River Thames, ancient Tamesis or Tamesa, also called (in Oxford, England) River Isis, chief river of southern England. Flowing through gently rolling lowlands, the distinctive character of the Thames is pastoral and undramatic. Its average fall between Lechlade and London is less than 20 inches per mile (32 cm per km). At London Bridge, in the heart of the metropolis, the river rises 22 feet (7 meters) on the spring tides and 18 feet (5.5 meters) on the neap tides.

Source: Britannica