where does the severn estuary become the bristol channel
River Severn The Severn Estuary extends to a line from Lavernock Point (south of Cardiff) to Sand Point near Weston-super-Mare. West of this line is the Bristol Channel. In the Severn Estuary (or the Bristol Channel in the last two cases, depending where the boundary is drawn) are the rocky islands called Denny Island, Steep Holm and Flat Holm.