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Specialists at Utrecht ľ¹Ï¸£ÀûÓ°ÊÓ's Faculty of Geosciences will digitally monitor fractures in the rampart near the outer moat of Loevestein Castle. The research should provide reliable data on the condition of the rampart over a long period of time, for example whether the situation is worsening and whether there is a connection with periods of drought. The results of the survey will be used to decide whether restoration of the rampart is necessary.

Usually Tjalling de Haas investigates debris flows, avalanches and other natural hazards in the Alps, but now Loevestein Castle makes grateful use of his services. It happened to the Utrecht ľ¹Ï¸£ÀûÓ°ÊÓ physical geographer after a family outing to the Dutch medieval castle. Coincidentally, de Haas heard from the caretaker about fractures in the rampart near the outer moat. The castle's staff were concerned about any worsening of those fractures. ‘As it happens, we have the right equipment to measure that', was De Haas’ response. Last April, de Haas and his colleague Daniel Draebing installed their precision instruments in the walls, allowing them to remotely monitor the situation. The first results will be announced on 5 June next.

Loevestein Castle will have reliable data on the condition of the rampart over a long period of time

Mapping weathering

De Haas and Draebing study landslides, both on site in the mountains and in their laboratory at Utrecht ľ¹Ï¸£ÀûÓ°ÊÓ's Faculty of Geosciences. For their research, they are interested, for example, in fractures that occur in rocks. The size of those fractures or the speed at which they occur can be an indication that a landslide or rock avalanche is imminent. The weathering in the rock should therefore be well monitored. The same applies to subsidence or fractures in a wall. ‘You can of course measure such a phenomenon with a ruler, but then you'd get just a snapshot,’ de Haas clarifies. ‘Besides, a ruler is not accurate enough. You'd also have to climb a ladder every time and enter the data by hand. We, on the other hand, can monitor the fractures from the inside, and not only measure whether they widen or perhaps diminish in size, but also how fast this happens and which environmental factors cause the fractures to grow in size and width. Now Loevestein Castle will have reliable data on the condition of the rampart over a long period of time.’

Water level

The fractures were first observed at the beginning of this century. The castle's caretakers suspect a correlation with low water levels in the Waal river during times of drought. Therefore, since 2017, measurements have been taken twice a year at different places in the ramparts by the company De Bonth van Hulten. Shrinkage could cause damage to the earthen rampart, somewhat similar to what happened in the extremely dry summer of 2003, when the peat dike near Wilnis gave way. ‘It won't be that dramatic, because there is no threat of flooding at our place, let alone visitors being bothered by the fractures,’ says Tim Schrijver, the castle's caretaker. ‘However, such an icon of our history must of course remain in good condition.’ The results of the Utrecht study will tell whether there is indeed a connection with periods of drought. ‘Based on these results, we can then make a decision on a possible restoration of the rampart,’ he says.

Fortifications

Construction of Loevestein Castle, located on the river Waal in the province of Gelderland, began around 1358. Earthen fortifications were erected around the castle in the late 16th century. On the north-eastern side (the river side), these ramparts were reinforced by a brick wall and it is this wall in which the fractures were observed. The research will continue at least until 2028.