitats provide the basis for a variety of flora and fauna. In winter and during periods of heavy rainfall, the bottom of the stream valley is damp and muddy and can be flooded in places, so rubber boots are recommended.
On the final stretch towards the outlet in the South Funen Archipelago, the stream valley widens out and here the stream runs through a salt marsh area, Syltemaden, which has given the stream its name. The name is a paraphrase of the older name Syddemaen, composed of the Old Danish words sudda or sydda, meaning 'wet', and mae, meaning 'meadow'. Today, most of Syltemaden is overgrown with reeds.
Just east of the mouth of Syltemade Ås is Ballen Marina. In the 1600s, there was a shipping pier here, which was one of the many illegal smuggling ports that in shady ways broke the market towns' exclusive trading rights.
From Hvidkilde Lake to the outlet in the archipelago, Syltemade Å has a drop of 19 m. Over time, the stream has powered 6-7 water mills, of which only Røde Mølle, Orte Mølle and Vester Mølle are preserved today. The small stone and concrete structures seen along the streak in Syltemade Ådal are remnants of former meadow irrigation systems built in the late 1800s.
Human presence in Syltemade Ådal is also evidenced by archaeological finds from the Stone Age, Bronze Age and Iron Age. A kitchen midden has been found near Eskilds Kilde.
Photo:Kort: GeoFyn. Illustration: Søren Skibsted.
The ice age landscape around Syltemade Ådal
Syltemade Ådal is part of a larger valley system that was created 18-17,000 years ago during the last ice age, Weichsel. At that time, the area was covered by the part of the Bælthav Ice Stream known as the 'Little Belt Glacier'. Between the towns of Sørup and Ollerup, meltwater streams excavated a 6 km long valley under the glacier. Today, this valley forms the beautiful tunnel valleys with the lakes Sørup, Hvidkilde, Nielstrup and Ollerup.
At one point, the ice edge was just east of Vester Skerninge. Here, the meltwater came out from under the glacier, after which the water masses found their way south towards the low-lying terrain south of Funen, which would later become the South Funen Archipelago. The meltwater cut into the moraine surface, creating the 20 m deep erosion valley we know today as Syltemade Ådal. At its narrowest point, the valley is only 100-130 m wide, while at its mouth it is 400 m wide.
After the end of the ice age 11,700 years ago, the bottom of Syltemade Ådal was partially covered by freshwater clay, sand and gravel, as well as thick layers of peat.
Several springs emerge from the steep slopes. One of these is Eskild's Spring, where the sick and infirm used to flock to seek healing - especially around the midsummerseve celebrations of Sct. Hans, when the forces of nature were at their strongest. At several of the springs along the trail, you can see how the lime-rich water encapsulates leaves, twigs, branches and pebbles with crusts of spring lime.
A little west of the mouth of the stream valley at Ballen is a small coastal cliff with gray and brown moraine clay, deposited by the 'Northeast Ice' (23-21,000 years ago) and the Young Baltic Ice (19-17,000 years before present) during the Weichselian Ice Age.
A few hundred meters further west is the protected Præstens Skov forest by the sea. Here you can see many large stones on the forest floor that have remained untouched since the Ice Age - a so-called stone litter. The Archipelago Trail passes through the forest and there is a parking lot and picnic area.
The landscape in the future
From a geological perspective, the glacial landscape in and around Syltemade Ådal is unlikely to change in the foreseeable future. Increased precipitation could generally affect the groundwater level and runoff conditions on the surrounding moraine surface and locally raise the water level in local depressions, which is detrimental to low-lying arable land and low-lying properties. This also applies to the landscapes, moors and wetlands further upstream in the stream system, including the tunnel valleys with the larger lakes.
Large parts of the moraine landscape are covered with vegetation and/or cultivated, which, together with the clay surface layers and moderate terrain slopes, is unlikely to lead to significant changes in surface erosion, even with an increasing frequency of cloudbursts. Even the steeper slopes in the tunnel valleys and in Syltemade Ådal are covered with vegetation.
A general increase in precipitation coupled with the expectation of future episodes of high precipitation intensity will have some influence on the flow pattern of the Stream of Syltemade. There may also be changes in the amount of sediments and organic matter carried by the stream, as well as increased leaching of nutrients from cultivated areas in the catchment area. In this way, the extensive salt marsh areas (Syltemaden) at the mouth of the valley, as well as the coastal areas around the stream's outlet in the South Funen Archipelago, may experience an increased load of unwanted nutrients.
It should be added that large parts of the upper reaches of the watercourse in the tunnel valleys are regulated in various ways, which also applies, for example, to the water level in Hvidkilde Lake, where there is a dam at Røde Mølle.
As the southernmost part of Syltemade Å has only a very slight drop towards the outlet into the archipelago and is generally low-lying, future sea level rise will have a relatively large impact on this part of the stream system. Even with a sea level rise of 1 m, the Syltemaden salt marsh would be permanently flooded and the sea would, in principle, penetrate more than 1 km upstream.
This phenomenon can already be observed during storm surges and high water situations accompanied by wind-driven stagnation of the water masses in the archipelago. This causes the sea level to be higher than the normal height of the stream outlet and the water from the stream is therefore dammed up in the lower, lowest parts of the stream. This damming gradually propagates backwards and upwards in the stream valley, where significant areas are gradually submerged. Such conditions occur relatively often during the winter months, when the southern pathway can remain inaccessible for long periods of time.
An extreme situation similar to the storm surge of 1872, with a water level rise of up to 3.5 m, would potentially mean that seawater could penetrate almost 2 km up the valley.
Located close to Svendborg, the area with Syltemade Ådal, the tunnel valleys and the manor landscape around Hvidkilde Manor offers a wide range of outdoor activities with a varied landscape, lakes, views, hiking and cycling opportunities and various sites of cultural and historical interest.
The site is geologically interesting in the form of the link between the largest tunnel valley system on South Funen and the beautifully shaped erosion valley of Syltemade Ådal (a so-called extramarginal meltwater valley).
In addition, the protected southern part of Syltemade Ådal contains a large number of important natural habitats.
Syltemade Ådal was protected in 1975 and 1977 and is classified as part of the National Geological Interest Area NGI 131, which also includes Egebjerg Bakker and Stenstrup Issø.
Likewise, the stone litter in the protected Præstens Skov is of high value, as such stone accumulations are rare in modern Denmark, where the vast majority of stones in the soil surface have been collected in connection with cultivation, forest planting, stone dykes and buildings.