Brahmaputra
brick brim broth brat brake brawl.............. oh and br br br br br
Brook
Brain, breast and bronchi are body parts. They begin with the letters BR.
brunt
It could be brio, bred, brag, brew, brie...
Phillip Rivers
No rivers starting with 'U'
the great animas
Ganges
OriginOutpour
There are 103 rivers in Sri Lanka, and almost all of them starts from the Central Mountains.
Brisling: small herring processed like a sardine