Afon Twrch
The Afon Twrch is a river which rises in the Black Mountain in south Wales. It forms the boundary between Powys and Carmarthenshire and, downstream of Ystradowen, between Powys and Neath Port Talbot.
Name
The name derives from Welsh afon / 'river' and twrch / 'boar'. In common with other rivers sharing the same name, it is believed to refer to the burrowing or snouting action of the waters of the river. The river has also been associated with the legend of Twrch Trwyth.Geography
The headwaters arise on the southern slopes of Carmarthen Fans and Fan Brycheiniog and are soon joined by the waters of the Twrch Fechan. The river flows south-west and then south and finally south-east for about to its confluence with the River Tawe at Ystalyfera. Tributaries include the Nant Gwys and the Nant Llynfell.Settlements on the lower section of the river include Ystradowen, Cwm-twrch-uchaf, Cwm-twrch-isaf and Gurnos.
Parts of Cwm Twrch on its Carmarthenshire side are designated as an SSSI because they expose a good example of a boundary between strata.