A troll terrorized those hoping to cross this river, until it was killed by Almerick Sawbridge in the 1600s (FW). The Wye River is in western England, and in fact forms part of the border between England and Wales. The river may also be the lair of the infamous Wyvern of Wye, battled famously by Sir Cadogan (Pm).
The Wye River forms the border between Wales and England near where it flows into the Severn River. This part of the border also separates Chepstowfrom Tutshill, where Rowling lived for some years starting in 1974. In the 1600s, according to a Famous Wizard card, a troll terrorized travellers crossing the Wye River; the troll was eventually defeated by Almerick Sawbridge (FW). While Rowling does not give the exact location of this troll-infested crossing, she might very well be thinking of the stretch of river near where she grew up.