Great river. The water is wet. 😂. The French Broad River flows 218 miles from near the town of Rosman, NC, into the state of Tennessee. Its confluence with the Holston River at Knoxville, TN is the beginning of the Tennessee River The French Broad is the third-oldest river on Earth by age (260 to 325 million years). Overall, E. coli levels in the French Broad River are low, and the river is safe for swimming.