This magnificent wall map shows a part of the Dutch region Gelderse Vallei, namely the Slaperdijk ‘streckende vande Stichtse bergen tot aan de hoogte van Gelderland’ (‘stretching from the Sticht mountains [= Utrecht hill range] up to the heights of Gelderland [= sand deposit hills of Gelderland]’. The map has been georeferenced and is part of the digital exhibition of Water management maps in Google Earth. A slaperdijk (literally: sleeping dike) is a dike which proves its use only after the ‘waking dike’ breaks. When that happens a sleeping dike has to turn the water and protect the remaining land.
The same goes for the famous Slaperdijk in the Gelderse Vallei which we see on this wall map. This dike became ‘active’ after the northern Rhine Dike or Grebbe Dike between Wageningen and Rhenen broke. Before the Slaperdijk was constructed, the collapses of the Rhine Dike often caused major flooding. For instance from 1595 onwards the city of Amersfoort was flooded several times, so in 1651 it was decided to construct an additional, secondary dike. In 1653 the dike was finished and the ‘College tot Directie of the Slaperdijk’ (‘Slaperdijk Managing Board’) was set up to manage dike affairs.
However, the building of the Slaperdijk did not result in solving the problem. Because the Utrecht part of the Gelderse Vallei is lower than the Gelderland part, especially Utrecht was visited by floods caused by the bursting of the dikes. As a result, the Slaperdijk was mainly a Utrecht interest and this province made the dike even heavier than the Grebbe Dike. Conflicts arose regularly with the States of Gelderland who were accused of neglecting the dikes. But for Gelderland, the dike caused a problem, because the water kept standing against it and so threatened the farmers from Gelderland. In the long run these farmers got the disposal of some culverts - small waterways - underneath the dike. About the capacity of these culverts quite a few discussions arose.
Conflicts seem to have been at the origin of this map of the Slaperdijk, mapped by Justus van Broeckhuijsen (ca. 1670-1724). This land surveyor who had been living in Utrecht since 1693 was commissioned by the Slaperdijk Managing Board in 1705 to produce the map. The board wanted to prevent the illegal cutting of trees: the map depicting the dike and the belonging jurisdiction had to serve as an instrument to enforce the law. Besides, the Lord of Renswoude had conceived a plan, in imitation of the palace of Versailles, to build a Grand Canal for his castle. For the water supply he needed a connection to the Lunteren Brook which required the Slaperdijk to be tunneled through.
The map of the Slaperdijk is not only functional in character, but also serves a representative purpose. For instance, the names of several board members and their coats of arms can be found on both sides of the map. When new members were admitted, the most recent names and coats of arms were stuck over the old ones. As a result, several versions of this map are known. Judging from the composition of the board, as represented on the map discussed here, the publication date must have been around 1800. However, from a cartographical point of view, the map did not change. The copy of this map is exceptionally fresh in its appearance and colour. This is because the map is stuck on linen in sections and has always been stored in a folded state. That is why daylight and cigar smoke never got a chance to damage the map.
The map clearly shows how the relief determined the route of the Slaperdijk. For instance, the lateral moraines of the Utrecht Hill range and the sand deposit ridges in the Gelderse Vallei have been represented pictorially. The first part of the route goes from the Egelmeer (now a swampy heathland) near the hill ranges to the Emmikhuizerberg, an isolated lateral moraine northwest of Veenendaal. From there it goes via the existing Schalmdijk in eastern direction to the sandy heights of the later Buursteeg Fort. The last part of the route runs in northwestern direction to the border of Gelderland. Here the border is followed for a while up to the higher sand deposit ranges in the north. This route was enough to ward off the danger of flooding from the southeast.
At the top right of the map we see a beautiful picture of the mansion of the Lord of Renswoude, Frederik Adriaan van Reede. At right angles to the castle the sightline of the new canal can be admired, mentioned as ‘‘Nieuw Gegrave Water Sloot na Renswoude’ (‘Newly dug water ditch after Renswoude’). The connection of this canal with the Lunteren Brook via a culvert is clearly shown and as said before was one the reasons for making the map. Below left we see the village of Veenendaal with in its direct vicinity many peat canals for digging out the peat. Also some sandy dunes are mapped as hills which are still recognizable near the church and the mills in the village.
Below right there is an inset map depicting the situation of the Grebbe Dike, the reason for the building of the Slaperdijk. Some wheels, pot-holes as a result of dike bursts, show the vulnerability of the Grebbe Dike in those days. Near the farm ‘Den Doove’ the dike collapsed in 1855. The dike and the farm were washed away and both were rebuilt more inland. The inset map shows the only known picture of the house ‘De Blauwe Kamer’ which has disappeared and after which the present nature reserve is named.
Digitizing and putting this map online is a good thing in itself. However, the document gets an extra dimension by linking it to a geographical medium such as Google Earth. This is called georeferencing. For the purpose of georeferencing this map, the web application Georeferencer was used. With the help of this application coordinates can rather simply be added to scanned maps. Next the georeferenced maps can be consulted by means of a KML link in Google Earth or in Georeferencer’s own viewer. It is also possible to judge the accuracy of the georeferenced map in Georeferencer.
As said, the map of the Slaperdijk is part of the digital exhibition of Water management maps in Google Earth. Per map the university library gives access to the scan in both Google Earth and Georeferencer. By clicking on a map in the digital exhibition it will be shown in the viewer of the library. In the left menu you will then find links to the scan in Google Earth (Document in Google Earth) and to Georeferencer (Georeferences). Both applications make it possible to zoom in sharply on the map. The map can also be made transparant which makes a comparison with the current situation possible. Past and present shake hands …
What happened to the Slaperdijk after it was built in 1653? When in 1711 the Grebbe Dike bursted again, the Slaperdijk managed to turn the rising water. That is how the Utrecht part of the Gelderse Vallei was protected from flooding. However, at the great collapse of the Grebbe Dike in 1855 the dike had to admit its defeat. By then one could make use of the Grebbelinie, a military defence line built during the Austrian Wars of Succession (1740-1748). This defence system cut through the Gelderse Vallei from south to north, with a number of inundation areas to the east. These areas were confined by cross dikes to prevent the water from running straight to the ‘Zuiderzee’. In those days the Slaperdijk was one of these cross dikes.
Although nowadays the Slaperdijk does not have to turn the waters anymore, the dike is still very recognizable as a line element in the landscape. Large parts are now being used for recreational purposes: hiking and cycling. The dike itself has gone to sleep forever …