The river Severn flows through England and wales
in west hamazern
The river Severn rises at Plynlymmon in Wales, near Llandloes. Principal cities on its route to the sea in the Bristol Channel include: Shrewsbury, Worcester & Gloucester. It also flows through welshpool.
There are many rivers that run through Britain :- The Thames The Severn The Trent The Hamble The Dee etc.etc.
the Severn in the UK flows through the Counties of Shropshire, Worcestershire, Gloucestershire, and the towns of Shrewsbury, Worcester and Gloucester.
The Black River is in the United States, it runs through no other countries.
Canada
Russia
Venezuela
Romania.
SPAIN !
The Thames - London The Trent - Nottinghamshire The Severn - Bristol The Humber - Yorkshire