As with most of Arthur's battles from Nennius, the location of this river is unknown today.
Another name for this river is believed to be "Tribruit", which would have been Tryfrwyd in old Welsh. This river is mentioned in Pa Gur yv y Portaur?, an old Welsh poem dating from the 11th century:
Another identification is with the River Brue in Somersetshire, where Sir Bedivere is believed by some to have thrown Excalibur after the Battle of Camlann.
The Battles of King Arthur