Building timber auxiliary forts in the Lower Rhine Delta in the Netherlands (AD 40 –140) Julia P. Chorus Zusammenfassung – Nach detaillierten Analysen der Ausgrabungen von neun hölzernen römischen Kastellen am Rhein Delta (Nieder- germanischen Limes) in Vechten, Utrecht, De Meern, Woerden, Bodegraven, Zwammerdam, Alphen aan den Rijn, Leiden-Roomburg und Valkenburg (Süd-Holland) sowie von einem Kleinkastell in Valkenburg-Marktveld können nahezu 40 Bauphasen unterschieden werden. Sie sind die Grundlage für den hier präsentierten Vergleich. Die frühkaiserzeitlichen Kastelle wurden alle aus Holz gebaut. Die später häufig anzutreffende kombinierte Holz- und Steinbauweise ist erst ab etwa 160 n. Chr. feststellbar. Frühe Kastelle wurden aus Bauhölzern errichtet, die den umliegenden Wäldern entstammen. Dagegen ist von etwa 70 n. Chr. an das meiste Holz aus Nutzwäldern entnommen, dadurch wurden im Laufe der Zeit andere Baumarten bevorzugt genutzt. Es gibt viele Unterschiede zwischen diesen Kastellen in den West-Niederlanden und denen im weiteren Verlauf der Rheingrenze. Layout, Baustil und Bautechniken zeigen markante Variationen. Dies könnte eine Beziehung zwischen den Soldaten, die die Kastelle bauten, ihrer Herkunft und ihren Bautraditionen aufzeigen, die sich aus der Kenntnis eisenzeitlicher Bautechniken in Holz erschließen läßt. Einige Kastelle wurden in einer Tradition gebaut die man von den Elbgermanen, der Przeworsk Kultur und möglicherweise auch von den Batavern kennt. Andere Kastelle zeigen wiederum Ähnlichkeiten zum murus gallicus aus Gallien. Schlüsselwörter – Römerzeit, Kastelle, Rheinmündung, Dendrologie, Fälljahr, Feuchtboden Title – Building timber auxiliary forts in the Lower Rhine Delta in the Netherlands (A.D. 40 –140) Summary – After studying the excavations of the nine Roman timber auxiliary forts in the Rhine delta at Vechten, Utrecht, De Meern, Woerden, Bodegraven, Zwammerdam, Alphen aan den Rijn, Leiden-Roomburg and Valkenburg (South Holland) and the fortlet at Valken- burg-Marktveld, almost 40 building phases are distinguished. Subsequently these are the base of this comparative study. The early forts in the research area were all built of timber. After several rebuilding phases only from AD 160 onward many of them were rebuilt in stone and wood. First, the forts had been constructed with wood supply from nearby forests, while after AD 70 most wood derived from managed woodlands. Later on the taxa of preferred trees also changed. Many differences occur between these forts in the West-Netherlands, and also abroad. Layout, building style and techniques show a striking variation. This might point to a similar relation between the soldiers who built the forts, their origin and their building traditions as appears from research at Iron Age building techniques in timber. Some forts have been built in a tradition known from Elbgermanen and Przeworsk culture and possibly also the Batavians. Other forts show similarities with the murus gallicus from the (recruitment) area of the Gauls. Key words – Early and Middle Roman period, auxiliary forts, Rhine Delta, Dendrology, Wetlands 1. Introduction has destroyed most of the evidence, except for dredge finds and some structures in Arnhem- During the course of the first century AD the Meinerswijk1. Roman army’s building campaigns at the south What information about the forts in the Rhine bank of the Lower Rhine River must have caused delta do we have? The timber remains in the a grand metamorphosis of the river area. Remains wetland area provide a lot of information. But the of nine timber auxiliary forts and a fortlet have way in which the remains have been documented been found in the West-Netherlands, in the Rhine varies. Sometimes the location is known and delta (fig. 1). An auxiliary fort was built on the small scale excavations give us some insights river front between Vechten, near Utrecht, and into the building phases. Other forts have been the North Sea coast every 12–15 kilometres, and studied and analysed more extensively. In some later on even closer. These forts were constructed cases, the research took place over a century ago, of timber and turf and had dimensions of 1–1,5 while at other sites parts of forts were excavated hectare (ha). They were small in comparison to only recently. contemporary forts in other parts of the Roman Despite these differences in levels of research Empire’s frontier zone. Yet, with ramparts of and publication, I have been able to reconstruct some five meters in height and even higher almost 40 building phases of the nine forts towers, these forts must have made an enormous at Vechten, Utrecht, De Meern, Woerden, impression on the local population. Bodegraven, Zwammerdam, Alphen aan den There are also indications of a Roman military Rijn, Leiden-Roomburg and Valkenburg (South presence further upstream, though few traces of Holland-ZH) and the fortlet at Valkenburg- this can be found in the area today. The Rhine Marktveld (fig. 1). The reconstruction is based Archäologische Berichte 27, 2017, 19-36 19 Julia P. Chorus Fig. 1 Research area: fortifications in the Lower Rhine area in the Early and Middle Roman period. 