Rivil
From Tolkien Gateway
The Rivil was a lesser tributary of the Sirion River. Its source was Rivil's Well in the highlands of Dorthonion, from which it flowed westward to meet the Sirion at the Fen of Serech.[1]
During the Nirnaeth Arnoediad King Turgon retreated down the Pass of Sirion. His escape was successful because Húrin and Huor formed a rearguard that used the Rivil as a defense. The host of Angband bridged the stream with the corpses of their dead. Huor was slain beside the Rivil and Húrin was captured.[2]