It then flows south for 32 kilometres (20 mi) through East Devon to the English Channel at the western end of Lyme Bay.
The Permian and Triassic sandstone aquifer in the Otter Valley is one of Devon's largest groundwater sources, supplying drinking water to Taunton.
Neighbouring natural regions are: the Devon Redlands to the west, the Vale of Taunton and Quantock Fringes to the north, the Mid Somerset Hills to the northeast, the Yeovil Scarplands to the east and the Marshwood and Powerstock Vales to the southeast.
Artifacts dating back 10,000 years have been found near Bear Butte.
In more recent times, however, the Cheyenne and Lakota people have maintained a spiritual tie to this mountain.
The plateau is dominated by hard chert bands of Upper Greensand with some remnants of chalk, and is cut through by river valleys.
The hills support an extensive range of wildlife leading to the designation of 16 Sites of Special Scientific Interest (SSSIs).
Bear Butte is considered to be a sacred mountain to many American Indians as it is seen as a place where the creator has chosen to communicate with them through visions and prayer.