1: fortress; 2: auxiliary fort; 3: probable auxiliary fort. on information from excavation reports, articles the Radboud University of Nijmegen (see and other publications, photographs and field acknowledgements)3. drawings of old and new excavations. These Excavations in the wet environment of the last two mentioned items were very important research area have provided an extraordinary sources for this research. They are fascinating to quantity of wood records of the forts, and also of study and show many details. roads, watchtowers and river quays. These data In this paper, I will make a comparison have provided insights into the Roman supply between the forts and discuss their similarities systems over time and have made it possible and differences and how these might be explained. to reconstruct the different types of wetland Most of the auxiliary forts in the research area woodlands from which supply took place. The were founded in the early 40´s AD. Only in the results show a use of different taxa through time, last quarter of the second century AD, around 160, the use of import wood and indications of local the greater part was rebuilt in stone. That is much woodland management. later than in other regions of the Roman Empire, Before discussing the use and origin of the such as Britannia, the most of Germania Inferior timber and the comparison of the forts, I will and in areas to the east. start with a short overview of the archaeological- Wood was available in the surrounding area historical context in which the forts of the lower and was used for building the forts2. I will deal Rhine delta were built. with the use and supply of wood for the Roman army in the Rhine delta, a focus of my colleague Pauline van Rijn’s research, in connection with 2. Early fortifications along the Rhine in the the building campaigns of the forts. Van Rijn is, Netherlands amongst others, a member of the research group of “A Sustainable Frontier? The establishment The river area between Vechten and the North of the Roman frontier in the Rhine delta” at Sea (fig. 1) offers exceptional information for 20 Building timber auxiliary forts in the Lower Rhine Delta in the Netherlands (AD 40–140) this research. Due to the high-water levels in The forts that probably do relate to Claudius, this wetland area artefacts, especially organic and possibly to his governor Corbulo and the material, are very well preserved. The structures events around the year 47, are those at Utrecht along the Lower Rhine are also well preserved (Dom Square), Zwammerdam and Leiden- in subsurface, as hardly any post-Roman river Roomburg18. Yet this year does not appear to erosion occurred. This is in contrast to the central be a ‘sacred’ date. Founding dates before 47 are and eastern part of the Dutch river area4. well imaginable. After recent research of old The first signs of Roman occupation in the excavations at Utrecht that were conducted in Rhine-Meuse delta relate to the military campaigns 1949 and 1956, for example, it was pointed out that of Augustus by Agrippa. A large military base there was pottery that could be dated from AD 40 at the Hunerberg in Nijmegen had already been onwards19. Of course, one needs more than pottery built probably between 19–16 B.C5. The camp had to date a site, like coins and dendrochronological been evacuated only in or shortly after 16, or at dates. Still, this tells us that the year 47 is of less the latest in 12 B.C. Auxiliary troops had their fort importance than had been assumed earlier. nearby, at the Kops Plateau. In the first decennia The first signs of Roman occupation at of the first century some small camps arose in that Bodegraven were supposed to be dated in area6. Meanwhile, the first forts appeared along the 60´s AD This was established by two the Rhine at Vechten7 (fig. 1) and, somewhat later, dendrochronological dates of a gateway’s posts around AD 10–20, most probably also at Arnhem- in the summer of AD 61 (the felling date). The Meinerswijk and – some kilometres to the west remains of the fort at Bodegraven could well be – Driel8. North of the river Rhine a fort with a of a somewhat later date than the ones mentioned harbour was built in the Oer-IJ region, at Velsen, before, but not as late as AD 61. This date actually and was connected with the forts on the Rhine appears not to relate to the oldest building phase through the river Vecht9. of the fort20. The wood samples belong to a rebuilding phase or to the repair of the gateway. Finds of pottery support a date earlier than AD 2.1.