Indeed, to keep the war machine fed there were many transport nodes in the war supply chain around the region. However, this operation being just too big in volume and wide in scope, so not all the transport was by means of military transport wagons . To help, the BA contracted in many Boer transport riders who carried vast quantities of war goods, criss crossing the region, in their 16 ox powered wagons carrying supplies for the forces. Some of these Boers became quite entrepreneurial and had 5-6 wagons in their fleet. A major part of this traffic was hay and grain/fodder for the horses. Of course this trade was very lucrative for them too..
There was a very nice picture, good quality for its time, posted by John Young of a supply node on the south bank of the Tugela at the pont crossing on the main route into Zululand, which clearly showed mega quantities of ammunition boxes and sacks of grain in a storage dump there. Perhaps he will post it again.
The south bank of the Tugela was obviously a stopping point for the coastal column