There has been considerable debate about the whereabouts of the canal. One thesis was that its course is identical to the river Vecht, which connects Utrecht (ancient Traiectum) to the IJsselmeer (ancient Lake Flevo), but this proposal was abandoned for an alternative: that the Canal of Drusus connected the rivers Rhine and IJssel and is identical to that part of the last-mentioned river which is now called Gelderse IJssel. This theory became the consensus among the archaeologists when the site of Drusus' mole was established near Carvium (modern Herwen), a bit east of the bifurcation of the Rhine and the Gelderse IJssel. At the beginning of the presumed canal was the fort of Castra Herculis, which was excavated near Arnhem-Meinerswijk.
This consensus was never without critics. A reinterpretation of the evidence, published in 1995, points to the fact that Suetonius speaks about the canals of Drusus, and suggests that a second canal connected Lake Flevo with the Wadden Sea. This makes sense, because if there had been one canal only, the Roman navy would have been forced to leave Lake Flevo in the west, at Flevum, and would have had to make a dangerous detour over the open sea. A second canal, leading to the Wadden Sea, would solve this problem. Geologists have established that at the beginning of our era, the Wadden Sea indeed got connected to what used to be Lake Flevo, but the cause of this breakthrough can no longer be established.
Radiocarbon-dates from the oldest deposits of the Gelderse IJssel, published in 2009, suggest that they date back to the tenth century. Of course, it remains possible that the Canal was between Arnhem and Doesburg, later changed its course, and that the samples were taken from this new meander. It can also mean that the consensus has to be abandoned.
- Kerst Huisman, "De Drususgrachten: een nieuwe hypothese", in: Westerheem 44 (1995) 188-194.
- B. Makaske, G.J. Maas & D.G. van Smeerdijk, "The age and origin of the Gelderse IJssel", in Netherlands Journal of Geosciences 87/4 (2008)