This beautiful wall map shows a part of the Gelderse Vallei, namely the Slaperdijk 'streckende vande Stichtse bergen [= Utrecht Hill Ridge] tot de hoogte van Gelderland [= studded sand ridges of the Gelderse Vallei]'. A 'slaperdijk', as the name suggests, is a 'sleeping' dike that only starts to serve when the 'waking' dike breaches. In that case, the dike takes over the water retaining function and must protect the remaining land.
This is also the case with the famous Slaperdijk in the Gelderse Vallei which is shown on this wall map. This dike became 'active' after the northern Rijndijk or Grebbedijk between Wageningen and Rhenen was breached. When the Slaperdijk was not yet in place, breaches of the Rijndijk often caused serious water nuisance. For example, from 1595 the city of Amersfoort was flooded several times, after which it was decided to construct the secondary dike in 1651. In 1653 the dike was completed and the Board for the Management of the Slaperdijk was established to manage it.
However, the construction of the Slaperdijk was not the end of the problems. Because the Utrecht part of Gelderse Vallei is somewhat lower than the Gelderse Vallei, Utrecht in particular suffered from flooding when the dike broke. Therefore, the Slaperdijk was mainly an Utrecht matter and this province even made the dike heavier than the Grebbe dike. There were frequent conflicts with the Gelderland States, which were blamed for a lack of dike maintenance. But for Gelderland, the Slaperdijk was of course a disadvantage, because the water stayed against it and formed a threat for the farmers in Gelderland. The latter therefore eventually got access to a few 'gullies' or culverts under the dyke. The capacity of these culverts was also a matter of dispute.
Conflicts also seem to have been at the basis of this map of the Slaperdijk, mapped by Justus van Broeckhuijsen (c. 1670-1724). This surveyor, who had lived in Utrecht since 1693, produced the map in 1705 at the request of the Board for the Management of Slaperdijk. This board wanted to combat the illegal felling of trees; the map showing the dyke and the associated jurisdiction was to serve as a means of enforcement. In addition, the lord of Renswoude had conceived the plan to provide his castle with a Grand Canal, following the example of the Palace of Versailles. For the water supply he wanted to make a connection with the Lunterse Beek, which required an excavation of the Slaperdijk.
The map of the Slaperdijk not only has a functional character, but also has a clear representative function. For example, the names of the various board members and their coats of arms are shown on both sides of the map. When the composition of the board changed, the previous names and coats of arms were often pasted over with the most recent ones. Several variants of the map are known in this way. Considering the composition of the board, as shown on the map presented here, the date of publication must have been around 1800. In cartographic terms, however, the map image did not change. This copy of the map is exceptionally fresh in appearance and colour. This is because the map was pasted in segments on linen and always kept in its folded state. Because of this, things like daylight and cigar smoke have not affected the map's appearance.
The map clearly shows how the relief has determined the course of the Slaperdijk. The lateral moraines of the Utrecht Hill Ridge and the sand ridges in the Gelderse Valley are clearly visible. The first part of the route runs from the Egelmeer (now a marshy area of heathland) near the ridge to the Emmikhuizerberg, an isolated moraine northwest of Veenendaal. From there, it goes east via the existing Schalmdijk to the sandy height of the later Fort aan de Buursteeg. The last part of the route then continues in a north-easterly direction until it reaches the border with Gelderland. Here, it follows the border for a while, until it reaches the higher sand ridges in the north. This route was sufficient to ward off the danger of flooding from the south-east.
On the top right of the map, the house of Frederik Adriaan van Reede, the lord of Renswoude, has been beautifully drawn. Perpendicular to this castle, the new canal can be admired as a line of sight, marked 'Nieuw Gegrave Water Sloot na Renswoude'. The connection of this canal with the Lunterse Beek via a 'heul' is clearly visible and, as mentioned, was one of the reasons for the production of the map. The village of Veenendaal is shown at the bottom left, with numerous peat canals for the peat industry in the immediate vicinity. Some sandy embankments are also mapped as hills, which are still clearly recognisable in the village near the church and the mills.
Below right is an inset map of the situation of the Grebbedijk, the reason for the construction of the Slaperdijk. Several wheels, gully holes caused by dike breaches, show the vulnerability of the Grebbedijk at the time. A major breach occurred near Den Doove farm in 1855. The dike and the farm were washed away and both were rebuilt further inland. The inset map also shows the only known picture of the vanished house De Blauwe Kamer, after which the present-day nature reserve is named.
How did the Slaperdijk fare after its construction in 1653? When the Grebbedijk burst again in 1711, the Slaperdijk was able to hold back the rising water. This kept the Utrecht part of Gelderse Vallei safe from flooding. However, when the Grebbedijk was breached in 1855, the dike had to give way. By then, the Grebbelinie, a military waterline constructed during the Austrian Succession War (1740-1748), was already in place. This defence system cut through the Gelderse Vallei from south to north, with a series of inundation areas on the eastern side. These areas were bordered by cross dykes to prevent the water from running into the Zuiderzee in one go. The Slaperdijk functioned as one of these cross dikes at the time.
Although the Slaperdijk no longer has a water-retaining function, the dike can still be recognised in the landscape as a line element. Large sections are now used as attractive walking and cycling paths. The dike itself has been put to sleep for good ...