The Welsh lowland zone consists of the north coastal plain, the island of Anglesey, part of the Llŷn Peninsula, a narrow strip of coast along Cardigan Bay, much of Pembrokeshire and southern Carmarthenshire, the Gower Peninsula and the Vale of Glamorgan. The main rivers are the River Dee, part of which forms the boundary between Wales and England, the River Clwyd and the River Conwy, which all flow northwards into Liverpool Bay and the Irish Sea. Further round the coast, the Rivers Mawddach, Dovey, Rheidol, Ystwyth and Teifi flow westwards into Cardigan Bay, and the rivers Towy, Taff, Usk and Wye flow southwards into the Bristol Channel. Parts of the River Severn form the boundary between Wales and England.