Vallum & DitchVallum et fossa
Vallum Crossing at Condercum
To the north of the Wall there is a ditch that runs the length of it east to west except where there are areas that the surrounding terrain means it was fruitless to dig, such as the Whin Sill. It does appear between dips and crags though along this stretch. The ditch itself was approximately 20 feet from the Wall on the stone built stretch and 6 feet on the turf built stretch with a flat piece of ground separating them. This ground is referred to as the berm. It is suggested the larger distance from the stone based Wall is because of the pressure of the stone against the ditch sides. The ditch varied between 26 and 40 feet in width with an average of 27 feet and was 9 to 10 feet deep. It had a V-shaped profile and in the bottom would be a square cut drainage channel. The soil and other material cut from the ditch would be stacked to the northern edge giving extra height and this would be smoothed at the sides. There is still evidence today that the ditch was never completed, or started, in parts such as Allolee and Cockmount Hill.
The Vallum consists of a flat bottomed ditch which, in Roman measurements, was 20 feet wide and 10 feet deep. It had one mound either side of the ditch which were also 20 feet wide and set back from the lip of the ditch to a distance of 30 feet. This would be extremely difficult to cross by anyone without the authority to do so without being hindered greatly and therefore unseen. It also leads scholars to believe the Vallum was built at the same time or just after the Wall - it wasn’t that far back in modern history when it was suggested the Vallum was built before the Wall although that has since been disproved. The system of the Vallum would have made it almost impossible to navigate around it if the Wall was built later.
Where the Wall at one time allowed almost unrestricted approach to it by merchants and the like the building of the Vallum gave the Romans more control of how the Wall was accessed. The north berm would be used for army patrols and force citizens to be routed through the gates of the Wall and across causeways over the Vallum and almost certainly not through the forts for obvious reasons. It seems that every fort along the Wall had a crossing at the Vallum to the south and each crossing was closed with huge double gates. An example of such a crossing is the superb remains south of the fort at Condercum (Benwell) showing the Vallum ditch and gateway. On the northern side of the Vallum gateway roads have been rebuilt over time and these appear as ‘steps’. The gates were always guarded and were purely to control access to the Wall and beyond and not there to protect the Wall itself. Originally the gates along the Wall numbered around 79 and the Vallum reduced this to a more manageable 14 approximately.